tnc(n)tnc(n)______________________________________________________________________________NAMEtnc - 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
_________________________________________________________________DESCRIPTIONtnc adds the C handler set "tnc" to a tcl expat parser obj. This han‐
dler set is a simple DTD validator. If the validator detects a valida‐
tion 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 com‐
mand 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 vali‐
dation command avaliable. The validation command can only get
received one time from the parser command. The created valida‐
tion 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 com‐
mand. 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 valida‐
tion command and, if yes, if the attributes of the ele‐
mentNode 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 recomen‐
dation 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 vali‐
date 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
Tcltnc(n)
