Web services are a major progress in the development of WebGIS, and are the core technology and important symbol of modern WebGIS. It combines the advantages of GIS, program components and the Internet, profoundly changing the way GIS is developed and applied. It bypasses the complex aspects of local data conversion and local software installation, allowing integration between different computer systems and different departments at the Web services level, providing a new basic module for software application development, and providing cross-department coordination and cooperation provides a new way to provide a technical framework for the National Spatial Data Infrastructure (NSDI ). More and more organizations are publishing and sharing their own data and functions as Web services for use by their own organization and often other organizations as well. These services can then be combined into other WebGIS applications.

This chapter focuses on the basics of Web services, including the concepts, impacts, functions and advantages of Web services, SOAP and REST-style Web services, related standards of Web services, such as WMS, WFS, WCS, CSW, GML, KML and GeoRSS, and optimization of Web services.