We focused on the maps in the book and almost always used the WMS protocol in our examples. As you learned in Chapter 1, GIS Fundamentals, a map is a representation of data. A map can include vector or raster data, but it always represents them as a raster output, that is, an image. While maps are an easy and useful way to show your data, there are other scenarios where users need not use a representation, but the original data, for example, to process the data on a client-side task. Here, two other OGC protocols come into use: WFS and WCS.
If a user needs to get your vector data, for example, the USA railroads, he can use the Web Feature Service (WFS) protocol. It is a standard protocol defined by OGC that refers to the sending and receiving of geospatial data through HTTP.
When delivering data, the most important thing to define is the data format. Vector data is usually stored in a binary format—think of a shapefile or a PostGIS table—but for practical...