Best Software Design Document Templates

Software Design Document Templates

Aran Davies is a full-stack software development engineer and tech writer with experience in Web and Mobile technologies. He is a tech nomad and has seen it all.

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Are you interested in good software design document templates? What parts of the process take significant time when undertaking a software development project? Activities such as gathering the requirements, planning the project, and designing the specifications are good examples. The good news is that you can utilize templates to help speed up these activities and write software documentation efficiently. What is a Software Design Document Template? Software Design Document Template (SDD) or Software Design Specification is a detailed guide created by software designers, engineers, project managers, or product owners to instruct software developers and development teams on what should be built and how specific features must be coded. In other words, it is a detailed plan for a future software project or project summary.

In this article

  1. A brief introduction to a software design document
  2. Software design document contents
  3. Key considerations while creating a system design document
  4. An example of software design document template
  5. Software design document aspects where you need to provide plenty of details
  6. FAQs on software design document templates

In this article, we talk about using software design document templates. If you are an entrepreneur or a software development project manager in an enterprise, these software design document templates will help you.

We start by briefly talking about software design description. We then move on to the best practices to create such design documents. Finally, we finish by providing a template for a software specification document.

A brief introduction to a software design document

Among the most important deliverables in a software development project is the software design document. Your project’s success depends on getting this right. Just to be crystal clear — your project will encounter huge problems, even if you have great developers, if you don’t get this right.

A software design document (SDD) spells out what your development team will code. It provides a detailed description of the technical solution behind your project. Irrespective of the development methodology used, you need to create an SDD early in the software development lifecycle (SDLC).

Your work to create an SDD starts when you have the software business requirements document. This document contains the functional requirements and the non-functional requirements (NFRs).

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The software architect in your project creates an SDD. This task requires close collaboration with the following roles:

Software architects need to collaborate with infrastructure, cloud architects, and information security specialists too.

Software design document contents

What should you write in a software design specification? You need to provide the following information:

Remember that you are addressing the needs of a wide range of stakeholders when you create an SDD. Developers, software designers, testers, DevOps engineers, reviewers, and project managers (PM) will all use this document frequently.

You need to create as detailed an SDD as you can. Use effective tools like Microsoft Word, Excel, Visio, etc. to communicate key information.

Key considerations while creating a system design document

Other than the considerations above, when creating a software design document you also need to keep the following key considerations in mind:

An example of software design document template

We will now take you through a useful SDD template. Bradford D. Appleton, the well-known enterprise Agile and DevOps coach has created this helpful SDD template. Several universities utilize this software design template as a part of their software development-related courses.

During this review, we talk about how you create an SDD using this template. The SDD template created by Appleton has the following sections and subsections:

1. Introduction to the SDD including the system overview

You need to provide a general introduction to your project. Talk about the organizational objectives, however, don’t repeat the content of the requirements document.

We don’t recommend you repeat the use cases and user stories in the SDD. Refer to the requirements document but only provide a brief summary of it here.

Talk about the target audience of your SDD. Explain the version-control and distribution mechanisms.

2. Software design considerations including metrics and the user interface design

In this section and associated subsections, you need to explain the specific considerations you factored in while creating the SDD. Touch upon the following aspects:

3. Decisions that you had to make while choosing the system architecture pattern

This section covers the very first set of decisions that you will make after you receive the software functional description. Architectural decisions influence the architectural pattern you choose. You make these decisions to address not only the functional requirements but NFRs too.

E.g., your architectural decisions influence the following:

Take a software system with multiple services, for example. Can you separate these services from each other completely? Do they have different peaks and troughs in their demand profile? If you answer affirmatively to these questions, then you can consider the microservices architecture.

4. Details concerning the chosen system architecture pattern

You have explained the project’s architectural decisions in the preceding section. Now, you need to choose an architecture pattern. This is a very important step when you create a technical solution, therefore, you need to get this right.

Large application systems might have several subsystems. You need to explain the architecture patterns for those too.

Remember that this section of the SDD carries plenty of importance. Not just the software development team, but testers and DevOps engineers study this section closely. You need to make this section as clear as you can. Schematic diagrams can help.

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We recommend you include relevant architectural diagrams, and these should cover the external interfaces.

There are several popular architecture patterns, e.g.:

Explain your decisions on why you choose a particular architecture pattern. For strategic software development projects, external software quality auditors might review the SDD. They look for the rationale behind architectural decisions. A well-documented SDD will help you in such cases.

