Software Architecture: An Overview

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Software Architecture An Overview

• Vanilson Burégio
• vaab_at_cin.ufpe.br

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Agenda

• History
• Software Architecture
• Definition
• Motivation
• Roles
• Architectural Styles
• Architectural Views
• Architectural Description Language (ADL)
• Architecture and Reuse
• DSSA based reuse
• PLA

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History 1950s

• Machine language
• programmers placed instructions and data
  explicitly in the computers memory
• Symbolic Assemblers
• Symbolic names
• Memory layout and update references could be
  automated
• High-level Programming Languages
• Procedures invocations, loops, modules,

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History 1960s

• Problems of developing large-scale software
  Systems
• Software structure
• Specifications
• Language issues
• Abstract Data Types

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History 1970s

• Software Design
• Design is an activity separate from
  implementation
• Research results
• Notation
• Techniques
• CASE tools

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History 1980s

• The focus of software engineering research
• Integrating designs and the design process
• Result
• many of the notations and techniques developed
  for software design have been absorbed by
  implementation languages

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History 1990s

• Software Architecture
• Design Vs Architecture
• "use the term architecture, in contrast to
  design, to evoke notions of codification, of
  abstraction, of standards, of formal training (of
  software architects), and of style " Perry and
  Wolf,92

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History Summary
Abstraction level

• 1950s - High-level Programming Languages
• 1960s - large-scale software Systems
• 1970s - Software Design
• 1980s - Integrating designs and the design
  process
• 1990s - Software Architecture

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Software Architecture Definition

• There are several different definitions of
  software architecture in the literature, all of
  them agree that it
• The most commonly used definitions
• Perry Wolf, 1992
• Garlan Shaw, 1994

Describes the organization of the overall system
concentrate on the topological view
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Software Architecture Definition

• Perry Wolf, 1992
• Set of architectural elements that have a
  particular form, and an underlying rationale
• Elements - processing, data and connecting
  elements
• Form - consists of weighted properties of
  architectural elements
• Rationale - captures the motivation for the
  choice of architectural style, the choice of
  elements, and the form
• It is the connecting elements ("glue") that
  especially distinguish one architecture from
  another

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Software Architecture Definition

• Garlan Shaw, 1994
• Define software architectures as including
  components, connectors and configurations.
  Where
• components - define the locus of computation,
• connectors - define the interactions between
  components
• configurations define the topology of the
  components and connectors

The structure of the components of a
program/system, their interrelationships, and
principles and guidelines governing their design
and evolution over time. Software architecture
discussion group at the SEI, 1994
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Software Architecture Motivation

• High cost of software
• Evolution
• customization

Software architecture simplifies our ability to
comprehend large systems by presenting them at a
level of abstraction at which high-level design
can be understood Garlan and Shaw 1993 Perry
and Wolf 1992
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Software Architecture Roles

• Eden Kazman, 2003
• Communication among stakeholders
• Early design decisions
• Transferable abstraction of a system
• Main considerations Szyperski, 2002
• Functionality
• Performance
• Reliability
• Security

Commonly, these aspects are ignored, emphasizing
functionality. The consequences can be fatal!
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Software Architecture Context
Requirements
Architecture
Design
Implementation
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Architectural styles
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Architectural styles

• Observation
• Many systems have a similar solution structure
• Defines a family of architectures constrained by
  Garlan Shaw, 1994
• Component/connector vocabulary
• Topology
• Semantic constraints
• Benefits of styles
• Reuse of experience
• Reuse of code
• Insight in/analysis of solution characteristics

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Most Common Architectural Styles Garlan Shaw

• Pipes and Filters
• Data Abstraction and Object-Oriented Organization
• Event-based, Implicit Invocation
• Layered Systems
• Repositories
• Table Driven Interpreters
• Heterogeneous Architectures

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Most Common Architectural Styles Garlan Shaw

• Pipes and Filters

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Most Common Architectural Styles Garlan Shaw

• Data Abstraction and Object-Oriented Organization

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Most Common Architectural Styles Garlan Shaw

• Event-based, Implicit Invocation

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Most Common Architectural Styles Garlan Shaw

• Layered Systems

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Most Common Architectural Styles Garlan Shaw

• Repositories

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Most Common Architectural Styles Garlan Shaw

• Table Driven Interpreters

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Most Common Architectural Styles Garlan Shaw

• Heterogeneous Architectures
• There are different ways in which architectural
  styles can be combined
• Hierarchy
• pipe connector may be implemented internally as a
  FIFO
• A single component using a mixture of
  architectural connectors
• an active database

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Architectural styles

• Formal approach Abowd, 1993

mapping
Abstract Sintaxe
Semantic Domain
Z especification
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Architectural views
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Architectural views

• Gacek, 1994
• To accommodate the different expectations of the
  various stakeholders,a software architecture
  must incorporate different, multiple views

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Architectural views

• Views of a Software Architecture Gacek, 1994
• Static Topological
• Behavioral / Operational
• Dataflow
• Computing Environment
• Process Environment

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Architectural views

• Kruchten, 1995
• The 41 View Model
• Logical view
• Process view
• Physical view
• Development view
• Scenarios
• Scenario-driven approach capture the systems
  critical functionality
• Style Vs View

End users, customers, data specialists
System engineers
Project managers, software-configuration staff
members
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ADL - Architecture Description Language
Architecture Description Languages (ADLs) lay
the formal basis for architecting

• ADLs differ in their scope of use Abd-Allah,
  1994

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ADL - Architecture Description Language

