An introduction to software architecture.

1. Introdução à Arquitetura de Software
Rodrigo Veiga – PUC-Rio
05/04/2009
1

2. Agenda
• Arquitetura – Definição
• Histórico
– Evolução do Desenvolvimento
– Trabalhos Pioneiros em Arquitetura de Software
– Processo de Maturação
• Conceitos
– Definição
– Termos Relacionados
– Conceitos errados
– Architectural Concerns
– Architectural Styles
• Critérios para uma boa Arquitetura
• O Papel de Arquiteto de Software
• Arquitetura Hoje
• Grupos e Sites sobre o assunto
• Bibliografia
2

3. Arquitetura
• “The art or science of building”
(Oxford Dictionary)
• “Is an imitation of Nature”
(Vitruvius on Architecture)
• “Should have Beauty (Venustas),
Firmness (Firmitas) and Utility (Utilitas)”
(Vitruvius on Architecture)
• “Arte ou a técnica de projetar e edificar
o ambiente habitado pelo ser humano”
(Wikipedia)
3

4. Arquitetura
• “Arte ou técnica de organizar e configurar
espaços”
(Wikipedia)
• “Se manifesta de duas formas: a atividade
e o resultado físico”
(Wikipedia)
• “Architecture defines the essential
structure and organization of something
abstracted in an appropriate pattern”
(Rob Beckmann , Caro Systems)
4

5. “Every thing has an architecture” (Grady Booch)
“In all disciplines, architecture provides a mean for solving a
common problem: assuring that a building, or bridge, or
composition, or book, or computer, or network, or system has
certain properties and behaviors when it has been built”
(Beautiful Architecture)
5

6. Desenvolvimento de Software
Evolução ao longo das últimas décadas
Extraído de: An Introduction to Software Architecture, David Garlan and Mary Shaw, 1994
6

7. Arquitetura de Software
• Trabalhos Pioneiros
– Edgar Dijkstra, 1968
• A Case against the GO TO Statement
– Não apenas programar uma solução satisfatória
– Introduz a idéia de que “a layered system results in
ease of development and maintenance”
– Fred Brooks Jr., 1975
• The Mythical Man-Month
– “Every part must reflect the same philosophies and
the same balancing of desiderata….Ease of
use, then, dictates unity of design, conceptual
integrity (Simplicity and Straightforwardness)”
7

8. Arquitetura de Software
• Trabalhos Pioneiros
– David Lorge Parnas, 1972:
• On the Criteria to Be Used in Decomposing
Systems into Modules
– “Information Hiding as the basis of decomposition for ease
of maintenance and reuse”
– “The separation of Interface from implementation of
components”
– Wolfram Bartussek e David Lorge Parnas,
1978:
• Using Assertions About Traces to Write Abstract
Specifications for Software Modules
– Princípios para detecção e tratamento de erros
(assertivas, exceções, etc)
8

9. Arquitetura de Software
Processo de Maturação da Arquitetura de Software
Extraído de: The Golden Age of Software Architecture, Mary Shaw and Paul Clements, 2006
9

10. Arquitetura de Software
• “Software architecture is what software architects do”
(Kent Beck at OOPSLA 92)
• “Software Architecture is a game of trade-offs - a decision
that improves one characteristic often diminishes another”
(Beautiful Architecture)
• “Architecting software is different from physical systems”
(Grady Booch)
• “A set of architectural (or design) elements that have a
particular form” ou “Architecture = {elements, form,
rationale}”
(Perry and Wolf, 1992)
10

11. Arquitetura de Software
• “A software system architecture comprises
– A collection of software and system components, connections, and
constraints
– A collection of system stakeholders' need statements
– A rationale which demonstrates that the components, connections, and
constraints define a system that, if implemented, would satisfy the
collection of system stakeholders' need statements”
(Boehm et al., 1995)
• “Software architecture is the fundamental organization of a
system, embodied in its components, their relationships to
each other and the environment, and the principles governing
its design and evolution”
(IEEE 1471-2000)
• “Is a set of principal design decisions made about the system”
(Software Architecture Foundations, Theory and Practice)
11

12. Arquitetura de Software
• “Architecture establishes the context for design
and implementation”
(Grady Booch)
“Architectural decisions are the
most fundamental decisions;
changing them will have
significant ripple effects.”
(Grady Booch)
12

13. Arquitetura de Software
• Termos Relacionados
– Components
• “An architectural element that encapsulates a subset of
system’s funcionality and/or data” (Software Architecture)
– Connections
• “An architectural element that effects and regulates interactions
among components” (Software Architecture)
– Stakeholders
• “Is an individual, team, or organization with interests in a
system (or part of it)” (Grady Booch)
– Models
• “Is a simplification of reality, created in order to better
understand the system being created; a semantically closed
abstraction of a system” (Grady Booch)
– Views / Dimensions
• “A view is a representation of a whole system from the
perspective of a related set of concerns” (Grady Booch)
13

