MIWP-8 (L) Unique Resource Identifier

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Ticket: https://ies-svn.jrc.ec.europa.eu/issues/2220

TG Requirement 6 suggests to use RS_identifier for the encoding of the resource identifier. This is a poor choice as it is (a) against the foreseen semantic in the ISO standard, which defines it as an “identifier used for reference systems” and (b) because it is not a CSW-queryable. As foreseen by the ISO-Standard the MD_Identifier (a “value uniquely identifying an object within a namespace”) should be suggested, which is also CSW-queryable. The task will be to recommend an “MD_Identifier” (a “value uniquely identifying an object within a namespace”).


Christian Ansorge
Rado Chudy 
Alejandro Guinea
Željko Hecimovic
Lucie Kondrova
Andrea Perego 
Martin Seiler    (Leader)
Kristian Senkler
Pawel Soczewski
Michael Östling


COMMISSION REGULATION (EC) No 1205/2008 (aka IR Metadata)

Part B, 1.5 Unique resource identifier

A value uniquely identifying the resource.
The value domain of this metadata element is a mandatory character string code, generally assigned by the data
owner, and a character string namespace uniquely identifying the context of the identifier code (for example, the
data owner).

OpenGIS® Catalogue Services Specification 2.0.2 - ISO Metadata Application Profile

Table 10: The CSW-queryable 'ResourceIdentifier' ('Identifier of the resource') is mapped to 'MD_Metadata.identificationInfo. AbstractMD_Identification.citation.CI_Citation.identifier.MD_Identifier.code'

Technical Guidelines based on EN ISO 19115 and EN ISO 19119

(see attached files for now)

Issues / Tasks:

  1. Check semantics of identifiers in ISO 1915
  2. Definition in section 2.2.5 is not inline with IR
    • TG: "Value uniquely identifying an object within a namespace"
    • IR: "A value uniquely identifying the resource"
  3. TG section 2.2.5 is inconsistent with suggestion of metadata element to use
    • In the table "205. MD_Identifier" is suggested
    • in TG Requirement 6 RS_Identifier is suggested.
  4. Need to ensure consistency with TG section 2.2.6 Coupled Resource and examples in the annex
  5. ...
  6. ...


What problems causes current solution ?


What can be a solution on current problem (proposed)?

  • Requirement
    • Namespace and code of the Unique Resource Identifiers shall be encoded (at least) in: MD_Metadata/identificationInfo[1]/MD_DataIdentification/citation/CI_Citation/identifier/MD_Identifier.code (e.g. https://namespace/code)
  • Recommandation
    • Unique Resource Identifiers should not change/be deleted. If necessary additional identifiers should be added
  • Requirements (Input for MIWP 4a : Set sub-group on Persistent Identifiers (PID))
    • Unique Resource Identifiers shall be in the http(s)-scheme
    • Unique Resource Identifiers should be dereferenceable


Use Cases for Unique Resource Identifier?

  • Uniquely identify a resource in the SDI
  • Realize data-service coupling
    • the operatesOn element in a metadata set describing a service points to the Unique Resource Identifier of the resource provided in the metadata set describing the resource 


How does it relate to IR ?

How will the solution affect existing tools ?

What other issues in MIWG-8 is related to this change ?

MIWP-8 (M) Coupled resources

What other groups within MIG-related workgroups could be linked to this issue ?

MIWP 4a: Set sub-group on Persistent Identifiers (PID)


Findings / Ideas / Solutions:

  • #1: As per ISO, an MD_Identifier is “value uniquely identifying an object within a namespace”, whereas its direct subclass RS_Identifier is an “identifier used for reference systems”. From an encoding perspective one can use an instance of RS_Identifier in lieu of an MD_Identifier instance, but this is not intended by ISO; hence, an RS_Identifier shall be used as an identifier for reference systems only (e.g. as defined by MD_CRS or MD_ReferenceSystem). Thus, regarding the TG it is clear, that only an instance of MD_Identifier is applicable to identify the resource.
  • #2: The TG is an implementation of requirements defined by the IR. This includes a representation of INSPIRE concepts in the ISO world, and that's what is happens here: the IR demands for a means to define "A value uniquely identifying the resource". This requirement is adressed by using the ISO elemtent MD_Identifier as its realization. Hence the ISO definition of MD_Identifier is a "value uniquely identifying an object within a namespace". So this is not an inconsistancy, but a mapping between the INSPIRE semantics (defined by the IR) and the semantics as defined by ISO.
  • #3: put both the codespace and the code in one string in MD_Identifier, interpret the last part of the string after a seperator as 'code', e.g.  'urn:eu:europa:ec:jrc:rdsi:id:dataset:ccm2.1:lakes'
    • codeSpace: 'urn:eu:europa:ec:jrc:rdsi:id:dataset:ccm2.1'
    • code: 'lakes'
    • <MD_Identifier><code>urn:eu:europa:ec:jrc:rdsi:id:dataset:ccm2.1:lakes</code></MD_Identifier>
  • # ...
  • # ...

URI_1.jpg (172 KB) Martin Seiler, 21 Nov 2014 01:01 pm

URI_2.bmp (541 KB) Martin Seiler, 21 Nov 2014 01:01 pm

URI_3.bmp (818 KB) Martin Seiler, 21 Nov 2014 01:01 pm

URI_4.bmp (687 KB) Martin Seiler, 21 Nov 2014 01:01 pm

URI_5.bmp (3.96 MB) Martin Seiler, 21 Nov 2014 01:01 pm