URL Creation: How is this done?

We are integrating our blog with our web application search. I would like to better understand how the urls for the blog are created so we can automate the search indexing – even for new posts and pages.

Looking at the guid was one way to go – but those are just what they are titled unique identifiers and nothing else. Most of the urls goto 404s at this point because of the changes to the structure of the blog.

I do use pretty perms – post urls are date structured and page urls are hierarchical

Your input is appreciated.