Explain the purpose (using only two sentence in each case) of eachof the following
components of uml
• use case diagram
• use case description
• class diagram
• sequence diagram
• business or domain model

UML - Unified Model Language

Explanation:

Use case diagram:

A use case diagram is used to tell how many ways a   user can interact with  a system. We use special   symbols and connectors to build use case   diagrams.  

We use  horizontal shaped ovals to represent use   cases, stick figures to represent actors, lines to   represent associations between use cases and  

actors, packages to put elements into  groups.  

Use case description:  

By the name itself, we can say that it is used to   describe the activities of user that  he can do with   the system and how the system responds to those.  Before use case diagram created, we need to write   a use case description.  

Class diagram:  

UML diagrams are of two types. They are,  

A class diagram comes under Structural UML   diagrams.

Classes are building blocks of an application that   uses OOPs concepts. Class diagrams are used to   represent classes, relationships, association,  

interface.  

Sequence diagram:  

A sequence diagram comes under  Behavioral UML   diagrams.It is used to tell the sequential order of   objects' interaction.We have many notations in this   diagram like actors, lifeline, create message, delete   message, lost message, found message etc. It is   used to tell how messages move between objects in   a system.  

Domain model :  

A domain model is a visual representation of real-  situation objects. In UML,  the Domain Model is   illustrated with a set of class diagrams

nope i prefer two because it is simpler, i don't like all the powers you get

explanation:

but that's my opinion