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<div id="headings" class="head"> <a href="http://www.w3.org/"><img alt="W3C" src="http://www.w3.org/Icons/w3c_home" height="48" width="72" /></a>
<a href="http://www.w3.org/2005/Incubator/XGR/">
<img alt="W3C Incubator Report" src="http://www.w3.org/2005/Incubator/images/XGR" height="48" width="160" /></a>
<h1>W3C Geospatial Ontologies</h1>

<h2>W3C Incubator Group Report 23 October 2007</h2>

<dl>

  <dt>This version:</dt>

  <dd><a href="http://www.w3.org/2005/Incubator/geo/XGR-geo-ont-20071023/">http://www.w3.org/2005/Incubator/geo/XGR-geo-ont-20071023/</a></dd>

  <dt>Latest version:</dt>

  <dd><a href="http://www.w3.org/2005/Incubator/geo/XGR-geo-ont/">http://www.w3.org/2005/Incubator/geo/XGR-geo-ont/</a></dd>

  <dt>Authors:</dt>

  <dd><a href="http://www.traversetechnologies.com">Joshua
Lieberman</a></dd>

  <dd><a href="http://www.opengeospatial.org/">Raj
Singh</a></dd>

  <dd><a href="http://www.platial.com/">Chris Goad</a></dd>

</dl>

<p class="copyright"><a href="http://www.w3.org/Consortium/Legal/ipr-notice#Copyright">Copyright</a>
&copy; 2007 <a href="http://www.w3.org/"><acronym title="World Wide Web Consortium">W3C</acronym></a><sup>&reg;</sup>
(<a href="http://www.csail.mit.edu/"><acronym title="Massachusetts Institute of Technology">MIT</acronym></a>,
<a href="http://www.ercim.org/"><acronym title="European Research Consortium for Informatics and Mathematics">ERCIM</acronym></a>,
<a href="http://www.keio.ac.jp/">Keio</a>), All
Rights Reserved. W3C <a href="http://www.w3.org/Consortium/Legal/ipr-notice#Legal_Disclaimer">liability</a>,
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and <a href="http://www.w3.org/Consortium/Legal/copyright-documents">document
use</a> rules apply.</p>

</div>

<hr />
<div id="abstract">
<h2>Abstract</h2>

<p>This is a report of the W3C Geospatial Incubator Group
(GeoXG) as specified in the Deliverables section of its charter.</p>

<p>In this report we provide an overview and description of
geospatial foundation ontologies&nbsp; to represent geospatial
concepts and properties for use on the Worldwide Web.</p>

<p>Specifically the report:</p>

<ul>

  <li>discusses the need for extending the <a href="http://www.w3.org/2005/Incubator/geo/XGR-geo/">updated geo</a>
vocabulary</li>

  <li>describes specific geospatial ontologies for realizing the
extensions</li>

  <li>proposes examples of existing work from which to define and
develop the ontologies</li>

</ul>

<p>The intention is
that this report form input for a subsequent W3C geospatial activity to
further develop geospatial ontologies and define critical use cases for
their application in forming and working with Web resources.</p>

</div>

<div id="status">
<h2>Status of this document</h2>

<p><em>This section describes the status of this document
at the time of its publication. Other documents may supersede this
document. A list of <a href="http://www.w3.org/2005/Incubator/XGR/">Final
Incubator Group Reports</a> is available. See also the <a href="http://www.w3.org/TR/">W3C technical reports index</a>
at http://www.w3.org/TR/.</em></p>

<p>This document was developed by the <a href="http://www.w3.org/2005/Incubator/geo/">W3C Geospatial
Incubator Group</a>. It represents the consensus view of the
group, in particular those listed in the <a href="#ack">acknowledgements</a>,
on the use cases, requirements and general approach that should be
taken in meeting the identified needs.&nbsp; This is the second
report of the Group. The first <a href="http://www.w3.org/2005/Incubator/geo/XGR-geo/">report</a>
presents a basic vocabulary and ontology as an update to the <a href="http://www.w3.org/2003/01/geo">2003 geo</a>
vocabulary. This report presents and overview of proposed foundation
geospatial ontologies as extensions and elaborations of the updated geo
vocabulary. Earlier
informal drafts of this
report are <a href="http://www.w3.org/2005/Incubator/wcl/XGR-report-20060811/">archived</a>.</p>

<p>Publication of this document by W3C as part of the <a href="http://www.w3.org/2005/Incubator/">W3C Incubator
Activity</a> indicates no endorsement of its content by W3C, nor
that W3C has, is, or will be allocating any resources to the issues
addressed by it. Participation in Incubator Groups and publication of
Incubator Group Reports at the W3C site are benefits of <a href="http://www.w3.org/Consortium/join">W3C Membership</a>.</p>

