Validating text input
For example, we may select all Regular grammars, as used in DTDs, can then be viewed as tree patterns where the only available axis is the parent-child axis [Jelliffe1999e].
Full use of tree pattern validation provides the maximum amount of freedom when modelling constraints for a schema.
More formally, the nodes and arcs within a graph of data can be traversed to both identify nodes, and then make assertions about the relationships of those nodes to others within the same graph.
The paper completes with some suggestions of possible future extensions.Other tutorial materials fulfill these roles already [Holman],[XPath],[XSLT] ,[Ogbuji C],[Ogbuji U].During the last few years a number of different XML schema languages have appeared as suggested replacements for the ageing Document Type Definition (DTD).Tree patterns are the schema paradigm underpinning Schematron as a validation language.There are reasons to believe that tree-pattern validation may be more suitable in an environment where documents are constructed from elements in several namespaces (often termed 'data islands').
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There is no enforcement that an IDREF must point to an ID on a particular element type, simply that is must point to an existing ID, and further that all IDs must be unique.