The document presents an introduction to resource-oriented architecture (ROA) and its relevance to geospatial data, discussing the transition from traditional data handling to a more dynamic, linked approach. It highlights various technologies and paradigms such as REST, SOA, and linked open data, emphasizing the importance of URLs and metadata in modern web-based systems. The presentation concludes with a summary of the web's structure, asserting that geospatial data plays a critical role in this architecture.

1. Introduction to the
Ressource Arnulf Christl
Oriented http://www.metaspatial.net
Architecture

2. Download
...this slide set and other stuff at:
http://arnulf.us/Publications
On slide share the next slide links to the
YouTube video.
Please fast forward to ~ minute 26
Download: http://arnulf.us/publications/resource­oriented­future_arnulf­christl.odp (pdf)
See also article on: Introduction to Semantic Web Technology and Geodata (pdf)
YouTube video: http://www.youtube.com/watch?v=DDIeR_JLO_o&feature=player_detailpage#t=1637s
SmartKorea 2011, Seoul, Korea Arnulf Christl 2 / 45

3. Arnulf Christl, Geospatial Systems Architect
● Member of OGC Architecture Board
● OSGeo President
● OpenStreetMap advocate
My alter ego Seven is an Ex­Borg
SmartKorea 2011, Seoul, Korea Arnulf Christl 3 / 45

4. Introduction
● Hypes
● SDI, SOA, SOAP, ESB, ROA, RESTful
● Architecture Models: RM­ODP View Points
● The components of the ROA
● The Internet and the Web
● RESTful, REST, Linked Open Data, ROA
● ...and how it all might come together
SmartKorea 2011, Seoul, Korea Arnulf Christl 4 / 45

5. Why?
Imagine you have data (population statistics)
and want to show them in a map.
Total | Male | Female | Unknown
What do you need to do?
SmartKorea 2011, Seoul, Korea Arnulf Christl 5 / 45

6. ETL, process, present
● Get the spatial data somewhere (hopefully)
● Download it (or > use a service)
● Transform it to your system (or > interoperate)
● Process your data to fit with the spatial data
● Configure your system (cartography, etc.)
● Present
SmartKorea 2011, Seoul, Korea Arnulf Christl 6 / 45

7. Then the spatial data changes!
What do you need to do?
Go back and over again...
Awww, Snap!
SmartKorea 2011, Seoul, Korea Arnulf Christl 7 / 45

8. But let's Imagine that...
every geometry has a URL...
...and you simply link your data to it.
...and if anything changes you are
automagically notified.
Sounds like Alice in Wonderland?
SmartKorea 2011, Seoul, Korea Arnulf Christl 8 / 45

9. Hypes
Geospatial Data Infrastructure
● The core idea goes back to the 90ies of the last
Millennium (no ubiquitous Internet yet)
● Paradigm change from desktop to
client­server architectures
(...before that it was called the Mainframe,
now we call it the Cloud...)
SmartKorea 2011, Seoul, Korea Arnulf Christl 9 / 45

10. Hypes
Service Oriented Architecture (SOA)
● Fairly loose concept, lots of room for
interpretation
● Software­centric (!)
● Single Point of Access (one single URL)
● OGC Standards WMS, WFS
SmartKorea 2011, Seoul, Korea Arnulf Christl 10 / 45

11. Hypes
Enterprise Service Bus
● Buzzword
● Many proprietary / closed solutions
● High potential for Vendor­Lock­In
● Came to some fame in the geospatial domain
because of early INSPIRE
SmartKorea 2011, Seoul, Korea Arnulf Christl 11 / 45

12. Enterprise Service Bus
SmartKorea 2011, Seoul, Korea Arnulf Christl 12 / 45

13. Internet & Web (2.0)
?
?
SmartKorea 2011, Seoul, Korea Arnulf Christl 13 / 45

14. Hypes
SOAP
● Just a similarity of name with "SOA"
● Basics: Remote Procedure Call & Messaging
● Message­oriented
● Client requires description (WSDL)
● Technology­ and Service­centric
● W3C Standard (several of them, and dying out)
SmartKorea 2011, Seoul, Korea Arnulf Christl 14 / 45

