• Xri2Cd02
• MetaData
• I1IdentifierTypeSection

Requirements/Proposal Page for Metadata Issue #1: Add $t Tag for Identifier Types

1. Introduction/Motivation

This issue has been motivated by discussions with Boeing and the Identifier Semantics Workgroup of the Network Applications Consortium about the need for enterprises to have a way to consistently represent different types of common identifiers in order to significantly increase interoperability both internal to an enterprise and in cross-domain or federated usage.

2. Status

• Version: 2
• Action: Needs discussion of requirements and proposal.

3. Requirements

1. To have a uniform, interoperable representation in XRI of different types of identifiers which do not have URI schemes yet are commonly used in enterprise systems.

2. For this uniform representation to facilitate matching in enterprise directory systems and other applications that need XRI equivalence checking (see Syntax Issue #1: Directory Attribute Appendix).

3. For this uniform representation to explicitly include the identifier type metadata so applications can take advantage of this metadata, for example to do a type-specific forms of local resolution or determine equivalent identifiers of other types.
4. For this uniform representation to be able to be independent of any specific authority that may assign identifiers of this type.
5. For this uniform representation to be able to be expressed in the context of any authority that assigns or accepts cross-references to identifiers of this type.
6. For this uniform representation to be able to be expressed in any other context which may accept an XRI cross-reference.
7. If identifier type metadata is best managed in a separate namespace, for management of this namespace to be handled independently of the Metadata specification and provide mechanisms for third party registrations.

4. Proposal

• Add "$t" to the Metadata specification to represent "identifier type" metadata. The definition of this tag would specify that it delegates to another XRI TC specification, tentatively titled the XRI Identifier Type Specification, for assignment of XRIs in the $t namespace.

• The XRI Identifier Type specification would specify:
  • The overall qualifications for identifiers to be registered in the $t namespace.
  • The initial set of identifiers to be registered in the $t space.
  • The procedure for other identifiers to be registered in the $t space.
  • The standard method (which applies to all XRIs) by which any authority can extend the $t namespace without explicit registration.

5. Discussion

This V2 proposal was generated via discussion on this email thread on the XRI TC list.

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