Software Engineering - Old Questions

Architectural design is a process for identifying the sub-systems making up a system and the framework for sub-system control and communication. The output of this design process is a description of the software architecture. Architectural design is an early stage of the system design process. It represents the link between specification and design processes and is often carried out in parallel with some specification activities. It involves identifying major system components and their communications.

Repository Model

A repository model is a system that will allow interfacing sub-systems to share the same data. Sub-system must exchange data so that they can work together effectively. This may be done in two ways:

1. All shared data is held in a central database that can be accessed by all subsystems. It is called repository model.

2. Each sub-system maintains its own database. Data is interchanged with other sub-systems by passing messages to them.

Example: CASE Toolset

Advantages:

• It is an efficient way to share large amounts of data. There is no need to transmit data explicitly from one sub-system to another.
• Sub-systems that produce data need not be concerned with how that data is used by other subsystems.
• Activities such as backup, security, access control and recovery from error are centralized.

Disadvantages:

• It is a compromise between the specific needs of each tool. Performance may be adversely affected by this compromise.
• Evolution may be difficult as a large volume of information is generated according to an agreed data model.
• Different sub-systems may have different requirements for security, recovery and backup policies. The repository model forces the same policy on all subsystems.