External PHP and urls: how to access them without hard coding the structure?

Question

How can i create the following urls without having to hard-code them in my external php script? The urls i'm talking about are

1. Question pages
2. User profile pages
3. Category pages

About the question pages i'm currently using the function qa_q_request(); that is working pretty well; how about the other two url types?

Comments

I want also to add that if i try to include qa-base.php from within a function (necessary to access to qa_q_request()) i get the following error: "qa_register_plugin_module() can only be called from a plugin qa-plugin.php file"; any chances to include that file from within a function without having to import it in the root scope of the script?