<hr /></div>

<div>
<h2><a name="toc" id="toc">Table of Contents</a></h2>

<ul class="toc">

  <li>1&nbsp;<a href="#intro">Introduction</a>
    <br />

    <ul>

      <li>1.1 <a href="#detailedRequirements">Detailed
Requirements</a></li>

      <li>1.2 <a href="#participants">Participants</a></li>

    </ul>

  </li>

  <li>2&nbsp;<a href="#ontologies">Geospatial
Ontologies for the Web</a> <br />

    <ul>

      <li>2.1 <a href="#features">Geospatial
Features</a></li>

      <li>2.2 <a href="#featuretypes">Feature Types</a></li>

      <li>2.3 <a href="#placenames">Toponyms /
Placenames</a></li>

      <li>2.4 <a href="#relationships">(Geo)
Spatial Relationships</a></li>

      <li>2.5 <a href="#crs">Coordinate Reference
Systems </a></li>

      <li>2.6 <a href="#metadata">Geospatial
Metadata</a></li>

      <li>2.7 <a href="#services">(Geo) Web Services</a></li>

    </ul>

  </li>

  <li>4&nbsp;<a href="#XGRsummary">Summary</a></li>

  <li>5&nbsp;<a href="#glossary">Glossary</a></li>

  <li>6&nbsp;<a href="#refs">Links and References</a></li>

  <li>7&nbsp;<a href="#ack">Acknowledgements</a></li>

</ul>

<hr /></div>

<div>
<h2><a name="intro" id="intro">1 Introduction</a></h2>

<p>The geospatial incubator group was <a href="http://www.w3.org/2005/Incubator/geo/charter">chartered</a>
to begin addressing issues of location and geographical properties of
resources for the Web of today and tomorrow, by taking a concrete step
to update the W3C GEO vocabulary, laying the groundwork for a more
comprehensive geospatial ontology, and formulating a proposal for a
W3C&nbsp; Working Group to develop recommendations to further the
Web representation of physical location and geography.</p>

<p>The group's work has been greatly influenced by the work
of the <a href="http://www.opengeospatial.org">Open
Geospatial Consortium (OGC)</a>,<a href="http://www.isotc211.org/"> ISO/TC 211,</a> and <a href="http://www.georss.org">georss.org</a>. While the
rigor of the OGC and ISO/TC 211 General Feature Model is essential for
clarity of spatial representations, the&nbsp;breadth and depth of
geographic
information handling developed by those organizations is considered to
be beyond the needs of most Web
use cases. The group has followed the lead of GeoRSS in seeking to
complement those efforts with a
simpler baseline implementation of geospatial resource description for
the Web. It has been clear in this work, however, that certain
extensions and additions to the baseline are important for fully
realizing the use
cases defined by the group.</p>

<p>A set of <a href="http://www.w3.org/2005/Incubator/geo/charter#cases">use
cases</a> demonstrates the aims in more detail. A set of high
level requirements was derived from the use cases that were then
formalized for the work presented in the group's reports.&nbsp;A
model of
foundation ontologies has
then been developed that encapsulates particular issues discussed and
discovered during the XG's work.&nbsp;&nbsp;Throughout the
Incubator Activity, decisions have
been taken
via consensus during regular telephone conferences, online
collaboration, and face to face meetings.</p>

<p>The Incubator Group is now considering the approach of
re-forming as a W3C geospatial interest group to further the activities
of developing geospatial foundation ontologies
and&nbsp;representing a
geospatial aspect of other W3C activities.</p>

<div id="detailedRequirements">
<h3><a name="detailedRequirements">1.2 Detailed
Requirements</a></h3>

<p>Based on the <a href="http://www.w3.org/2005/Incubator/geo/charter#cases">use
cases</a> and the original high level requirements that were
derived from them, a set of more detailed requirements was established.
The group decided to adopt the GeoRSS feature model as their baseline
representation, following the
essential nature of the ISO General Feature Model, which
separates the discernment of a feature object such as a city from the
particular coordinate geometry property such as a point or a polygon by
which it may be represented.</p>

