UML provides various basic elements for building models. Basic elements may be grouped into composite elements. Relational elements deal with various kinds of relationships between the model elements. Other elements are there to describe object states and interactions. Annotations are provided for clarifying the meaning. Specifications are saved in files to document responsibilities and capabilities of the model elements. Adornments make symbols mean specific things. In order to cover every possible situation UML provides notation extending mechanisms. One such mechanism is stereotyping which specialises the general notation to specific application areas. Standard stereotypes and icons are provided, though domain specific stereotypes and icons may be introduced as and when required. Notation extension uses tagged values to add more information. Constraints are used to show restrictions that apply.