A System Requirements Specification (SRS) or a Software Requirements Specification is a document or set of documents that describe the features of a system or software application. It includes a variety of elements which define the intended functionality required by the stakeholders and customer to satisfy the end users.
In addition to that, an SRS provides a high-level idea of the system and its behavior, the main supported business processes, the assumptions and the key performance parameters for the system. The key elements of an SRS are:
Scope of Work
Functional Requirements
Non-Functional Requirements
Dependencies
Data Model
Assumptions
Constraints
Acceptance Criteria