Re: Documentation and explanatory diagrams

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Tom Lane wrote:

> But we need to do some experimentation with specific
> tools and see what the output really looks like and how it changes
> given small changes in the diagram, before we choose anything.
>

I did some tests sometime ago for my proposal (DIA) and the result were
sent to the list:
http://archives.postgresql.org/pgsql-docs/2010-04/msg00038.php

I have testet this again and here is the result:

* The XML file used by DIA has a block of xml definitions per object in
the diagram. This block contains all the attributtes of the object, from
color and position to lines style, witdh, etc. In addition to this,
there is a block at the begynning of the xml file with some general
information about the diagram, background, boundaries, etc.

* Changing one of the attributes of an object only change the value of
this attribute in the xml file. Tha same for the global information
attributtes.

* The objects in a diagram are saved always in the same order they were
created. e.g. if you create a diagram with 3 objetcs they will get
asigned an internal ID (00,01,02) and they will continue having this ID
(and position in the xml file) as long as they are not deleted. e.g. If
we delete the second object created, the IDs in the xml file will get
reasigned (00->00 and 02->01)

All this means that xml files generated by DIA er VCS friendliness, they
only change the attributes/objects changed between versions of the
diagram. It can be used without problems to diff the contents and create
patches that modify the last version of the diagram.

For all this to work this way, the xml files generated by DIA can not be
compressed (this is defined when you save a diagram). They will use more
diskspace in the VCS system but very little in the compressed gz/bz
source file distributted with every release. This can be a problem if a
few extra MB in the VCS system is a problem.

With this e-mail and my last summary
http://archives.postgresql.org/pgsql-docs/2010-07/msg00096.php, I think
I do not have more to say about my proposal.

regards,
- --
Rafael Martinez, <r(dot)m(dot)guerrero(at)usit(dot)uio(dot)no>
Center for Information Technology Services
University of Oslo, Norway

PGP Public Key: http://folk.uio.no/rafael/
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