I’ve discovered a funny thing when I was searching some information about EnableUrlSmashing (I love the name), Microsoft created in 2006, published in 2008, a patent about the search API in SharePoint.

That patent ("Simplified search interface for querying a relational database") covers the Query, KeyWordQuery class and more.

An extract from the abstract:

Methods and computer-readable media are provided for performing a search on a relational database. According to one method, a query class is provided that includes properties that specify how a query is to be performed and how results from the query are to be returned, and an execute method that is called to perform the actual query. A keyword query class derived from the query class is also provided that includes keyword query properties and an execute method for performing the keyword query.

Link to the full patent: http://www.freepatentsonline.com/y2008/0114745.html