Service Oriented Architecture: Web GIS Services

2008 MidAmerica

GIS Symposium

Service Oriented Architecture:

Web GIS Services

Lisa Hallberg, Web Developer

Kansas Data Access & Support Center (DASC)

2008 MidAmerica

GIS Symposium

Service Oriented Architecture

•

What is “Service Oriented Architecture”?

–

SOA is a development and architectural model that

has grown out of the need to share data across

many different applications and operating systems.

–

In the business world, legacy software applications

were often stand-alone, and not intrinsically capable

of sharing data with other applications.

–

The SOA model enforces the idea of building

“services” that are independent of platform,

operating system, database or application.

–

Such services expose data and functionality through

2008 MidAmerica

GIS Symposium

SOA Standards

•

Examples

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TCP/IP – standard protocols, including HTTP and HTTPS

• TCP/IP protocols include requests and responses (success or

failure), but do not require a persistent connection (“stateless”)

–

XML – data format standard

• XML = “Extensible Markup Language”

–

JSON – data format standard used with Ajax in Web pages

• JSON = “JavaScript Simple Object Notation”

• Ajax = “Asynchronous JavaScript”

–

SOAP – data transfer standard using XML

• From the W3C spec: “SOAP is fundamentally a stateless, one- way message exchange paradigm”

–

REST – URL-based data transfer standard

• REST = “Representational State Transfer”

–

Other application programming interfaces (APIs)

• APIs are methods for interfacing with published services.

Examples include SOAP and REST. APIs can also be built for JavaScript libraries for use with Web clients.

2008 MidAmerica

GIS Symposium

Some (mostly GIS) Examples

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JavaScript API examples:

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Google Maps

http://code.google.com/apis/maps/

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OpenLayers

http://trac.openlayers.org/wiki/Documentation

•

SOAP example:

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http://www.arcwebservices.com/services/v2006_1/

AddressFinder?wsdl

–

Note that SOAP is self-documenting

•

REST example:

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GIS Symposium

SOA in a GIS Context

•

Serve GIS layers in a stateless, platform-

independent interface.

•

Provide clear documentation for how to access

and use the services.

•

Provide a variety of service options.

•

Leverage the service-oriented model as a

means to collect statewide data:

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Online digitizing tools: web-interface and REST

–

SOAP-based batch processing

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GIS Symposium

Overhauling KANSASGIS.ORG

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DASC’s Web site –

www.kansasgis.org

– has

been developed over the past three years as a

geoportal for sharing DASC’s GIS data.

•

Services include:

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Catalog of GIS data

•

Data for download

•

ArcSDE services

•

Entries categorized

–

ArcIMS web applications

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“Build your own map” application

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Custom web sites for various agencies

–

Data sharing services

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GIS Symposium

2. URL request received by the web server (Apache). 3. Server-side code (ColdFusion) interprets the request, sending it to an ArcIMS service to create the map image on the fly.

The Web GIS Context: The Old Way

The Internet

The Internet 1. Use the browser to request

GIS map data. 4. The server sends the custom web page and map image back to the requestor.

5. The web browser receives the content and interprets the content for display. Every change to the map (pan, zoom, change layers) requires all 5 steps to be repeated. User interface is not intuitive.

Example:

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GIS Symposium

KANSASGIS.ORG in an SOA context

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The future vision of our geoportal site will

include:

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Map caches as independent, customizable services

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Data catalog searchable by format as well as

category

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New technologies for sharing GIS-related topics

•

“Web 2.0” concepts such as blogs, RSS feeds, Wikipedia-

style documentation

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Self-documenting services

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Custom web development using GoogleMaps-style

(map caches + Ajax/DHTML) interfaces

•

Intuitive user interface

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Very fast response to tabular/database data through

asynchronous calls to ArcSDE/Oracle

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GIS Symposium

The Kansas “Recreation Finder” example

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Current web site is an ArcIMS application

utilizing inline frames to display the map and

tabular data:

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http://maps.kansasgis.org/recfinder

•

New version of the site uses a map cache and

JavaScript / Ajax interface to display map and

tabular data:

–

http://geoportal.kgs.ku.edu/navdatdb/

kdwpgoogle_dev7/public/

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GIS Symposium

Current Examples

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REST-based wrapper to ESRI’s ArcWeb

Services:

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http://www.kansasgis.org/rest/geocode.cfm

•

REST-based wrapper for KBI mapping service:

–

http://www.kansasgis.org/rest/index.cfm

•

SOAP service for uploading KBI point data (as

lat-long):

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http://www.kansasgis.org/soap/kbi.cfc?wsdl

–

http://www.kansasgis.org/soap/test.cfm

•

REST interface for creating ArcIMS images:

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GIS Symposium

Future Development Possibilities

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OpenLayers digitizing example:

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http://www.openlayers.org/dev/examples/editingtool

bar.html

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ArcGIS Server 9.3 JavaScript API examples

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http://giselle.kgs.ku.edu:8399/arcgis/rest/services

–

http://neutrino.kgs.ku.edu/restapi/qid2.cfm

2008 MidAmerica

GIS Symposium