OSGeodata metadata exchange model: Unterschied zwischen den Versionen

Version vom 11. August 2006, 15:58 Uhr

Proposal of an information model to exchange spatial metadata

Initial version by S.F. Keller. See also OSGeodata.

Idea: Take the smallest possible information model for geographic metadata which describes data and filter services. Dublin Core (DC) is the most well known model. This must be extended using the known DC specs.

There is strong evidence that the architecture should be centered around data resources. Therefore metadata describes primary data resources. As a consequence, a probably specialized type attribute/XML element 'dc:type' contains data access values like File API, JDBC, HTTP GET, WMS, WFS, etc. These are all services which provide a programming interface to access data.

But there is also a need to describe services on its own, also called filter - finally as own metadata records: Normally you feed some data in and get data out. For these kinds of services it’s interesting to know what kind of data you can feed in and get back. Examples are format conversion or coordinate transformation services.

Dublin Core and its interpretation in geographic metadata

This is the full list of (possibly repeatable) attributes from DC together with its proposed semantic interpretation and/or enumeration list (needs probably an own XML namespace):

• Relation: reference - Reference to other metadata records - especially useful for map service types (WxS) pointing to data service types (= file, database?)
• Type: text or enum - Protocol type, e.g. file, WMS layer, WFS feature set, etc... IMPORTANT FOR SERVICE DISCOVERY
• Identifier: string - Unique id to identify an object in a certain context (use a URI for dc:identifier).
• Title: string - Title
• Coverage.box: - Rectangular box (mandatory) in WGS84
• Coverage.name: String - (optionally) a geographic name
• Description: string - Some free text
• Subject: enum - Classification from ISO 19115 as enum type (original: The topic of the resource. Typically, subject will be expressed as keywords or phrases that describe the subject or content of the resource. The use of controlled vocabularies and formal classification schemas is encouraged.)
• Language: enum - ISO Code
• Format: string - File type or name of originating source system
• Source: string - Lineage information
• Date: date - Publication date or date of last change
• Creator: string - Data owner, else: data capturer
• Contributor: string - Leave unused?
• Publisher: string - Distribution informatione
• Rights: string - License information about the data
• Audience: string - Not used or 'GIS' as a constant

Attributes to discuss further (all are probably enums): Type (protocol), Identifier, Coverage.box and Coverage.name and Subject.

Example in GeoRSS (simple) encoding

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