2) Unified Modelling Language

Unified Modelling Language (UML)
is a well-defined, easy to express, powerful and universally applicable modelling language. Its scope is not limited to supporting object-oriented analysis and design, but also supports the whole process of software development, starting with requirements analysis.The structure of UML: The structure of UML consists of the basic building blocks, the rules that govern how these building blocks are put together (the architecture) and a number of mechanisms that apply to the whole of UML.