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 valida-tor. validator.
tor. 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 com-pletely completely
pletely 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, other-wise otherwise
wise 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 var-Name varName
Name 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 other-wise. otherwise.
wise. 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 sub-tree. subtree.
tree.
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 Appen-dix Appendix
dix 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 docu-ment. document.
ment.
KEYWORDS
Validation, DTD
Tcl tnc(n)
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