<p>While the group completed work on the
geometric model described above, along with its instantiation in RDF
and OWL, the group was not able to get as far with models and
vocabularies for other more complete and/or advanced geospatial
concepts, properties, and relationships. The most common spatial
relationships in use, for example, are <strong>equals,
disjoint, intersects, touches, crosses, within, contains, and overlaps</strong>.
These can be tremendously useful in many of the group's <a href="http://www.w3.org/2005/Incubator/geo/charter#cases">use
cases</a>. For example, in use case 4 the researcher wants to
find county-level recycling programs. One would need to describe the
fact that a recycling program is <strong>within</strong> a
particular county; or that a semantic model of a facility would want to
describe that a printer was <strong>within</strong> a
certain room, and that the room <strong>touches</strong>
hallway A-14. While these core spatial relationships are well
established
within the geographic sciences, this group was not able to validate
them as a necessary and sufficient representation in the Web context,
nor develop
specific semantic encodings in the
initial time frame. The group was able to describe in overview form,
however, a
set of 7 such geospatial foundation ontologies as a basis for future
work.</p>

<p>In summary, the Geo XG has successfully developed a basic
geography model that can update the W3C GEO vocabulary, as stated in
its charter. The group identified a core set of spatial relationships
as well as other significant geospatial
ontology components or categories which are described in the present
report,
but implementation of these in W3C is presented as&nbsp;an item for
future work.</p>

</div>

<div>
<div id="participants">
<h3><a name="s1_1">1.3 Participants</a></h3>

<p>The companies and organizations that participated in or
supported GEO XG are as follows:</p>

<ul>

  <li>Open Geospatial Consortium</li>

  <li>SRI</li>

  <li>USC ISI</li>

  <li>Stanford University</li>

  <li>Oracle Corporation</li>

  <li>Traverse Technologies</li>

  <li>Platial</li>

  <li>High Earth Orbit</li>

  <li>BBN</li>

</ul>

</div>

</div>

<h2><a name="ontologies" id="ontologies">2
Geospatial
Ontologies for the Web</a></h2>

<p>As enabling technologies for the Semantic Web have developed,
such as RDF, OWL, SPARQL, and SWRL, much work has been done to
build the ontologies required for expressing the common elements of
disparate knowledge artifacts. This is true in the
realm of geospatial and temporal concepts and relationships, yet
the work has not yet reached a level of either consensus or
<i>actionability</i> which would allow it to be the basis
of
knowledge interoperability. In other words, it is not yet ready to
support the functionality of a Geospatial Semantic Web, where the
geographic properties of knowledge resources can be expressed,
discovered, acted upon by machines, and understood by diverse
communities.</p>

<p>The group considered a more comprehensive system of spatial /
geospatial foundation ontologies and has described in overview form the
following critical examples.
</p>

<h3><a name="features" id="features">2.1
Geospatial Features</a></h3>

<p>This ontology is intended to provide formal representation of
ISO and OGC standards for feature
discernment (General Feature Model or GFM). The GFM is the general
model of which the geo vocabulary has been developed as a very
restricted subset. While the latter can adequately represent a large
proportion of Web resource, many important applications such as
routing, earth observation, and imagery interpretation require a more
complete representation. Sub-ontologies of the&nbsp;<span style="font-style: italic;">Feature Ontology</span>
included here cover <span style="font-weight: bold;">geometries</span>,&nbsp;<span style="font-weight: bold;">coverages</span> (primarily
rasters and grids), and <span style="font-weight: bold;">observations</span>.
Several draft translations of relevant ISO and OGC standards into OWL
ontologies are found at <a href="http://loki.cae.drexel.edu/%7Ewbs/ontology/list.htm">http://loki.cae.drexel.edu/~wbs/ontology/list.htm</a></p>

<h3><a name="featuretypes" id="featuretypes">2.2
Feature Types</a></h3>

<p>This ontology might be thought of as the "50 types of features
that everyone can agree on".</p>

<p>As an example of this type of ontology, the Ordnance Survey
has published an ontology of administrative boundaries in the UK, which
can be found at <a class="http" href="http://www.ordnancesurvey.co.uk/ontology">http://www.ordnancesurvey.co.uk/ontology</a>
along with ontologies for other feature types. </p>

<h3><a name="relationships" id="relationships">2.3
(Geo) spatial Relationships</a></h3>

<p>There are at least 8 commonly accepted 2D topological
relationships such as RCC8 or Egenhofer relations, but there are
probably a number of other "vernacular" relationships which would be
useful, such as "next-door-to". One of many examples of spatial
relationship ontologies has been published by Ordnance Survey at <a href="http://www.ordnancesurvey.co.uk/ontology/SpatialRelations.owl">http://www.ordnancesurvey.co.uk/ontology/SpatialRelations.owl</a>
</p>

