OSGeodata: Unterschied zwischen den Versionen
Aus Geoinformation HSR
K (→Comparison between WFS and OAI-PMH) |
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== Comparison between WFS and OAI-PMH == | == Comparison between WFS and OAI-PMH == | ||
| + | |||
| + | Relative (biased?) comparison: | ||
| + | * OAI-PMH is a set of simple harvesting protocols whereas WFS allows a client to retrieve geospatial data encoded in GML. | ||
| + | * WFS though originated in GIS could cover a smaller community than OAI-PMH which today probably has a larger user base and is supported even by Google. | ||
| + | * Both have in common that they can be made (WFS) or are (OAI-PMH) RESTful and both can be profiled to respond an 'output content model' - which has yet to be defined. | ||
| + | * WFS needs to be profiled whereas OAI-PMH needs probably to be extended - so WFS seems more complex and more costly to implement. | ||
WFS: | WFS: | ||
* WFS is short for 'Web Feature Service' | * WFS is short for 'Web Feature Service' | ||
* Background: A de-facto standard in GIS world owned by OGC | * Background: A de-facto standard in GIS world owned by OGC | ||
| − | * | + | * Request operations (Basic WFS, read only WFS): |
| + | ** GetCapabilities - describes service capabilities; | ||
| + | ** DescribeFeatureType - descibes structure of a feature type | ||
| + | ** GetFeature - retrieves feature instances | ||
* Query: | * Query: | ||
** Standard query includes spatial constraints (but no temporal?) | ** Standard query includes spatial constraints (but no temporal?) | ||
| − | ** | + | * Peculiarities: |
| + | ** Knows version negotiation (which isn't implemented yet...) | ||
| + | ** Uses URN as unique identifier | ||
* Availability and outreach of services, tools and (open source) software: | * Availability and outreach of services, tools and (open source) software: | ||
** Open source software see [http://www.freegis.org freegis.org] | ** Open source software see [http://www.freegis.org freegis.org] | ||
| − | * ... | + | * Expected changes to spec. (profile or extension): |
| + | ** Profile to KVP binding | ||
| + | ** Profile Filter to Boolean and Wildcard matches as well as 'within' | ||
| + | ** ... | ||
OAI-PMH: | OAI-PMH: | ||
* OAI is short for [http://en.wikipedia.org/wiki/Open_Archives_Initiative 'Open Archives Initiative'], PMH is short for 'Protocol for Metadata Harvesting'. | * OAI is short for [http://en.wikipedia.org/wiki/Open_Archives_Initiative 'Open Archives Initiative'], PMH is short for 'Protocol for Metadata Harvesting'. | ||
* Background: Was initiated by libraries, universities, museums and galleries to 'open access' (OA) free online availability of digital content. | * Background: Was initiated by libraries, universities, museums and galleries to 'open access' (OA) free online availability of digital content. | ||
| − | * | + | * Request operations: |
| + | ** Identify | ||
| + | ** ListMetadataFormats | ||
| + | ** ListSets | ||
| + | ** ListIdentifiers | ||
| + | ** ListRecords | ||
| + | ** GetRecord | ||
* Query: | * Query: | ||
** Standard query includes temporal constraints (but no spatial). | ** Standard query includes temporal constraints (but no spatial). | ||
| − | ** | + | * Peculiarities: |
| + | ** Uses identifier mechanism (numbers) from digital archives. | ||
| + | ** Has no version negotiation | ||
* Availability and outreach of services, tools and (open source) software: | * Availability and outreach of services, tools and (open source) software: | ||
** Open source software see [http://www.openarchives.org/tools/tools.html OAI-PMH tools] | ** Open source software see [http://www.openarchives.org/tools/tools.html OAI-PMH tools] | ||
** Gateways available from publishing files to others | ** Gateways available from publishing files to others | ||
** Google reads it as a Sitemaps file ([http://www.google.com/support/webmasters/bin/answer.py?answer=34655 how to submit]) and Internet Archive uses it among others. | ** Google reads it as a Sitemaps file ([http://www.google.com/support/webmasters/bin/answer.py?answer=34655 how to submit]) and Internet Archive uses it among others. | ||
| − | * . | + | * Expected changes to spec. (profile or extension): |
| − | + | ** Needs to be extended if spatial constraints are needed | |
| − | + | ** Add version negotiation | |
| − | * | + | ** ...? |
| − | * | ||
== Weblinks == | == Weblinks == | ||
Version vom 3. August 2006, 23:08 Uhr
Experimental pages for OSGeodata Mailing List on OSGeo.org.
Goal
Citation from Jo Walsh: "Managing metadata well is the key to making a repository of open geographic data really useful and re-usable. Creating metadata can be a dull chore. Part of the problem is over-focus on production, rather than consumption; on standards, rather than on usage. The Geodata Committee at OSGeo has been working on a "simplest useful thing" approach to geographic metadata...".
Comparison between WFS and OAI-PMH
Relative (biased?) comparison:
- OAI-PMH is a set of simple harvesting protocols whereas WFS allows a client to retrieve geospatial data encoded in GML.
- WFS though originated in GIS could cover a smaller community than OAI-PMH which today probably has a larger user base and is supported even by Google.
- Both have in common that they can be made (WFS) or are (OAI-PMH) RESTful and both can be profiled to respond an 'output content model' - which has yet to be defined.
- WFS needs to be profiled whereas OAI-PMH needs probably to be extended - so WFS seems more complex and more costly to implement.
WFS:
- WFS is short for 'Web Feature Service'
- Background: A de-facto standard in GIS world owned by OGC
- Request operations (Basic WFS, read only WFS):
- GetCapabilities - describes service capabilities;
- DescribeFeatureType - descibes structure of a feature type
- GetFeature - retrieves feature instances
- Query:
- Standard query includes spatial constraints (but no temporal?)
- Peculiarities:
- Knows version negotiation (which isn't implemented yet...)
- Uses URN as unique identifier
- Availability and outreach of services, tools and (open source) software:
- Open source software see freegis.org
- Expected changes to spec. (profile or extension):
- Profile to KVP binding
- Profile Filter to Boolean and Wildcard matches as well as 'within'
- ...
OAI-PMH:
- OAI is short for 'Open Archives Initiative', PMH is short for 'Protocol for Metadata Harvesting'.
- Background: Was initiated by libraries, universities, museums and galleries to 'open access' (OA) free online availability of digital content.
- Request operations:
- Identify
- ListMetadataFormats
- ListSets
- ListIdentifiers
- ListRecords
- GetRecord
- Query:
- Standard query includes temporal constraints (but no spatial).
- Peculiarities:
- Uses identifier mechanism (numbers) from digital archives.
- Has no version negotiation
- Availability and outreach of services, tools and (open source) software:
- Open source software see OAI-PMH tools
- Gateways available from publishing files to others
- Google reads it as a Sitemaps file (how to submit) and Internet Archive uses it among others.
- Expected changes to spec. (profile or extension):
- Needs to be extended if spatial constraints are needed
- Add version negotiation
- ...?
Weblinks
- OGC's CSW 2.0
- OGC's WFS
- OAI-PMH - Open Archives Initiative Protocol for Metadata Harvesting 2.0
