DCP-5

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DCP-5: Valids and restrictions for query elements

Progress

1. Submitted on: 24 Apr 2012
2. Review period: 24 Apr 2012 to 24 May 2012
3. Revision: TBD
4. Vote: http://www.doodle.com/rw4kg7w6yxc5yfdf
5. Final review: TBD
6. Ratified / Rejected: TBD

• Facilitator: Ian Truslove (Ian Truslove (Truslove))

Description

Provide a mechanism to describe valid and invalid inputs for query elements in ESIP Discovery services.

Problem Addressed

OpenSearch does not have a mechanism for indicating valid options for search parameters. The OpenSearch Parameter extension (http://www.opensearch.org/Specifications/OpenSearch/Extensions/Parameter/1.0) has options for specifying the number of times a particular parameter may or should be included in the search request, but this does not meet our needs.

Proposed Solution

Add a validpatterns role to the OpenSearch <query> element, and specify valid values for attributes with a regular expression.

Example:

<OpenSearchDescription xmlns="http://a9.com/-/spec/opensearch/1.1/">
  <Url type="application/atom+xml" template="http://somedataprovider.com/?q={searchTerms}&datum={datum?}&gridSize={gridSize}&format=atom"/>
  <Query role="example" searchTerms="map" datum="WGS84" gridSize="1km" />
  <Query role="http://esipfed.org/ns/discovery/1.1/#validpatterns" searchTerms="WGS84|EGM96" gridSize="1m|10m|100m|500m|1km|10km" />
</OpenSearchDescription>

Rationale for the Solution

• Terse - a single parameter's options fit into a single attribute value.
• Well-understood - this is the same mechanism HTML5 uses for input field validation (http://www.whatwg.org/specs/web-apps/current-work/multipage/common-input-element-attributes.html#the-pattern-attribute). Implementors will undoubtedly be familiar with this web technology.
• Powerful - regular expressions are a powerful pattern matching mechanism.

Discussions

• There are a proliferation of regex "flavors" - see http://www.regular-expressions.info/refflavors.html. We should standardize on one of these flavors.
  • The HTML5 specification uses the ECMAScript flavor of regex. This seems a reasonable, standardized regex standard to implement as part of DCP-5.

Consensus

TBD

Voting results

TBD