The Web Feature Service (WFS) Implementation Specification allows a client to retrieve and update spatial data encoded in Geography Markup Language (GML) from one or multiple sources. The specification defines interfaces for spatial data access and manipulation operations. Through these interfaces, a Web user or service can combine, use and manage spatial data from different sources. In addition, the transactional version of the WFS specification includes the option to insert, update, or delete features from a vector data source.