Geodata Discovery: Unterschied zwischen den Versionen

Aus Geoinformation HSR
Wechseln zu: Navigation, Suche
(→‎Introduction)
(→‎Part B Geotag Icon in HTML (OPTIONAL))
 
(17 dazwischenliegende Versionen von 2 Benutzern werden nicht angezeigt)
Zeile 3: Zeile 3:
 
== Status ==
 
== Status ==
  
−
* Version 1.00, 19.4.2010, Stefan Keller -- First release of the specification.
+
* Version 0.1, 2010-04-10, Stefan Keller -- First release of the specification.
  
 
== Introduction ==
 
== Introduction ==
 +
 +
=== Overview ===
  
 
The discovery of geodata and geospatial services is crucial of almost every project which involves geoprocessing and therefore also to every (geo) data infrastructure!  
 
The discovery of geodata and geospatial services is crucial of almost every project which involves geoprocessing and therefore also to every (geo) data infrastructure!  
  
−
General purpose search engines are not capable of recognizing geodata formats and geospatial services. Thus, here is a strong need to support geospatial search services, especially repositories and webcrawlers. The solution is twofold: first help machines find explicitely resources they are looking for (through relation links) and, second, let users realize and control that they are browsing a web site which is enhanced with those machine readable relationships (through an icon).
+
General purpose search engines are not capable of recognizing geodata formats and geospatial services. Thus, here is a need to support geospatial search services, especially repositories and webcrawlers. The solution is twofold: first help machines find explicitely resources they are looking for (through relation links) and, second, let users realize and control that they are browsing a web site which is enhanced with those machine readable relationships (through an icon).
  
 
Instead of a web of (HTML) documents, this is part of a vision about a web of services (and XML) which what (semantic) Web 2.0 is mostly about. "So it is vital at the GeoWeb align itself with the web and the multitude of sources and endpoints that the web is reaching into." (citation form High Earth Orbit blog).
 
Instead of a web of (HTML) documents, this is part of a vision about a web of services (and XML) which what (semantic) Web 2.0 is mostly about. "So it is vital at the GeoWeb align itself with the web and the multitude of sources and endpoints that the web is reaching into." (citation form High Earth Orbit blog).
−
 
−
The specification can be explained in two steps: syndication and visualization.
 
  
 
=== Relationship to other standards ===
 
=== Relationship to other standards ===
  
−
This specification doesn't require any change to any of the formats and standards mentioned. In fact, it's just a recommendation for a common usage of these formats.
+
This specification doesn't require any change to the formats and standards mentioned except for OGC's WxS where it's an add-on. In fact, it's mostly a recommendation for a common usage of these formats.
  
−
* KML from Google: "KML is HTML for the geospatial web"
+
robots.txt and sitemaps.xml from Google are somehow similar because they refer to (forbidden) contents. The harvesting protocol [[OAI-PMH]] includes also a "See also" element. Beyond this there is no similar standard for discovery known to us.  
−
* sitemaps.xml from Google
 
  
 
== Specification ==
 
== Specification ==
  
−
The Geodata Discovery standard consists of following parts A and B (both in turn are based standards extensions, called substandards):
+
The Geodata Discovery standard consists of part A and B (both are pure standards extensions, called substandards):
 +
 
 +
* Part A specifies extensions to the syndication formats GeoRSS and Atom as well as protocol extensions to OGCs Webservices.
 +
* Part B specifies how to use an icon in HTML webpages inclunding GetTags (and eventually microformats).
 +
 
 +
Syndication formats and protocols use xlinks to refer in a semantically clear way to geospatial webservices and geodata. These links provide semantics to help focussed crawlers to find OGC Services, like [[WMS]], [[WFS]], [[WCS]], [[WPS]] and/or [[CSW]].
 +
 
 +
The Geotag icon (i.e. its href HTML encoding) links back to the syndication formats and protocols.
 +
 
 +
=== Part A Syndication Format and Protocol Extensions (CONDITIONAL MANDATORY) ===
  
