This document proposes using operating guidelines to model service interactions in a service-oriented architecture (SOA). It introduces a formal model of workflow services called open workflow nets that can be composed to model interacting services. The paper suggests that providers publish an operating guideline describing all compatible requesters, rather than details of their own service. This allows brokers to efficiently match requesters to providers by checking if a requester's behavior is allowed by an operating guideline.
This document introduces a reference model for analyzing internet service provider (ISP) businesses and business relationships. The model defines basic roles that stakeholders can play, including consumer, service provider, connectivity provider, information provider, and end user. It also outlines two layers of services - the infrastructure layer involving network components, and the internet service layer. The reference model is intended to help describe ISP business models and relationships in detail beyond existing classifications.
A Formal Framework For Describing Information Providing Web ServicesSamantha Martinez
This document introduces a formal framework for describing information providing web services using description logic. It proposes extending service descriptions in OWL-S to include specifications of relationships between inputs and outputs in the form of conjunctive queries. Matching services is defined as query subsumption with respect to an ontology, which reduces the problem to standard reasoning tasks. The framework aims to overcome limitations of only considering input and output types for discovery of information providing services.
Transitioning Enterprise Architectures to Service Oriented ArchitecturesNathaniel Palmer
This document discusses transitioning from an enterprise architecture to a service-oriented architecture (SOA). It defines what an SOA is and why organizations transition to one. It then describes how to identify the key components of an SOA by analyzing business processes, including identifying roles, objects, boundaries, potential services, and interfaces. This allows an organization to develop IT services based on relationships between business actors and realize those services through platform-independent interfaces.
Transitioning Enterprise Architectures to Service Oriented ArchitecturesNathaniel Palmer
This document discusses transitioning from an enterprise architecture to a service-oriented architecture (SOA). It defines what an SOA is and why organizations adopt them. It then describes how to identify the key components of an SOA by analyzing business processes, including identifying roles, objects, boundaries, potential services, and interfaces. The method provides a roadmap for transitioning an enterprise architecture to an SOA by developing business and IT services and defining platform-independent interfaces.
An artifact centric view-based approach to modeling inter-organizational busi...Dr. Sira Yongchareon
This document proposes an artifact-centric view-based framework for modeling inter-organizational business processes. The framework consists of an artifact-centric collaboration model and a conformance mechanism between public and private views. The artifact-centric collaboration model uses artifacts, roles, services, and business rules to model inter-organizational processes. Public and private views are defined, where the public view represents agreed lifecycles of shared artifacts and the private view represents an organization's local processes and shared artifacts. Lifecycle modifications in private views, such as refinement of shared artifacts and extension with local artifacts, are allowed as long as they conform to the public view based on lifecycle coverage. View conformance is checked using state transition systems
The document discusses the relationship between web services and primitive SOA. It defines web services as a technology framework that includes architectures, technologies, concepts and models. The key aspects of the web services framework are service descriptions using WSDL, SOAP messaging, and service registration/discovery using UDDI. Web services can take on different roles like service provider, requestor, or intermediary. The document also discusses different service models including business, utility, and controller services.
This document provides an overview of service-oriented architecture (SOA) and metrics to measure coupling in SOA. It first defines key concepts in SOA like loosely coupled services, service orientation, and service-oriented computing. It then discusses the three planes of SOA - service foundations, service composition, and service management and monitoring. Finally, it proposes using metrics to measure coupling between services to predict maintainability during the design phase of SOA systems.
This document provides an overview of service-oriented architecture (SOA) and metrics to measure coupling in SOA. It first defines key concepts in SOA like loosely coupled services, service orientation, and service-oriented computing. It then discusses the three planes of SOA - service foundations, service composition, and service management and monitoring. Finally, it proposes using metrics to measure coupling between services to predict maintainability during the design phase of SOA systems.
This document introduces a reference model for analyzing internet service provider (ISP) businesses and business relationships. The model defines basic roles that stakeholders can play, including consumer, service provider, connectivity provider, information provider, and end user. It also outlines two layers of services - the infrastructure layer involving network components, and the internet service layer. The reference model is intended to help describe ISP business models and relationships in detail beyond existing classifications.
A Formal Framework For Describing Information Providing Web ServicesSamantha Martinez
This document introduces a formal framework for describing information providing web services using description logic. It proposes extending service descriptions in OWL-S to include specifications of relationships between inputs and outputs in the form of conjunctive queries. Matching services is defined as query subsumption with respect to an ontology, which reduces the problem to standard reasoning tasks. The framework aims to overcome limitations of only considering input and output types for discovery of information providing services.
Transitioning Enterprise Architectures to Service Oriented ArchitecturesNathaniel Palmer
This document discusses transitioning from an enterprise architecture to a service-oriented architecture (SOA). It defines what an SOA is and why organizations transition to one. It then describes how to identify the key components of an SOA by analyzing business processes, including identifying roles, objects, boundaries, potential services, and interfaces. This allows an organization to develop IT services based on relationships between business actors and realize those services through platform-independent interfaces.
Transitioning Enterprise Architectures to Service Oriented ArchitecturesNathaniel Palmer
This document discusses transitioning from an enterprise architecture to a service-oriented architecture (SOA). It defines what an SOA is and why organizations adopt them. It then describes how to identify the key components of an SOA by analyzing business processes, including identifying roles, objects, boundaries, potential services, and interfaces. The method provides a roadmap for transitioning an enterprise architecture to an SOA by developing business and IT services and defining platform-independent interfaces.
An artifact centric view-based approach to modeling inter-organizational busi...Dr. Sira Yongchareon
This document proposes an artifact-centric view-based framework for modeling inter-organizational business processes. The framework consists of an artifact-centric collaboration model and a conformance mechanism between public and private views. The artifact-centric collaboration model uses artifacts, roles, services, and business rules to model inter-organizational processes. Public and private views are defined, where the public view represents agreed lifecycles of shared artifacts and the private view represents an organization's local processes and shared artifacts. Lifecycle modifications in private views, such as refinement of shared artifacts and extension with local artifacts, are allowed as long as they conform to the public view based on lifecycle coverage. View conformance is checked using state transition systems
The document discusses the relationship between web services and primitive SOA. It defines web services as a technology framework that includes architectures, technologies, concepts and models. The key aspects of the web services framework are service descriptions using WSDL, SOAP messaging, and service registration/discovery using UDDI. Web services can take on different roles like service provider, requestor, or intermediary. The document also discusses different service models including business, utility, and controller services.
This document provides an overview of service-oriented architecture (SOA) and metrics to measure coupling in SOA. It first defines key concepts in SOA like loosely coupled services, service orientation, and service-oriented computing. It then discusses the three planes of SOA - service foundations, service composition, and service management and monitoring. Finally, it proposes using metrics to measure coupling between services to predict maintainability during the design phase of SOA systems.
This document provides an overview of service-oriented architecture (SOA) and metrics to measure coupling in SOA. It first defines key concepts in SOA like loosely coupled services, service orientation, and service-oriented computing. It then discusses the three planes of SOA - service foundations, service composition, and service management and monitoring. Finally, it proposes using metrics to measure coupling between services to predict maintainability during the design phase of SOA systems.
EXTENDING WS-CDL TO SUPPORT REUSABILITYijwscjournal
WS-CDL is a very rich language that is specially designed to describe choreography of services. However it is very poor to adopt reusability mechanisms for making the choreography easy to design and confident to use. The main challenge is that there is no mechanism to make a reusable sub choreography which is able to expose an interface. Therefore, it is impossible to inject variables like exception variables from performing choreography into performed sub choreography.
