Software requirements for a messaging service: what’s the purpose and how to write

6 min read

What is software requirements?

The description of functional capabilities and limitations imposed on a software system is called the requirements for this system, and the process of building, analyzing, documenting and verifying these functional capabilities and limitations is called requirements engineering.

The term software requirements can be interpreted differently. In some cases, the requirements are understood as high-level generalized statements about the functionality and limitations of the system. Another extreme situation is a detailed mathematical formal description of system functions.

Requirements for the software should be sufficiently specified that it would be possible to create code based on them. Therefore, they must be "verifiable", i.e. specific enough to be able to check whether the system actually implements a certain specified requirement.

Functional software requirements describe how the system behaves. These requirements are usually action-oriented and contain formulations like: "When the user does X, the system will do Y". Most products and applications designed to do useful work contain many functional software requirements. The software is used to implement most of the functionality.

When defining functional requirements for software, one should look for a middle ground between too specific wording of the requirement and too general and ambiguous. For example, as a rule, it is not necessary to have a generalized functional requirement of the following form: "When the user presses the “Start” button, the system launches and starts working.” On the other hand, the wording of the requirement, which consists of several pages of text, seems to be too specific, although it may be legitimate in some particular cases. Experience shows that the definition of a requirement consisting of one or two sentences is usually best when it is necessary to correlate the user's need with the level of concretization acceptable for the work of the development team.

Specifying software requirements for messaging service

In general, the rules for writing requirements for a messaging service will be just a special case of writing requirements for any software system. Consider them in more detail.

First you need to decide what kind of messaging application you would like to receive. There are quite a few quality messengers on the market, so you need to decide not only on the basic functionality, but also on how your messaging service will stand out from a number of similar ones. As soon as you prepare a list of problems that your application will solve, you can begin writing functional requirements. The resulting document should contain the most complete information about all the functions of the developing software. It will become a source of necessary information for all members of the development company team. In this case, you can be sure that your product will not lose any necessary functions and will not provide unnecessary ones.

In order to start writing high-level requirements, you need to give a rough estimate. Brainstorming is usually used for this. It is most convenient to present this part of the requirements as a mind map. It is based on the main idea of the product, such as an “instant messaging application”. Further, it divides into sub-themes, each of which represents one of the functionalities of the application. Mind maps makes sense to write in short and simple words to take into account all the ideas and focus on them. Then they will become a convenient tool that clearly demonstrates the relationship between the functions of the product.

User stories as an instrument of writing proper software requirements

When the mind map is prepared, you can go to the description of the details. Here you can use a tool such as user stories, which will describe how exactly the functions of the application will be used from the user's point of view.

Each user story should describe in simple and understandable words one user interaction with the program. It should show what the user wants to do in this situation, and why. Thus, the entire functionality of the program should be described.

Speaking about the functionality of the messaging application, it is worth mentioning such key elements as registration, adding contacts, creating conversations and group chats, the ability to make calls in voice or video format. They should start to be described in the form of simple actions - user stories. For example, when describing the registration functionality, you should describe in the form of user stories such moments as user interaction with the registration form, linking the created account to the user's phone number, activating the account via SMS or e-mail, etc.

Why it is necessary to write detailed requirements before starting the development

These examples describe far from all the necessary functionality, but from them it is already possible to get an idea of how many details should be taken into account, and why it would not be enough to simply indicate the “registration function” in requirements - it will not give any sufficient information for estimating. If you want to implement a truly innovative idea, you need to pay maximum attention to a detailed description of the software requirements so that you can be sure that the development team and you understand well each other and are really working on the product you want. In addition, the carefully described software requirements will enable developers to make the most accurate assessment of the resources required for development, thereby avoiding unanticipated budget increases, as well as violation of the product’s time-to-market deadlines.

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