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An XML schema was produced for the definition of a GUI specification language, eXtensible User Interface (XUI). This schema describes how to parameterize each representation type. An XUI description is always written for a certain XML instance (Instance), or for the quantity of all XML instances that belong together (in regards to one of XML schema).
Note: This XML instance can be processed by the rendering engine only if it has a valid reference to an XML schema.
Both the XML schema referred by an XML instance and the schema for the GUI descriptions (XUIs) are written in the XML schema language, standardized by the W3C (World Wide Web Consortium). Thus, they are instances of the official W3C schema specification.
Figure 1: Addressing XML-nodes in XUI
Parts or sub-ranges of the XML instance are addressed with XPath Path expressions can be formulated with XPath, which localize parts of an XML document. and enriched with layout and rule specific definitions. The possibilities for this GUI refinement are described in an XML schema. Thus, the XUI pattern represents all possible adaptations of the graphical interface.