This presentation is about a lecture I gave within the "Software systems and services" immigration course at the Gran Sasso Science Institute, L'Aquila (Italy): http://cs.gssi.infn.it/. http://www.ivanomalavolta.com

1. Ivano Malavolta
AADL
VRIJE
UNIVERSITEIT
AMSTERDAM

2. Outline of this lecture
• Part 1: Basics on AADLv2 core
– Syntax, semantics of the language
• Part 2: Example
– The radar illustrative example

3. Basics on AADL

4. Basics on AADL
1. Quick overview
2. AADL key modeling constructs
1. Software components
2. Execution platform components
3. Properties
4. Modelling large scale systems
3. Tool support

5. Introduction
AADL: Architecture Analysis and Design Language
– Goal : modeling software and hardware architectures
• to master complexity
• to perform analysis
• to generate code
• ….
– Concepts : components, connections, deployments.

6. AADL for analysis

7. Different representations of an AADL model

8. The AADL language in one slide

9. Outline
1. Quick overview
2. AADL key modeling constructs
1. Software components
2. Execution platform components
3. Properties
4. Modelling large scale systems
3. Tool support

10. Summary of AADL elements

11. Three levels of description
• Category (predefined)
• Type
– specification of the external interface
• Implementation
– specification of the content
• Instance
– instantiation of a type
or an implementation
– you do not model it, it is created by the tool

12. Software components categories
• Process : address space. It must
hold at least one thread
• Thread : schedulable execution
flow, Ada or VxWorks task, Java
or POSIX thread. Execute
programs
• Data : data placeholder, e.g. C
struct, C++ class, Ada record
• Subprogram : a sequential
execution flow. Associated to a
source code (C, Ada) or a model
(SCADE, Simulink)
• Thread group : hierarchy of
threads

13. Software components
Example: process composed of two threads
thread receiver
end receiver;
thread implementation receiver.impl
end receiver.impl;
thread analyser
end analyser;
thread implementation analyser.impl
end analyser.impl;
process processing
end processing;
process implementation processing.others
subcomponents
receive : thread receiver.impl;
analyse : thread analyser.impl;
. . .
end processing.others;

14. Software components
a thread may call different subprograms
thread receiver
end receiver;
thread implementation receiver.impl
calls CS : {
call1 : subprogram Receiver_Spg;
call2 : subprogram ComputeCRC_Spg;
};
end receiver.impl;
subprogram Receiver_Spg
end Receiver_Spg;
subprogram ComputeCRC_Spg
end ComputeCRC_Spg;
. . .

22. Subprogram
A subprogram component represents an execution entry point in source
text
No component can contain subprogram subcomponents.
A subprogram call in the implementation of a thread or another
subprogram may be “seen as” the inclusion of a subprogram
subcomponent
A thread can have call sequences for its states:
– initialization, finalization, activation, deactivation, computation, and recovery
Each thread dispatch executes the computation call sequence once

23. States of a thread

24. Subprogram local call example

25. Subprogram remote call example

26. Data
It represents static data (e.g., numerical data or source text)
and data types within a system
– (e.g., used as data types on ports and parameters)
Components may have a shared access to a data
component
Good practice: to store data definitions in a separate file

27. Example of data

28. Component connection

30. Component connection
Features of subcomponents are connected in the
“connections” subclause of the enclosing component
Example
thread analyser
features
analyser_out : out data port
Target_Position.Impl;
end analyser;
thread display_panel
features
display_in : in data port Target_Position.Impl;
end display_panel;
process implementation processing.others
subcomponents
display : thread display_panel.impl;
analyse : thread analyser.impl;
connections
port analyse.analyser_out -> display.display_in;
end processing.others;

32. Ports compatibility

33. Port groups

34. Modes
A mode represents an operational state of a system
A mode of a component can influence:
– property values
– activation of specific subcomponents
– existence of connections
Example - Modes of a cruise controller:
{initialize, disengaged, engaged}

35. Modes transitions
Mode transitions represent configuration changes as reaction
to events
– Triggered through ports (from outside or from a subcomponent)
– Triggered internally by implementation software
– Triggered internally in an execution platform component or a
device
• Note: Modes are not intended for modeling detailed
internal behavior of threads or subprograms ( AADL
Behavior Annex)

36. Mode example

37. Internal mode
transition
example

38. Outline
1. Quick overview
2. AADL key modeling constructs
1. Software components
2. Execution platform components
3. Properties
4. Modelling large scale systems
3. Tool support

