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Reuse

Introduction

Can explain software reuse

Reuse is a major theme in software engineering practices. By reusing tried-and-tested components, the robustness of a new software system can be enhanced while reducing the manpower and time requirement. Reusable components come in many forms; it can be reusing a piece of code, a subsystem, or a whole software.

Can explain the costs and benefits of reuse

While you may be tempted to use many libraries/frameworks/platforms that seem to crop up on a regular basis and promise to bring great benefits, note that there are costs associated with reuse. Here are some:

The reused code may be an overkill (think using a sledgehammer to crack a nut), increasing the size of, and/or degrading the performance of, your software.
The reused software may not be mature/stable enough to be used in an important product. That means the software can change drastically and rapidly, possibly in ways that break your software.
Non-mature software has the risk of dying off as fast as they emerged, leaving you with a dependency that is no longer maintained.
The license of the reused software (or its dependencies) restrict how you can use/develop your software.
The reused software might have bugs, missing features, or security vulnerabilities that are important to your product, but not so important to the maintainers of that software, which means those flaws will not get fixed as fast as you need them to.
Malicious code can sneak into your product via compromised dependencies.

One of your teammates is proposing to use a recently-released “cool” UI framework for your class project. List the pros and cons of this idea.

Pros

The potential to create a much better product by reusing the framework.
Learning a new framework is good for future job prospects.

Cons

Learning curve may be steep.
May not be stable (as it was recently released).
May not allow you to do exactly what you want. While frameworks allow customization, such customization can be limited.
Performance penalties.
Might interfere with the learning objectives of the module.

Note that having more cons does not mean you should not use this framework. Further investigation is required before you can make a final decision.

APIs

Can explain APIs

An Application Programming Interface (API) specifies the interface through which other programs can interact with a software component. It is a contract between the component and its clients.

A class has an API (e.g., API of the Java String class, API of the Python str class) which is a collection of public methods that you can invoke to make use of the class.

The GitHub API is a collection of web request formats that the GitHub server accepts and their corresponding responses. You can write a program that interacts with GitHub through that API.

When developing large systems, if you define the API of each component early, the development team can develop the components in parallel because the future behavior of the other components are now more predictable.

Choose the correct statements.

a. A software component can have an API.
b. Any method of a class is part of its API.
c. Private methods of a class are not part of its API.
d. The API forms the contract between the component developer and the component user.
e. Sequence diagrams can be used to show how components interact with each other via APIs.

(a) (c) (d) (e)

Explanation: (b) is incorrect because private methods cannot be a part of the API.

Defining component APIs early is useful for developing components in parallel.

True
False

True

Explanation: Yes, once you know the precise behavior expected of each component, you can start developing them in parallel.

Reuse

Introduction

What

When

APIs

What