Object-oriented stuff and postgres

What's the best way to do this in postgres? (basicly finding the type of
objects).

I want to run a web site with different types of content - question and
answers, stories etc. I propose an object hierarchy...
webobject (title, body)
   question inherits webobject
   story (image) inherits (webobject).

The idea being you could have a search screen that searches questions
AND stories with the one SELECT query.

But then each result would have a link to examine the body of the search
result. But different types of objects would have different URLs to
display that content.

So basicly I need to know the type of objects returned.

I am loath to store the object type inside the object because it is
wasteful. PG obviously already knows the type of objects, the question
is how to get at that info.