39. Hardware components categories
• Processor/virtual processor
– schedule component (combined CPU and RTOS scheduler). A
processor may contain multiple virtual processors
• memory
– model data storage (memory, hard drive)
• device
– component that interacts with the environment. Internals (e.g.
firmware) is not modeled.
• bus/virtual bus
– data exchange mechanism between components
Device Memory bus Processor

47. Software/platform binding
Maps application software elements to execution platform
elements using binding properties

48. Software/platform binding
• Actual_Processor_Binding
– Specify which processor schedules and executes a thread or
executes a (kernel mode) device driver
• Actual_Memory_Binding
– Specify the memory components in which executable code
(process components) and data (data component) reside
• Actual_Connection_Binding
– Specify the communication channels that are used by logical
connections (see next section)

49. Bus access
Access to buses is declared
explicitly in AADL

51. Outline
1. Quick overview
2. AADL key modeling constructs
1. Software components
2. Execution platform components
3. Properties
4. Modelling large scale systems
3. Tool support

52. AADL properties
Property:
– Typed attribute, associated to one or more components
– Property = name + type + allowed components
– Property association = property name + value
Allowed types in properties:
– aadlboolean, aadlinteger, aadlreal, aadlstring,
enumeration, many others …
Can be propagated to subcomponents: inherit
Can override parent’s one, case of extends

53. Property types

54. AADL properties
Properties are associated to a component type (1) or
implementation (2), as part of a subcomponent instance (3),
or a contained property association (4).
process implementation processing.others
subcomponents
receive0 : thread receiver.impl;
receive1 : thread receiver.impl;
receive2 : thread receiver.impl
{Deadline => 200 ms;}; -- (3)
properties -- (4)
Deadline => 300 ms applies to receive1;
end processing.others;
thread receiver
properties -- (1)
Compute_Execution_Time => 3ms .. 4ms;
Deadline => 150 ms ;
end receiver;
thread implementation receiver.impl
properties -- (2)
Deadline => 160 ms;
Compute_Execution_Time => 4ms .. 10ms;
end receiver.impl;

55. Property sets
Property sets :
– Group property definitions
– They can be either
• part of the standard, e.g. Thread_Properties
• or user-defined, e.g. for a new analysis
Example :
property set Thread_Properties is
. . .
Priority : aadlinteger applies to (thread, device, …);
Source_Text : inherit list of aadlstring applies to (data, port, thread, …);
. . .
end Thread_Properties;

56. AADL predefined property sets

57. Measurement units
Properties are typed with units to model physical systems,
related to embedded real-time critical systems
property set AADL_Projects is
Time_Units: type units (
ps,
ns => ps * 1000,
us => ns * 1000,
ms => us * 1000,
sec => ms * 1000,
min => sec * 60,
hr => min * 60);
-- …
end AADL_Projects;
property set Timing_Properties is
Time: type aadlinteger
0ps .. Max_Time units Time_Units;
Time_Range: type range of Time;
Compute_Execution_Time: Time_Range
applies to (thread, device, subprogram,
event port, event data port);
end Timing_Properties;

58. Outline
1. Quick overview
2. AADL key modeling constructs
1. Software components
2. Execution platform components
3. Properties
4. Modelling large scale systems
3. Tool support

59. AADL packages
A package provides a means to organize the descriptions by
the use of namespaces
A package can contain:
– component types
– component implementations
– port group types
– annex libraries

60. AADL package example

61. AADL systems
Help structuring an architecture, with its own hierarchy of
subcomponents.
A system can include one or several subsystems
In an AADL specification there is always a root system
component
Bindings : model the deployment of components inside the
component hierarchy
System

62. subprogram Receiver_Spg …
thread receiver …
thread implementation receiver.impl
… call1 : subprobram Receiver_Spg; …
end receiver.impl;
process processing
end processing;
process implementation processing.others
subcomponents
receive : thread receiver.impl;
analyse : thread analyser.impl;
. . .
end processing.others;
AADL systems
system radar
end radar;
system implementation radar.simple
subcomponents
main : process processing.others;
cpu : processor leon2;
properties
Actual_Processor_Binding =>
reference cpu applies to main;
end radar.simple;
device antenna
end antenna;
processor leon2
end leon2;

63. A full AADL system : a tree of
component instances
• Component types and
implementations only define a
library of entities (classifiers)
• An AADL model is a set of
component instances (of the
classifiers)
• System must be instantiated
through a hierarchy of
subcomponents, from root
(system) to the leafs
(subprograms, ..)
• We must choose a system
implementation component as
the root system model !
Root System
Sub
System
Process Processor
Thread Data
Subprogram

