Here is a reference to the UML class diagram symbols:
(Taken from a number of sources.)

Class
-----
A Class description containing a 
   ____________
  | Class Name |
  |------------|
  | Attributes | 
  |------------|
  | Operations |
  |____________|

Association
-----------
An association represents a physical or conceptual connection 
betwen objects.  This is represented by a line between the two objects.
If the association has a name it would often be written on top.

          AssocName
  Class1 ----------- Class2

There is a possiblity of a multidirectional association that would be 
represented by a diamond connecting the related sets.
                

  Class1 -----<O>---- Class3
               |
            Class2

Arrows can be used to indicate the navigablity of a association.
So an arrow from one class to another would indicate that Class1
uses the services of Class2 but Class2 is not aware of Class1.
It also indicates that nature of Class2 scope.  Since there
is no aggregation relationship here, Class2 may outlive Class1
instances.  This would be used to indicate a pointer or reference
relationship.

  Class1 -------> Class2

In some places it is necessary to represent that a Class can
be associated with a set instead of a single instance.  This
will be represented by a star at the end of the association.

  Class1 ------->* Class2

Composition (Strong Aggregation) 
---------
This means that Class2 is a part of Class1.  It is a strong form
of aggregation in that when Class1 is destroyed Class2 goes with it.

The symbol for a composition relationship is a diamond filled to an arrow.

 Class1 <*>----->  Class2  

Aggregation
-----------
A weaker form of aggregation than composition is represented with
an unfilled diamond.  It still demotes the life time of Class2 is 
restricted to Class1, but Class2 is not part of Class1.  This may
be implemented by a pointer in Class1 to Class2 with the dtor 
destroying Class2.    

 Class1 <>------> Class2
 

Inheritance
-----------

Inheratance is indicated with an triangle pointing up to the 
class form which the other derives.  (Having no triangles a
A will do.)
  
Class1
  A
  |
Class2


So now a quick example:

         +--> Shape
         |      A
 parent_ |      |
         |      |         points_
         +--- Polygon <>------------->* Point

This would indicate that a Polygon is derived from a Shape.  It also
indicates that Polygon can have a reference to a Shape.  Further,
Polygon contains a set of Points that it is responsible for.

This might be implemented like

  class Shape 
    {//...
    };

  class Polygon: public Shape
    {
     private:
       Shape*         parent_;
       list<auto_ptr<Point>> points_;
     public:
       //...
    };
          
     
References:
  UML Class Diagrams
    Robert C. Martin
    Engineering Notebook Column
    C++ Report, August, 1997 
    http://www.oma.com/PDF/umlClassDiagrams.pdf

  OML Object Model
    http://wwwis.cs.utwente.nl:8080/dmrg/MEE/misop007/