5. Explanations for the design-related choices

While some software development projects can be straightforward, other projects involve complexities. You will face several choices. You need to contend with trade-offs. Design-related decisions and choices are often functions of these trade-offs.

You need to explain your choices and trade-offs. These could involve one or more of the following:

You might have many more choices and trade-offs, and the above list is an example only.

6. Detailed system design

In this section, you cover the details at a program or module level. The development team and testers pay plenty of attention to this section, especially software developers who consider this section very important.

Accordingly, you need to provide sufficient details here for everyone who needs them. Avoid jargon and acronyms. Talk about the following aspects:

If you have several subsystems that make up the proposed system, then you need to provide a detailed design for each subsystem.

Software design document aspects where you need to provide plenty of details

By now, you can see that a software design document requires a lot of details. A few aspects require special attention though.

A software development project always requires a lot of close collaboration, therefore, team members will always share a few details informally. That’s both normal and desirable.

However, this informal approach will simply not work in all cases so you need to provide details upfront. Without that, you can’t consider an SDD complete.

We now talk about these aspects, which are as follows:

1. Capabilities involving cutting-edge technologies

You might choose to offer advanced capabilities in your application, which requires cutting-edge technologies. E.g., you might use Artificial Intelligence (AI) or Machine Learning (ML).

In addition to the standard details in an SDD, you need to explain the technical solutions around these technologies in great detail. E.g., you might need to develop ML algorithms to meet your requirements. Talk about them in detail.

Cutting-edge technologies like ML and blockchain require you to hire a software engineer with niche skills. Naturally, you will want the best value from their effort. An SDD with sufficient details will help developers to become productive far more quickly.

2. Application Security

Security is a key non-functional requirement (NFR), therefore, you might have already talked about it in your SDD. It’s a vast area though. You need to provide sufficient details about your application security solutions.

Talk about the following:

3. Data models and database design

When you create an SDD, you need to talk about the data models and database design in detail. You need to work closely with the database administrator (DBA) in your organization.

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Your development team, testers, and DBA will use the information concerning data models and database design. Cover the following aspects:

4. Your approach to cloud computing

You might use a cloud computing platform in your project. There are different kinds of cloud platforms, which are as follows:

Your project requirements will determine which type of cloud platform you will use. Explain your choice and decision-making process in the SDD.

You might also need to choose a cloud computing delivery model. The various models are as follows:

Your decision-making process will depend on your project requirements, information security considerations, and regulatory requirements. Explain your choice and the decision-making process in your SDD.

5. API development

You might use APIs in various ways in your proposed system. In some cases, you might choose to use an external API. It might make sense if you find a well-established provider. Remember that you will add an external dependency for every external API that you use. This could adversely impact the performance of your system, therefore, think through this carefully.

You will likely create your APIs to reflect your core business capabilities. Describe your API development plans in the SDD. Talk about how you would secure the API, furthermore, plan the API endpoint carefully. Formulate the rules for API requests and responses.

Ready to Get Started with Software Design Document Templates?

In this article, we have covered software design documents or technical specification documents. We discussed their importance and what should go into them. Subsequently, we reviewed some key considerations while creating an SDD.

We reviewed a useful software design documentation template. Finally, we highlighted the aspects where you need to provide sufficient details.

If you, as a business CEO or CTO, require help with software product design and development, DevTeam.Space can help you via its expert software developers community.

Write to us your initial project specifications and one of our account managers will get back to you for further assistance.

FAQs on software design document templates

1. How important is it to use the right template to create a software design document?

You need to use an appropriate template to create an SDD. An SDD is a very important input to a software developer. It needs to cover all key information, and this is where the right software design document templates come into play. Great software design document templates serve as reminders so that you provide information on all key aspects.

2. Is a software design document the same as a high-level design?

A software design document should include high-level design as well as low-level design of a software system. By itself, an SDD isn’t the same as a high-level design (HLD) document. Instead, HLD is a subset of SDD. An SDD carries much more information than an HLD does.

3. Is the software architecture section important in a software design document template?

The software architecture section is indeed very important in a software design document. A software engineer needs to know which architecture pattern is chosen for a proposed system. The development team uses an SDD as input to the software development process, and it should contain information about the architecture of the proposed solution.

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