14. Arquitetura de Software
• Termos Relacionados (cont.)
– Concerns
• “Interests related with aspects that are important to one or
more stakeholders” (Grady Booch)
– Patterns
• “Is a kind of rule that states a problem to be solved and a
solution to that problem” (Patterns of Software)
– Architecture Erosion / Entropy
• “The consequences of actions that disorganizes a software
architecture over time” (Stephen J. Mellor foreword to Beautiful
Architecture)
– Architecture Style
• “Style is the classification of an architecture according to those
with similar patterns” (Grady Booch)
– Reference Architecture
• “Is a set of principal design decisions that are simultaneously
applicable to multiple related systems” (Software Architecture)
14

15. Conceitos Errados sobre
Arquitetura de Software
• “Architecture is just paper
• Architecture and design are the same things
• Architecture and infrastructure are the same
things
• <my favorite technology> is the architecture
• A good architecture is the work of a single
architect
• Architecture can be represented in a single
blueprint (or is flat)
• Architecture is a science
• Architecture is an art”
(Handbook of Architecture, Grady Booch)
15

16. Arquitetura de Software
• Architectural Concerns
(Adaptado de Beautiful Architecture e Patterns of Software)
Functionality
Ecosystem Usability
Security Modularity
Performance
Habitability
Reusability
Changeability
Scalability
Reliability
16

17. Arquitetura de Software
• Architectural Styles (Software Architecture)
Language • Main Program and Subrotines
Influenced Styles • Object-Oriented
• Virtual Machines
Layered
• Client-Server
• Batch-sequential
Dataflow
• Pipe-and-filter
Implicit • Publish-subscribe
Invocation • Event-based
Peer-To-Peer • P2P
17

18. Critérios para uma boa Arquitetura
 “One fact in one place
 Automatic Propagation
 High Modularity
 Simplicity: Simple but not Simpler
 Versatility
 Conceptual Integrity / Resist Entropy
 Elegance (Doing the most with least)
 Use of Patterns
 Standard Compliance
 Habitability / Comprehensibility
 Productivity
 Interoperability”
(Adaptado de: Beautiful Architectures, Handbook of Architecture, Patterns of Software)
18

19. O Papel de Arquiteto de Software
• Responsabilidades
– Responsável pela Arquitetura
– Manter a integridade da Arquitetura
– Definir e validá-la
– Facilitar a comunicação entre equipes
– Atuar como mentor dos times
• Características
– Tem que ter flexibilidade / adaptabilidade
– Comunicação e Liderança
– Não deve impor as regras / Saber ouvir
– Visão holística
(Handbook of Software Architecture, Grady Booch)
19

20. O Papel de Arquiteto de Software
• Maus hábitos
– Perfeccionismo
– Inflexibilidade
– Micromanagement
– Isolacionismo
(Software Architecture)
20

21. Arquitetura de Software Hoje
• Crescimento de ferramentas e mecanismos que
ajudam a manter a integridade da Arquitetura
– Model Driven Design
– Menos código para implementar mais funcionalidades
• Maior interoperabilidade
– Orientação a serviços
– Utilização de Agentes
– Cada vez mais sistemas heterogêneos (várias linguagens)
• Virtualização, Cloud Computing
• Processos
– Arquitetura deixando de ser encarada como uma fase de
projeto, mas como uma necessidade de ponta a ponta
• Web 2.0
– Novos níveis de exigência
21

22. Grupos e Sites sobre o assunto
– Pangea (http://pangeanet.org)
– Highscalability (http://highscalability.com)
– Infoq (http://www.infoq.com)
– The Server Side
(http://www.theserverside.com)
22

23. Referências
• Diomidis Spinellis & Georgios ousios, Beautiful Architecture,
O’Reilly 2009
• Revista MundoJava, edições 15 e 25
• Richard N. Taylor, Nenrad Medvidovic, Eric M. Dashofy, Software
Architecture – Foundations, Theory and Practice, Wiley 2009
• Richard P. Gabriel, Patterns of Software, 1996
• Handbook of Software Architecture, Grady Booch, IBM
• Mary Shaw and Paul Clements, The Golden Age of Software
Architecture, 2006
• Visão Geral de Arquitetura de Software, Marco Aurélio S. Mendes,
Instituto GTI
• David Garlan and Mary Shaw, An Introduction to Software
Architecture, 1994
• Dewayne E. Perry & Alexander L. Wolf, Foundations for the Study
of Software Architecture, 1992
• Ane Cristina Varoto, Visões em arquitetura de software, 2002
23

24. Referências
• Wikipedia
– http://pt.wikipedia.org/wiki/Arquitetura, Acesso em 04/2009
– http://pt.wikipedia.org/wiki/Arquitetura_de_software, Acesso
em 04/2009
– http://pt.wikipedia.org/wiki/Arquitetura_(desambigua%C3%A
7%C3%A3o), Acesso em 04/2009
• Scaling Twitter: Making Twitter 10000 Percent Faster | High
Scalability, http://highscalability.com/scaling-twitter-making-
twitter-10000-percent-faster, Acesso em 04/2009
• A Quick Look at Architectural Styles and Patterns;
http://www.infoq.com/news/2009/02/Architectural-Styles-
Patterns, Acesso em 04/2009
• Architectural Styles, Patterns, and Metaphors;
http://shapingsoftware.com/2008/08/10/architectural-styles-
patterns-and-metaphors, Acesso em 04/2009
24