The Vector Markup Language (VML) Format Writer module enables FME to be used in conjunction with the world wide web to translate vector data on-the-fly for display in web browsers. VML is an Extensible Markup Language (XML) based exchange, editing, and delivery format for vector graphics on the web. This section assumes familiarity with the VML format and the XML standard.
Overview
VML, which is written using the XML syntax, is a text-based markup language used for describing vector graphics that can be viewed and edited by a wide variety of tools. It provides for the description of lines, polygons, curves, images, and text objects. Positioning and layout of the vector graphics are accomplished by using the Cascading Style Sheets, Level 2 (CSS2) visual rendering model. For more information on VML, XML, CSS1, and CSS2 see the World Wide Web Consortium Web site at http://www.w3.org.
The two primary objects that VML describes are the shape and group elements. The shape element is used to define a visible vector graphic element whereas the group element is used to group together several shapes so that they may be transformed together as one unit. These are top-level elements that may define their own local coordinate system. The shape and group coordinate spaces define a CSS2 block level box.
In addition, VML defines several auxiliary top-level elements to help make the editing and representation of graphical information more compact and convenient. These auxiliary elements are the shapetype element and the predefined shape elements line, polyline, curve, rect, roundrect, oval, arc and image. The usage of some of these VML elements currently supported by FME are explained in subsequent sections.