How Can a Plugin Hijack a URL in WordPress?

[dr.satman]

Of course I can always edit WordPress' .htaccess file, but that would kind of make my WP plugin a little non-standard. Instead, what is the way to hijack a URL via a custom plugin in WordPress?For instance, let's say I want to build an elaborate product catalog that could be installed in WordPress as a plugin. Once activated, you could go into an admin panel on the plugin and tell it that all URLs starting with "/catalog" (or whatever you choose) would go to this product catalog app. Now the app would reside in the wp-content/plugins/mycatalog folder. So, /catalog/product/400 would go to wp-content/plugins/mycatalog/app.php which would then parse "product" and "400" out of the URL.