A software requirement specification (SRS) includes information about all the functional and non-functional requirements for a given piece of software. The SRS serves as the main point of reference for the software development team who’ll build the software product, as well as for all other involved stakeholders.
What Are the Components of a Software Requirement Specification (SRS)?
- Product Description
- Software Requirements
- External Interface Requirements
- Non-Functional Requirements
Do We Need Software Requirement Specification?
Yes because an SRS acts as the single source of truth for the lifecycle of the software. The SRS will contain information about all the software components that make up the product or deliverable. The SRS describes those components in detail so the reader can understand what the software does functionally as well as how, and for what purpose, it’s been developed. Finally, the SRS will contain sections that describe the target non-functional behavior of the software product, which include performance and security.
Why Is a Software Requirement Specification Important?
Having a solid SRS is of massive importance to software projects. This documentation brings everyone involved to the same shared understanding about the project’s purpose and scope. This documentation helps avoid misalignment between development teams so everyone understands the software’s function, how it should behave and for what users it is intended.
Through the SRS, teams gain a common understanding of the project’s deliverable early on, which creates time for clarification and discussion that otherwise only happens later (during the actual development phase). This means teams are more likely to deliver a software product that fits the original scope and functionality as set forth in the SRS, and that are in line with user, customer and stakeholder expectations.
How to Write Software Requirement Specification
Writing an SRS is just as important as making sure all relevant participants in the project actually review the document and approve it before kicking off the build phase of the project. Here’s how to structure your own SRS.
This section presents the purpose of the document, any specific conventions around language used and definitions of specific terms (such as acronyms or references to other supporting documents), the document’s intended audience and finally, the specific scope of the software project.
This section outlines the high-level context that motivates the software product’s development, including a summary of its main features and functionality. A very important component of the product description is an explanation of the product’s intended user, what processes developers will use to accomplish their goal and for which type of environment this product is most well suited (business, customer, industry and so forth). The product descriptions will also contain any external dependency by which the product’s development will be affected.
The meat of the document, the software requirements section, describes in detail how the software will behave and the functionality it offers the user.
For example, a functional requirement may state a user will be able to upload videos using the user interface.
Detailed requirement information is usually laid out in the document as a written list of requirements broken down by key topic areas that are specific to the product. For example, gaming software may have functional requirements specific to players and the surrounding environment. Otherwise, you might have an external attachment to a requirements template wherein this template is a simple file that contains a granular list, or table, of requirements with key information (description of the requirement, who it’s for, which version of the product it refers to and more).
Both options are a valid way of building out this section.
External Interface Requirements
This section contains a description of how the user interacts with the software product through its interface, as well as a description of the hardware necessary to support that interface.
In addition, this section usually features a description of how the software will communicate with other software using the various available communication standards. For example, you might have descriptions of compatible message formats (such as audio or visual) as well as standards for the data size the product can send or receive by way of a specific user action.
This section speaks to the software’s target behavior considering performance, security, safety and quality. Questions this section may answer include:
- Performance: How fast do users receive results upon executing a certain action?
- Security: How will the software manage data privacy?
- Safety: Is there any potential harm the product may create and what guardrails exist to protect the user, the company and (potentially) the public at large?
- Quality: How reliable is the product?