In this paper, a complex element namely Template is added to WS-CDL making it more adequate to support reusability. A template is an abstract definition of an interaction pattern which is appeared frequently through a family of business services choreographies. The paper is also details how to use the template as black box in main choreography including assigning the variables to template interface parameters. We enhanced meta model of WS-CDL by adding template related elements, then produced a simple engine that loads the our enhanced meta model of WS-CDL, the file paths of main and template choreographies and automatically generate an output file includes a compiled choreography code expressed with standard WS-CDL.
EXTENDING WS-CDL TO SUPPORT REUSABILITY ijwscjournal
This document discusses extending the WS-CDL (Web Service Choreography Description Language) specification to better support reusability of choreographies. The authors propose adding a new "Template" element to WS-CDL that would allow abstract choreographies to be defined independently and then reused by mapping their interfaces to specific instances in other choreographies. Currently, WS-CDL's "Perform" activity does not support parameterizing or injecting variables into performed sub-choreographies, limiting its reusability. The Template element is intended to address this by allowing abstract choreographies defined in templates to expose parameterized interfaces that can be customized when reused.
EXTENDING WS-CDL TO SUPPORT REUSABILITY ijwscjournal
WS-CDL is a very rich language that is specially designed to describe choreography of services. However it is very poor to adopt reusability mechanisms for making the choreography easy to design and confident to use. The main challenge is that there is no mechanism to make a reusable sub choreography which is able to expose an interface. Therefore, it is impossible to inject variables like exception variables from performing choreography into performed sub choreography.
In this paper, a complex element namely Template is added to WS-CDL making it more adequate to support reusability. A template is an abstract definition of an interaction pattern which is appeared frequently through a family of business services choreographies. The paper is also details how to use the template as black box in main choreography including assigning the variables to template interface parameters. We enhanced meta model of WS-CDL by adding template related elements, then produced a simple engine that loads the our enhanced meta model of WS-CDL, the file paths of main and template choreographies and automatically generate an output file includes a compiled choreography code expressed with standard WS-CDL.
EXTENDING WS-CDL TO SUPPORT REUSABILITY ijwscjournal
WS-CDL is a very rich language that is specially designed to describe choreography of services.
However it is very poor to adopt reusability mechanisms for making the choreography easy to design and
confident to use. The main challenge is that there is no mechanism to make a reusable sub choreography
which is able to expose an interface. Therefore, it is impossible to inject variables like exception variables
from performing choreography into performed sub choreography.
In this paper, a complex element namely Template is added to WS-CDL making it more adequate to
support reusability. A template is an abstract definition of an interaction pattern which is appeared
frequently through a family of business services choreographies. The paper is also details how to use the
template as black box in main choreography including assigning the variables to template interface
parameters. We enhanced meta model of WS-CDL by adding template related elements, then produced a
simple engine that loads the our enhanced meta model of WS-CDL, the file paths of main and template
choreographies and automatically generate an output file includes a compiled choreography code
expressed with standard WS-CDL.
Performance Prediction of Service-Oriented Architecture - A surveyEditor IJCATR
Performance prediction and evaluation for SOA based applications assist software consumers to estimate their applications
based on service specifications created by service developers. Incorporating traditional performance models such as Stochastic Petri
Nets, Queuing Networks, and Simulation present drawbacks of SOA based applications due to special characteristics of SOA such as
lose coupling, self-contained and interoperability. Although, researchers have suggested many methods in this area during last decade,
none of them has obtained popular industrial use. Based on this, we have conducted a comprehensive survey on these methods to
estimate their applicability. This survey classified these approaches according to their performance metrics analyzed, performance
models used, and applicable project stage. Our survey helps SOA architects to select the appropriate approach based on target
performance metric and researchers to identify the SOA state-of-art performance prediction
This document proposes a framework for automatically bundling services to fulfill customer needs based on customer and supplier perspectives. A broker matches customer desires expressed through an ontology with supplier offerings also expressed in an ontology to dynamically establish business-to-customer relationships. The framework aims to bridge gaps in strategic service bundling and value co-creation within service networks by taking a business-oriented approach. The document outlines related work on automatic service composition and the problem of dynamically bundling multiple services to meet varying customer needs.
Dynamic Interface Adaptability in Service Oriented SoftwareMadjid KETFI
Dynamic Interface Adaptability in Service Oriented Software
M. Ketfi and N. Belkhatir
8th International Workshop on Component-Oriented Programming (WCOP'03),
Darmstadt, Germany, July 2003.
This document describes SWORD, a toolkit for composing web services. SWORD represents each service as a rule specifying its inputs and outputs. When a user wants to create a composite service, SWORD uses a rule engine to determine if it can be realized by composing existing services. If so, SWORD generates a composition plan specifying the sequence of services to invoke. SWORD has been implemented in a prototype and can compose information-providing services like those providing data about people, movies, etc. without requiring emerging standards like WSDL or SOAP.
This document compares the RPC and REST architectural styles for building web services. It finds that RPC-style services can face scalability issues as applications grow larger, due to tight coupling between clients and servers and complex interface definitions. REST addresses these issues by emphasizing a uniform interface based on HTTP methods, representing resources with URIs, and keeping client-server interactions stateless and loosely coupled through hypermedia links. The document analyzes how REST provides better scalability, low coupling, and security compared to RPC for web-scale applications.
A Novel Testing Model for SOA based ServicesAbhishek Kumar
This document proposes a novel testing model for generating and selecting test cases for service-oriented architecture (SOA) based applications. The model involves:
1) A service provider publishing a service and its Web Service Description Language (WSDL) file.
2) A service tester generating test cases by applying XML schema constraints to the WSDL and creating a test data set.
3) The tester using a tool like SoapUI to create test suites containing automatically generated test cases based on the service operations.
4) The tester selecting additional test cases to cover any "missed coverage items" revealed when testing new versions of a service against previous test results.
6 ijmecs v7-n1-5 a novel testing model for soa based servicesAbhishek Srivastava
SOA (Service-Oriented Architecture) filled the gap between software and commercial enterprise. SOA integrates multiple web services. We bear to secure the caliber of web services that gives guarantee about what network services work and their output results. There is close to work has to be performed for an automatic test case generation for SOA based services. But, full coverage of XML elements is missing. To the best of our knowledge this all works do not attempt to cover all possible elements of the XML schema presents in the WSDL file. There is also a need to apply different assertions on each service operation for generating the test cases. To overcome this problem we proposed a novel testing model for SOA based application. This new testing model helps us to get the automatic test cases of SOA based application. We build up our new test model with the aid of our proposed test case generation algorithm and test case selection algorithm. In the end, we generate the test suite execution results and find the coverage of XML schema elements present in the WSDL file.
The document describes a conceptual model for services in the PLASTIC project. It builds on previous work modeling mobile distributed computing platforms. The conceptual model represents components, services, and their relationships using a UML-like notation. It extends an existing SeCSE conceptual model by introducing new concepts like context, location, adaptation, and relationships between services and software components. The goal is to develop a common vocabulary that all project partners can use to facilitate communication and modeling tasks.
Project - UG - BTech IT - Cluster based Approach for Service Discovery using ...Yogesh Santhan
Abstract— Web services that are appropriate to a user specific request are usually not considered in discovering the exact service since they are present without explicit related semantic descriptions. In our approach, we deal with the issue of service discovery provided non-explicit service description semantics that match a particular service request. We propose a system that involves semantic-based service categorization which is performed at the UDDI with a key for achieving the service categorization at functional level based on an ontology skeleton. Also, clustering is used for literally systemizing the web services based on functionality which is achieved by using analytic algorithm. An efficient matching for the relevant services is achieved by the enhancing the service request semantically and involves expanding the additional functionality (obtained from ontology) that are related for the requested service. The pattern recognition algorithm is used to select appropriate service from the cluster formation of related (grouped) web services.
