XML is a web-based language used to interact data behind the scenes. With projects like GML by the Open GIS Consortium, XML is fast becoming an essential tool for GIS.
ESRI programmer’s refence for ArcXml. ArcXML is designed as the protocol for data exchange between the ArcIMS Spatial Server, Application Server, and Application Server connectors.
Basic Guide to ArcXML
Learning how to work with ArcXML is integral to customizing ArcIMS, ESRI’s web mapping software. Introduce yourself to this flavor of XML here.
GeoSciML is a markup language specific to the geosciences and is designed to support the exchange of geoscience information.
GML or Geography Markup Language is an XML based encoding standard for geographic information developed by the OpenGIS Consortium (OGC). The objective is to allow internet browsers the ability to view web based mapping without additional components or viewers.
Google announced on April 14,2008 that KML has become an Open Geospatial Consortium (OGC) Standard. This means that Google will no longer be responsible for maintaining the KML file format which, instead, will be handled by OGC. KML (Keyhole Markup Language) is a file format that uses XML-based language to manage geographic information. Originally, KML was used to display data in Google Earth and Google Maps but with the adoption by the OGC, KML files will become a standard for managing spatial data across a variety of mapping applications. The statement from Google’s LatLong Blog:
KML was originally created as a file format for Google Earth, allowing users to overlay their own content on top of our base maps and imagery. It’s since become something much larger — KML has become the HTML of geographic content, the dominant way to share user-created maps online. There are now tens of millions of KML files available online, hosted on more than 100,000 unique domain names. KML is supported by a large and growing number of vendors and products, and can no longer simply be described as Google Earth’s file format. Because it has transcended Google Earth in scope, and even outgrown Google itself, we have decided to give it away.
The statement about KML being the HTML of geographic content is debatable.