Ashwin,

when we talk of object orientation for analysis, we will be going to explore every nuts and bolts of requirements by following classes and objects principles (OOAD methodology). In general OO analysis starts with mapping of problem domain with a high level Class and Object diagram where all business entity with attributes and there responsibilities are properly mapped to the problem domain (refer to UML class diagrams for more details).  

Then all relationships b/w these entities are highlighted along with associated business rules.

 Before completing the final domain model several walkthrough and reviews are made to fine tune the model according to the requirements. After freezing this model will act as a central concept for developing a business engine. Also several other modeling techniques will be also deployed for analyzing classes behavior and states when some event goes on.

That will demonstrated by dynamic modeling like extensive flow charts/Activity diagram and state chart diagrams. Then more detailed version like UML sequence diagram comes.

           why we need OO analysis is a matter of approach and methodology, as structured techniques are now outdated due its complexity and non-flexibility today the most complex problem domain can be solved by this tecniques and is very well known for reducing complexity. But actually there is nothing like that, which

can gaurantee successfull projects.

Cheers,

Kumar Rohit