This is my UG Final Year Project - BTech Information Technology.
Service Oriented Software Engineering: Services as reusable components, Service Engineering, Software Development with Services. Service-oriented architectures, RESTful services
An Approach To Enable Replacement Of SOAP Services And REST Services In Light...Joaquin Hamad
This document presents an approach to enable the dynamic replacement of SOAP services with REST services and vice versa within lightweight processes at runtime. Semantic annotations using MicroWSMO are added to REST service descriptions to establish compatibility with SAWSDL descriptions of SOAP services. At runtime, if a SOAP service fails, the execution engine can select a semantically equivalent REST service using the annotations and adapt the request/response through a service adapter using mapping scripts. The approach was implemented in a prototype to execute lightweight processes containing alternative SOAP and REST services.
Research Inventy : International Journal of Engineering and Scienceinventy
Research Inventy : International Journal of Engineering and Science is published by the group of young academic and industrial researchers with 12 Issues per year. It is an online as well as print version open access journal that provides rapid publication (monthly) of articles in all areas of the subject such as: civil, mechanical, chemical, electronic and computer engineering as well as production and information technology. The Journal welcomes the submission of manuscripts that meet the general criteria of significance and scientific excellence. Papers will be published by rapid process within 20 days after acceptance and peer review process takes only 7 days. All articles published in Research Inventy will be peer-reviewed.
An Adaptive Service Choreography approach based on Ontology-Driven Policy Ref...dannyijwest
Business corporations usually require choreography of services to be dynamic and adaptable. One way
for answering this demand is to develop the services having dynamic behaviours. However, it is not
enough and their behaviours must be composed dynamically too.
The current model such as WS-CDL has a static structure to specify choreography and is not able to
describe the choreography of services in a dynamic fashion. From another view, there are various types
of changes that each needs to be handled diversely. This work is going to bring adaptability into service
choreography model in response to policy changes. Precisely, this target will be met when choreography
model has dynamic structure and also the policy changes can be automatically (semi-automatically)
refined and propagated into the elements of model. Our proposal is describing choreography model on
the basis policy-enabled UML state machine which the policy can be refined through a ontology based
process
The document discusses service engineering as a new paradigm for designing services rather than material products. It proposes representing services using three sub-models: a flow model depicting relationships between service agents, a view model representing how receiver state parameters are evaluated, and a scope model handling multiple view models. The authors developed a computer-aided design tool called Service Explorer to model services. Service engineering aims to design services defined as activities that change a receiver's state, with the goal of increasing consumer satisfaction over material consumption.
WEB SERVICES DISCOVERY AND RECOMMENDATION BASED ON INFORMATION EXTRACTION AND...ijwscjournal
This paper shows that the problem of web services representation is crucial and analyzes the various factors that influence on it. It presents the traditional representation of web services considering traditional textual descriptions based on the information contained in WSDL files. Unfortunately, textual web services descriptions are dirty and need significant cleaning to keep only useful information. To deal with this problem, we introduce rules based text tagging method, which allows filtering web service description to keep only significant information. A new representation based on such filtered data is then introduced. Many web services have empty descriptions. Also, we consider web services representations based on the
WSDL file structure (types, attributes, etc.). Alternatively, we introduce a new representation called symbolic reputation, which is computed from relationships between web services. The impact of the use of these representations on web service discovery and recommendation is studied and discussed in the
experimentation using real world web services.
AGENTS AND OWL-S BASED SEMANTIC WEB SERVICE DISCOVERY WITH USER PREFERENCE SU...IJwest
Service-oriented computing (SOC) is an interdisciplinary paradigm that revolutionizes the very fabric of
distributed software development applications that adopt service-oriented architectures (SOA) can evolve
during their lifespan and adapt to changing or unpredictable environments more easily. SOA is built
around the concept of Web Services. Although the Web services constitute a revolution in Word Wide Web,
they are always regarded as non-autonomous entities and can be exploited only after their discovery. With
the help of software agents, Web services are becoming more efficient and more dynamic.
The topic of this paper is the development of an agent based approach for Web services discovery and
selection in witch, OWL-S is used to describe Web services, QoS and service customer request. We develop
an efficient semantic service matching which takes into account concepts properties to match concepts in
Web service and service customer request descriptions. Our approach is based on an architecture
composed of four layers: Web service and Request description layer, Functional match layer, QoS
computing layer and Reputation computing layer.
The Writing Process Poster With InformatiAndrea Erdman
The document discusses the game Qwirkle. It explains that the game involves matching colored tiles to those already placed on the board. Players take turns adding tiles to create rows of matching colors or shapes. The goal is to be the first player to use all their tiles. It's a game that requires tactical thinking and strategy. The brightly colored tiles and simple rules make it entertaining and easy to learn for children and adults alike.
Writing Analytical Essays - Top 7 Rules For Writing AAndrea Erdman
The document provides instructions for creating an account on the HelpWriting.net website in order to request writing assistance. It outlines a 5-step process: 1) Create an account with a password and email. 2) Complete an order form with instructions, sources, and deadline. 3) Review bids from writers and choose one. 4) Review the completed paper and authorize payment. 5) Request revisions until satisfied. The purpose is to help students obtain original, high-quality content writing assistance while maintaining confidentiality and satisfaction.
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EXTENDING WS-CDL TO SUPPORT REUSABILITYijwscjournal
WS-CDL is a very rich language that is specially designed to describe choreography of services. However it is very poor to adopt reusability mechanisms for making the choreography easy to design and confident to use. The main challenge is that there is no mechanism to make a reusable sub choreography which is able to expose an interface. Therefore, it is impossible to inject variables like exception variables from performing choreography into performed sub choreography.
In this paper, a complex element namely Template is added to WS-CDL making it more adequate to support reusability. A template is an abstract definition of an interaction pattern which is appeared frequently through a family of business services choreographies. The paper is also details how to use the template as black box in main choreography including assigning the variables to template interface parameters. We enhanced meta model of WS-CDL by adding template related elements, then produced a simple engine that loads the our enhanced meta model of WS-CDL, the file paths of main and template choreographies and automatically generate an output file includes a compiled choreography code expressed with standard WS-CDL.
EXTENDING WS-CDL TO SUPPORT REUSABILITY ijwscjournal
This document discusses extending the WS-CDL (Web Service Choreography Description Language) specification to better support reusability of choreographies. The authors propose adding a new "Template" element to WS-CDL that would allow abstract choreographies to be defined independently and then reused by mapping their interfaces to specific instances in other choreographies. Currently, WS-CDL's "Perform" activity does not support parameterizing or injecting variables into performed sub-choreographies, limiting its reusability. The Template element is intended to address this by allowing abstract choreographies defined in templates to expose parameterized interfaces that can be customized when reused.
EXTENDING WS-CDL TO SUPPORT REUSABILITY ijwscjournal
WS-CDL is a very rich language that is specially designed to describe choreography of services. However it is very poor to adopt reusability mechanisms for making the choreography easy to design and confident to use. The main challenge is that there is no mechanism to make a reusable sub choreography which is able to expose an interface. Therefore, it is impossible to inject variables like exception variables from performing choreography into performed sub choreography.
In this paper, a complex element namely Template is added to WS-CDL making it more adequate to support reusability. A template is an abstract definition of an interaction pattern which is appeared frequently through a family of business services choreographies. The paper is also details how to use the template as black box in main choreography including assigning the variables to template interface parameters. We enhanced meta model of WS-CDL by adding template related elements, then produced a simple engine that loads the our enhanced meta model of WS-CDL, the file paths of main and template choreographies and automatically generate an output file includes a compiled choreography code expressed with standard WS-CDL.
