Architectural Design Lecture 11 Chapter 6

Study Notes

Architectural Design

Architectural Design is the process of identifying the sub-systems making up a system and the framework for sub-system control and communication.
It is an early stage of the system design process, representing the link between specification and design processes.
It involves identifying major system components and their communications.

Architecture and System Characteristics

Performance can be achieved by localizing critical operations and minimizing communications, using large rather than fine-grain components, and using a layered architecture with critical assets in the inner layers.
Security can be achieved by localizing critical operations and minimizing communications.
Safety can be achieved by localizing safety-critical features in a small number of sub-systems.
Availability can be achieved by including redundant components and mechanisms for fault tolerance.
Maintainability can be achieved by using fine-grain, replaceable components.

Architectural Conflicts

Using large-grain components improves performance but reduces maintainability.
Introducing redundant data improves availability but makes security more difficult.
Localizing safety-related features usually means more communication so degraded performance.

Box and Line Diagrams

They are very abstract and do not show the nature of component relationships nor the externally visible properties of the sub-systems.
They are useful for communication with stakeholders and for project planning.

Architecture Reuse

Systems in the same domain often have similar architectures that reflect domain concepts.
Application product lines are built around a core architecture with variants that satisfy particular customer requirements.
The architecture of a system may be designed around one or more architectural patterns or ‘styles’.

Layered Architecture

It is used to model the interfacing of sub-systems.
It organizes the system into a set of layers (or abstract machines) each of which provide a set of services.
It supports the incremental development of sub-systems in different layers.
When a layer interface changes, only the adjacent layer is affected.

Repository Architecture

Sub-systems must exchange data, which can be done in two ways: shared data is held in a central database or repository and may be accessed by all sub-systems, or each sub-system maintains its own database and passes data explicitly to other sub-systems.
When large amounts of data are to be shared, the repository model of sharing is most commonly used as it is an efficient data sharing mechanism.

Client-Server Architecture

It is a distributed system model that shows how data and processing is distributed across a range of components.
It can be implemented on a single computer.
It consists of a set of stand-alone servers which provide specific services, and a set of clients which call on these services.
It also consists of a network which allows clients to access servers.

Description

Test your understanding of architectural design, its process, and its relation to software architecture. Learn about the early stages of system design and how it links specification and design processes.