How do you decide which software components are necessary?

1 Software components

A software component is a unit of software that has a well-defined interface and can be reused, replaced, or composed with other components. Examples of software components are classes, modules, libraries, frameworks, services, and microservices. Software components can vary in size, complexity, and granularity, depending on the design goals and constraints of the system.

2 Design principles

Design principles are general guidelines that can help you create software components that are cohesive, decoupled, modular, and reusable. The single responsibility principle suggests that a component should have one and only one reason to change. Additionally, the open-closed principle states that a component should be open for extension but closed for modification. The Liskov substitution principle states that a component should be substitutable by any of its subtypes without breaking the system. Furthermore, the interface segregation principle suggests that a component should not depend on interfaces that it does not use. Finally, the dependency inversion principle implies that a component should depend on abstractions rather than concretions.

3 Design methods

Design methods are systematic approaches that can assist in identifying, analyzing, and decomposing the software components of a system. Common design methods include use cases, which can help define the functional requirements and the interactions of the system; domain-driven design, which models the software components based on domain knowledge and business logic; component-based design, which designs the software components as independent and interchangeable units; and service-oriented design, which designs the software components as services that provide specific functionality and communicate via standard protocols and contracts.

4 Design trade-offs

Design trade-offs are the compromises that you have to make when choosing the software components of a system. There is no one-size-fits-all solution for software design, and different components may have different advantages and disadvantages in terms of performance, scalability, reliability, security, testability, maintainability, and usability. When making design trade-offs, you must consider the requirements which specify the functional and non-functional expectations of the system; the constraints which limit the choices and possibilities of the system; and the context which defines the situation and environment of the system. This includes balancing the needs and preferences of stakeholders, users, and developers; taking into account technical, financial, legal, ethical, and environmental constraints; and adapting to changes in the market, competition, regulations, and technology.

5 Design feedback

Design feedback is an important process for evaluating and improving the software components of a system. To get feedback on your design, you can use reviews, prototypes, and metrics. Reviews involve presenting and discussing your design with other developers, experts, or stakeholders to identify errors, inconsistencies, gaps, or improvements. Prototypes are simplified or partial versions of the system that can be built and tested quickly to validate assumptions and test ideas. Metrics are quantitative or qualitative measures that can help you monitor, compare, and optimize your design.

6 Here’s what else to consider

This is a space to share examples, stories, or insights that don’t fit into any of the previous sections. What else would you like to add?