What Is a Software Design Document (SDD)?

FAQ on Technical Writing

A software design document (SDD) is a detailed plan of how to develop a piece of software. It contains information on a product’s functionality and a team’s goals.

Why do we need an SDD when working on a piece of software? Why do we have to outline what and how we should do instead of using our inspiration to see where it can get us? If we have no plan, we will hardly get from point A to point B, as creating a software product is a complex process. We don’t want to waste time and money. Using a software design document gives the following advantages:

• Saves time. Your team can define the scope of work and get organized right at the very beginning. It is hard, but it can save you from choosing the wrong way. No one likes unnecessary work.
• Efficient collaboration. An SDD is a basic document for almost all teams. When all teams refer to the same document, they move in the same direction. That is vital when we talk about coordination in a company in general.
• Transparency of processes. When all the processes and aims are described, there should be no misunderstanding within a team and between you and external teams or stakeholders. So, an SDD contributes to efficient communication as well.

Here is what a software design document should contain:

• Title, name, date, authors, reviewers.
• Overview of functions: how your software works and what features it has.
• Software design considerations: assumptions, dependencies, general constraints, guidelines, goals, methods.
• User interface design: how users interact with your software.
• System architecture: overall structure, relations of components in the system.
• Testing and monitoring: failure conditions, expert testing, etc.
• Glossary.
• Style guide, best practices, etc.

Here are some tips on how to create an efficient SDD:

1. Make sure the whole team is involved in writing an SDD. You’ll be able to establish the main processes at the early stages. You can collect feedback from all the participants promptly.
2. Include visuals. If your document has text only, it is difficult to read it. Diagrams, charts, screenshots, or even screencasts make the information vivid.
3. Use clear language. That is vital. Ideally, a technical writer should work on an SDD. In case there is no tech writer in your team, pay attention to how you write: no ambiguity, clear sentences, the right amount of terms. If everyone can understand your document, it was written perfectly.
4. Keep in mind your final goal. Your SDD should clearly show it though it should contain a lot of additional information. Don’t lose it.
5. Update your SDD. This document should always contain relevant information, as team members often refer to it. The project may change, it should be reflected in SDD.

So, an SDD is a crucial document in software development. Most developers don’t like to deal with writing texts and working on documentation, they prefer to dive into coding. But documentation like that is a must as it streamlines all the processes and answers the question HOW.

How did I become a technical writer? What skills do you need? Read FAQ on Technical Writing.