Definition

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.

Importance of Software Architecture

• Inhibits/enables quality attributes
• Helps reasoning about/managing change
• Helps predict system qualities
• Allows communication among Stakeholders
• Carries early design decisions
• Defines constraints on implementation
• Influences the organizational structure
• Enables evolutionary prototyping
• Helps with cost and schedule estimates
• Transferable, reusable model
• Allows the assembly of independent components
• Channels the creativity of developers
• Foundation for training

Views

Modules View

• organization as modules and relations
  • subsystems, layers, components, classes
  • decomposition, use, inheritance
• develops, managers concerns
  • modifiability, testability, schedule
• component, package, class diagrams

Concurrency View

• runtime view of the system
  • processes, threads, services, peers, clients, servers, peers
  • run with, preempt
  • calls, messages, events, shared memory
• integrators, operators
  • integrity, fault-tolerance, performance
• component, interaction, activity diagrams

Deployment View

• topology and Deployment
  • physical/virtual nodes
  • physical/virtual links
• system engineers, operators
  • availability, reliability, performance, scalability
• deployment diagrams

Architecture Process

• Architectural Requirements Selection
• Architecture Structuring
• Architecture Validation

Architecture Requirements Selection

Design Context and Purpose

• Nature of development
• Business Goal

Quality Attributes

• Measurable properties
• Product Fitness
• Stakeholders needs
• Should be measureable

Primary Functionality

• Critical to Business Goals
• Main Motivation
• Core Use Cases/Features
• Architecture affects Changes

Constraints

• Predetermined Decisions
  • Technologies
  • Interoperating Systems
  • Laws, Standards
  • Developers abilities
  • Strict deadlines

Architectural Concerns

• Need to be considered
  • General concerns
  • Specific concerns
  • Internal Requirements
  • Issues

Architectural Design Concepts

• Facilitate architecture design
• realizations of design principles
  • reference architectures
  • patterns
  • frameworks

Reference architectures

• overall logical structure in a domain
  • reference model
  • patterns/styles

Architectural Patterns/Styles

• conceptual solutions to recurring design problems in a defined context
  • influences satisfaction architectural drivers
  • specify architectural structures

Sample categories

• data flow
• independent components
• virtual machines
• data centered
• layered

Architectural Tactics

• fundamental design technique
  • controls a specific quality attribute

Frameworks

• concrete reusable realization of architecture elements
  • from patterns, tactics, reference architectures
• full-stack framework
  • covers whole reference architecture
• non-full-stack framework
  • covers specific concerns

Architecture Validation

• to ensure correctness of an architecture
  • architecture review
  • scenario-based evaluation
  • quantitative evaluation
  • prototype development

Architectural Drift

• introduction of architectural design decisions in descriptive architecture that are:
  • not included in, encompassed by, or implied by prescriptive architecture
  • but do not violate any of the prescriptive architecture's design decisions

Architectural Erosion

• introduction of architectural design decisions in descriptive architecture that
  • violate prescriptive architecture.