15. Hypes
RESTful
● Core idea: Everything is the representation of a
resource
● Data (not technology) centric
● Web­centric: Implements HTTP correctly
● No official encoded standard (yet – but
increasing usage all the same)
● Optimized scalable
SmartKorea 2011, Seoul, Korea Arnulf Christl 15 / 45

16. IT­Architectures
RM­ODP
● Refrence Model – Open Distributed Computing
● Model to describe software architectures
● Developed in the mid 90s (US DoD)
● ISO Standard
● Applicable in enterprise systems (B.I.G.)
● Separation in so called "View Points"
SmartKorea 2011, Seoul, Korea Arnulf Christl 16 / 45

17. RM­ODP View Points
People
● Enterprise View Point (organization)
● Business View Point (processes, work flows)
● Information View Point (data schema, ROA)
● Computational View Point (services, SOA)
● Technology View Point (technology, software,
SOAP, RESTful APIs, etc.)
Technology
SmartKorea 2011, Seoul, Korea Arnulf Christl 17 / 45

18. Basics of the ROA I.
● The Resource Orientied Architecture (ROA) is
an information modell.
● It is not a distinct technology...
● ...but Web technology (HTTP + URLs) are
currently the best fit
● The ROA describes conditions in which the
Web works optimally.
SmartKorea 2011, Seoul, Korea Arnulf Christl 18 / 45

19. Basics of the ROA II.
● All data is designed in resources.
● Data can be delivered in different ways.
● Each delivery is simply a different
representation of the same resource
● The representation is the form of the content
● The separation of form and content is crucial.
Immeasurably important!
(We do have heard this before: think HTML and CSS)
SmartKorea 2011, Seoul, Korea Arnulf Christl 19 / 45

20. Basics of the ROA III.
Looking at geospatial data as a resource, it can come
in a variety of representations:
● A map image (OGC WMS, tile, static, PNG)
● OGC Capabilities Document (XML)
● Metadata (in an ISO profiel, as HTML­file, etc.)
● Coordinates (GML, KML, WKT, Shape, etc. )
● Legend image (PNG)
● and so on...
SmartKorea 2011, Seoul, Korea Arnulf Christl 20 / 45

21. Map Image
http://www.metaspatial.net/cgi­bin/germany­wms?
VERSION=1.1.1&REQUEST=GetMap&SERVICE=WMS&LAYERS=Topographie,Topographie,Staatsgrenze,Bundeslaender,Staedte,Postleitzahlbereiche,Postleitzahlen,Bahnlinien,Fluesse,Strassen&STYL
ES=,,,,,,,,,&SRS=EPSG:4326&BBOX=7.05,50.69004999999999,7.161,50.78995&WIDTH=500&HEIGHT=450&FORMAT=image/png&BGCOLOR=0xffffff&TRANSPARENT=TRUE&EXCEPTIONS=applicatio
n/vnd.ogc.se_xml
SmartKorea 2011, Seoul, Korea Arnulf Christl 21 / 45

22. Legend
http://www.metaspatial.net/cgi­bin/mapserv?
map=/home/data/germany/germany.map&version=1.1.1&service=WMS&request=GetLeg
endGraphic&layer=Topographie&format=image/png
SmartKorea 2011, Seoul, Korea Arnulf Christl 22 / 45

23. OGC Capabilities Document
http://metaspatial.net/cgi­bin/germany­wms?REQUEST=GetCapabilities&SERVICE=wms&VERSION=1.1.1
SmartKorea 2011, Seoul, Korea Arnulf Christl 23 / 45

24. metadata (e.g. INSPIRE)
http://www.metaspatial.net/geoportal/php/mod_showMetadata.php?resource=layer&id=20145
SmartKorea 2011, Seoul, Korea Arnulf Christl 24 / 45

