GIS Web Services

First, lets define the generic term Web services. Applications or components that can be published, found and used on the World Wide Web are called Web services.  Webservices are XML based (Now, to understand that, you don't need to study XML, I promise!) and the pudding of using web services is that it is highly inter-operable and is designed to  handle specific or limited set of tasks.

So, from the above snippet, the obvious things are

a) Web services communicates between applications
b) Information can be published or distributed to a large audience or users
c) Web Services can be reused for existing services
d) Great in handling specific task


Now, with the above four things let me show you, how this model of web services can be replicated for GIS Mapping.

a) Web Services are building block of any mapping software. Take for example ArcMap which is nothing but clusters of ArcObjects tools and components, integrated to provide users with Geo-spatial analysis capabilities. One step further, Sharing map services between application of ArcMap to ArcServer (and Web Adaptors between, indeed), that's another classic case of demostrating Web Services framework

b)  The ArcServer, ArcOnline, Portal for ArcGis all come with capabilities to publish mapping services to large user base, either on web or within organizations or between organisations.

c) The map services so published, can be constantly overwritten over existing services, so for the spatial data sets to be up to date or current.

d) Specific Task. This is my favorite and i would prefer to elaborate it the ESRI way!!! The user/client capabilities on the mapping interface, like

•  downloading maps for a specific location (Map Services)
• enabling the client to use all the ArcMap tool capabilities (Geo-processing Services) 
• data or feature updates (In DB terms "INSERT"), performed by the client (Feature Services)
• enabling the user to convert descriptive address or location names into lat/lon coordinates (Geocoding services)
• enabling the user to perform analysis of published route networks (Network Analysis)
• enabling clients to generate 3D maps (3D Scene Services)

• enabling user to measure, create buffers and project (GeoEvent "Extension" but also follows the Services model.

A Note on Framework:

Now, we get to the basics of actual Web Mapping. 

Any application is hosted on an Interface - what a user sees on the web page (Front-end), from the Server (Back-end) through data sets stored in Databases (Middleware). 

This framework applies for GIS, as well.

On an Open Source: The maps generated from QGis are stored in PostgreSQL and hosted through Geoserver service directory. These published maps can be either viewed on client viewers like uDig or further processed with OpenLayers and published on Web.

In ESRI: The maps generated from ArcMap, which of course of stored in Geo-databases, can be published directly are service through Arcserver.  The Service Directory of ArcServer lets you verify and test the web maps (and it's services), after which the map services can be further distributed to target clients.

The beauty lies in the details!... and i will elaborate on each of the segment and software in the upcoming posts....