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Software Architecture

Software Architecture. Agenda. Why architect? What is architecture? What does an architect do? What principles guide the process of architecting? What's involved in creating architectural documents?. Why Architect?. to build a better dog house to handle large, complex tasks

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Software Architecture

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  1. Software Architecture

  2. Agenda • Why architect? • What is architecture? • What does an architect do? • What principles guide the process of architecting? • What's involved in creating architectural documents?

  3. Why Architect? • to build a better dog house • to handle large, complex tasks • to coordinate work • to communicate ideas and design • to validate against goals • to resolve conflicting goals • to reduce costs • to improve delivery times • products or product lines

  4. Architecture: Definitions • "the art or science of building" • "formation or construction as or as if as the result of conscious act" • "a unifying or coherent form or structure" • "a method or style of building" • "the manner in which the components of a computer or computer system are organized and integrated" • Merriam-Webster's Collegiate Dictionary, Tenth Edition

  5. Develop: Definitions • "to set forth or make clear by degrees or in detail" • "to work out the possibilities of" • "to make available or usable" • "to cause to unfold gradually" • "to expand by a process of growth" • "to come into being gradually" • Merriam-Webster's Collegiate Dictionary, Tenth Edition

  6. What is Architecture? • Form • structure, organization • Function • behavior, use • Style • appearance, elegance, way of doing things (tao)

  7. Examples of Architecture Score Picture Section Class Layout

  8. Influences on Architecture • Environment/Context • Relationship to surroundings, orientation, and climate • History • Changes in technology, materials, and ideals of beauty over time • Technology • Current know-how

  9. Uses of Architecture • Means of communicating design information amongst stakeholders • Embodiment of early design decisions • Reusable entity

  10. What Does an Architect Do? • leads • champions, coordinates, interfaces, aligns with business strategies • provides vision • translates • designs • criticizes • consults

  11. Guiding Principles • integrity • simplicity • loose coupling/separation of concerns • high cohesion • abstraction • postponement of decisions

  12. Creating Architectural Documents • Source • "Architecture-Based Development", Len Bass & Rick Kazman, Carnegie Mellon University, 1999 • Iterative process, involving both construction and validation • Six-step process

  13. Architectural Document Creation Process Summary • Elicit architectural requirements • Design the architecture • Document the architecture • Analyze the architecture • Realize the architecture • Maintain the architecture

  14. Elicit Architectural Requirements • functional requirements • non-functional requirements or qualities • such as: • modifiability • performance • security • reliability • includes priorities, relative importance, etc.

  15. Design the Architecture • make design decisions based on: • knowledge of architectural styles • design patterns • use of of particular tools • reason about decisions by • considering architectural structures* and views • validate the design by • determining if scenarios are achievable

  16. Architectural Structures • components, connectors, and properties • Based on: Architectural Blueprints -- The “4+1” View Model of Software Architecture, P. Kruchten, IEEE Software V12N6, 1995 • view: perspective; part of or combination of parts of structures • functional structure/logical view • concurrency structure/process view • physical structure/physical view • code structure/development view • developmental structure (not in Kruchten) • Kruchten includes “scenarios”

  17. Functional Structure • decomposition of functionality • system’s services to clients • identification of common mechanisms and design elements • identification of connections • represented in UML by class diagrams

  18. Concurrency Structure • processes, threads, distribution, messages • some non-functional requirements handled • performance, availability, security, reliability • how functionality maps to processes/threads • major tasks use inter-process communication (IPC) • no assumptions about collocation • minor tasks may use shared memory • can be used to estimate message flows and loads

  19. Physical Structure • mapping software to hardware • primarily non-functional requirements • e.g., availability, reliability (fault tolerance), performance (throughput), scalability • several different configurations possible

  20. Code Structure • key code abstractions (e.g., packages, classes) • addresses: • software reuse, portability • software management (work allocation, monitoring, etc.) • software development issues • software module organization • often, layered subsystem

  21. Scenarios • walk-through scripts • sequences of interactions among objects and among processes • instances of use cases (what a system does from the standpoint of an external observer) • intentionally redundant with other views: • to help discover architectural elements • to validate and illustrate architecture

  22. Document the Architecture • Key characteristics: • complete and navigable • includes infrastructure • enough use cases to help understand how system will implement functionality • includes constraints on communications, resource management, time management, etc. • publicly available to everyone concerned

  23. Analyze the Architecture • Review by concerned parties • Intent is to: • detect problems early • improve the architecture

  24. Realize the Architecture • Turn the architecture into code

  25. Maintain the Architecture • Keep the architecture on track over time

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