25. Raw Geospatial Data (yummy)
<?xml version='1.0' encoding="ISO­8859­1" ?>
<wfs:~FeatureCollection
xmlns:wfs="!http://www.opengis.net/wfs"
<gml:featureMember>
<Postleitzahlbereiche>
<gml:polygonProperty>
<gml:Polygon srsName="epsg:31467">
<gml:outerBoundaryIs>
<gml:LinearRing>
<gml:coordinates>
3365496.566430,5624978.448441
3365521.124423,5625013.908323
3365458.518013,5624832.944095
[...]
3365502.496403,5624908.664231
3365531.735324,5624963.958282
3365496.566430,5624978.448441
</gml:coordinates>
</gml:~LinearRing>
</gml:outerBoundaryIs>
</gml:Polygon>
</gml:polygonProperty>
<gid>3695</gid>
<oid>15223704</oid>
<plz99>53111</plz99>
<item_plz>53111</item_plz>
</Postleitzahlbereiche>
</gml:featureMember>
</wfs:FeatureCollection>
</pre>
http://arnulf.us/PLZ#Download
SmartKorea 2011, Seoul, Korea Arnulf Christl 25 / 45

26. Any Geospatial Data
SmartKorea 2011, Seoul, Korea Arnulf Christl 26 / 45

27. The Internet
● DNS (Domain Name System)
● Internet Protocol Suite
● TCP/IP, TLS
● HTTP
● URL Human error
● ...
http://en.wikipedia.org/wiki/Internet
● Simple Mail Transfer Protocol (SMTP) Spam
SmartKorea 2011, Seoul, Korea Arnulf Christl 27 / 45

28. Domain Name System
de Country code: "de" is Deutschland (Germany)
tum Domain: Technical University of Munich
bv Sub domain: Bauingenieur­ und Vermessungswesen
rtg Sub domain: runder Tisch GIS e.V
www ...superfluous leftover from the 90s
index.php Document (in this case a script that will dynamically
create an HTML document).
More (ugly) parameters the script needs:
option=com_content&task=view&id=535&Itemid=9&Itemid=110
As a link: This Link is opaque but still delivers the same
document.
SmartKorea 2011, Seoul, Korea Arnulf Christl 28 / 45

29. Web sites
can have different
adresses (URL)
SmartKorea 2011, Seoul, Korea Arnulf Christl 29 / 45

30. The Flexibility of the DNS
The private Web site of the author can be reached through
any of the following (and maybe more) unique URL:
http://arnulf.us
http://www.arnulf.us
http://arnulf.us/Main_Page
http://arnulf.us/Runder_tisch_gis/introduction_to_the_Web
http://bit.ly/arnulf_christl
http://zpatial.org
http://r32916.ovh.net
http://94.23.196.65
http://178.32.100.197/
SmartKorea 2011, Seoul, Korea Arnulf Christl 30 / 45

31. HTTP
Hyptertext Transfer Protocol knows four basic
operations:
● Get HTTP is the Application
Protocol of the Internet.
● Put
The Web is the
● Post Application.
● Delete
These are sufficient to read, write, update and
delete. Voila: CRUD.
SmartKorea 2011, Seoul, Korea Arnulf Christl 31 / 45

32. The Web is: Documents
<html xmlns="http://www.w3.org/1999/xhtml" xml:lang="de­de" lang="de­de">
<head>
<meta http­equiv="content­type" content="text/html; charset=utf­8" />
<meta name="robots" content="index, follow" />
<meta name="description" content="Die Seite informiert über die
Studienangebote, die Forschungseinrichtungen und Organisation
der Fakultät für Bauingenieur­ und Vermessungswesen der
Technischen Universität München" />
<style type="text/css" style="display:none"> […] </style>
</head>
<body>
<a href="http://www.tum.de"><img src="http://.../tum_logo.gif"
alt="TUM" width="227" height="117" /></a>
[...]
Willkommen an der Fakultät für Bauingenieur­ und Vermessungswesen
[...]
</body>
http://www.bv.tum.de/
</html>
SmartKorea 2011, Seoul, Korea Arnulf Christl 32 / 45

33. HTTP URI – Links
The most important aspect of the Web are links. Links are
always directed graphs (relationships):
Subject >>> Relation >>> Object
Metaspatial >>> Link >>> Scrum Alliance
<a href="http://www.scrumalliance.org/">Scrum Alliance</a>
Coincidence? Geospatial data has similar relations...
postal code < > is neighbour of < > postal code
county < > contains < > town
SmartKorea 2011, Seoul, Korea Arnulf Christl 33 / 45

