<manpage id="tnc" cat="cmd" title="tnc">
  <namesection>
    <name>tnc</name>
    <desc>tnc is an expat parser object extension, that validates the XML
stream against the document DTD while parsing.</desc>
  </namesection>
  
  <synopsis>
    <syntax>package require tdom
package require tnc

set parser [expat]

tnc $parser enable</syntax>
  </synopsis>

  <section>
    <title>DESCRIPTION</title>
    
    <p><m>tnc</m> adds the C handler set &quot;tnc&quot; 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.</p>

    <p>This handler set has only three methods:</p>

    <commandlist>
      <commanddef>
        <command><cmd>tnc</cmd> <m>parserObj</m> <method>enable</method></command>

        <desc><p>Adds the tnc C handler set to a Tcl expat parser object.</p></desc>
      </commanddef>

      <commanddef>
        <command><cmd>tnc</cmd> <m>parserObj</m> <method>remove</method></command>

        <desc><p>Removes the tnc validatore from the parser <m>parserObj</m>
and frees all information, stored by it.</p></desc>
      </commanddef>

      <commanddef>
        <command><cmd>tnc</cmd> <m>parserObj</m> <method>getValidateCmd</method> <option>?validateCmdName?</option></command>

        <desc><p>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 <m>validateCmdName</m>, 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:</p>

<syntax><cmd>validationCmd</cmd> <m>method</m> <m>?args?</m></syntax>

    <p>The valid methods are:</p>

    <commandlist>
      <commanddef>
        <command><method>validateDocument</method> <m>domDocument</m> <m>?varName?</m></command>
        <desc>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 <m>varName</m> 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.</desc>
      </commanddef>

      <commanddef>
        <command><method>validateTree</method> <m>elementNode</m> <m>?varName?</m></command>

        <desc>Checks, if the given subtree with <m>domNode</m> 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
<m>varName</m> 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.</desc>

      </commanddef>

      <commanddef>
        <command><method>validateAttributes</method> <m>elementNode</m> <m>?varName?</m></command>

        <desc>Checks, if there is an element declaration for the name of the
<m>elementNode</m> in the DTD represented by the validation command and, if
yes, if the attributes of the <m>elementNode</m> 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 <m>varName</m> 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.</desc>

      </commanddef>

      <commanddef>
        <command><method>delete</method></command>
        <desc>Deletes the validation command and frees the memory used by
it. Returns the empty string.</desc>
      </commanddef>

      </commandlist>
     </desc>
      </commanddef>
    </commandlist>
  </section>

  <section>
    <title>BUGS</title>

    <p>The validation error reports could be much more informative and
user-friendly.</p>

    <p>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.</p>

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

    <p>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.</p>

  </section>
  <keywords>
    <keyword>Validation</keyword>
    <keyword>DTD</keyword>
  </keywords>
  
</manpage>
