RESTful Web Processing Service

RESTful Web Processing Service Theodor Foerster, Andre Bruehl, Bastian Schaeffer AGILE 2011, Utrecht, the Netherlands

Why RESTful WPS?
Representational State Transfer (Fielding, 2000)
RESTful Web Services are available
For mapping & data
GeoWeb & Mashups
Producers = Consumers
Processing missing, but essential
Seamless integration
OGC WPS compatibility

Web-based Geoprocessing
Data  Information
GetCapabilities Execute WPS Process 1 Process 2 Process n DescribeProcess

REST – architectural style
“ ... a hybrid style derived from several of the network-based architectural styles [...] and combined with additional constraints that define a uniform connector interface.” (Fielding, 2000)
REST properties
Addressability, statelessness, connectedness, uniform interface
Resources accessible through URLs
HTTP Verbs
GET, POST, PUT, DELETE,…
Hypermedia approach
Representations & content negotiation

REST for Geo
Services available
Google, Yahoo, GeoCommons, etc.
Documents & specifications too

Design approach
Identify resources
What are the relevant resources?
Link resources
How does the client navigate between the resources?
Interaction with HTTP verbs
How to build the functionality
Multiple representations for the resources
Which are the relevant representations?

Resources
Links & navigation
Jobs & processes

HTTP verbs - Examples
Perform process
GET: processes/[process_ID]?[parameters]
Jobs
POST: processes/[process_ID]/jobs
GET: processes/[process_ID]/jobs
Job
GET: processes/[process_ID]/jobs/[job_ID]
DELETE: processes/[process_ID]/jobs/[job_ID]

Representations
ATOM, KML, GML, OGC WPS, JSON
Example – processes/buffer

WPS Compatibility
Processes modelled as resources
OGC WPS return formats possible through content negotiation
OGC WPS functionality fully reflected
Process by reference
Synchronous & asynchronous processing

Implementation

Client
JavaScript & RESTful APIs

Humanitarian relief workflow
Evaluating campsites for medical access
Inspired by OGC testbed
GeoCommons
Medical facilities
Campsites
Interactive & client-based chaining
Buffer, intersection & symDifference

Qualitative evaluation
Addressability
Each process & job is a resource and addressed via URL
Statelessness
Required information available at runtime
Connectedness
Resources are connected
Uniform interface
HTTP

Discussion & Outlook
Difference to ESRI GeoServices
Towards modular specifications at OGC
Incorporating WPS-T
Link to open linked data to be investigated

Conclusion
REST is a hot topic
GeoWeb & APIs
Process as a resource
Seamless integration through REST
OGC compatibility
Humanitarian relief use case

Thanks for your attention!
swsl.uni-muenster.de
Theodor Foerster
[email_address]

RESTful Web Processing Service

by Theodor Foerster

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