On 09/05/11 15:09, Chuck Huber wrote:
On 09/03/2011 02:17 PM, Robert Pearce wrote:
>> On Fri, 2 Sep 2011, Jorge Garcia wrote to us saying :
>>>
>>> To clarify, the XML file format will be implemented in Version 6 so
>>> from that point on version control systems will be very easily able to
>>> handle our files.
>>>
>> I think it needs to be pointed out that merely being a text file does
>> NOT mean version control systems will "be able to handle" the files any
>> better.
>>
>> All version control systems can "handle" binary files to the extent of
>> storing them. The extra features they can provide for text files are
>> diff and merge methods. However, these functions are universally
>> implemented on a line-by-line basis, such that the tool can identify
>> lines that have been added, deleted, moved etc. For most programming
>> languages, this line-by-line approach works well. For XML it absolutely
>> does not. The thing is, XML is fundamentally not line-based - it's
>> simply a token stream where the tokens are in ASCII rather than binary.
Rob makes an excellent point. This reflects on the long standing
requests for an ascii file format. The motivation for this is to be
able to merge changes just as we do with programming languages.
Consider, for a moment, all the loop elements within the ULP spec, and
how these would be expressed in XML. Wires, for example, don't seem to
be in any particular order. Are they sorted by layer, or by starting
location, or perhaps just unsorted and occur in the order in which they
were defined? A straight-out dump of these in XML format could mean
that a slight change to a wire (changing the width of the wire) would
cause it to be placed at the end of the list, which would generate a
significant change in the XML file rather than just a change in the
width tag.
So the new format not only needs to be an ascii format (XML is fine),
but also must be formatted to accommodate the intent behind the
requests. I assume that the software engineers at cadsoft will be
mindful of this.
Of course we have gone to great lengths to make sure that
modifications remain "local" as far as possible.
The change of a wire width you mentioned above will surely
result in only one single line changed in the XML file.
Klaus Schmidinger
--
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Klaus Schmidinger Phone: +49-8635-6989-10
CadSoft Computer GmbH Fax: +49-8635-6989-40
Pleidolfweg 15 Email: kls@cadsoft.de
D-84568 Pleiskirchen, Germany URL: www.cadsoft.de
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