Introduction

What is software architecture?

• fundamental concepts/properties of system in its environment
• embodied in its elements, relationships, and principles of its design/evolution
• so: design + design decisions

Why?

• vehicle for stakeholder communication
• way for manager to reason about cost and schedule
• manifests earliest set of design decisions
• transferable abstraction of system

Characteristics of Software Architecture

• Iteration on functional/quality requirements
• Many stakeholders involved
• Balancing of functional/quality requirements

Architecturally significant requirements (ASRs):

• architectures are driven by quality attribute requirements (e.g. system must be modular, shall meet users’ performance expectations)
• features/functionality shape architecture to lesser extent

Business goals:

• e.g. “we want to differentiate our product from competition and capture market share)
• may directly affect architecture
• often lead to quality attribute requirements

Architecture representations & styles

Structure: coherent set of architectural elements View: representation of structure (picture)

Structures:

• modules: module is unit of implementation with assigned areas of functionality
• component-connector: elements with runtime behavior (components) and interactions (connectors)
• allocation: relationship between software elements and environment

Architectural style: description of component and connector types, pattern of their runtime control/data transfer

Design patterns: recurring structures of communicating components that solve general design problem in a context (e.g. Model-View-Controller)

Architecture assessment

Assesses whether architecture meets quality goals.

Software Architecture Analysis Method (SAAM)

• develop scenarios for
  • activities system must support
  • changes anticipated
• describe architectures
• classify scenarios
  • direct: use requires no change
  • indirect: use requires change
• evaluate indirect scenarios wrt changes and cost
• reveal scenario interaction
• overall evaluation

Architecture influence cycle

architecture affects:

• structure of developing organisation
• goals of developing organisation
• requirements for next systems

Building a system affects architect’s experience

Role of software architect

Ineffective: police agent, documentalist, isolationist (no communication with stakeholders) Effective: key tech consultant, decision maker, coach of dev team, design coordination, implementing key parts

A good architect (1) has experience, (2) has domain knowledge, (3) communicates.