What is the definition of a software specification?

A software specification is a comprehensive document that outlines the expected functionality and requirements of the software being developed. It serves as a guide for the development team, depicting what the software should do, detailing its capabilities, features, and constraints. By providing clarity and direction, it ensures that all stakeholders have a mutual understanding of what the software is intended to achieve.

The correct answer emphasizes that a specification can have legal significance, as it may also define the obligations and expectations of the parties involved in the software development process. This can include performance metrics, usability standards, and other functional requirements that the final product must satisfy.

In contrast, other options focus on different aspects of software development. A detailed source code is the implementation of the software itself, representing a technical build rather than a specification. An interface design document, while important, only covers a part of the overall specification concerning how users interact with the software. Lastly, a financial cost estimate addresses budgeting and cost management rather than defining the software's functional requirements. Thus, the selected answer accurately encapsulates a core purpose and function of a software specification.