<h3><a name="placenames" id="placenames">2.4
Toponyms (Place names)</a></h3>

<p>Place names are an important means of geolocating resources,
at least to some approximation. Some work has been done on globally
useful placename ontologies and individual taxonomies exist, but have not really been brought
together as a common reference. A useful reference is the
ontology work at <a href="http://www.geonames.org/ontology/">http://www.geonames.org/ontology/</a>&nbsp;
</p>

<h3><a name="crs" id="crs">2.5 Coordinate
Reference Systems / Spatial Reference Grids</a></h3>

<p>The numerical counterpart of a place
name scheme, in a similar sense that&nbsp;TCP-IP is a counterpart of
DNS, are coordinate reference systems (CRS) and spatial reference
grids. While
WGS84 might be sufficient globally, other CRS's are important for local
geography, for measurement, or for different views of the globe (e.g.
polar). OGC and ISO
provide standards (for example, ISO 19111)&nbsp; for models
and&nbsp;
XML encodings of coordinate reference systems. A draft ontology for
this standard was developed at Drexel University&nbsp;(<span style="text-decoration: underline;"></span><a href="http://loki.cae.drexel.edu/%7Ewbs/ontology/2004/09/iso-19111.owl">http://loki.cae.drexel.edu/~wbs/ontology/2004/09/iso-19111.owl</a>)</p>

<p>A useful
quantitative way of both geolocating and indexing a resource involves
identifying the grid cell of a geospatial grid scheme (pyramid of
successively smaller cell sizes) in which it is located. Correspondence between grid scheme
and map tile scheme allows background map tiles to be easily discovered and presented together
with co-located resources. </p>

<h3><a name="metadata" id="metadata">2.6
Geospatial Metadata</a></h3>

<p>Data quality
and provenance are critical to deriving real benefit from geography and
geolocation on the Web. A general approach to descriptive metadata is
modeled in ISO 19115 and rules for XML encoding are specified in ISO
19139. Metadata which is operational specifically for use with Web resources have not yet
been either modeled or codified in the form of an ontology. Fundamental
issues such as the time relevance and time validity of a geospatial Web
resource (for example, a map image) as well as representation of such
properties in a URI have yet to be resolved.</p>

<h3><a name="services" id="services">2.7
(Geospatial) Web Services</a></h3>

<p>Evolving standards such as OWL-S have
raised the bar on formal and actionable descriptions of Web services,
but elaborations are needed of the manner in which the closely coupled
content of most geospatial Web services affects their process model and
expected interface behavior. Some work on geospatial semantic service
models can be found in the OGC Discussion Paper 06-002r1 at <a href="http://portal.opengeospatial.org/files/?artifact_id=15198">http://portal.opengeospatial.org/files/?artifact_id=15198</a></p>

<div>
<h2><a name="XGRsummary" id="XGRsummary">4&nbsp;Summary</a></h2>

<p>The Geospatial Incubator Group began with a simple mission and
a
likely candidate vocabulary. Consideration of the charter use cases
indicated that extensions of this vocabulary were likely to be
necessary, but were a more ambitious Web standards challenge. The group
has proposed 7 foundation ontologies as the basis for future work to
provide these extensions.</p>

<p>The open questions raised throughout the XG process as
reported in this document are collated and presented below in no
particular order of priority.</p>

<ul>

  <li>Should the vocabulary be extended to include temporal terms
which
reference specifically the temporal extent / validity of features, or
are existing vocabularies such as OWL Time sufficient?</li>

  <li>Should the vocabulary be extended to include modeling of dynamic
features in which any properties, including geometry, may be functions
of time.</li>
  <li>Should the vocabulary be extended to include address
encoding, or are existing vocabularies such as vCard sufficient? </li>

  <li>How can the vocabulary be used for searching and querying?
Is it
a matter of just implementing SPARQL, or are specific extensions /
additions needed to enable spatial comparisons.</li>

  <li>What formalizations of the non-geometric property literals,
such
as &lt;relationshiptag&gt; are needed to fully satisfy the
group's use
cases and others like them?</li>

  <li>What is the best way to carry forward the work on these
questions
and stewardship of the geo vocabulary within W3C and elsewhere?</li>

</ul>

</div>

<div>
<h2><a name="glossary" id="glossary">5&nbsp;Glossary</a></h2>

<p>The following terms are used throughout this report.
Definitions have been collected from <a href="http://www.w3.org/2003/glossary/">W3C glossaries</a>
where possible and provided <em>a priori</em> where
necessary.</p>

