in reply to Re^3: Pulling out sections of an XMI file with XML::Twig
in thread Pulling out sections of an XMI file with XML::Twig

Thank you for trying to help - I am still very new to XML::Twig and I am probably not doing things as efficiently as I could be. (Sorry for the typo with $xml in the above code - I fixed it.)

I'm trying to extract certain attributes from a small set of tags in the XML document referenced above. Specifically, the UML:Class tags contain UML:Attribute tags, and I want to extract the name and xmi.id attributes from them. The general structure of this portion of the document looks like this: 

<UML:Class>
    <UML:Attribute></UML:Attribute>
    <UML:Attribute></UML:Attribute>
    <UML:Attribute></UML:Attribute>
</UML:Class>

[download]
A complete example is shown under the readmore. 
    <UML:Class name="Gel2d" xmi.id="EAID_6AF3DB85_3AFE_4843_B8D3_0E61B
+46C6D92" visibility="public" namespace="EAPK_AEE09178_6653_49a3_91E8_
+7CD6004767CA" isRoot="false" isLeaf="false" isAbstract="false" isActi
+ve="false">
      <UML:GeneralizableElement.generalization xmi.id="EAID_6AF3DB85_3
+AFE_4843_B8D3_0E61B46C6D92_fix_0">
        <Foundation.Core.Generalization xmi.idref="EAID_8E74DB6E_6F4A_
+451b_A1E2_17F60ED264AE" xmi.id="EAID_6AF3DB85_3AFE_4843_B8D3_0E61B46C
+6D92_fix_0_fix_0" />
      </UML:GeneralizableElement.generalization>
      <UML:Classifier.feature xmi.id="EAID_6AF3DB85_3AFE_4843_B8D3_0E6
+1B46C6D92_fix_2">
        <UML:Attribute name="loading" changeable="none" visibility="pu
+blic" ownerScope="instance" targetScope="instance" xmi.id="EAID_6AF3D
+B85_3AFE_4843_B8D3_0E61B46C6D92_fix_2_fix_0">
          <UML:StructuralFeature.multiplicity xmi.id="EAID_6AF3DB85_3A
+FE_4843_B8D3_0E61B46C6D92_fix_2_fix_0_fix_0">
            <UML:Multiplicity xmi.id="EAID_6AF3DB85_3AFE_4843_B8D3_0E6
+1B46C6D92_fix_2_fix_0_fix_0_fix_0">
              <UML:Multiplicity.range xmi.id="EAID_6AF3DB85_3AFE_4843_
+B8D3_0E61B46C6D92_fix_2_fix_0_fix_0_fix_0_fix_0">
                <UML:MultiplicityRange lower="1" upper="1" xmi.id="EAI
+D_6AF3DB85_3AFE_4843_B8D3_0E61B46C6D92_fix_2_fix_0_fix_0_fix_0_fix_0_
+fix_0" />
              </UML:Multiplicity.range>
            </UML:Multiplicity>
          </UML:StructuralFeature.multiplicity>
          <UML:Attribute.initialValue xmi.id="EAID_6AF3DB85_3AFE_4843_
+B8D3_0E61B46C6D92_fix_2_fix_0_fix_1">
            <UML:Expression xmi.id="EAID_6AF3DB85_3AFE_4843_B8D3_0E61B
+46C6D92_fix_2_fix_0_fix_1_fix_0" />
          </UML:Attribute.initialValue>
          <UML:StructuralFeature.type xmi.id="EAID_6AF3DB85_3AFE_4843_
+B8D3_0E61B46C6D92_fix_2_fix_0_fix_2">
            <Foundation.Core.Classifier xmi.idref="eaxmiid3" xmi.id="E
+AID_6AF3DB85_3AFE_4843_B8D3_0E61B46C6D92_fix_2_fix_0_fix_2_fix_0" />
          </UML:StructuralFeature.type>
        </UML:Attribute>
        <UML:Attribute name="minPhRange" changeable="none" visibility=
