XML Mapfiles... are we looking to far?

[Kralidis,Tom [Burlington]]

Sounds like this would be a worthwhile discussion in Lausanne :)


> -----Original Message-----
> From: UMN MapServer Developers List 
> [mailto:MAPSERVER-DEV at LISTS.UMN.EDU] On Behalf Of Julien, Heryk
> Sent: Wednesday, July 19, 2006 2:04 PM
> To: MAPSERVER-DEV at LISTS.UMN.EDU
> Subject: Re: [UMN_MAPSERVER-DEV] XML Mapfiles... are we 
> looking to far?
> 
> 
> Hi,
> I made a first try at creating an xml mapfile schema (xsd) 
> this morning. It's not finished yet but the general idea is 
> there... I just wanted to have your comments before pushing 
> on. I used the same element names as in the text mapfile. 
> This will permit us to write a stylesheet (xsl) that loops 
> loop thru the xml file and reuses the element names in the 
> mapfile text output format... this way the xsl will be easy 
> to maintain in future xsd versions.
> 
> I have to point out that I do not know all of Mapserver's 
> mapfile elements so I just went thru the map and layer 
> reference documentation to write the xsd. I usually work with 
> only the basic mapfile tags needed to create wms and wfs services. 
> 
> (The xsd is attached to this email. Is there a special way to 
> send an attached file to the dev group mailing list?)
> 
> Héryk
> 
> -----Message d'origine-----
> De : Steve Lime [mailto:Steve.Lime at dnr.state.mn.us] 
> Envoyé : 19 juillet 2006 10:51
> À : MAPSERVER-DEV at LISTS.UMN.EDU; Julien, Heryk
> Objet : Re: [UMN_MAPSERVER-DEV] XML Mapfiles... are we looking to far?
> 
> I've thought for sometime that using XSL might be a nice 
> bridge as we move in that direction. At least one could 
> manage their configuration in XML than transform as necessary 
> to create a mapfile for run-time use. There were some folks 
> comtemplating developing a configuration schema file as a 
> start a while back but they've disappeared as far as I know. 
> 
> I think that would be a nice first step if someone were to 
> take it on: create mapfile XSD and XSL files. Ultimately we 
> probably will have to be able to read a XML config file. I've 
> toyed with using expat in developing a mapfile_xml.c. The 
> underlying C structures would be the same, but a SAX parser 
> would be used instead of Flex to tokenize the config file. 
> Just never had time.
> 
> Steve
> 
> >>> "Julien, Heryk" <hjulien at NRCAN.GC.CA> 7/18/2006 8:45 AM >>>
> 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
> 
>  
> 
> 
>