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 available 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  chosen  name.  A validation command is available 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 available. 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 possible valid subtree of  a
                     document  conforming  to  the  DTD information represented by the 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(3tcl)