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tnc(n)                                                                  tnc(n)

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NAME
       tnc - tnc is an expat parser object extension, that validates the XML
       stream against the document DTD while parsing.

SYNOPSIS
       package require tdom
       package require tnc

       set parser [expat]

       tnc $parser enable
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DESCRIPTION
       tnc adds the C handler set "tnc" to a tcl expat parser obj. This
       handler set is a simple DTD validator. If the validator detects a
       validation error, it sets the interp result, signals error and stops
       parsing. There isn't any validation error recovering. As a consequence,
       only valid documents are completely parsed.

       This handler set has only three methods:

       tnc parserObj enable

              Adds the tnc C handler set to a Tcl expat parser object.

       tnc parserObj remove

              Removes the tnc validatore from the parser parserObj and frees
              all information, stored by it.

       tnc parserObj getValidateCmd ?validateCmdName?

              Returns a new created validation command, if one is avaliable
              from the parser command, otherwise it signals error. The name of
              the validation command is the validateCmdName, if this optional
              argument was given, or a random choosen name. A validation
              command is avaliable in a parser command, if the parser with tnc
              enabled was previously used, to parse an XML document with a
              valid doctype declaration, a valid external subset, if one was
              given by the doctype declaration, and a valid internal subset.
              The further document doesn't need to be valid, to make the
              validation command avaliable. The validation command can only
              get received one time from the parser command. The created
              validation command has this syntax:

                     validationCmd method ?args?

              The valid methods are:

              validateDocument domDocument ?varName?
                     Checks, if the given domDocument is valid against the DTD
                     information represented by the validation command.
                     Returns 1, if the document ist valid, 0 otherwise. If the
                     varName argument is given, then the variable it names is
                     set to the detected reason for the validation error or to
                     the empty string in case of a valid document.

              validateTree elementNode ?varName?
                     Checks, if the given subtree with domNode as root element
                     is a posible valid subtree of a document conforming to
                     the DTD information represented by teh validation
                     command. IDREF could not checked, while validating only a
                     subtree, but it is checked, that every known ID attribute
                     in the subtree is unique. Returns 1, if the subtree is
                     OK, 0 otherwise. If the varName argument is given, then
                     the variable it names is set to the detected reason for
                     the validation error or to the empty string in case of a
                     valid subtree.

              validateAttributes elementNode ?varName?
                     Checks, if there is an element declaration for the name
                     of the elementNode in the DTD represented by the
                     validation command and, if yes, if the attributes of the
                     elementNode are conform to the ATTLIST declarations for
                     that element in the DTD. Returns 1, if the attributes and
                     there value types are OK, 0 otherwise. If the varName
                     argument is given, then the variable it names is set to
                     the detected reason for the validation error or to the
                     empty string in case the element has all its required
                     attributes, only declared attributes and the values of
                     the attributes matches there type.

              delete Deletes the validation command and frees the memory used
                     by it. Returns the empty string.

BUGS
       The validation error reports could be much more informative and user-
       friendly.

       The validator doesn't detect ambiguous content models (see XML
       recomendation Section 3.2.1 and Appendix E). Most Java validators also
       doesn't, but handle such content models right anyhow. Tnc does not; if
       your DTD has such ambiguous content models, tnc can not used to
       validate documents against such (not completely XML spec compliant)
       DTDs.

       It isn't possible to validate XML documents with standalone="yes" in
       the XML Declaration

       Violations of the validity constraints Proper Group/PE Nesting and
       Proper Conditional Section/PE Nesting are not detected. They could only
       happen inside a invalid DTD, not in the content of a document.

KEYWORDS
       Validation, DTD

Tcl                                                                     tnc(n)