[Openstreetmap-dev] More on GPX schema

Immanuel Scholz immanuel.scholz at gmx.de
Thu Sep 22 08:08:28 BST 2005


> How about (to cut down on file size...)

If your goal is small uncompressed files, don't use XML ;-)

Compressed xml usually eliminates all or most of the redundance
introduced by starting/ending tags, so this could be an option.

You are right, that using very common keys such as "foot" or "car"
reduce the uncompressed xml size by an remarkable amout of bytes. My tip
is, that the reduction of a compressed xml is not significant (but I
haven't tried).

> <trk>
> <number>50521</number>
>  <name>Lodge Road</name>
>  <extensions>
> <permissions foot="yes" horse="yes" car="yes"/>
> <class>secondary</class>
> </extensions>

If key's must be in xml-attribute-format, this seems to be ok. But I see
keys as some kind of data too.

How do you try to transfer key: "Gauß/Krüger" value: "RD83" ? ;-)

Next thing is, that you try to assign some keys to a type. How do you
decide, that "foot" is a permission, while "class" is not? I thought key
and value names are freely choosen by the user. How do you going to
transfer key:"foo", value:"bar" ? as <foo>bar</bar> ? Or maybe as
<unknown foo="bar" /> ? 

But: How do you define such "common keys"? Once and for all? The world
will change, so will the key names used. If you alter the structur of a
key/value pair after it is introduced, you have to recode all
applications which use this key to parse the new format correct (except
you define a very complex way of telling the xml-structure within the
xml document or something like that).

I prefer "the simplest way that could possible work", which is some
plain enumeration of key/value pairs. If this is unacceptable in file
size, try simple things (because already implemented in many places)
like gzip-compression. If it is still unacceptable, argue again for a
more complex data representation ;-)

Ciao, Imi.

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