XOM API for Processing XML with Java

[Marcelo Schneider <marcelo.schneider AT digitro.com.br>]

Just found a small bug in my test case - now different attribute order 
and different <a /> / <a></a> pass. My fault.

Order element isn't really significant in my use-case, anyway I just 
sorted them alphabetically before sending assuring they are always in 
the same order - not really the best solution, but probably the fastest 
one.

About whitespace, just found 
https://lists.ibiblio.org/sympa/arc/xom-interest/2005-December/002760.html 
and NormalizingFactory (on the examples). These appear to work just as 
expected, so I (hopefully) won't need something as robust as Saxonica.

Thanks a lot for the help!

--
Marcelo Frantz Schneider
SIC - TCO - Tecnologia em Engenharia do Conhecimento DÍGITRO 
TECNOLOGIA


Michael Kay escreveu:
> Your XML examples aren't well-formed, which makes it difficult to help you
> as we can't run your test cases.
>
> Whitespace is significant: if you want to eliminate it from the comparison,
> you'll have to do this by hand (e.g. by a transformation applied before
> canonicalizing).
>
> Attribute order, and the difference between <a></a> and <a/>, should not be
> significant.
>
> Order of elements is significant.
>
> You might like to look at the saxon:deep-equal() function as an alternative
> approach. 
>
> http://www.saxonica.com/documentation/extensions/functions/deepequal.html
>
> It takes a set of flags to define what features of the XML you consider
> significant or insignificant, and there is also an option to get
> explanations if the documents are deemed non-equal (though that doesn't seem
> to be needed for your application). It can be called from XPath and is also
> available directly from Java as the static method
> net.sf.saxon.functions.DeepEqual.deepEquals().
>
> Michael Kay
> http://www.saxonica.com/ 
>
>   
> > -----Original Message-----
> > From: xom-interest-bounces AT lists.ibiblio.org 
> > [mailto:xom-interest-bounces AT lists.ibiblio.org] On Behalf Of 
> > Marcelo Schneider
> > Sent: 10 October 2008 12:59
> > To: xom-interest AT lists.ibiblio.org
> > Subject: [XOM-interest] Comparing two semantically equal XML files
> >
> > Good morning list.
> >
> > In our company we currently store some graphs in XML form: 
> > the client can create a graph in a Java applet, that is sent 
> > to the server and stored as a file. Currently, all the graph 
> > <-> XML transformation is done using JDom.
> >
> > What I need to do is, when a user opens an already existing 
> > graph and tries to save it, compare the new XML sent with the 
> > previously existing XML in the server, saving only if they 
> > are different (so changing dates are correct).
> >
> > Googling around for a while I found out that a possible way 
> > to do that without worrying with XML structure was to use 
> > Canonicalization, and that XOM could possibly help me with 
> > that. Is this assumption correct? 
> > Here is what I'm currently doing:
> >
> > | public boolean areSemanticallyEqual(String oldXML, String newXML) {
> > |     Builder builder = new Builder();
> > |     Document oldDoc = builder.build(oldXML);
> > |     Document newDoc = builder.build(newXML);
> > |     // here canonicalize the old xml
> > |     ByteArrayOutputStream oldStream = new ByteArrayOutputStream();
> > |     Canonicalizer outputter = new Canonicalizer(oldStream , false);
> > |     outputter.write(oldDoc);
> > |     // here canonicalize the new xml
> > |     ByteArrayOutputStream newStream = new ByteArrayOutputStream();
> > |     Canonicalizer outputter = new Canonicalizer(newStream, false);
> > |     outputter.write(newDoc);
> > |     return Arrays.equals(oldStream.toByteArray(),
> > newStream.toByteArray());
> > | }
> >
> > However, the above code returns false when I compare XMLs 
> > like these (they all start with "<?xml version="1.0" 
> > encoding="UTF-8"?>"):
> >
> > xml1: "<tag1><tag2 id="1" name="a">Some 
> > Text</tag2></tag1><other tag />"
> > xml2: "<tag1>\n\t<tag2 id="1" name="a">Some 
> > Text</tag2>\r</tag1><other tag />" (with new lines, tabs and 
> > carriage returns)
> > xml3: "<tag1><tag2 id="1" name="a">Some Text</tag2></tag1><other 
> > tag></other tag>" (other valid xml representation)
> > xml4: "<tag1><tag2 name="a" id="1">Some 
> > Text</tag2></tag1><other tag />" 
> > (attributes order reversed)
> > xml5: "<other tag /><tag1><tag2 id="1" name="a">Some 
> > Text</tag2></tag1>" 
> > (yet another thing that looks the same, but I'm probably 
> > wrong assuming this should count as equal)
> >
> > I would expect the return to be always true, except for 
> > (maybe?) xml1 > xml5. Is this correct? Any hints are highly 
> > appreciated (:
> >
> > --
> > Marcelo Frantz Schneider
> > SIC - TCO - Tecnologia em Engenharia do Conhecimento DÍGITRO 
> > TECNOLOGIA
> >
> >
> >
> > --
> > Esta mensagem foi verificada pelo sistema de antivírus da Dígitro e
> > acredita-se estar livre de perigo.
> >
> > _______________________________________________
> > XOM-interest mailing list
> > XOM-interest AT lists.ibiblio.org
> > http://lists.ibiblio.org/mailman/listinfo/xom-interest

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