EXTENDING WS-CDL TO SUPPORT REUSABILITY ijwscjournal
WS-CDL is a very rich language that is specially designed to describe choreography of services.
However it is very poor to adopt reusability mechanisms for making the choreography easy to design and
confident to use. The main challenge is that there is no mechanism to make a reusable sub choreography
which is able to expose an interface. Therefore, it is impossible to inject variables like exception variables
from performing choreography into performed sub choreography.
In this paper, a complex element namely Template is added to WS-CDL making it more adequate to
support reusability. A template is an abstract definition of an interaction pattern which is appeared
frequently through a family of business services choreographies. The paper is also details how to use the
template as black box in main choreography including assigning the variables to template interface
parameters. We enhanced meta model of WS-CDL by adding template related elements, then produced a
simple engine that loads the our enhanced meta model of WS-CDL, the file paths of main and template
choreographies and automatically generate an output file includes a compiled choreography code
expressed with standard WS-CDL.
Performance Prediction of Service-Oriented Architecture - A surveyEditor IJCATR
Performance prediction and evaluation for SOA based applications assist software consumers to estimate their applications
based on service specifications created by service developers. Incorporating traditional performance models such as Stochastic Petri
Nets, Queuing Networks, and Simulation present drawbacks of SOA based applications due to special characteristics of SOA such as
lose coupling, self-contained and interoperability. Although, researchers have suggested many methods in this area during last decade,
none of them has obtained popular industrial use. Based on this, we have conducted a comprehensive survey on these methods to
estimate their applicability. This survey classified these approaches according to their performance metrics analyzed, performance
models used, and applicable project stage. Our survey helps SOA architects to select the appropriate approach based on target
performance metric and researchers to identify the SOA state-of-art performance prediction
This document proposes a framework for automatically bundling services to fulfill customer needs based on customer and supplier perspectives. A broker matches customer desires expressed through an ontology with supplier offerings also expressed in an ontology to dynamically establish business-to-customer relationships. The framework aims to bridge gaps in strategic service bundling and value co-creation within service networks by taking a business-oriented approach. The document outlines related work on automatic service composition and the problem of dynamically bundling multiple services to meet varying customer needs.
Dynamic Interface Adaptability in Service Oriented SoftwareMadjid KETFI
Dynamic Interface Adaptability in Service Oriented Software
M. Ketfi and N. Belkhatir
8th International Workshop on Component-Oriented Programming (WCOP'03),
Darmstadt, Germany, July 2003.
This document describes SWORD, a toolkit for composing web services. SWORD represents each service as a rule specifying its inputs and outputs. When a user wants to create a composite service, SWORD uses a rule engine to determine if it can be realized by composing existing services. If so, SWORD generates a composition plan specifying the sequence of services to invoke. SWORD has been implemented in a prototype and can compose information-providing services like those providing data about people, movies, etc. without requiring emerging standards like WSDL or SOAP.
This document compares the RPC and REST architectural styles for building web services. It finds that RPC-style services can face scalability issues as applications grow larger, due to tight coupling between clients and servers and complex interface definitions. REST addresses these issues by emphasizing a uniform interface based on HTTP methods, representing resources with URIs, and keeping client-server interactions stateless and loosely coupled through hypermedia links. The document analyzes how REST provides better scalability, low coupling, and security compared to RPC for web-scale applications.
A Novel Testing Model for SOA based ServicesAbhishek Kumar
This document proposes a novel testing model for generating and selecting test cases for service-oriented architecture (SOA) based applications. The model involves:
1) A service provider publishing a service and its Web Service Description Language (WSDL) file.
2) A service tester generating test cases by applying XML schema constraints to the WSDL and creating a test data set.
3) The tester using a tool like SoapUI to create test suites containing automatically generated test cases based on the service operations.
4) The tester selecting additional test cases to cover any "missed coverage items" revealed when testing new versions of a service against previous test results.
6 ijmecs v7-n1-5 a novel testing model for soa based servicesAbhishek Srivastava
SOA (Service-Oriented Architecture) filled the gap between software and commercial enterprise. SOA integrates multiple web services. We bear to secure the caliber of web services that gives guarantee about what network services work and their output results. There is close to work has to be performed for an automatic test case generation for SOA based services. But, full coverage of XML elements is missing. To the best of our knowledge this all works do not attempt to cover all possible elements of the XML schema presents in the WSDL file. There is also a need to apply different assertions on each service operation for generating the test cases. To overcome this problem we proposed a novel testing model for SOA based application. This new testing model helps us to get the automatic test cases of SOA based application. We build up our new test model with the aid of our proposed test case generation algorithm and test case selection algorithm. In the end, we generate the test suite execution results and find the coverage of XML schema elements present in the WSDL file.
The document describes a conceptual model for services in the PLASTIC project. It builds on previous work modeling mobile distributed computing platforms. The conceptual model represents components, services, and their relationships using a UML-like notation. It extends an existing SeCSE conceptual model by introducing new concepts like context, location, adaptation, and relationships between services and software components. The goal is to develop a common vocabulary that all project partners can use to facilitate communication and modeling tasks.
Project - UG - BTech IT - Cluster based Approach for Service Discovery using ...Yogesh Santhan
Abstract— Web services that are appropriate to a user specific request are usually not considered in discovering the exact service since they are present without explicit related semantic descriptions. In our approach, we deal with the issue of service discovery provided non-explicit service description semantics that match a particular service request. We propose a system that involves semantic-based service categorization which is performed at the UDDI with a key for achieving the service categorization at functional level based on an ontology skeleton. Also, clustering is used for literally systemizing the web services based on functionality which is achieved by using analytic algorithm. An efficient matching for the relevant services is achieved by the enhancing the service request semantically and involves expanding the additional functionality (obtained from ontology) that are related for the requested service. The pattern recognition algorithm is used to select appropriate service from the cluster formation of related (grouped) web services.
This is my UG Final Year Project - BTech Information Technology.
Service Oriented Software Engineering: Services as reusable components, Service Engineering, Software Development with Services. Service-oriented architectures, RESTful services
An Approach To Enable Replacement Of SOAP Services And REST Services In Light...Joaquin Hamad
This document presents an approach to enable the dynamic replacement of SOAP services with REST services and vice versa within lightweight processes at runtime. Semantic annotations using MicroWSMO are added to REST service descriptions to establish compatibility with SAWSDL descriptions of SOAP services. At runtime, if a SOAP service fails, the execution engine can select a semantically equivalent REST service using the annotations and adapt the request/response through a service adapter using mapping scripts. The approach was implemented in a prototype to execute lightweight processes containing alternative SOAP and REST services.
Research Inventy : International Journal of Engineering and Scienceinventy
Research Inventy : International Journal of Engineering and Science is published by the group of young academic and industrial researchers with 12 Issues per year. It is an online as well as print version open access journal that provides rapid publication (monthly) of articles in all areas of the subject such as: civil, mechanical, chemical, electronic and computer engineering as well as production and information technology. The Journal welcomes the submission of manuscripts that meet the general criteria of significance and scientific excellence. Papers will be published by rapid process within 20 days after acceptance and peer review process takes only 7 days. All articles published in Research Inventy will be peer-reviewed.
An Adaptive Service Choreography approach based on Ontology-Driven Policy Ref...dannyijwest
Business corporations usually require choreography of services to be dynamic and adaptable. One way
for answering this demand is to develop the services having dynamic behaviours. However, it is not
enough and their behaviours must be composed dynamically too.
