Hello. My application is a product which will have reporting capabilities. The product, when in production, is expected to have several ad-hoc report defined by the end users.

I am looking for a platform that can be tailored to harness the business entities and extend reporting capabilities (definition & execution) to the end user.

Here are some constraints:

• From the usability standpoint, I like what MS Access reports offer. But of course it is not suitable for the target web application. However, it certainly is a source of inspiration usability wise.
• Cost is a constraint. So something recommended from open source world will be appreciated. Otherwise too I'd like to know.
• The product in question is somewhat 'generic' in nature.

Mine is a ASP.Net platform.