[mapserver-dev] pre-RFC - Add an HTTP request data provider to mapserver

[Lime, Steve D (DNR)]

What would process the data on the back end? OGR? If so what about a parameterized (e.g. URL template)
that it would do the work on. E.g.:

  CONNECTIONTYPE OGR
  CONNECTION 'a url that we substitute some values (e.g. extent, scale, projection) into'

and take advantage of OGR's format recognition. Seems like a useful addition to that library if it doesn't
do it already. As long as the URL returned data OGR could process it would work in MapServer.

Steve

-----Original Message-----
From: mapserver-dev-bounces at lists.osgeo.org [mailto:mapserver-dev-bounces at lists.osgeo.org] On Behalf Of Stephen Woodbridge
Sent: Tuesday, July 27, 2010 3:14 PM
To: mapserver-dev
Subject: [mapserver-dev] pre-RFC - Add an HTTP request data provider to mapserver

Hi Mapserver Devs,

I am interested in getting input and interest in doing some possibly or 
partially funded development of the following.

USE CASE:

User has spatial data stored in a proprietary system, database, search 
engine, whatever. They want to pull that data into mapserver for 
rendering, querying, etc like any other data layer. They can access that 
data via PHP and possibly other tools. They would like to have a generic 
HTTP data provider LAYER added to mapserver where mapserver would make 
URL requests based on some defined template URL and the URL would return 
data in some  well know format like GeoJSON, GPX, KML, others.

The LAYER definition would look something like:

LAYER
   NAME "mylines"
   CONNECTIONTYPE HTTP
   CONNECTIONFORMAT GEOJSON|GPX|KML|...
   DATA "http://localhost/mydata.php"
   TYPE LINE
   ...
END

or maybe:

LAYER
   NAME "mylines"
   CONNECTIONTYPE HTTP/(GEOJSON|GPX|KML|...)
   DATA "http://localhost/mydata.php[?optional=user_args&...]"
   TYPE LINE
   ...
END

Mapserver would add well defined arguments to the URL like:

MODE=render|query|etc      - might be needed to set context of request
BBOX=xmin,ymin,xmax,ymax   - area of interest
FILTER=...                 - this could be a filter string of some kind
ATTRS=gid,color,name,...   - list of expected/required? attributes
TYPE=POINT|LINE|POLYGON    - type of spatial data expected
FORMAT=GEOJSON|GPX|KML|... - format to respond in
...                        - others as required


The idea here is to forward the data request to the URL and it would 
validate the request and throw an error or handle the request and return 
the results as expected. Mapserver would then handle this like any other 
LAYER.

BENEFITS:

In general this opens up mapserver to easily be glued into any data 
source by writing an small external adapter in PHP, Perl or anything 
thing that can be queried via a URL that can conform to whatever 
protocol we require for mapserver.

Much of the code already exists in mapserver for this, it is just 
getting reused as a new data provider.

ISSUES:

Other than the fact this this will not be the fastest data provider 
available, I can not think of any major one.

FUNDING:

I may be able to get some funding for this if we can get it into 6.0 and 
back ported to 5.6 even if it is not released on 5.6. Please contact me 
off list if you are interested in developing this. Currently on one 
format would need to be supported.

COMMENTS:

Please toss in your 2 cents on this. Raise issues, etc. The idea is to 
make this GENERIC so it can by used by anyone.
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