The current model such as WS-CDL has a static structure to specify choreography and is not able to
describe the choreography of services in a dynamic fashion. From another view, there are various types
of changes that each needs to be handled diversely. This work is going to bring adaptability into service
choreography model in response to policy changes. Precisely, this target will be met when choreography
model has dynamic structure and also the policy changes can be automatically (semi-automatically)
refined and propagated into the elements of model. Our proposal is describing choreography model on
the basis policy-enabled UML state machine which the policy can be refined through a ontology based
process
The document discusses service engineering as a new paradigm for designing services rather than material products. It proposes representing services using three sub-models: a flow model depicting relationships between service agents, a view model representing how receiver state parameters are evaluated, and a scope model handling multiple view models. The authors developed a computer-aided design tool called Service Explorer to model services. Service engineering aims to design services defined as activities that change a receiver's state, with the goal of increasing consumer satisfaction over material consumption.
WEB SERVICES DISCOVERY AND RECOMMENDATION BASED ON INFORMATION EXTRACTION AND...ijwscjournal
This paper shows that the problem of web services representation is crucial and analyzes the various factors that influence on it. It presents the traditional representation of web services considering traditional textual descriptions based on the information contained in WSDL files. Unfortunately, textual web services descriptions are dirty and need significant cleaning to keep only useful information. To deal with this problem, we introduce rules based text tagging method, which allows filtering web service description to keep only significant information. A new representation based on such filtered data is then introduced. Many web services have empty descriptions. Also, we consider web services representations based on the
WSDL file structure (types, attributes, etc.). Alternatively, we introduce a new representation called symbolic reputation, which is computed from relationships between web services. The impact of the use of these representations on web service discovery and recommendation is studied and discussed in the
experimentation using real world web services.
AGENTS AND OWL-S BASED SEMANTIC WEB SERVICE DISCOVERY WITH USER PREFERENCE SU...IJwest
Service-oriented computing (SOC) is an interdisciplinary paradigm that revolutionizes the very fabric of
distributed software development applications that adopt service-oriented architectures (SOA) can evolve
during their lifespan and adapt to changing or unpredictable environments more easily. SOA is built
around the concept of Web Services. Although the Web services constitute a revolution in Word Wide Web,
they are always regarded as non-autonomous entities and can be exploited only after their discovery. With
the help of software agents, Web services are becoming more efficient and more dynamic.
The topic of this paper is the development of an agent based approach for Web services discovery and
selection in witch, OWL-S is used to describe Web services, QoS and service customer request. We develop
an efficient semantic service matching which takes into account concepts properties to match concepts in
Web service and service customer request descriptions. Our approach is based on an architecture
composed of four layers: Web service and Request description layer, Functional match layer, QoS
computing layer and Reputation computing layer.
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An Operating Guideline Approach To The SOA
1. An Operating Guideline Approach to the SOA
Peter Massuthe, Wolfgang Reisig, and Karsten Schmidt
Humboldt-Universität zu Berlin
Institut für Informatik
Unter den Linden 6
D-10099 Berlin
{massuthe, reisig, kschmidt}@informatik.hu-berlin.de
Abstract Interorganizational cooperation is more and more organized
by the paradigm of services. The service-oriented architecture (SOA)
provides a general framework for service interaction. It describes three
roles, service provider, service requester, and service broker, together with
the three operations publish, find, and bind.
We provide a formal method based on Petri nets to model services and
their cooperation. We characterize well-behaving pairs of requester’s and
provider’s services and suggest operating guidelines as a convenient and
intuitive artifact to realize publish. Then, the find operation reduces to
a matching problem between the requester’s service and the operating
guideline. Binding of a requester’s and a provider’s service is therefore
guaranteed to result in a well-behaving cooperating service.
Keywords: Services, SOA, Petri nets, Operating guidelines
1 Introduction
A service can be viewed as an artifact consisting of an identifier (id),
an interface (e.g. specified in WSDL [4]), and internal control (e.g. a
workflow). A service can typically not be executed in isolation – services
are designed for being invoked by other services, or for invoking other
services themselves.
The service-oriented architecture (SOA) [6] is a promising and increas-
ingly influential software architecture providing a general framework for
service interaction. It describes three roles of service owners: service
provider, service requester, and service broker. A service provider pub-
lishes information about his service to a repository. The service broker
manages the repository and allows a service requester to find an ade-
quate service provider. Then, the service of the provider and the service
of the requester may bind and start interaction.
Such cooperating services may cause non-trivial communication. Thus,
for a given requester’s service R, the broker’s task is to select from the
repository only those provided services P that are guaranteed to inter-
act properly with R: The services R and P must not deadlock in their
interaction or send unanticipated messages, for instance. Thereby, com-
patibility of the interfaces of R and P is not sufficient to guarantee proper
interaction.
2. The broker must decide this task by help of the published information
about P. In a currently quite popular approach, the published informa-
tion is a so-called public view [7, 8], i.e. an abstract version P′
of P with
a communication behavior equivalent to P.
In this paper, we suggest an alternative: The provider does not pub-
lish information about his service P, but information about all proper
services R of potential requesters, instead. This information is called op-
erating guideline, OGP , for P. In our approach, the operating guideline
for P describes, in a compact way, the set of all services R that interact
properly with P.
We claim that matching a requester’s service R with an operating guide-
line OGP is less complex than matching R with the public view P′
of P.
If R matches OGP , we can guarantee that R and P interact properly.
In this paper, we show that services have canonical operating guidelines
and it is even possible to compute them. Furthermore, the operating
guideline for P typically hides a lot of details about the internal control
structure of P, that the owner of P might want to keep secret.
In our approach, we consider workflow services, an important subclass of
services with operational behavior described as a workflow. We suggest
a formal model based on Petri nets, called open workflow nets (oWFNs),
to represent workflow services. An oWFN is basically a liberal version
of a van der Aalst workflow net [1], enriched with communication places
for asynchronous communication. In this paper, we present our approach
only for acyclic nets.
With oWFNs, we can model services of providers, as well as services
of requesters. We can furthermore compose two oWFNs and obtain a
model for both services in interaction. The composition of two oWFNs
results in an oWFN, again. Composition can therefore be seen as the re-
sult of the SOA bind operation. In our approach, we abstract from every
other aspect of bind as resolving URI, routing, and establishment of com-
munication channels. We assume this to be managed by an underlying
middleware.
We can formulate proper interaction between services as a property of the
corresponding composed oWFN, called weak termination. Each partner
oWFN R that weakly terminates with P, is called a strategy for P.
Considering the behaviors of all strategies for P, it turns out that there is
a unique most permissive behavior, i.e. every strategy for P has a behav-
ior that can be obtained through restricting the most permissive one. The
most permissive behavior itself then provides the basis for the operating
guidelines: We can provide annotations to the most permissive behav-
ior that characterize the allowed restrictions to obtain the behaviors of
all strategies. Operating guidelines (i.e. the annotated most permissive
behavior) is then provided to the service broker, thus realizing publish.
This way, matching a requester’s service R with a published operating
guideline OGP reduces to check whether or not the behavior of R is a
subtree of OGP that satisfies the annotations.
The rest of the paper is structured as follows. In Sec. 2, we consider
the essential aspects of services, and characterize the class of workflow
services. Section 3 introduces the schema of the service-oriented architec-
2
3. ture with the three roles for service owners and the standard operations
publish, find, and bind.
Our model of workflow services, open workflow nets, is described in
Sec. 4. This includes operational behavior, means of communication,
composition, and desired properties of cooperating oWFNs.
Section 5 then introduces our main construct, operating guidelines. Op-
erating guidelines turn out to be a convenient and elegant instrument
to realize publish. Finally, in Sec. 6, we apply operating guidelines to
decide the existence of a fitting provider’s service for a given service of
a requester, thus realizing find.
