Is this class diagram correct according to this use case diagram?

Question

I am trying to create a class diagram which shows generalisation and maybe some form of aggregation or composition from this use case diagram. The intended system is to be a site/application similar to facebook social networking.

USE CASE DIAGRAM:

CLASS DIAGRAM:

I am pretty sure something is wrong with the class diagram please could someone help me out, thanks.

Answer 1

There is no direct relation between a class diagram and a use case diagram. One is used to understand requirements and the other to model the system's static structure.

Answer 2

I find the best way to get to the class diagram stage is to produce a derived class diagram taking information (i use nouns and noun phrases) from the Use case specification. Because as @vainolo says there is no direct link between a Use case diagram and a class diagram.