−
* Part A specifies specialized weblinks which provide semantics to help focussed crawlers to find OGC Services, like [[WMS]], [[WFS]], [[WCS]], [[WPS]] and/or [[CSW]].
+
Specifies "See" and "See also" links (also called 'cross-links') in well known formats ("carrier formats") containing typified weblinks (whenever possible 'xlink' or "Atom link relation types").  
−
* Part B 
 
  
−
=== Part A (CONDITIONAL MANDATORY) ===
+
;Syndication format extensions:
 +
* GeoRSS file format: Use of GeoRSS to syndicate KML content, similar to RSS support in HTML. See the [http://highearthorbit.com/a-proposal-georss-kml/ proposal] here.
 +
* Atom file format: rel and type attributes for (See IETF Web Linking Draft, chap. 6.2)  
  
−
"See and See also" links (also called 'cross-links') in well known formats ("carrier formats") containing typified weblinks (whenever possible 'xlink' or "Atom link relation types").
+
  <link rel="alternate" type="text/html"
 +
    href="http://www.naturschutz.zh.ch/internet/bd/aln/ns/de/nsdaten/Geodaten/fns_wms.html"/>
 +
  <link rel="alternate" type="application/vnd.google-earth.kml+xml"
 +
    href="http://example.org/kml_georss.kml"/>
 +
  <link rel="alternate" type="text/xml"
 +
    href="http://www.gis.zh.ch/scripts/wmsFNSSVO.asp"/> 
  
−
Extensions to folowing substandards:
+
;Syndication extensions to OGC Web Services (protocol):  
−
* GeoRSS file format: Use of GeoRSS to syndicate KML content, similar to RSS support in HTML.. See the [http://highearthorbit.com/a-proposal-georss-kml/ proposal] here.
+
Extensions of GetCapabilities request with xlink tags ... (tbd.)!
−
* Atom file format: rel and type attributes for See chap. 6.2
 
−
* OGC WxS protocols: Extension of GetCapabilities with xlink tags ... (tbd.)!
 
  
−
=== Part B (OPTIONAL) ===
+
'CONDITIONAL MANDATORY' means that at least one of the mentioned substandards needs to implemented in order to comply to the "Geodata Discovery" standard.
  
−
Webpages that include a Geotag icon (Microformat). This is for human readability and trustworthiness (Google's principle of visual control) pointing to the "see and see also" links (see above).
+
=== Part B Geotag Icon in HTML (OPTIONAL) ===
  
−
CONDITIONAL MANDATORY means that at least one of the mentioned substandards in A needs to implemented in order to comply to the "Geodata Discovery" standard.
+
Specifies the placement of a Geotag icon ([[Microformat]] 'Geo') in a HTML webpage. This is for human readability and trustworthiness as well as for general purpose webcrawlers (Google's principle of visual control) pointing to the syndication format (specified in Part A).
  
−
== Compliance Tests ==
+
== Compliance ==
  
 
tbd. Ideally there should be a website which lists conformances tests given a website which was enhanced according to this specifications.
 
tbd. Ideally there should be a website which lists conformances tests given a website which was enhanced according to this specifications.
Zeile 62: Zeile 74:
 
* [http://www.w3.org/TR/xlink/ XML Linking Language (XLink) Version 1.0].
 
* [http://www.w3.org/TR/xlink/ XML Linking Language (XLink) Version 1.0].
 
* [http://www.opensearch.org OpenSearch.org] > OpenSearch Geo extension (Draft) - A leightweight harvesting interface (Remarks: "rel='search'" notifes an application that here is a service that it can query to get at additional resources. Applies often also to webapplications capable which can be called with Permalinks).
 
* [http://www.opensearch.org OpenSearch.org] > OpenSearch Geo extension (Draft) - A leightweight harvesting interface (Remarks: "rel='search'" notifes an application that here is a service that it can query to get at additional resources. Applies often also to webapplications capable which can be called with Permalinks).
 +
* [http://microformats.org/wiki/geo Microformats.org 'Geo']
 
* [[CSW]]
 
* [[CSW]]
  

Aktuelle Version vom 6. Juni 2011, 15:25 Uhr

Geodata Discovery Specification - Discovery of Geodata and Geospatial Services

Status

  • Version 0.1, 2010-04-10, Stefan Keller -- First release of the specification.