<p><strong><a name="gtAssertion" id="gtAssertion">Assertion</a></strong>
Any <span class="glossTerm">expression</span> which
is claimed to be true. [<a href="http://www.w3.org/2003/glossary/subglossary/rdf-mt.rdf/">W3C
definition source</a>]<strong></strong></p>

<p><strong><a name="gtResource" id="gtResource">Resource</a></strong>
Anything that might be identified by a URI. [<a href="http://www.w3.org/2003/glossary/subglossary/webarch.rdf/">W3C
definition source</a>]</p>

<p><strong><a name="gtSchema" id="gtSchema">Schema</a></strong>
(pl., schemata) A document that describes an <a href="http://www.w3.org/XML/">XML</a> or <a href="http://www.w3.org/RDF/">RDF</a> <span class="glossTerm">vocabulary</span>. Any document
which describes, in a formal way, a language or parameters of a
language. [ <a href="http://www.w3.org/2003/glossary/subglossary/weaving.rdf/60">W3C
definition source</a>]</p>

<p><strong><a name="gtVocab" id="gtVocab">Vocabulary</a></strong>
A collection of <span class="glossTerm">vocabulary terms</span>,
usually linked to a document that defines the precise meaning of the <span class="glossTerm">descriptors</span> and the domain in
which the vocabulary is expected to be used. When associated with a <span class="glossTerm">schema</span>, attributes are
expressed as URI references. [This definition is an amalgam of those
provided in <a href="http://www.w3.org/2003/glossary/subglossary/CCPP-struct-vocab.rdf/">Composite
Capability/Preference Profiles (CC/PP): Structure and Vocabularies 1.0</a>
and <a href="http://www.w3.org/2003/glossary/subglossary/owl-guide.rdf/20">OWL
Web Ontology Language Guide</a>.]</p>

<p><strong><a name="gtVocabTerm" id="gtVocabTerm">Vocabulary
term</a></strong> An attribute that can describe one or
more <span class="glossTerm">resources</span> using
a defined set of values or data type. Attributes may be expressed as a
URI reference. See also <span class="glossTerm">descriptor</span>
and <span class="glossTerm">expression</span>.</p>

<p><strong><a name="gtWellFormed" id="gtWellFormed">Well-formed</a></strong>
Syntactically legal. [<a href="http://www.w3.org/2003/glossary/subglossary/rdf-mt.rdf/20">W3C
definition source</a>]</p>

</div>

<div>
<h2><a name="refs" id="refs">6&nbsp;Links
and References</a></h2>

<dl>

  <dt><a name="dc" id="dc">Dublin Core</a></dt>

  <dd><a href="http://dublincore.org/">http://dublincore.org/</a></dd>

  <dt><a name="foaf" id="foaf">Georss.org</a></dt>

  <dd><a href="http://www.georss.org/">http://www.georss.org/</a></dd>

  <dt><a name="date" id="date">OWL Time</a></dt>

  <dd>Defined in the&nbsp;<a href="http://www.isi.edu/%7Epan/OWL-Time.html">http://www.isi.edu/~pan/OWL-Time.html</a></dd>

  <dt><a name="rdf" id="rdf">RDF</a></dt>

  <dd><a href="http://www.w3.org/RDF/">http://www.w3.org/RDF</a></dd>

  <dt><a name="atom" id="atom">ATOM</a></dt>

  <dd><a href="http://www.atomenabled.org/developers/syndication/atom-format-spec.php">http://www.atomenabled.org/developers/syndication/atom-format-spec.php</a></dd>

  <dt><a name="RSS1.0" id="rss1.0">RSS 1.0</a></dt>

  <dd><a href="http://web.resource.org/rss/1.0/spec">http://web.resource.org/rss/1.0/spec</a></dd>

  <dt><a name="RSS2.0" id="rss2.0">RSS 2.0</a></dt>

  <dd><a href="http://cyber.law.harvard.edu/rss/rss.html">http://cyber.law.harvard.edu/rss/rss.html</a></dd>

  <dt><a name="sparql" id="sparql">SPARQL</a></dt>

  <dd><a href="http://www.w3.org/TR/rdf-sparql-query/">SPARQL
Query Language for RDF</a></dd>

</dl>

</div>

<div>
<h2><a name="ack" id="ack">7&nbsp;Acknowledgements</a></h2>

<p>The editors acknowledge significant contributions from:</p>

</div>

<ul>

  <li>John Goodwin, Ordnance Survey</li>

  <li>Andrew Turner, High Earth Orbit</li>

  <li>Mike Liebhold, Institute for the Future</li>

  <li>Mike Dean, BBN</li>

</ul>

<hr />
</div>

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