Software design deals with transforming the customer requirements, as described in the SRS document, into a form (a set of documents) that is suitable for implementation in a programming language. A good software design is seldom arrived by using a single step procedure but rather through several iterations through a series of steps.
Design activities can be broadly classified into two important parts:
• Preliminary (or high-level) design and
• Detailed design.
preliminary design:
High-level design means identification of different modules and the control relationships among them and the definition of the interfaces among these modules. The outcome of high-level design is called the program structure or software architecture. Many different types of notations have been used to represent a high-level design. A popular way is to use a tree-like diagram called the structure chart to represent the control hierarchy in a high-level design.
Detailed design:
During detailed design, the data structure and the algorithms of the different modules are designed. The outcome of the detailed design stage is usually known as the module-specification document.
Difference between analysis and design:
The aim of analysis is to understand the problem with a view to eliminate any deficiencies in the requirement specification such as incompleteness, inconsistencies, etc. The model which we are trying to build may be or may not be ready.
The aim of design is to produce a model that will provide a seamless transition to the coding phase, i.e. once the requirements are analyzed and found to be satisfactory, a design model is created which can be easily implemented.
Items developed during the software design phase:
For a design to be easily implemented in a conventional programming language, the following items must be designed during the design phase.
• Different modules required to implement the design solution.
• Control relationship among the identified modules. The relationship is also known as the call relationship or invocation relationship among modules.
• Interface among different modules. The interface among different modules identifies the exact data items exchanged among the modules.
• Data structures of the individual modules.
• Algorithms required to implement each individual module.
Characteristics of a good software design:
• Correctness: A good design should correctly implement all the functionalities identified in the SRS document.
• Understandability: A good design is easily understandable.
• Efficiency: It should be efficient.
• Maintainability: It should be easily amenable to change.
Features of a design document:
• It should use consistent and meaningful names for various design components.
• The design should be modular. The term modularity means that it should use a cleanly decomposed set of modules.
• It should neatly arrange the modules in a hierarchy, e.g. in a tree-like diagram.
Design activities can be broadly classified into two important parts:
• Preliminary (or high-level) design and
• Detailed design.
preliminary design:
High-level design means identification of different modules and the control relationships among them and the definition of the interfaces among these modules. The outcome of high-level design is called the program structure or software architecture. Many different types of notations have been used to represent a high-level design. A popular way is to use a tree-like diagram called the structure chart to represent the control hierarchy in a high-level design.
Detailed design:
During detailed design, the data structure and the algorithms of the different modules are designed. The outcome of the detailed design stage is usually known as the module-specification document.
Difference between analysis and design:
The aim of analysis is to understand the problem with a view to eliminate any deficiencies in the requirement specification such as incompleteness, inconsistencies, etc. The model which we are trying to build may be or may not be ready.
The aim of design is to produce a model that will provide a seamless transition to the coding phase, i.e. once the requirements are analyzed and found to be satisfactory, a design model is created which can be easily implemented.
Items developed during the software design phase:
For a design to be easily implemented in a conventional programming language, the following items must be designed during the design phase.
• Different modules required to implement the design solution.
• Control relationship among the identified modules. The relationship is also known as the call relationship or invocation relationship among modules.
• Interface among different modules. The interface among different modules identifies the exact data items exchanged among the modules.
• Data structures of the individual modules.
• Algorithms required to implement each individual module.
Characteristics of a good software design:
• Correctness: A good design should correctly implement all the functionalities identified in the SRS document.
• Understandability: A good design is easily understandable.
• Efficiency: It should be efficient.
• Maintainability: It should be easily amenable to change.
Features of a design document:
• It should use consistent and meaningful names for various design components.
• The design should be modular. The term modularity means that it should use a cleanly decomposed set of modules.
• It should neatly arrange the modules in a hierarchy, e.g. in a tree-like diagram.
Software design and its types