This document discusses several open source web mapping frameworks: OpenLayers, ExtJS, and GeoExt. OpenLayers is a JavaScript library that supports OGC standards and has a large user and developer community. ExtJS is a JavaScript framework for building rich web applications with user interface components like forms and tables. GeoExt brings together OpenLayers and ExtJS to allow building of spatial rich internet applications with maps integrated with user interface elements like toolbars, legends, and tables.