Introduction

Overview

The discovery of geodata and geospatial services is crucial of almost every project which involves geoprocessing and therefore also to every (geo) data infrastructure!

General purpose search engines are not capable of recognizing geodata formats and geospatial services. Thus, here is a need to support geospatial search services, especially repositories and webcrawlers. The solution is twofold: first help machines find explicitely resources they are looking for (through relation links) and, second, let users realize and control that they are browsing a web site which is enhanced with those machine readable relationships (through an icon).

Instead of a web of (HTML) documents, this is part of a vision about a web of services (and XML) which what (semantic) Web 2.0 is mostly about. "So it is vital at the GeoWeb align itself with the web and the multitude of sources and endpoints that the web is reaching into." (citation form High Earth Orbit blog).

Relationship to other standards

This specification doesn't require any change to the formats and standards mentioned except for OGC's WxS where it's an add-on. In fact, it's mostly a recommendation for a common usage of these formats.

robots.txt and sitemaps.xml from Google are somehow similar because they refer to (forbidden) contents. The harvesting protocol OAI-PMH includes also a "See also" element. Beyond this there is no similar standard for discovery known to us.

Specification

The Geodata Discovery standard consists of part A and B (both are pure standards extensions, called substandards):

  • Part A specifies extensions to the syndication formats GeoRSS and Atom as well as protocol extensions to OGCs Webservices.
  • Part B specifies how to use an icon in HTML webpages inclunding GetTags (and eventually microformats).

Syndication formats and protocols use xlinks to refer in a semantically clear way to geospatial webservices and geodata. These links provide semantics to help focussed crawlers to find OGC Services, like WMS, WFS, WCS, WPS and/or CSW.

The Geotag icon (i.e. its href HTML encoding) links back to the syndication formats and protocols.

Part A Syndication Format and Protocol Extensions (CONDITIONAL MANDATORY)

Specifies "See" and "See also" links (also called 'cross-links') in well known formats ("carrier formats") containing typified weblinks (whenever possible 'xlink' or "Atom link relation types").

Syndication format extensions
  • GeoRSS file format: Use of GeoRSS to syndicate KML content, similar to RSS support in HTML. See the proposal here.
  • Atom file format: rel and type attributes for (See IETF Web Linking Draft, chap. 6.2) 
 <link rel="alternate" type="text/html"
   href="http://www.naturschutz.zh.ch/internet/bd/aln/ns/de/nsdaten/Geodaten/fns_wms.html"/>
 <link rel="alternate" type="application/vnd.google-earth.kml+xml"
   href="http://example.org/kml_georss.kml"/>
 <link rel="alternate" type="text/xml"
   href="http://www.gis.zh.ch/scripts/wmsFNSSVO.asp"/>
Syndication extensions to OGC Web Services (protocol)

Extensions of GetCapabilities request with xlink tags ... (tbd.)!

'CONDITIONAL MANDATORY' means that at least one of the mentioned substandards needs to implemented in order to comply to the "Geodata Discovery" standard.

Part B Geotag Icon in HTML (OPTIONAL)

Specifies the placement of a Geotag icon (Microformat 'Geo') in a HTML webpage. This is for human readability and trustworthiness as well as for general purpose webcrawlers (Google's principle of visual control) pointing to the syndication format (specified in Part A).

Compliance

tbd. Ideally there should be a website which lists conformances tests given a website which was enhanced according to this specifications.

Background

At OGC there exists an interest group about discovery but there's no specification activity there yet.

This proposal does not compete with existing standards like CSW. In contrary, it is a supplement of those. It's the basis for better domain-specific search engines, like e.g. geocat.ch or geometa.info.

This proposal is based on own experiences and - among others - on the sources mentioned below.

References

Normative references:

Miscellaneous Weblinks:

History

  • Version 1.00, 19.4.2010, Stefan Keller -- First release of the specification.
Von «https://giswiki.hsr.ch/index.php?title=Geodata_Discovery&oldid=32994»