64. About subcomponents
Some restrictions apply on subcomponents
– A hardware cannot contain software, etc
data data, subprogram
thread data, subprogram
thread
group
data, thread, thread group, subprogram
process thread, thread group, data
processor Memory, virtual processor, bus
memory Memory, bus
system ALL except subprogram, thread, and thread
group
64

65. System instances
Component types and implementations are “only” blueprints
System instances represents the runtime architecture of an
operational physical system
Composed of software components + execution platform
XML for storing system instances

66. System instances 2
System instances are automatically generated by OSATE
starting from complete system implementations

67. Components extension & refinement
Extension: to define a new extended classifier based on an
existing classifier
Allows incremental refinement of a model
• Component extension
– Component types
– Component implementations
WHY extensions?
– Add elements to a classifier
• features, subcomponents, connections, flows, etc.
– Refine existing elements in a component
– Add or override properties

68. Extension example

69. Subcomponents array

70. Feature arrays

71. Connecting arrays

72. Connection patterns

73. Outline
1. AADL a quick overview
2. AADL key modeling constructs
1. AADL components
2. Properties
3. Component connection
3. AADL: tool support

74. AADL & Tools
• OSATE (SEI/CMU, http://aadl.info)
– Eclipse-based tools. Reference implementation. AADLv1 and v2
– Textual editors + various plug-ins
• STOOD, ADELE (Ellidiss, http://www.ellidiss.com )
– Graphical editors for AADLv1 and v2, code/documentation generation
• Cheddar (UBO/Lab-STICC, http://beru.univ-brest.fr/~singhoff/cheddar/ )
– Performance analysis, AADLv1 only
• AADLInspector (Ellidiss, http://www.ellidiss.com)
– Lightweight tool to inspect AADL models. AADLv1 and v2
– Industrial version of Cheddar + Simulation Engine
• Ocarina (ISAE, http://www.openaadl.org)
– Command line tool, library to manipulate models. AADLV1 and V2
– AADL parser + code generation + analysis (Petri Net, WCET, …)
• Others: RAMSES, PolyChrony, ASSIST, MASIW, MDCF, TASTE, …

75. Example

76. Example
Goal: to model a simple radar system
Let us suppose we have the following requirements:
1. System implementation is composed of physical devices (Hardware
entity): antenna + processor + memory + bus
2. and software entities : running processes and threads + operating system
functionalities (scheduling) implemented in the processor that represent a
part of execution platform and physical devices in the same time
3. The main process is responsible for signals processing : general pattern:
transmitter -> antenna -> receiver -> analyzer -> display
4. Analyzer is a periodic thread that compares transmitted and received
signals to perform detection, localization and identification

77. Radar case study
Hardware/Software breakdown: components
PACKAGE radar
PUBLIC
PROCESS processing
-- …
END processing;
DEVICE antenna
-- …
END antenna;
END RADAR;

78. Radar case study
Hardware/Software breakdown: features
in/out ports
bus access
PROCESS processing
FEATURES
to_screen : OUT EVENT PORT;
send_pulse : OUT EVENT PORT;
receive_pulse : IN DATA PORT;
get_angle : IN DATA PORT;
END processing;
DEVICE antenna
FEATURES
antenna_in : IN EVENT PORT;
VME : REQUIRES BUS ACCESS VME;
END antenna;

79. Radar case study
Hardware/Software breakdown: connections
Logical cnx
Hardware cnx

80. Radar case study
Hardware/Software breakdown: connections
SYSTEM IMPLEMENTATION radar.simple
SUBCOMPONENTS
aerial : DEVICE antenna;
rotor : DEVICE motor;
monitor : DEVICE screen;
main : PROCESS processing.others;
cpu : PROCESSOR leon2;
VME : BUS VME;
RAM : MEMORY RAM;
CONNECTIONS
PORT aerial.antenna_out -> main.receive_pulse;
PORT rotor.motor_out -> main.get_angle;
PORT main.send_pulse -> aerial.antenna_in;
PORT main.to_screen -> monitor.screen_in;
BUS ACCESS VME -> aerial.VME;
BUS ACCESS VME -> rotor.VME;
BUS ACCESS VME -> monitor.VME;
BUS ACCESS VME -> cpu.VME;
BUS ACCESS VME -> RAM.VME;