+"public" ownerScope="instance" targetScope="instance" xmi.id="EAID_6A
+F3DB85_3AFE_4843_B8D3_0E61B46C6D92_fix_2_fix_1">
          <UML:StructuralFeature.multiplicity xmi.id="EAID_6AF3DB85_3A
+FE_4843_B8D3_0E61B46C6D92_fix_2_fix_1_fix_0">
            <UML:Multiplicity xmi.id="EAID_6AF3DB85_3AFE_4843_B8D3_0E6
+1B46C6D92_fix_2_fix_1_fix_0_fix_0">
              <UML:Multiplicity.range xmi.id="EAID_6AF3DB85_3AFE_4843_
+B8D3_0E61B46C6D92_fix_2_fix_1_fix_0_fix_0_fix_0">
                <UML:MultiplicityRange lower="1" upper="1" xmi.id="EAI
+D_6AF3DB85_3AFE_4843_B8D3_0E61B46C6D92_fix_2_fix_1_fix_0_fix_0_fix_0_
+fix_0" />
              </UML:Multiplicity.range>
            </UML:Multiplicity>
          </UML:StructuralFeature.multiplicity>
          <UML:Attribute.initialValue xmi.id="EAID_6AF3DB85_3AFE_4843_
+B8D3_0E61B46C6D92_fix_2_fix_1_fix_1">
            <UML:Expression xmi.id="EAID_6AF3DB85_3AFE_4843_B8D3_0E61B
+46C6D92_fix_2_fix_1_fix_1_fix_0" />
          </UML:Attribute.initialValue>
          <UML:StructuralFeature.type xmi.id="EAID_6AF3DB85_3AFE_4843_
+B8D3_0E61B46C6D92_fix_2_fix_1_fix_2">
            <Foundation.Core.Classifier xmi.idref="eaxmiid3" xmi.id="E
+AID_6AF3DB85_3AFE_4843_B8D3_0E61B46C6D92_fix_2_fix_1_fix_2_fix_0" />
          </UML:StructuralFeature.type>
        </UML:Attribute>
        <UML:Attribute name="maxPhRange" changeable="none" visibility=
+"public" ownerScope="instance" targetScope="instance" xmi.id="EAID_6A
+F3DB85_3AFE_4843_B8D3_0E61B46C6D92_fix_2_fix_2">
          <UML:StructuralFeature.multiplicity xmi.id="EAID_6AF3DB85_3A
+FE_4843_B8D3_0E61B46C6D92_fix_2_fix_2_fix_0">
            <UML:Multiplicity xmi.id="EAID_6AF3DB85_3AFE_4843_B8D3_0E6
+1B46C6D92_fix_2_fix_2_fix_0_fix_0">
              <UML:Multiplicity.range xmi.id="EAID_6AF3DB85_3AFE_4843_
+B8D3_0E61B46C6D92_fix_2_fix_2_fix_0_fix_0_fix_0">
                <UML:MultiplicityRange lower="1" upper="1" xmi.id="EAI
+D_6AF3DB85_3AFE_4843_B8D3_0E61B46C6D92_fix_2_fix_2_fix_0_fix_0_fix_0_
+fix_0" />
              </UML:Multiplicity.range>
            </UML:Multiplicity>
          </UML:StructuralFeature.multiplicity>
          <UML:Attribute.initialValue xmi.id="EAID_6AF3DB85_3AFE_4843_
+B8D3_0E61B46C6D92_fix_2_fix_2_fix_1">
            <UML:Expression xmi.id="EAID_6AF3DB85_3AFE_4843_B8D3_0E61B
+46C6D92_fix_2_fix_2_fix_1_fix_0" />
          </UML:Attribute.initialValue>
          <UML:StructuralFeature.type xmi.id="EAID_6AF3DB85_3AFE_4843_
+B8D3_0E61B46C6D92_fix_2_fix_2_fix_2">
            <Foundation.Core.Classifier xmi.idref="eaxmiid3" xmi.id="E
+AID_6AF3DB85_3AFE_4843_B8D3_0E61B46C6D92_fix_2_fix_2_fix_2_fix_0" />
          </UML:StructuralFeature.type>
        </UML:Attribute>
        <UML:Attribute name="firstDimDate" changeable="none" visibilit
+y="public" ownerScope="instance" targetScope="instance" xmi.id="EAID_
+6AF3DB85_3AFE_4843_B8D3_0E61B46C6D92_fix_2_fix_3">
          <UML:StructuralFeature.multiplicity xmi.id="EAID_6AF3DB85_3A
