A typical wiki is a collection of pages, with each page containing an unstructured blob of text. Wikis like Wagn and Semantic Mediawiki are an attempt to find

A typical wiki is a collection of pages, with each page containing an unstructured blob of text. Wikis like Wagn and Semantic Mediawiki are an attempt to find a middle ground between a typical wiki (where each content page is unstructured) and a database-driven CMS (where each content page is a view of a row of a database). The idea is that you get the benefits of a wiki, where you can build as you go, plus the benefits of a database, because you can add structure (new fields in content pages) as you need it. The added structure gives you the ability to create new pages using queries (e.g. a list of all country names in Africa), rather than manually (as is the case for a typical "List of ____" page on Wikipedia).