81. Radar case study
• Hardware/Software breakdown: bindings
Bindings
PROPERTIES
Actual_Memory_Binding => reference (ram) applies to main;
Actual_Processor_Binding => reference (cpu) applies to main;
END radar.simple;

82. Radar case study
• Software elements

83. Radar case study
• Software elements
PROCESS IMPLEMENTATION processing.others
SUBCOMPONENTS
receive : THREAD receiver.impl;
analyse : THREAD analyser.impl;
display : THREAD display_panel.impl;
transmit : THREAD transmitter.impl;
control_angle : THREAD controller.impl;
CONNECTIONS
A10:PORT receive_pulse -> receive.receiver_in;
A11:PORT display.display_out -> to_screen;
A12:PORT transmit.transmitter_out -> send_pulse;
A13:PORT get_angle -> control_angle.controller_in;
A14:PORT receive.receiver_out -> analyse.from_receiver;
A15:PORT analyse.analyser_out -> display.display_in;
A16:PORT transmit.transmitter_out -> analyse.from_transmitter;
A17:PORT control_angle.controller_out -> analyse.from_controller;
END processing.others;

84. Radar case study
• Software elements
PROCESS IMPLEMENTATION processing.others
SUBCOMPONENTS
receive : THREAD receiver.impl;
analyse : THREAD analyser.impl;
display : THREAD display_panel.impl;
transmit : THREAD transmitter.impl;
control_angle : THREAD controller.impl;
CONNECTIONS
A10:PORT receive_pulse -> receive.receiver_in;
A11:PORT display.display_out -> to_screen;
A12:PORT transmit.transmitter_out -> send_pulse;
A13:PORT get_angle -> control_angle.controller_in;
A14:PORT receive.receiver_out -> analyse.from_receiver;
A15:PORT analyse.analyser_out -> display.display_in;
A16:PORT transmit.transmitter_out -> analyse.from_transmitter;
A17:PORT control_angle.controller_out -> analyse.from_controller;
END processing.others;
THREAD IMPLEMENTATION receiver.impl
CALLS CS : {
RS : SUBPROGRAM Receiver_Spg;
};
CONNECTIONS
A18:PARAMETER RS.receiver_out -> receiver_out;
A19:PARAMETER receiver_in -> RS.receiver_in;
PROPERTIES
Priority => 63;
Dispatch_Protocol => Periodic;
Compute_Execution_Time => 10 ms .. 20 ms;
Deadline => 150 ms;
Period => 1500 ms;
END receiver.impl;

85. What this lecture means to you?
AADL = Architecture Analysis & Design Language
AADL is for architectural description, period
à Not to be compared with UML suites
– Behavior, types, link with source code is not required
Keep in mind models support an objective
– In this lecture, it is just a high-level view of the design
What is not covered by this lecture:
flows, annexes, multidimensional arrays, virtual
processors/buses, analyses with external tools

86. Suggested readings
1. The SAE Architecture Analysis & Design Language (AADL) Standard.
Peter H. Feiler, January 2008. [Introduction to the language]
2. The Architecture Analysis & Design Language (AADL): An
Introduction, Peter H. Feiler David P. Gluch John J. Hudak, February
2006. [Use this as reference manual]
3. OSATE plugin: SEI validation plugins. SEI. [AADL analysis in general]
4. Developing AADL Models for Control Systems: A Practitioner’s
Guide. John Hudak Peter Feiler. July 2007. [Flow latency analysis]
5. http://www.informit.com/articles/article.aspx?p=1959953
[Simple running example]

87. Links
Tool:
• http://www.aadl.info/aadl/osate/stable/2.0.8/products/
Example projects (other than the ones on Schoology):
1. https://github.com/yoogx/AADLib
2. https://github.com/osate/examples
3. http://www.santoslab.org/pub/high-assurance/module-
aadl/slides/AADL-Isolette.pdf

88. Acknowledgements
Parts of this lecture have been elaborated from:
• AADLv2, a Domain Specific Language for the Modeling, the Analysis
and the Generation of Real-Time Embedded Systems. Frank Singhoff
and Jérôme Hugues, MODELS 2014 tutorial.
• SAE AADL V2: An Overview. Peter Feiler. © 2010 Carnegie Mellon
University.
• Overview of AADL Syntax. J-P. Rosen, J-F. Tilman. AADL Workshop
2005.

89. Contact
Ivano Malavolta |
Assistant professor
Vrije Universiteit Amsterdam
iivanoo
i.malavolta@vu.nl
www.ivanomalavolta.com