2 Services
Nowadays, cooperation across borders of enterprises is increasingly im-
portant. Functionalities are sourced out or so-called virtual enterprises
for specific tasks are formed.
In this setting, services play an important role. A service basically en-
capsulates self-contained functions that interact through a well-defined
interface. Recent publications apply the term service in different con-
texts with varying denotations. In this paper, we assume the essentials
of a service to include an identifier (id), its interface, and its operational
behavior. Thereby, the interface of a service describes means to commu-
nicate with its environment during execution. The operational behavior
of a service is basically a set of operations to be executed according to
some internal control structure.
The well-known class of web services is an implementation of services
with an interface specified in WSDL and an id given by an URI.
In this paper, we concentrate on services with operational behavior de-
scribed as a workflow, i.e. an implemented business process. Such services
will be denoted as workflow services. Workflow services have become
particularly important since the establishment of BPEL [5] as a widely
excepted language to describe web services. BPEL provides control struc-
tures that typically occur in workflows.
T C
T C
B
Figure 1. A vending machine that sells, for 1 Euro, either a cup of tea (button T), or
coffee (button C).
3
4. Examples of workflow services include online banking systems (which
are web services as well) and car rentals (which are not necessarily web
services). A Java program is certainly no workflow services (but may be
a web service).
As a running example, we consider the workflow service of a beverage
vending machine, as outlined in Fig. 1. The service provided by this
machine expects a coin (C
–
– ) to be inserted and one of the buttons T and
C being pressed. The service then reacts with delivering a beverage, i.e. a
cup of tea (in case T has been pressed) or a cup of coffee (in case C has
been pressed).
3 The Service-Oriented Architecture (SOA)
Generally, services are not executed in isolation, but in cooperation with
other services (e.g. by exchanging messages). For that purpose, service
interaction is organized by the SOA. The SOA assumes that services are
run by agents, with agents entering (and leaving) the scene dynamically.
The services of these agents are intended to communicate with each
other. This requires an agent to establish new communication facilities
with other agents (in particular in case the agent entered the scene only
recently).
In the SOA, such communication facilities are established by help of a
service broker. Each agent is assumed to approach the broker in one of
two roles: As a service provider, i.e. in the role of delivering some service,
or as a service requester, i.e. in the role of using an already provided
service.
Service
Broker
Service
Provider
Service
Requester
publish
find
bind
Service
Broker
Service
Provider
Service
Requester
publish
find
bind
Figure 2. The service-oriented architecture (SOA).
Therefore, the provider, requester, and broker agents execute the follow-
ing three operations:
A service provider sends information to the service broker, indicating
how a service requester may use his service. The service broker then
stores this information together with the provider’s id in a repository.
This operation is called publish.
The SOA operation find means that a requester sends a description of
his requested service to the service broker. The broker selects a fitting
one and returns the corresponding provider’s id.
4
5. Finally, the requester establishes a connection with the provider, and
both agents jointly run their respective services, described by the SOA
bind operation.
The three roles of agents, together with the three standard operations
are outlined in the SOA triangle, depicted in Fig. 2.
The above operations come up with a number of problems:
Publish: The provider has good reasons to keep published information
about his service at a minimum. He usually wants (1) to cover business
secrets, (2) to retain maximal flexibility to update his service without
giving notice to providers and brokers, and (3) to shield requesters from
details they do not need to know.
In this paper, we suggest operating guidelines (to be introduced in Sec. 5)
as information to be published about a provider’s service. Operating
guidelines serve well as an abstraction from internal details and support
flexibility.
Find: Given a service of a requester and the operating guideline for a
provider, a broker has to decide whether or not the requester’s and the
provider’s services would interact properly.
In this paper, we describe how a broker may decide this question by
matching the requester’s service with operating guidelines.
Bind: Through our operating guidelines approach to publish and find, a
requester’s service is guaranteed to successfully cooperate with the ser-
vice of a broker’s recommended provider (e.g. they do not deadlock). We
completely abstract from implementation details concerning the estab-
lishing of communication channels between provider and requester (such
as resolving an URI, routing, etc.). We just suggest means to describe
the behavior of single services as well as their cooperation.
Summing up, the SOA schema requires a proper representation of ser-
vices and their cooperation, together with adequate descriptions of the
operations publish and find.
The rest of this paper suggests corresponding features for the subclass
of services, called workflow services.
4 Models of Workflow Services
A solution to the problems described above requires a proper model of
workflow services. A model of workflows was already suggested by van der
Aalst [1]. He defines a special class of Petri nets, workflow nets (WFNs),
that adequately describe the control structure of workflows. Since work-
flow services are supposed to communicate with other workflow services,
additional constructs for modeling communication channels are needed.
We suggest open workflow nets (oWFNs) for this endeavour, essentially a
liberal version of van der Aalst workflow nets, enriched with communica-
tion places. Each communication place of an oWFN models a channel to
send (receive) messages to (from) another oWFN. Thereby, we abstract
from data and just model the occurrence of messages as undistinguish-
able tokens.
We assume the usual representation of Petri nets N = (P, T, F), with P
and T the set of places and transitions (graphically, circles and squares),
5
6. and a set F ⊆ (P ×T)∪(T ×P) of arcs, graphically: arrows. A marking is
a mapping m : P → N (graphically, m(p) black tokens on p). As usual, a
transition t is enabled at a marking m if for each place p with (p, t) ∈ F,
m(p) ≥ 1.
If enabled at m, occurrence of t then yields the marking m′
with m′
(p) =
m(p) − 1 if (p, t) ∈ F and (t, p) /
∈ F, m′
(p) = m(p) + 1 if (t, p) ∈ F and
(p, t) /
∈ F, and m′
(p) = m(p) otherwise.
An open workflow net is a Petri net N = (P, T, F) together with
1. two sets in, out ⊆ P, such that for all transitions t ∈ T holds: if
p ∈ in (p ∈ out) then (t, p) /
∈ F ((p, t) /
∈ F),
2. a distinguished marking m0, called the initial marking, and
3. a set Ω of distinguished markings, called the final markings of N.
The places in in (out) are called input (output) places. The set in ∪ out
is called the interface of N. The inner of N can be obtained from N by
removing all interface places, together with their adjacent arcs.
Graphically, N is surrounded by a dashed box, with the interface places
on its boundary. As a convention, we label a transition t connected to
an input (output) place x with ?x (!x).
✂✁
?T ?C
!B !B
p0
p1
p2 p4
p3 p5
✁
C
T
B
V
Figure 3. An oWFN V for the vending machine of Fig. 1.
As an example, Fig. 3 shows an oWFN, V , modeling the vending machine
of Fig. 1. The places C
–
– , T, C, and B denote an inserted coin, the button T
or C pressed, and a beverage delivered, respectively. There are two final
markings of V : a single token on p3 or a single token on p5.
We are now ready to define the composition of oWFNs, reflecting the
interplay between workflow services.
Conceiving the vending machine of Fig. 1 as a provider’s service, a cor-
responding customer would insert a coin, press one of the buttons and
later on receive the beverage.
6
7. ✁
!C
?B
q0
q1
q2
q3
✁
C
B
C
Figure 4. A customer’s oWFN, C, for the vending machine V that wants coffee.
Fig. 4 models a customer, C, of the vending machine, pressing the coffee
button. This model is again an oWFN. Further examples can be found
in [12].
