Manual Reference Pages - TNC (n)
tnc - tnc is an expat parser object extension, that validates the XML
stream against the document DTD while parsing.
package require tdom
package require tnc
set parser [expat]
tnc $parser enable
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 isnt 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
doesnt 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
Deletes the validation command and frees the memory used by
it. Returns the empty string.
The validation error reports could be much more informative and
The validator doesnt detect ambiguous content models (see XML
recomendation Section 3.2.1 and Appendix E). Most Java validators also doesnt,
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 isnt possible to validate XML documents with standalone="yes" in the
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.
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