[Mapserver-users] ArcIMS vs MapServer Functionality

[Charlton Purvis]

I have been asked similar questions, and I want to make sure that I've
got the right answers.  Unfortunately, I haven't had time to test these
things out myself, so I can't speak from experience.

They appear on our bulletin board here,
http://caro-coops.org/bb/viewtopic.php?p=346#346, in a more legible
format.  But I'll include a subset as part of this post for your review
below.

Thanks for your help.

Charlton

=========================================

(a) What is done on the MapServer end? 

    MapServer can act as a WMS server and a WMS client. Who cares? See
(b). 

(b) What is done on the ArcIMS end? 

    MapServer can access data on an ArcIMS box. But using only this
ArcIMS Servlet Connector does not enable ArcIMS boxes to understand
MapServer-served data. That is addressed in (c). 

Quote: 
From
http://www.alexandria.ucsb.edu/dev/doc/esri/Documentation/Installing_Arc
IMS/introduction/overview.htm which is reference material for ArcIMS
4.0.1. 

The ArcIMS Servlet Connector is the standard connector used for ArcIMS,
and it supports the OpenGIS Consortium (OGC) Web Map Service (WMS) 1.1.0
implementation specification. It uses the ArcIMS language, ArcXML, to
communicate from the Web server to the ArcIMS Application Server. The
ArcIMS Servlet Connector provides Map Service-level user password
authentication. You need the ArcIMS Servlet Connector to administer your
ArcIMS site and author and design ArcIMS Web pages. 

(c) Caveat: MapServer jumps through hoops in order to accommodate ESRI
users: bypass a WMS approach. Instead, have MapServer provide output in
native ESRI formats (i.e. shapefiles). 

Quote: 
According to Dave McIlhagga of DM Solutions: 

    This can be achieved with the latest versions of MapServer (v. 4.0)
which is currently in Beta. It has been re-designed to support the
capacity to output data in one of a number of directly accessible data
formats such as Shapefiles and MapInfo MITab files. 

    Of course, the exact manner in which this would happen is very
application specific so work would have to be done in one of the
scripting environments to allow the application to control the area of
extraction you are interested in pulling out, the layers you want to
receive, and the format you want to receive them in. 


(d) If all else fails, fake out the ESRI clients (like ArcMap,
ArcCatalog, etc.) by acting as an ArcIMS emulator. This involves the use
of a PostgreSQL database (w/ PostGIS extensions installed). 

Quote: 
According to Paul Ramsey, a PostGIS-er: 

    On the bright side, ArcXML is (relatively) easy to emulate. I have
written an emulator (http://postgis.refractions.net/download.php) called
IMSEmu which puts an ArcIMS interface around mapserver, allowing ArcMap
to connect to it directly, as if it were an ArcIMS server. Ed McNierney
and Steve Greenwood will shortly be releasing a PHP script which has the
same functionality and some enhancements they have added. 


Bottom line is that: 
* MapServer can be a WMS server and a WMS client. 
* ESRI ArcIMS (w/ the servlet extention) can only be a WMS server. 
* The missing piece is that ArcIMS cannot be a WMS client. That's where
(c) comes in. 

So let's answer some questions that were posed earlier: 

(1) Can an ArcIMS user looking at a Mapserver page overlay their own
local arc/shape files, or alternatively easily "pull" the data from the
mapserver application into their local arc-Ims application? 

Yes: using (a) and (c). Incidentally, ESRI might be moving toward
becoming a WMS client, but IMS isn't there yet; other Arc products are.
http://www.esri.com/software/opengis/interopdownload.html 

(2) Can we do the above in reverse, i.e. data served via arc-IMS to be 
pulled easily over mapserver plots? 

Yes: using (a) and (b). 

(3) I am not sure exactly how the OPeNDAP protocol would function via
Mapserver. In our case, we offer our data via DODS but this is [not]
accessible regardless of what tools we provide via ArcIMS. Perhaps I am
missing something here. 

An interesting point. As things stand right now, the answer is yes and
no. We have netCDF data (and eventually HDF data) on DODS servers that
needs to be shared and mapped. DODS allows the sharing. No problem. But
to map them, I've had to create scripts that retrieve these shared
datasets and through a few automatable steps, end up populating a
MapServer map. 

We're happy to share!