When you need to show abstract view of group of components 
then go in for package Diagram.

If one usecase must use another usecase, then use include
relationship. If one use case may use another usecase, then
use extends relationship. uses relationship is defined in
UML 1.1.

Includes:

if(TRUE)

   include the use case

Extends:

if(condition)

   extend the use case

It's a matter of unconditional VS. conditional insertion

(Source : Uml 2002--The Unified Modeling Language
 By Jean-Marc Jézéquel, Heinrich Hussmann, Stephen Cook)

Uses:

Defined in UML 1.1

The <<include>> relationship means that the flow of that 
use case is always included.
But a <<extend>> relationship means that the flow of the 
extending use case is only
included under specific conditions, which must be specified 
as the extension point of the
use case being extended.

"X uses Y" indicates that the task "X" has a subtask "Y"; 
that is, in the process of completing task "X", task "Y" 
will be completed at least once. 

"X extends Y" indecates that "X" is a task of the same type 
as "Y", but "X" is a special, more specific case of 
doing "Y". That is, doing X is a lot like doing Y, but X 
has a few extra processes to it that go above and beyond 
the things that must be done in order to complete Y.

Sequence Diagrams : Diagrams used in OOAD, to describe the
event flow, w.r.t. the objects and their timelines.

Collaboration Diagrams : Diagrams used in OOAD, to describe
the interaction between the different entities(objects) in
the system.

Composition : Defines a strong-coupled relationship between
two entities, where the one entity is part of another, and
both need each other for their existence. e.g. Human body
and the Heart.

Aggregation : Defines a weak-coupled relationship between
two entities, where one entity could be part of another, but
either can exist without the other, independantly. e.g.
School and teacher.

Composition can be used to model by-value aggregation which
is semantically equivalent to an attribute. In fact
composition was originally called aggregation-by-value in an
earlier UML draft with “normal” aggregation being thought of
as aggregation-by-reference. The definitions have changed
slightly but the general ideas still apply. The distinction
between aggregation and composition is more of a design
concept and is not usually relevant during analysis.

It is used to division for sub subclassess.Abstractclassess 
are not allowed in inheritance because it has no body.

Inheritance is a type of relationship among classes, wherein
one class shares the structure or behaviour defined in one
(single inheritance) or more (multiple inheritance) other
classes. Inheritance defines a "kind of" hierarchy among
classes in which a sub class inherits from one or more
super-classes; a sub-class typically augments or redefines
the existing structure and behaviour of its super-classes.

Creating new class with existing one.