I have recently started playing with XOOPS and I am interested in using XOOPS as a general PHP application framework. By framework I mean separation of logic, data and presentation, reduced repetitive programming and component reuse, user/group, authentication and content management.

My application is in the field of ERP (Supply chain) and has lot of data entry, which has to be validated on server side. Is there a general module for server side data validation with redirecting back to entry form if invalid and displaying some error messages? If there is, can you point me to the module that uses server side data validation?
Here is a typical problem: I was able to add an empty category in FAQ module. Not even JavaScript check.

On positive side, I like XOOPS coding style, I find it to be very elegant and easy to follow.

I hope XOOPS is not ment to be just for developing community sites?

XOOPS can be used for whatever you want - sometimes you'll need special modules for it, but if it is possible in PHP, it is possible in XOOPS, I generally say.

There is a basic required/not required setting in the XoopsForm classes, which will perform a javascript check if set to required. If the category is not set as required in the FAQ module, then that is an error from the developer, I think.

Apart from that, there is not a general module for validation, but what you describe is possible to do.