Geodata Discovery: Unterschied zwischen den Versionen

Version vom 19. April 2010, 11:22 Uhr

Geodata Discovery Specification - Discovery of Geodata and Geospatial Services

Status

• Version 1.00, 19.4.2010, Stefan Keller -- First release of the specification.

Introduction

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.

Instead 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).

Specification

The Geodata Discovery standard consists of following parts A and B (both in turn are based standards extensions, called substandards):

• Part A specifies specialized weblinks which provide semantics to help focussed crawlers to find OGC Services, like WMS, WFS, WCS, WPS and/or CSW.
• Part B

Part A (CONDITIONAL MANDATORY)

"See and See also" links (also called 'cross-links') in well known formats ("carrier formats") containing typified weblinks (whenever possible 'xlink').

Extensions to folowing substandards:

• Atom file format: rel and type attributes ... (tbd.) analoguous to Google's 'sitemaps.xml' specification.
• GeoRSS file format: xlinks attributes ... (tbd.)
• KML file format: Metadata section tags containing xlink tags ... (tbd.)
• OGC WxS protocols: Extension of GetCapabilities with xlink tags ... (tbd.)!

Part B (OPTIONAL)

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).

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.

Compliance Tests

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.

Related standards and Weblinks

Related standards:

• CSW
• OpenSearch-Geo: A leightweight harvesting interface (Remarks: its simply some HTML tags and especially applies to webapplications capable of being called with Permalinks).
• XML Linking Language (XLink) Version 1.0.
• OpenSearch.org > OpenSearch Geo extension (Draft)

Miscellaneous Weblinks:

• GeoWeb Standards – Discoverability from High Earth Orbit Blog, 2009-08-28.
• "Proposed standard for web linking" from Sean Gillies Blog, 2010-01-25.

History

• Version 1.00, 19.4.2010, Stefan Keller -- First release of the specification.