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To: python-list@python.org
From: Robert Kern <robert.kern@gmail.com>
Subject: Re: enumerate XML tags (keys that will become headers) along with text (values) and write to CSV in one row (as opposed to "stacked" values with one header)
Date: Mon, 29 Jun 2015 14:04:45 +0100
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On 2015-06-28 22:00, Denis McMahon wrote:
> On Sun, 28 Jun 2015 09:46:36 +0200, Stefan Behnel wrote:
>
>> Denis McMahon schrieb am 26.06.2015 um 09:44:
>>> xml data is an unordered list, and are trying to assign an order to it.
>>>
>>> If the xml data was ordered, either each tag would be different, or
>>> each tag would have an attribute specifying a sequence number.
>>
>> XML is not unordered. The document order is well defined and entirely
>> obvious from the data. Whether this order is relevant and has a meaning
>> or not is, however, not part of XML itself but is left to the semantics
>> of the specific document format at hand. Meaning, XML document formats
>> can choose to ignore that order and define it as irrelevant. That
>> doesn't mean it's not there for a given document, but it may mean that a
>> re-transmission of the same document would be allowed to use a different
>> order without changing the information.
>>
>> This property applies to pretty much all structured data formats and not
>> just XML, by the way, also to CSV and other tabular formats.
>
> The point I am trying to make to OP is that the following two XML
> fragments define the same data:
>
> <things>
>    <thing>string 1</thing>
>    <thing>string 2</thing>
>    <thing>string 3</thing>
> </things>
>
> and:
>
> <things>
>    <thing>string 3</thing>
>    <thing>string 2</thing>
>    <thing>string 1</thing>
> </things>
>
> Each <thing> is just a member of the collection things, the xml does not
> contain sufficient information to state that <things> is an ordered
> collection containing a specific sequence of <thing>.

Without reference to a schema that explicitly defines the children of <things> 
to be unordered, this is not true. The XML Information Set defines the children 
of all elements to be an ordered set (in contrast to attributes, which are 
unordered). A particular XML schema may choose to consider the order of children 
of a particular element to be irrelevant, but XML itself keeps them ordered.

http://www.w3.org/TR/xml-infoset/#infoitem.element

If it didn't, then XHTML would have a hell of a time with ordered constructs 
like this:

   <ol>
     <li>First item</li>
     <li>Second item</li>
     <li>Third item</li>
   </ol>

-- 
Robert Kern

"I have come to believe that the whole world is an enigma, a harmless enigma
  that is made terrible by our own mad attempt to interpret it as though it had
  an underlying truth."
   -- Umberto Eco