+FE_4843_B8D3_0E61B46C6D92_fix_2_fix_3_fix_0">
            <UML:Multiplicity xmi.id="EAID_6AF3DB85_3AFE_4843_B8D3_0E6
+1B46C6D92_fix_2_fix_3_fix_0_fix_0">
              <UML:Multiplicity.range xmi.id="EAID_6AF3DB85_3AFE_4843_
+B8D3_0E61B46C6D92_fix_2_fix_3_fix_0_fix_0_fix_0">
                <UML:MultiplicityRange lower="1" upper="1" xmi.id="EAI
+D_6AF3DB85_3AFE_4843_B8D3_0E61B46C6D92_fix_2_fix_3_fix_0_fix_0_fix_0_
+fix_0" />
              </UML:Multiplicity.range>
            </UML:Multiplicity>
          </UML:StructuralFeature.multiplicity>
          <UML:Attribute.initialValue xmi.id="EAID_6AF3DB85_3AFE_4843_
+B8D3_0E61B46C6D92_fix_2_fix_3_fix_1">
            <UML:Expression xmi.id="EAID_6AF3DB85_3AFE_4843_B8D3_0E61B
+46C6D92_fix_2_fix_3_fix_1_fix_0" />
          </UML:Attribute.initialValue>
          <UML:StructuralFeature.type xmi.id="EAID_6AF3DB85_3AFE_4843_
+B8D3_0E61B46C6D92_fix_2_fix_3_fix_2">
            <Foundation.Core.Classifier xmi.idref="eaxmiid4" xmi.id="E
+AID_6AF3DB85_3AFE_4843_B8D3_0E61B46C6D92_fix_2_fix_3_fix_2_fix_0" />
          </UML:StructuralFeature.type>
        </UML:Attribute>
        <UML:Attribute name="secondDimDate" changeable="none" visibili
+ty="public" ownerScope="instance" targetScope="instance" xmi.id="EAID
+_6AF3DB85_3AFE_4843_B8D3_0E61B46C6D92_fix_2_fix_4">
          <UML:StructuralFeature.multiplicity xmi.id="EAID_6AF3DB85_3A
+FE_4843_B8D3_0E61B46C6D92_fix_2_fix_4_fix_0">
            <UML:Multiplicity xmi.id="EAID_6AF3DB85_3AFE_4843_B8D3_0E6
+1B46C6D92_fix_2_fix_4_fix_0_fix_0">
              <UML:Multiplicity.range xmi.id="EAID_6AF3DB85_3AFE_4843_
+B8D3_0E61B46C6D92_fix_2_fix_4_fix_0_fix_0_fix_0">
                <UML:MultiplicityRange lower="1" upper="1" xmi.id="EAI
+D_6AF3DB85_3AFE_4843_B8D3_0E61B46C6D92_fix_2_fix_4_fix_0_fix_0_fix_0_
+fix_0" />
              </UML:Multiplicity.range>
            </UML:Multiplicity>
          </UML:StructuralFeature.multiplicity>
          <UML:Attribute.initialValue xmi.id="EAID_6AF3DB85_3AFE_4843_
+B8D3_0E61B46C6D92_fix_2_fix_4_fix_1">
            <UML:Expression xmi.id="EAID_6AF3DB85_3AFE_4843_B8D3_0E61B
+46C6D92_fix_2_fix_4_fix_1_fix_0" />
          </UML:Attribute.initialValue>
          <UML:StructuralFeature.type xmi.id="EAID_6AF3DB85_3AFE_4843_
+B8D3_0E61B46C6D92_fix_2_fix_4_fix_2">
            <Foundation.Core.Classifier xmi.idref="eaxmiid4" xmi.id="E
+AID_6AF3DB85_3AFE_4843_B8D3_0E61B46C6D92_fix_2_fix_4_fix_2_fix_0" />
          </UML:StructuralFeature.type>
        </UML:Attribute>
      </UML:Classifier.feature>
      <UML:Namespace.ownedElement xmi.id="EAID_6AF3DB85_3AFE_4843_B8D3
+_0E61B46C6D92_fix_3">
        <UML:Generalization child="EAID_6AF3DB85_3AFE_4843_B8D3_0E61B4
+6C6D92" parent="EAID_68C27150_2324_4f98_AECD_172A1251AB21" xmi.id="EA
+ID_8E74DB6E_6F4A_451b_A1E2_17F60ED264AE" visibility="public" />
      </UML:Namespace.ownedElement>
    </UML:Class>