The interaction of two oWFNs is reflected by their composition. Two
oWFNs M and N may have some elements in common. Nevertheless,
without loss of generality we may assume that M and N only share
input- and output elements:
(PM ∪ TM ) ∩ (PN ∪ TN ) ⊆ (inM ∪ outM ) ∩ (inN ∪ outN ) (1)
This property in fact holds for the two oWFNs V and C: They share
nothing but the interface places C
–
– , C, and B.
Assuming (1), composition of two oWFNs M and N is an oWFN again,
denoted M ⊕N, and constructed essentially as the component-wise union
of M and N. So let M ⊕ N be defined by PM⊕N =def PM ∪ PN ,
TM⊕N =def TM ∪ TN , FM⊕N =def FM ∪ FN .
Each place in outM ∩ inN (or in inM ∩ outN ) turns into an inner place
of M ⊕ N. With I =def (outM ∩ inN ) ∪ (inN ∩ outM ), let inM⊕N =def
(inM ∪ inN ) I and outM⊕N =def (outM ∪ outN ) I.
For markings mM and mN of M and N, respectively, let mM ⊕ mN be
a marking of M ⊕ N, defined for p ∈ PM⊕N by (mM ⊕ mN )(p) =def
mM (p) + mN (p), where mM (p) = 0 if p /
∈ PM and mN (p) = 0 if p /
∈ PN .
Then, let m(M⊕N)0
=def mM0 ⊕ mN0 and mM⊕N ∈ ΩM⊕N iff mM⊕N =
mM ⊕ mN for some mM ∈ ΩM and some mN ∈ ΩN .
As an example, Fig. 5 shows the oWFN C ⊕ V . This oWFN has two
terminal markings, m1 and m2, with m1(q3) = m1(p3) = 1, m2(q3) =
m2(p5) = 1, and no tokens on all other places. Notice that inC⊕V = {T}
and outC⊕V = ∅.
Fig. 6 shows another oWFN, E. Assume one terminal marking for E, with
a token on r2 and no token elsewhere. E models an erroneous customer
service of the vending machine, as the customer apparently
”
forgets“ to
7
8. ✁
!C
?B
q0
q1
q2
q3
✁
✂
✁
?T ?C
!B !B
p0
p1
p2 p4
p3 p5
C
T
B
C ⊕ V
Figure 5. The composed oWFN C ⊕ V of Fig. 3 and Fig. 4.
press one of the machine buttons, and both services deadlock. Summing
up, the oWFN C is an
”
adequate“ partner for V , whereas E is not.
✁
?B
r0
r1
r2
✁
B
E
Figure 6. An erroneous partner oWFN E for V .
In technical terms, a marking m of an oWFN is a deadlock if m enables
no transition at all. It is easy to see that in the composed oWFN C ⊕ V ,
the only reachable deadlock is a final marking. In contrast, in the oWFN
E ⊕ V (not shown here), the marking m with m(r1) = m(p1) = 1 and
m(p) = 0 for all other places p ∈ PE⊕V is a reachable deadlock which is
no final marking.
An oWFN in which all deadlocks are final markings is called weakly
terminating. Given an oWFN N, we call an oWFN M a strategy for N
iff the oWFN N ⊕M is weakly terminating. For example, C is a strategy
for V , whereas E is not.
8
9. 5 Publish
As mentioned earlier in this paper, information published by a ser-
vice provider on his service P must enable the service broker to decide
whether or not a requester’s service R is a strategy for P (otherwise,
binding P with R may result in unexpected behavior). Whether or not
R is a strategy for P depends on the internal control structure of P.
Hence, it has been proposed to publish a public view P′
of P to the
service broker. It is supposed that, by knowing P′
, the broker can decide
whether or not R will interact properly with P.
We propose a different approach: Instead of a description of the provided
service P, we suggest to publish a description of the set of all strategies
(i.e. all properly interacting oWFNs) R for P, directly. In fact, we provide
a description of the behaviors of all strategies R. We call this description
operating guideline for P and write OGP .
In the remainder of this section, we give brief answers to the following
questions for a given oWFN P: (1) What is a behavior? (2) How does
the operating guideline OGP look like? (3) How can it be computed? (4)
Why does it cover all strategies for P?
r1
r2
r3
r4
✁
!C
?B
C
B p1
p2
p3
p5
p4
p6
✂✁
?C
!B
!B
?T
V
B
Figure 7. The behaviors BC and BV of the oWFNs C and V , resprespectively.
The behavior of a usual Petri net can be represented as a reachability
tree. This notion is, however, not adequate for oWFNs, since the marking
on the interface places can be changed by the environment. Thus, we
describe the behavior of an oWFN N by a slightly different structure.
We first compute the reachability tree of the inner of N (see Sec. 4).
Due to our restriction to acyclic oWFNs, the reachability tree is finite.
Then, each edge in the reachability tree is annotated with !x (?x) if the
corresponding transition in N is connected to an output (input) place x,
and with τ, otherwise. This answers question (1) stated above.
Figure 7 shows the behaviors BC and BV of the oWFNs C and V of
Fig. 4 and Fig. 3, respectively.
In the following, to answer question (2), we first present the two in-
gredients to operating guidelines for P: the most permissive behavior
of strategies for P and annotations how to derive the behaviors of all
9
10. strategies. Then, we sketch the algorithms to compute both ingredients,
answering questions (3) and (4).
These answers rely on results proven in [13, 11] concerning behaviors of
strategies. For the purpose of simplicity only, we constrain the consider-
ations in this paper to deterministic behaviors of strategies. A behavior
is deterministic iff every edge of the behavior has exactly one expression
!x or ?y attached (i.e. there is no silent move τ), and there is no node in
the behavior where two leaving edges have the same expression attached.
All behaviors shown in this paper are deterministic.
Let the set of the (deterministic) behaviors BR of all strategies R for
P be denoted by BP . We can establish a (partial order) relation, more
permissive, to behaviors of BP : A behavior B is more permissive than a
behavior B′
if B′
is isomorphic to a subtree of B containing the root.
s1
s2
s3
s5
s4
s6
✁
!C
?B
?B
!T
D
B
Figure 8. A more permissive behavior BD of a customer, who decides.
As an example, Fig. 8 shows the behavior BD of some customer D of
the vending machine, who first inserts a coin and then decides for coffee
or tea. BD is more permissive than BC , whereas neither BC is more
permissive than BV , nor BV is more permissive than BC .
In [13, 11], we show that, for every oWFN P, the set BP has a unique most
permissive element, the most permissive behavior, B∗
. Consequently, we
call every oWFN R with the most permissive behavior as its behavior
(i.e. BR = B∗
), a most permissive strategy for P. While the most per-
missive behavior is unique, most permissive strategies are not. There are
typically many structurally different Petri nets that share the same be-
havior. In particular, our presented concept of behavior does not distin-
guish arbitrary interleaved transitions from truly concurrent transitions.
The main property of the most permissive behavior B∗
is that it com-
prises all behaviors of strategies for P: Every behavior BR of a strategy
R for P is (isomorphic to) a subtree of B∗
. Thus, the most permissive
behavior serves as the first ingredient to the operating guideline for P.
Unfortunately, the converse is not true. Not every subtree of the most
permissive behavior is itself a behavior of a strategy. Thus, the remaining
problem is to distinguish those subtrees of the most permissive behavior
which are behaviors of strategies from those subtrees which are no be-
10
11. haviors of strategies. Our solution to this task is again based on a result
proven in [13, 11]:
Given a provided oWFN P and a behavior BR of some requester’s service
R, we can decide for each node qR of BR whether or not it can cause
a deadlock in R ⊕ P. This is basically determined by the edges that
leave qR: Whether or not R is a strategy for P depends on present or
missing edges in BR. Thus, we code the constraints for edges leaving qR
as a boolean formula over edge labels and annotate it to qR. BR satisfies
these constraints if and only if R is a strategy.
