Document	Purpose
Software Requirements Specification	A software requirements specification (SRS) is a document that describes what the software will do and how it will be expected to perform. It also describes the functionality the product needs to fulfill all stakeholders (business, users) needs.
Game Design Document	A game design document (GDD) is a software design document that serves as a blueprint from which your game is to be built. It helps you define the scope of your game and sets the general direction for the project, keeping the entire team on the same page.
UML Modeling	The Unified Modeling Language (UML) is a general-purpose, developmental, modeling language in the field of software engineering that is intended to provide a standard way to visualize the analysis and design of a system.