34. Resource Description Framework
The RDF (Resource Description Framework) format
(which is a standard) implements these directed relations
in so called triples.
● Geospatial data can be transformed into RDF
notation. But this does not help much (yet).
● More interesting (right now) is the association of
spatial data with other data using RDF.
SmartKorea 2011, Seoul, Korea Arnulf Christl 34 / 45

35. The Web – Links
Linked Geodata: http://linkedgeodata.org/Datasets
SmartKorea 2011, Seoul, Korea
Arnulf Christl
35 / 45

36. Problem!
The Instability of the Web:
<html>
<head>
<title>404 Not Found</title>
</head>
<body>
<h1>Not Found</h1>
<p>The requested URL /asdfg was not found on this server.</p>
<hr>
<address>Apache Debian Server at www.metaspatial.net Port 80</address>
</body>
</html>
But the solution is already contained within HTTP!
SmartKorea 2011, Seoul, Korea Arnulf Christl 36 / 45

37. HTTP Status Codes
● Informational 1xx
● Successful 2xx (200 OK)
● Redirection 3xx (301 Moved Permanently)
● Client Error 4xx (404 not found)
● Server Error 5xx (500 internal server error)
http://www.rfc­editor.org/rfc/rfc2616.txt
SmartKorea 2011, Seoul, Korea Arnulf Christl 37 / 45

38. Web 2.0 Concepts
● Technology: REST­architectures allows simple,
flexible creation, update and searching of data.
● Process: Updating metadata can be automatized
using GeoRSS.
● Content: Data belongs in open buckets so that
ontologies can grow on them.
● Ontologies are creaed by communities actually
using things (tagging, rating: "+1 and like")
SmartKorea 2011, Seoul, Korea Arnulf Christl 38 / 45

39. Technology: Using REST
Four Concepts Four properties:
● the Ressource ● Addressability
● her name (URL) ● Statelessness
● her representation ● Connectedness
● her links (relationships) ● Idempotence
The corresponding architectur model is the
Resource Oriented Architecture (short: ROA).
SmartKorea 2011, Seoul, Korea Arnulf Christl 39 / 45

40. Linking Geo und Meta Data
Geospatial data is always also metadata:
kml ­ Keyhole Markup Language (OGC)
xml ­ eXtensible Markup Language (W3C)
rss ­ Really Simple Syndication (W3C)
rdf ­ Resource Description Framework (W3C)
This can be so much more because it is all linked!
SmartKorea 2011, Seoul, Korea Arnulf Christl 40 / 45

41. Web 2.0
!
SmartKorea 2011, Seoul, Korea Arnulf Christl 41 / 45

42. Denmark http://geo.oiorest.dk/
SmartKorea 2011, Seoul, Korea Arnulf Christl 42 / 45

43. The Five Stars for Linked Open Data
From an idea by Tim Berners Lee:
make your stuff available on the Web (whatever format) under
★ an open license
make it available as structured data (e.g., Excel instead of
★★ image scan of a table)
★★★ use non­proprietary formats (e.g., CSV instead of Excel)
use URIs to identify things, so that people can point at
★★★★ your structured data (make data adressable)
★★★★★ Link your data with other data to create new information
http://inkdroid.org/journal/2010/06/04/the-5-stars-of-open-linked-data/
SmartKorea 2011, Seoul, Korea Arnulf Christl 43 / 45

44. Summary
● The Web "Operating System" is the Internet
● The Web is based on HTTP
● The Web is a gigantic App(lication)
● The API of the Web is RESTful
● The ROA is the architecture model of the Web
● Geospatial data is important! Software is just an
(exchangeable) tool and comes and goes.
SmartKorea 2011, Seoul, Korea Arnulf Christl 44 / 45

45. Many thanks for
your patience!
September 2012
Beijing, China
The annual Conference on
Free and Open Source Software
for Geospatial
Dieser Foliensatz darf zu jedem Zweck und
kopiert, weiterverwendet und verändert
werden. Siehe auch: Copystraight.
Copyright: Arnulf Christl 2010
Download: Foliensatz: http://arnulf.us/publications/resource­oriented­future_arnulf­christl.odp (pdf)
Artikel: http://arnulf.us/publications/Introduction_to_Semantic_Web_Technology_and_Geodata_v4.odt (pdf) 45 / 45