[XML-SIG] how to check "grammar" of xml using a schema or DTD with elementtree

[Margie Levine]

I'm new to XML parsing and am using elementtree to parse a very simple
xml file that is similar to the one below:

 

<groceries>

  <category name="fruit">

    <item name="apple" number="8"/>

    <item name="banana" number="12"/>

  </cagetory>

  <category name="frozen">

    <item name="icecream" flavor="chocolate" number="1"/>

    <item name="pizza" make="tombstone" type="cheese" number="3"/>

  </category>

</groceries>

 

Basically I am just trying to parse out the values and do something with
them in my program.  I'd like to define what the "correct" syntax for
this file is and have it checked automatically.  For example, in this
simple example I'd like to check that only a single type of subelement
is allowed under <groceries>, namely <category>  And that a only a
single type of sublement is allowed under <cagetory>, namely <item>.
Further, I'd like to check that <item> can have the attributes 'name'
and 'number', but no others.  Etc, etc.

 

Right now I am using elementtree to check this within my program.  IE, I
traverse the tree and make sure the xml meets the specifications.  Based
on my reading, it seems that I can use a DTD or scheme to define the
"grammar" of my xml, but I can't figure out how to actually set this up.
It seems like I should just be able to specify my DTD or Schema and then
call ElementTree's parse method and Elementtre should just give me
errors if the xml doesn't conform to the rules.  Maybe Elementtree just
doesn't support this?  I see some doc that says lxml supports schema's,
will lxml do this for me?

 

What are other folks doing to deal with this?  It seems like such an
obvious need, yet when I google I don't find anything pointing me to a
simple solution.

 

Thanks!

 

Margie

 

 

 

 

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