XML Mapfiles... are we looking to far?

[Tamas Szekeres]

Hi,

There is no doubt about the usability and the wide audience of the
XML/XSL technology in general. However in the mapserver's perspective
it's just another format to persist the map configuration. At the
developer's perspective another parser and writer is to be
implemented. The parsed xml document object is to be immediately
translated into the mapserver structures that can be handled
regularly. If one would extend the schema at least the internal
structures and conversion method should be modifyed accordingly, not
easier than with the current implementation.

At the user's perspective if the configuration is generated
automatically using xml and xsl configuration templates creating xml
or text base output seems to be equivalent in complexity.

If the user creates the configuration by hand using xml is slightly
more benefical due to the high number of the tools for editing the xml
files. However in the mapserver's case making sure the file is
syntactically correct is not too much. One would like to see the
generated map immediately using a WYSWYG tool, so mapserver will come
into the picture and ensures the validation of that file by the way.

However in my opinion it would be benefical to provide support for
multiple configuration formats in a provider based fashion controlled
by compilation switches. It would be crucial to retain the
compatibility with the existing map file format, and the user could
decide to include a provider and all of the dependent libraries on
demand. This approach could support the conversation between theese
formats easily.

Besides the file based configurations we should also consider to
support other location types to read and write the configuration data.


Tamas



2006/7/18, Julien, Heryk <hjulien at nrcan.gc.ca>:
>
>
>
>
> Hi Tamas,
>
> I think there are many advantages in using xml. First, XML files are easy to
> create and schema validation can check document structure while you are
> writing it. Schema aware editors can also give you hints and do automatic
> inputs of required tags while writing mapfile document. Yes Mapserver
> validates mapfiles, but I think the addition of a mapfile structure
> validator like xsd would facilitate mapfile creation and debugging.
>
>
>
> Schemas can help newbie's to create there first config files and advanced
> users and developers visualise, communicate and work on the current mapfile
> format. I also think that it would be easier to extend the mapfile structure
> in future Mapserver versions if we where using an xml format... for example
> adding new OGC tags to mapfiles would be very easy.
>
>
>
> Plus with all the new xml editing tools out there, schema creation,
> visualisation and validation has become a child's play (hmmm.... well
> almost!).
>
>
>
> Just as you said earlier, automating map config creation would be another
> great benefit. And if Mapserver could read non static mapfiles (via URL's),
> xml would be a great way to create dynamically generated mapfiles. If we
> consider mapfiles as being a kind of database (or database pointer),
> wouldn't it be great to be able to easily process it on the fly? XML coupled
> with xsl, xpath and databases would be one great way to do that kind of
> manipulation. A little like OGC WMC layers that are pointing to different
> data layers (wms layers), we could have dynamically generated mapfiles
> instead of one huge static file containing all data layers.
>
>
>
> Xml being rapidly more and more widespread, ways for developers to input
> serialization data into Mapserver would be much greater and flexible.
> Mapfile management would be more open and greatly enhanced with the use of
> xml. For example a url fetched xml mapfile would enable us to easily modify
> a mapfile service according to certain parameter like language. We could
> thus have an automated multilingual mapfile. Currently we have to save a
> static mapfile for every language. They all point to the same data but
> containing language specific titles and metadata.
>
>
>
> Being an OGC fan, I think there decision to use xml to disseminate data and
> ease interop has been a good choice. In that same line of thought, I think
> an xml mapfiles format to serialize Mapserver would be a logical next step.
>
>
>
> Cheers
>
> Héryk
>
>
>
>
>
> _____________________________
>
> Héryk Julien
>
> Research Officer
>
> Natural Resources Canada
>
> 490 rue de la Couronne
>
> Québec, Canada
>
>