storri has asked for the wisdom of the Perl Monks concerning the following question:

I am trying to validate an XML using a DTD file. I have captured the output but I don't know what line/what word, etc. is causing the validation to fail. Here is the code:

my ($dtd_file) = @_; my $file_target = "$main::args{xml_dir}/$main::args{file}"; my $dtd_target = "$main::args{xml_dir}/$dtd_file"; my $dtd = XML::LibXML::Dtd->new("", $dtd_target); my $parser = XML::LibXML->new(); $parser->validation(1); my $document; if (! -f $file_target) { print "Cannot find required file: $file_target\n"; exit(0); } if (! -f "$dtd_target") { print "Cannot find required file: $dtd_target\n"; exit(0); } eval { $document = $parser->parse_file($file_target); $document->validate($dtd_file); }; if ($@) { print "XML not valid because of $@ !\n"; }

If I use this code I get the error message:
XML not valid because of is_valid: argument must be a DTD object at ./ line 146.

Line 146 is the line were $document->validate($dtd_file) is called. Stephen

2003-06-07 edit ybiC: <code> tags

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Re: Gathering more verbose output from XML file validation
by arturo (Vicar) on Jun 08, 2003 at 00:39 UTC

    Going by the message and the documentation for the modules in question, it would not seem that the error message is incorrect or misleading. What you've passed in to the validate method of the XML::LibXML::Document object in your eval block is the name of a DTD file. But that's not the right sort of critter -- when it says it wants a DTD object, it wants a XML::LibXML::Dtd object, as is made manifest by the man page for XML::LibXML::Document

    You may also pass in a XML::LibXML::Dtd object,
    to validate against an external DTD:
    if (!$dom->is_valid($dtd)) {
        warn("document is not valid!");

    So yu need to get from the file to the object, and that you would do with something like:

    eval { $document = $parser->parse_file($file_target); my $dtd = XML::LibXML::Dtd->new($dtd_file); $document->validate($dtd); };


    Update: whoops, no that isn't enough. In order to create a DTD object, you need both the PUBLIC id (e.g. -//OASIS//DTD DocBook XML V4.1.2//EN -- to pick a favourite of mine) and a SYSTEM id (which can be the name of the file, including all relevant path information). You can also read the file into a string and pass that in, but in testing I found that didn't play nicely if the DTD references entities defined in still other files.

    Also, if the XML file has a DOCTYPE line in it,, that should be sufficient, since creating the DTD object is only necessary if that line is not present.

    For more info, try perldoc XML::LibXML::Dtd on your system =)

    If not P, what? Q maybe?
    "Sidney Morgenbesser"