• Goals
• Rapid Prototyping
• Reengineering
• Better understanding of overall system
• Main problem
• A lot of ADLs are loosely coupled to
  implementation languages, causing problems in
• Analysis
• Implementation
• Understanding
• evolution

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ADL - Architecture Description Language

• Early ADLs were restricted to static connectivity
• Rapide
• Darwin
• Wright
• DICAM
• Later ADLs added support for dynamic connectivity
  and dynamic reconfiguration
• ArchJava Aldrich, 2002

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ADL ArchJava

• Key concept Communication Integrity Luckham
  Vera, 1995
• A system has Communication Integrity if
  implementation components only communicate
  directly with the components they are connected
  to in the architecture
• Example

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ADL Design Model

• Integrating ADL with a Standard Design Method
  Robbins, 1998

Wrights CSP constructor
C2 architecture expressed in UML
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Architecture and Reuse

• DSSA Based Reuse
• Product-line architecture (PLA)

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Domain Specific Software Architecture Based Reuse

• Artifact involved
• Reference architecture, design, requirements and
  code
• General characteristics
• Requires thorough domain understanding
• Domain specific repository
• Domain model, reference architecture and
  repository evolution
• Example
• SGS Reference Architecture Gacek, 1995

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DSSA Based Reuse

• Lifecycle Balzer et al. 1993

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Product-line architecture Context

• Product-line architecture (PLA) have received
  special attention in software industry
• Increase reuse
• minimize product-specific development
• Competitive advantage
• Recent Area

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PLA Cases

• Bosch, 1999
• Axis Communications AB
• Securitas Larm AB

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PLA Problems

• Background knowledge
• Information Distribution
• Multiple versions of assets
• Dependencies between assets
• Assets in new contexts
• Documentation
• Tool support
• Effort estimation

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PLA recently

• PLA Development toolkit Lesaint
  Papamargaritis, 2004
• Support two operations
• Application configuration
• Application generation
• Process
• Specifying the architecture
• Configuring the application
• Generating applications

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References

• Abd-Allah, 1994 Ahmed A. Abd-Allah.
  Architecture Description Languages. 1994.
• Abowd, 1993 Gregory Abowd, Robert Allen, David
  Garlan. Using Style to Understand Descriptions of
  Software Architecture. 1993.
• Aldrich, 2002 Jonathan Aldrich, Craig Chambers,
  David Notkin. ArchJava Connecting Software
  Architecture to Implementation. 2002.
• Balzer et. al. 1993 R. Balzer, C. Braun, F.
  Belz, L. Coglianese, L. Erman, K. Harbison, R.
  Might, R. Platek, and S. Vestal. DSSA Process
  Summary. Copies available from Chris Braun
  (braun_at_europa.eng.gtefsd.com), 1993.
• Bosch, 1999 Jan Bosch Product-Line
  Architectures in Industry A Case Study. 1999.
• Clements, 1996 Paul C. Clements. A Survey of
  Architecture Description Languages. 1996.
• Eden Kazman, 2003 Amnon H. Eden, Rick Kazman.
  Architecture, Design, Implementation. 2003.
• Gacek et. al. 1995 Cristina Gacek, Ahmed
  Abd-Allah, Bradford Clark, Barry Boehm. On the
  Definition of Software System Architecture. 1995.
  
• Gacek, 1994 Cristina Gacek. Domain Specific
  Software Architecture Based Reuse. 1994.

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References

• Gacek, 1995 Cristina Gacek. Exploiting Domain
  Architectures in Software Reuse. 1995.
• Garlan Shaw, 1994 David Garlan, Mary Shaw. An
  Introduction to Software Architecture. 1994.
• Garlan et. al.. 1995 David Garlan, Robert
  Allen, Jihn Ackerbloom. Architectural Mismatch
  Why Reuse is So Hard. 1995.
• Garlan, 1995 David Garlan. Research Directions
  in Software Architecture. 1995.
• Kruchten, 1995 P. Kruchten. The 41 View Model
  of Architecture. IEEE Software, Nov 1995.
• Lesaint Papamargaritis, 2004 David Lesaint,
  George Papamargaritis. Aspects and Constraints
  for Implementing Configurable Product-Line
  Architectures. 2004.
• Luckham Vera, 1995 David C. Luckham, James
  Vera. An Event Based Architecture Definition
  Language. IEEE Trans. Software Enginering 21(9),
  Sep 1995.
• Lutz Gannod, 2003 Robyn R. Lutz, Gerald C.
  Gannod. Analysis of a software product line
  architecture an experience report. 2003.
• Meekel, 2001 Jacques Meekel, Thomas B. Hortont,
  Robert B. Francet, CharlieMellone L Sajid Dalvi.
  From Domain Models to Architecture Frameworks.
  1997.

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References

• Perry Wolf, 1992 Dewayne E. Perry, Alexander
  L. Wolf. Foundations for the Study of Software
  Architecture. 1992.
• Robbins, 1998 Jason E. Robbins, Nenad
  Medvidovic, David F. Redmiles, David S.
  Rosenblumart.Integrating Architecture Description
  Languages with a Standard Design Method. 1998.
• Shaw, 1995 Mary Shaw. Comparing Architectural
  Design Styles. 1995.
• Szyperski, 2002 C. Szyperski, D. Gruntz, S.
  Murer, Component Software Beyond Object-Oriented
  Programming, Addison-Wesley, 2002, pp. 588
• Wallnau, 2001 Kurt Wallnau, Judith Stafford,
  Scott Hissam, Mark Klein. On the Relationship of
  Software Architecture to Software Component
  Technology. 2001.