SSWL (Syntactic Structure of the World's Languages) is a open-ended database of syntactic, morphological and semantic properties. Each language is characterized by a set of property-value pairs (e.g., Object Verb: Yes), and examples that illustrate these property value pairs. A rich variety of search functions are available, as well as mapping and the creation of similarity trees. The database is open-ended in the sense that (a) new language experts may sign up to add new languages, and (b) new properties may be added.