Since the most permissive behavior B∗
is a behavior of some strategy, we
can annotate B∗
, too. A subtree of B∗
is thus a behavior of a strategy
if and only if it still satisfies the attached annotations. The annotations
to the nodes of B∗
constitute the second ingredient and complete the
operating guideline for P. This answers question (2) stated above.
As an example, the operating guideline OGV for the vending machine V
(of Fig. 3) is depicted in Fig. 9. The possibility to first press a button and
then inserting a coin comes from the proposed asynchronous communi-
cation. The annotations to nodes which have only one outgoing edge are
skipped.
1
3
5
9
8
12
✁
!C
?B
?B
!T
!T
✁
✁
!C
2 4
7
11
?B
6
10
?B
✂✄✆☎✞✝✟✂✠✡☎☛✝✟✂☞
!T OR !C
OGV
Figure 9. The operating guideline OGV for the vending machine V .
The rest of this Section is devoted to questions (3) and (4). We sketch
the algorithms to construct the most permissive behavior and to anno-
tate the nodes and argue why operating guidelines cover all behaviors of
strategies.
The most permissive behavior for an oWFN P can be constructed as
follows. Consider, as a starting point, the complete, deterministic behav-
ior BC
of some partner oWFN R where for every node and every input
(output) place x of P, there is an outgoing edge labeled !x (?x). We can
limit the depth of BC
by the depth of the behavior BP of P. Obviously,
every behavior BR of a strategy for P is a subtree of BC
.
Next, we compute a transition system from the composition of BC
with
BP . A state of the composed system consists of a state q of BC
, a state
p of BP , and a multiset (bag) M of pending messages.
11
12. Then, we remove, in an iterative process, those nodes q from BC
for
which there is a bad node [q, p, M] in the composed system, i.e. a node
which represents an undesired situation like a deadlock that is no final
marking, or unconsumable pending messages. For the removed states, we
can show that they cannot be part of the behavior of any strategy for P.
Thus, every behavior of strategies remains a subtree of BC
obtained after
each iteration. Finally, we can show that as soon as the iterative process
of removing states terminates, the remaining behavior (if any) is in fact
the behavior of a strategy - and even the most permissive behavior B∗
.
This problem is, in fact, a problem known in the literature as controller
synthesis [3, 10].
To annotate the nodes of B∗
, consider again the transition system com-
posed from B∗
and BP . In that tree there is no bad node (since it would
have been removed by the above algorithm). Removing further nodes
(with adjacent edges) in B∗
results in removing multiple nodes (and
edges) in the composed system. This may cause deadlocks or pending
messages are not consumed anymore. Hence, other nodes in the com-
posed system may become bad nodes. If this happens, the considered
node must not be removed. This can easily be expressed by a boolean
formula over the labels of outgoing edges. These formulae are attached to
each node in B∗
and express exactly, which subtrees of B∗
are strategies
itself. This completes the answers to the questions (3) and (4).
To summarize, the operating guideline for an oWFN P can be con-
structed automatically and only by knowing P. As we assume the con-
struction is done by the owner of P, this is acceptable. Furthermore,
the annotations just reflect needed actions of the environment such that
the composed system does not deadlock. The annotations do not reflect
why a deadlock can be reached, nor how the deadlock looks like. When
published, operating guidelines therefore hide most details about the in-
ternal control structure of the provided service, that the service provider
might want to keep secret.
The presented algorithm to construct the most permissive behavior is
just a theoretic algorithm that comes from a constructive proof of the
existence of B∗
in the set BP . Its starting point, the complete, determin-
istic behavior BC
may become rather large for realistic services. Even
larger is the composed system of BC
and BP , needed to characterize the
nodes of BC
.
In current research, we develop efficient representations of operating
guidelines as binary decision diagrams (BDDs) [2], as well as the con-
struction of operating guidelines directly as a BDD. BDDs are a data
structure that proved to be capable of representing large transition sys-
tems in the area of model checking. Preliminary results in the application
of BDDs representing operating guidelines are promising.
6 Find
Matching a requester’s service with an operating guideline OGP is rather
simple. Given an oWFN R of the requester, we first compute its behavior,
BR. This is simple and well-understood state space generation. Then, we
12
13. need to check whether BR (a) is isomorphic to a subtree of OGP and (b)
satisfies the annotations. Thereby, a literal ?x (!x) at some node of OGP
is evaluated to true if there is an outgoing edge from the corresponding
node in BR labeled ?x (!x) and evaluated to false, otherwise.
It is easy to see that BC and BD match OGV , whereas the behavior BE
of the erroneous partner oWFN E would not match OGV .
Checking the subtree property can be solved by a coordinated depth-first
search through both behaviors. Its run-time is linear in the size of R’s
behavior. Checking the annotations amounts to computing a value of a
boolean formula and can thus be implemented efficiently. Thus, the find
procedure based on operating guidelines turns out to be very efficient.
In contrast, a find based on public views is a more complex operation.
Given a requesting service R and a public view P′
of a provided service P,
a service broker must decide whether R is a strategy for P. Currently, the
only available approach to this problem is to build the system composed
of P′
and R and to check its state space for deadlocks and end states
with unconsumed messages. The size of the state space is typically in the
same order of magnitude as the number of states of P′
times the number
of states of R. Checking the state space for deadlocks is linear in that
number and thus more complex than matching R with OGP .
The reader might argue that a more complex find may be compensated
by the fact that public view generation is less complex than generating
operating guidelines. We cannot verify statements about the complexity
of public view generation, since we do not know any convincing solu-
tion to public view generation. The only formal approach known to us is
[8] where a few sound abstraction rules for services are proposed which
preserve strategies. It is, however, unclear whether the generated pub-
lic views satisfy the requirement of being sufficiently distinct from the
original service to keep the service itself secret. Besides these doubts, an
efficient find is still more important than an efficient publish. The publish
operation is performed once by a provided service. Find instead, that
is, matching a requesting service against a public view or an operating
guideline, is performed many times. This is due to the fact that one and
the same requesting service must be checked against many provided ser-
vices before a matching service can be found. We thus believe that the
operating guidelines approach is more suitable to the SOA than the pub-
lic view approach. For a more detailed discussion on public views and
operating guidelines see [9].
7 Conclusion
We propose oWFN as a formal model for services that use workflows as
their internal control structure. We showed that it is possible to auto-
matically compute, for an oWFN P, an operating guideline OGP which
characterizes the set of all (deterministic) behaviors of strategies for P.
We propose to use OGP as information published in service repositories.
This way, it is easy for the service broker to assign well-behaving pairs
of provider’s and requester’s services: the requester’s service must match
the operating guideline published for the provided service. Generating an
13
14. operating guideline may be complex, but we expect that this complexity
can be managed through the use of advanced technology developed in
the area of model checking. In turn, matching a service with an operat-
ing guideline is considerably simpler than checking compliance between
a requester’s service and a public view of a provided service.
We see several directions for future research. First, we need to extend
the approach to services containing cycles. We have a number of pre-
liminary results on this matter. Second, we study specialized operating
guidelines, characterizing, e.g., the set of all those strategies of the con-
sidered vending machine that inevitable lead to the delivery of coffee.
Third, we investigate further important aspects which are relevant for
selecting a service such as real-time constraints or cost models. We want
to extend the concept of operating guidelines to those aspects.
We are convinced that our approach is well suited to implement the ser-
vice discovery outlined in the SOA triangle. Our concept is quite close to
those guidelines that are attached to real vending machines. The concept
of operating guidelines has thus been already successful in every-day life
for a long time.
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