It is a reasonably common use case to fetch a list of content objects based on a common attribute implemented across multiple content classes. For example, to fetch all articles, blog posts and comments published by a given author. Certainly one could do multiple fetches and then massage the result sets together, but that's a lot of work. In this post I'll create a custom template operator (which is not the same as a custom fetch function, although the latter might be a better extension if one were a fan of doing things 'semantically') The operator will do the fetch with one SQL query. And I hope to shine some light on the eZ Publish db schema around objects, along the way.
Many products -- PDF books, songs, and online games, among others, are well suited for a pay-per-download workflow. In such a case, customers buy products online and receive immediate access, without requiring any action from the seller. Mugo Web has written an article outlining how eZ Publish provides a framework to quickly set up pay-per-download products.