Adding features from a WFS server

The Web Feature Service (WFS) is an OGC standard, which provides independent platform calls to request geographical features to a server. In practice, it means a client makes a HTTP request to a server that implements the WFS standard and gets a set of features in the GML (Geographic Markup Language, http://en.wikipedia.org/wiki/Geography_Markup_Language) format.

Note

A nice introduction to WFS can be found in the tutorial about WFS available at https://www.e-education.psu.edu/geog585/book/export/html/1724. If you want to learn more about this, there is a complete specification on the OGC site http://www.opengeospatial.org/standards/wfs.

From the OpenLayers point of view, the WFS is nothing more than another data source we can read to fill a vector layer.

Before continuing, there is an important point to take into account. Most of the requests made by OpenLayers when data is loaded, say GML, KML, or GeoRSS files, are made asynchronously through the helper...