Software Architecture

Question 1

Software Architecture:

Two Parts

Answer 1

Architectural Design Process

The design process for identifying the sub-systems and the framework for sub-system control and communication

Software Architecture

The output of the Architectural Design Process

Question 2

Architectural Design Process:

Basic Description

Answer 2

• An early stage of the system design process
• Represents the link between specification and the design processes
• Often carried out in parallel with some specification activities
• Involves identifying major system components and their communications/interactions

Question 3

Architectural Design:

Important Concepts

Answer 3

Architectural Representations

Architectural Reuse

Architectural Patterns

Question 4

Architectural Design:

Architectural Representations

Answer 4

Simple, informal block diagrams showing major entities/components and relationships

• Basic, “Box and Line” diagrams
• Very abstract, but useful for communication with stakeholders and for project planning

Question 5

Architectural Design:

Architectural Reuse

Answer 5

A principle of design. Do not reinvent the wheel.

• Systems in the same domain often have very similar architectures which reflect domain concepts
• The architecture of a system may be designed around one or more Architectural Patterns or Styles

Question 6

Architectural Design:

Architectural Patterns:

Overview

Answer 6

• “Patterns” are a means of representing, sharing and reusing knowledge
• An Architectural Pattern is a description of good design practice, which has been tried and tested in different environments
• Patterns should include information about when they are and are not useful
• Patterns may be represented using tabular and graphical descriptions

Question 7

Architectural Patterns:

Some Major Architectural Patterns (6)

Answer 7

• Client-Server Architecture
• Model-View-Controller
• Model-View-View Model
• Layered Architecture
• Repository Architecture
• Pipe and Filter Architecture

Note: this is far from comprehensive

Question 8

Architectural Patterns:

Client-Server Architecture

Answer 8

• A distributed system model
• Shows how data and processing are distributed across a range of components
• Set of stand-alone servers which provide specific services
• Set of Clients which call on these Servers
• Network which allows Clients to access Servers

Question 9

Architectural Patterns:

Model-View-Controller

Answer 9

• Separates the Presentation and Interaction from System Data
• System is split into three major layers:
  
  • Model (Data Layer):
    
    • Encapsulates Application State
    • Notifies View of state changes
  • View (Presentation Layer)
    
    • Renders the Model
    • Requests Model updates
    • Sends User Events to the Controller
  • Controller (Interaction Layer)
    
    • Maps User Events to model updates
    • Selects View

Question 10

Architectural Patterns:

Layered Architecture

Answer 10

• Used to model the interfacing of multiple subsystems
• Organizes the system into a set of layers, each of which provide a set of services
• Supports incremental development of subsystem in different layers
• Upper layers depend on lower layers

Question 11

Architectural Patterns:

Repository Architecture

Answer 11

Represents a data repository that is shared by many subsystems

• Subsystems must exchange data in one of two ways:
  
  • Shared data is held in a central database or repository
  • Each subsystem maintains its own database and passes data explicitly to other subsystems
• When large amounts of data need to be shared, repository model is most commonly used

Question 12

Architectural Patterns:

Pipe and Filter Architecture

Answer 12

• Functional transformations:
  
  • Process Inputs
  • Produce Outputs
• Models a “Pipeline”
• Not really suitable for interactive systems
• Good when there is a well known “work flow”
• Early Components/Stages take in inputs and provide inputs into later Components/Stages
• Final Components/Stages produce outputs