[download]

If I understand how XML::Twig works, a section of the tree is sent to a handler when the closing tag is reached. Therefore, for the simplified example above, each of the UML:Attribute sections will get parsed before the corresponding UML:Class section is parsed. I would like to parse the Class first (so I don't have to jump through hoops to associate the Attribute data with the Class data later), which is why the handler for UML:Attribute is located in the handler for UML:Class.

I admit that it seems inefficient to call sprint and then parse. I took that snippet from GrandFather's example. Is there a better way to do it?

I hope that clarifies what I'm trying to do. I'd appreciate any suggestions that you might have. Thanks.

Replies are listed 'Best First'.
Re^5: Pulling out sections of an XMI file with XML::Twig
by mirod (Canon) on Sep 28, 2006 at 16:52 UTC

    2 things can help you here: you can use start_tag_handlers, which are called after the start tag of the element has been parsed (and the element object has been created, empty at that point). This also means taht the UML:Attribute element will get completely parsed before the UML:Class, but when you're in their handler the opening tag of UML:Class has already been parsed. If you don't use twig_roots but regular twig_handlers the element exists, it's an ancestor of the UML:Attribute element, and it's attributes are already available. If space is a problem, you cant sprinkle purge call to taste.

    So in your case I would write something like (untested):

    use strict;
use warnings;

use Data::Dumper;
use XML::Twig;

my $twig = XML::Twig->new(
  start_tag_handlers => { 'UML:Class' => \&ulm_class, }, 
  twig_handlers      => { 'UML:Class' =>  sub { $_[0]->purge }, # purg
+e at the end of each section,
                          'UML:Attribute' => \&uml_attr,
 } );
$twig->parsefile( 'testfile.xmi' );


sub uml_class
{
    my ( $twig, $section ) = @_;

    print "data for class:\n";
    print "   name = ", $section->att( 'name' ), "\n";
    print "   xmi.id = ", $section->att( 'xmi.id' ), "\n";
}


sub uml_attr
{
    my ( $twig, $attr ) = @_;
    # if you need the class id, it's in $attr->parent( ''UML:Class')->
+attr( 'xmi.id')
    $attr->print;

    print Dumper( $struct );
    # parse the block and extract the data elements

    $twig->purge;
}

    [download]

    Does it make sense? It probably doesn't matter that much if your files are small, but it feels better to parse only once each section.

[reply]
[d/l]

      Thank you for the example code and the detailed explanation. After cross-referencing them with the docs I think I have a better understanding of how to use the different types of handlers. The files are not that big (all should be < 10 MB), but I agree that there is no need to do extra parsing if there are more elegant ways to do it.

      Thanks again for your help, and for writing XML::Twig. I am thoroughly impressed with how little code I will have to write to accomplish this task. :-)

[reply]

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