Overview#Software design is design of an Application and is typically part of the Software Development Life Cycle
Software design Concepts#The design concepts provide the software designer with a foundation from which more sophisticated methods can be applied. A set of fundamental design concepts has evolved. They are as follows:
- Abstraction - Abstraction is the process or result of generalization by reducing the information content of a concept or an observable phenomenon, typically in order to retain only information which is relevant for a particular purpose.It is an act of Representing essential features without including the background details or explanations.
- Refinement - It is the process of elaboration. A hierarchy is developed by decomposing a macroscopic statement of function in a step-wise fashion until programming language statements are reached. In each step, one or several instructions of a given program are decomposed into more detailed instructions. Abstraction and Refinement are complementary concepts.
- Modularity - Software architecture is divided into components called Software libraries or modules.
- Software Architecture - It refers to the overall structure of the software and the ways in which that structure provides conceptual integrity for a system. Good software architecture will yield a good return on investment with respect to the desired outcome of the project, e.g. in terms of performance, quality, schedule and cost.
- Control Hierarchy - A program structure that represents the organization of a program component and implies a hierarchy of control.
- Structural Partitioning - The program structure can be divided into both horizontally and vertically. Horizontal partitions define separate branches of modular hierarchy for each major program area of operation. Vertical partitioning suggests that control and work should be distributed top down in the program structure.
- Data Structure - It is a representation of the logical relationship among individual elements of data.
- Software Procedure - It focuses on the processing of each module individually.
- Information Hiding - Modules should be specified and designed so that information contained within a module is inaccessible to other modules that have no need for such information.
In his object model, Grady Booch mentions Abstraction, Encapsulation, Modularisation, and Hierarchy as fundamental software design principles. The acronym PHAME (Principles of Hierarchy, Abstraction, Modularisation, and Encapsulation) is sometimes used to refer to these four fundamental principles
Software design Requirements#Each application has two categories of requirements.
- Functional Requirements - The functional requirements, are what the Software design must do. They are usually in the form of Use cases or User Story. Architecture has little to do with the functional requirements. You can implement functional requirements with almost any architecture, even a big ball of mud.
- Non-functional requirements - Architecture is important because it enables an application to satisfy the define the Non-functional requirements such as runtime qualities such as scalability, and reliability.