Chapter 6 Flashcards
Architectural Design
What is Architectural Design?
Add some specifics.
The design process for identifying the sub-systems making up a system and the framework for sub-system control and communication is architectural design.
An early stage of the system design process.
Represents the link between specification and design processes.
Often carried out in parallel with some specification activities.
It involves identifying major system components and their communications.
What is Software Architecture?
The output of this design process is a description of the software architecture.
Talk about Architectural Abstraction
Architecture in the small:
▪ is concerned with the architecture of individual programs.
▪ is concerned with the way that an individual program is decomposed into components.
Architecture in the large:
▪ is concerned with the architecture of complex enterprise systems that include other systems, programs, and program components.
▪ these enterprise systems are distributed over different computers, which may be owned and managed by different companies.
What are the advantages of explicit architecture?
Stakeholder communication
▪ Architecture may be used as a focus of discussion by system stakeholders.
System analysis
▪ Analysis of whether the system can meet its non-functional requirements is possible.
Large-scale reuse
▪ The architecture may be reusable across a range of systems.
Talk about Architectural Representations.
Simple, informal block diagrams showing entities and relationships are the most frequently used method for documenting software architectures.
But these have been criticized because they lack semantics, do not show the types of relationships between entities nor the visible properties of entities in the architecture.
Depends on the use of architectural models. The requirements for model semantics depends on how the models are used.
Talk about Box and Line diagrams.
Very abstract - they do not show the nature of component relationships nor the externally visible properties of the sub-systems.
However, useful for communication with stakeholders and for project planning.
Talk about the use of architectural models.
As a way of facilitating discussion about the system design
▪ A high-level architectural view of a system is useful for communication with system stakeholders and project planning because it is not cluttered with detail. Stakeholders can relate to it and understand an abstract view of the system. They can then discuss the system as a whole without being confused by detail.
As a way of documenting an architecture that has been designed
▪ The aim here is to produce a complete system model that shows the different components in a system, their interfaces and their connections.
What are the architectural design decisions?
Is there a generic application architecture that can be used?
How will the system be distributed?
What architectural styles are appropriate?
What approach will be used to structure the system?
How will the system be decomposed into modules?
What control strategy should be used?
How will the architectural design be evaluated?
How should the architecture be documented?
What is 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 of more architectural patterns or ‘styles’.
Talk about architecture and system characteristics
Performance
▪ Localize critical operations and minimize communications. Use large rather than fine-grain components.
Security
▪ Use a layered architecture with critical assets in the inner layers.
Safety
▪ Localize safety-critical features in a small number of sub-systems.
Availability
▪ Include redundant components and mechanisms for fault tolerance.
Maintainability
▪ Use fine-grain, replaceable components.
Talk about Architectural Views (4+1 model).
A logical view, which shows the key abstractions in the system as objects or object classes.
A process view, which shows how, at run time, the system is composed of interacting processes.
A development view, which shows how the software is decomposed for development.
A physical view, which shows the system hardware and how software components are distributed across the processors in the system.
Related using use cases or scenarios (+1)
Talk about Architectural Patterns.
Patterns are a means of representing, sharing and reusing knowledge.
An architectural pattern is a stylized description of good design practice, which has been tried and tested in different environments.
Patterns should include information about when they are and when the are not useful.
Patterns may be represented using tabular and graphical descriptions.
Talk about Layered Architecture.
Used to model the interfacing of sub-systems.
Organizes the system into a set of layers (or abstract machines) each of which provide a set of services.
Supports the incremental development of sub-systems in different layers. When a layer interface changes, only the adjacent layer is affected.
Talk about Repository Architecture.
Sub-systems must exchange data. This may be done in two ways:
▪ Shared data is held in a central database or repository and may be accessed by all sub-systems;
▪ 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 a this is an efficient data sharing mechanism.
Talk about Client-Server Architecture.
Distributed system model which shows how data and processing is distributed across a range of components.
Can be implemented on a single computer.
Set of stand-alone servers which provide specific services such as printing, data management, etc.
Set of clients which call on these services.
Network which allows clients to access servers.
