Software design is a process to transform user requirements into some suitable form, which helps the programmer in software coding and implementation. Software design may refer to either all the activity involved in conceptualizing, framing, implementing, commissioning, and ultimately modifying complex systems.
For assessing user requirements, an SRS (Software Requirement Specification) document is created whereas for coding and implementation, there is a need of more specific and detailed requirements in software terms.
Software design is the first step in SDLC (Software Design Life Cycle), which moves the concentration from problem domain to solution domain. It tries to specify how to fulfill the requirements mentioned in SRS.
Software Design Levels
- Architectural Design – The architectural design is the highest abstract version of the system. It identifies the software as a system with many components interacting with each other. At this level, the designers get the idea of proposed solution domain.
- High-level Design- The high-level design breaks the ‘single entity-multiple component’ concept of architectural design into less-abstracted view of sub-systems and modules and depicts their interaction with each other. High-level design focuses on how the system along with all of its components can be implemented in forms of modules. It recognizes modular structure of each sub-system and their relation and interaction among each other.
- Detailed Design- Detailed design deals with the implementation part of what is seen as a system and its sub-systems in the previous two designs. It is more detailed towards modules and their implementations. It defines logical structure of each module and their interfaces to communicate with other modules.
Is a technique to divide a software system into multiple discrete and independent modules, which are expected to be capable of carrying out task(s) independently.
Is implemented by splitting the software into multiple independent units of execution, like modules and executing them in parallel. In other words, concurrency provides capability to the software to execute more than one part of code in parallel to each other.
Coupling and Cohesion
When a software program is modularized, its tasks are divided into several modules based on some characteristics. Modules are set of instructions put together in order to achieve some tasks. There are measures by which the quality of a design of modules and their interaction among them can be measured. So this measures are the Coupling and Cohesion.
Is a measure that defines the degree of intra-dependability within elements of a module. The greater the cohesion, the better is the program design. it have differents types that are: Co-incidental cohesion, Logical cohesion, Temporal Cohesion, Procedural cohesion, Communicational cohesion, Sequential cohesion and Functional cohesion.
is a measure that defines the level of inter-dependability among modules of a program. It tells at what level the modules interfere and interact with each other. The lower the coupling, the better the program. it has five types: Content coupling, Common coupling, Control coupling, Stamp coupling and Data coupling.
The output of software design process is design documentation, pseudo codes, detailed logic diagrams, process diagrams, and detailed description of all functional or non-functional requirements. The next phase, which is the implementation of software, depends on all outputs mentioned above.