Architectural Design

Question 1

Architectural Design

Answer 1

Identifying sub-systems making up a system and the framework for sub-system control and communication.
Should be an early stage of the system design process, representing links between specification and design process.

Question 2

Three Aspects of Architectural Design

Answer 2

System structuring
Control modelling
Modular decomposition

Question 3

System Structuring

Answer 3

Decomposed into several principal sub-systems, and communications between these sub-systems are identified.

Question 4

Control Modelling

Answer 4

A model of the control relationships between the different parts of the system is established (essentially, states overall charge).

Question 5

Modular Decomposition

Answer 5

Identified sub-systems are decomposed into modules.

Question 6

Modules

Answer 6

System components that provides services to other components, like a class.

Question 7

Benefit of sub-system modelling

Answer 7

Can build a new system with these sub-systems if well-defined.

Question 8

Types of design process models

Answer 8

• static structural model
• dynamic process model
• relationships model

Question 9

Static Structural Model

Answer 9

Shows major system components.

Question 10

Dynamic Process Model

Answer 10

Shows the process structure of the system.

Question 11

Relationships Model

Answer 11

Defines sub-system interfaces.

Question 12

System Architecture Representation

Answer 12

System architecture is normally represents as a block diagram presenting an overview of the system structure.

Question 13

Sub-system data exchange

Answer 13

The exchange of data is done by either:
- central databases or repositories which can be accessed by all systems (repository models).
- sub-systems maintain their own databases and pass data explicitly.

Question 14

Client-server Architecture

Answer 14

Type of distributed system model which shows how data and processing is distributed across a range of components.

Question 15

Client-server Architecture attributes

Answer 15

• stand-alone servers
• clients (computers etc)
• network which allows clients to access servers
• can sometimes contain cache/local servers for frequently used data

Question 16

Client-server advantages and disadvantages

Answer 16

Easy distribution of data.
Easy to add new servers and clients.

Sub-systems use different data organisation, therefore leading to confusion.
No central register of names and services, therefore we are unable to know which servers are available.

Question 17

Control Models

Answer 17

Concerned with the control flow between sub-systems, and can be represented one of two ways:
- centralised control
- event-based control

Question 18

Centralised Control

Answer 18

One sub-system has overall responsibility for control, which is a control sub-system. Two example models include:
- Call-return Model
- Manager Model

Question 19

Event-Based Control

Answer 19

Each sub-system can respond to externally generated events, with timing of the event being out of control of the sub-systems which process the event.
Models include:
- Broadcast model
- Interrupt-driven models.

Question 20

Model Decomposition

Answer 20

Another structural level where sub-systems are decomposed into module, with two being covered:
- Object model
- Data-flow model

Question 21

Object Model

Answer 21

Decomposed into interacting objects, and is concerned with identifying object classes, attributes and operations.

Question 22

Data-flow Model

Answer 22

Decomposed into functional modules which transform inputs to outputs. May be referenced as a pipe and filter model (UNIX).