What is software design?
It is the process by which an agent creates a specification of a software artifact, intended to accomplish goals, using a set of primitive components and subject to constraints.
Software design may refer to either “all the activity involved in conceptualizing, framing, implementing, commissioning, and ultimately modifying complex systems” or “the activity following requirements specification and before programming, as a stylized software engineering process.”
Software design usually involves problem solving and planning a software solution. This includes both a low-level component and algorithm design and a high-level, architecture design.
There are several basic design principles that enable the software engineer to navigate the design process:
- The design process should not suffer from “tunnel vision.” A good designer should consider alternative approaches, judging each based on the requirements of the problem, the resources available to do the job.
- The design should be traceable to the analysis model. Because a single element of the design model can often be traced back to multiple requirements, it is necessary to have a means for tracking how requirements have been satisfied by the design model.
- The design should not reinvent the wheel. Systems are constructed using a set of design patterns, many of which have likely been encountered before. These patterns should always be chosen as an alternative to reinvention. Time is short and resources are limited; design time should be invested in representing truly new ideas and integrating patterns that already exist when applicable.
- The design should “minimize the intellectual distance” between the software and the problem as it exists in the real world. That is, the structure of the software design should, whenever possible, mimic the structure of the problem domain.
- The design should exhibit uniformity and integration. A design is uniform if it appears fully coherent.
order to achieve this outcome, rules of style and format should be defined for a design team before design work begins. A design is integrated if care is taken in defining interfaces between design components.
- The design should be structured to accommodate change. The design concepts discussed in the next section enable a design to achieve this principle.
- The design should be structured to degrade gently, even when aberrant data, events, or operating conditions are encountered. Well- designed software should never “bomb”; it should be designed to accommodate unusual circumstances, and if it must terminate processing, it should do so in a graceful manner.
- Design is not coding, coding is not design. Even when detailed procedural designs are created for program components, the level of abstraction of the design model is higher than the source code. The only design decisions made at the coding level should address the small implementation details that enable the procedural design to be coded.
- The design should be assessed for quality as it is being created, not after the fact. A variety of design concepts and design measures are available to assist the designer in assessing quality throughout the development process.
- The design should be reviewed to minimize conceptual (semantic) errors. There is sometimes a tendency to focus on minutiae when the design is reviewed, missing the forest for the trees. A design team should ensure that major conceptual elements of the design (omissions, ambiguity, inconsistency) have been addressed before worrying about the syntax of the design model.
TIME FOR A BREAK
Things to consider when software designing
There are many aspects to consider in the design of a piece of software. The importance of each consideration should reflect the goals and expectations that the software is being created to meet. Some of these aspects are:
- Compatibility – The software is able to operate with other products that are designed for interoperability with another product. For example, a piece of software may be backward-compatible with an older version of itself.
- Extensibility – New capabilities can be added to the software without major changes to the underlying architecture.
- Modularity – the resulting software comprises well defined, independent components which leads to better maintainability. The components could be then implemented and tested in isolation before being integrated to form a desired software system. This allows division of work in a software development project.
- Fault-tolerance – The software is resistant to and able to recover from component failure.
- Maintainability – A measure of how easily bug fixes or functional modifications can be accomplished. High maintainability can be the product of modularity and extensibility.
- Reliability (Software durability) – The software is able to perform a required function under stated conditions for a specified period of time.
- Reusability – The ability to use some or all of the aspects of the pre existing software in other projects with little to no modification.
- Robustness – The software is able to operate under stress or tolerate unpredictable or invalid input. For example, it can be designed with a resilience to low memory conditions.
- Security – The software is able to withstand and resist hostile acts and influences.
- Usability – The software user interface must be usable for its target user/audience. Default values for the parameters must be chosen so that they are a good choice for the majority of the users.
- Performance – The software performs its tasks within a time-frame that is acceptable for the user, and does not require too much memory.
- Portability – The software should be usable across a number of different conditions and environments.
- Scalability – The software adapts well to increasing data or number of users.
We will extend this topic in another blog I will be uploading soon, so be patient and enjoy life.
Source: https://en.wikipedia.org/wiki/Software_design
