Resource Oriented Future for Geospatial Data

Introduction to the
Ressource Arnulf Christl

Oriented http://www.metaspatial.net

Architecture

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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

Arnulf Christl, Geospatial Systems Architect
● Member of OGC Architecture Board
● OSGeo President
● OpenStreetMap advocate

My alter ego Seven is an ExBorg

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


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?


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


Then the spatial data changes!

What do you need to do?

Go back and over again...

Awww, Snap!

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?

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...)


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


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


Enterprise Service Bus


Internet & Web (2.0)

?

?

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)

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

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"

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

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.


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)


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...


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


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

OGC Capabilities Document

http://metaspatial.net/cgibin/germanywms?REQUEST=GetCapabilities&SERVICE=wms&VERSION=1.1.1


metadata (e.g. INSPIRE)

http://www.metaspatial.net/geoportal/php/mod_showMetadata.php?resource=layer&id=20145

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

Any Geospatial Data


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

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.


Web sites
can have different
adresses (URL)


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/


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.

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>

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


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.


The Web – Links
Linked Geodata: http://linkedgeodata.org/Datasets

SmartKorea 2011, Seoul, Korea
Arnulf Christl
35 / 45

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!


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


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")


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).

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!


Web 2.0

!


Denmark http://geo.oiorest.dk/


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/


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.

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

Resource Oriented Future for Geospatial Data

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