Internet Engineering Task Force (IETF)
Request for Comments: 6338
Category: Informational
ISSN: 2070-1721
V. Giralt
Univ. Malaga
R. McDuff
Univ. Queensland
August 2011

Definition of a Uniform Resource Name (URN) Namespace

for the Schema for Academia (SCHAC)


This document describes a Uniform Resource Name (URN) namespace for the Schema for Academia (SCHAC).

The namespace described in this document is for naming persistent resources defined by the SCHAC participants internationally, their working groups, and other designated subordinates. The main use of this namespace will be for the creation of controlled vocabulary values for attributes in the SCHAC schema. These values will be associated with particular instances of persons or objects belonging to any of the SCHAC object classes.

Status of This Memo

This document is not an Internet Standards Track specification; it is published for informational purposes.

This document is a product of the Internet Engineering Task Force (IETF). It represents the consensus of the IETF community. It has received public review and has been approved for publication by the Internet Engineering Steering Group (IESG). Not all documents approved by the IESG are a candidate for any level of Internet Standard; see Section 2 of RFC 5741.

Information about the current status of this document, any errata, and how to provide feedback on it may be obtained at

Copyright Notice

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This document is subject to BCP 78 and the IETF Trust's Legal Provisions Relating to IETF Documents ( in effect on the date of publication of this document. Please review these documents carefully, as they describe your rights and restrictions with respect to this document. Code Components extracted from this document must include Simplified BSD License text as described in Section 4.e of the Trust Legal Provisions and are provided without warranty as described in the Simplified BSD License.

1. Introduction

The Schema for Academia (SCHAC) international activity was born inside the Task Force on European Middleware Coordination and Collaboration (TF-EMC2) of the Trans-European Research and Education Networking Association (TERENA) [6]. The initial aim of SCHAC was to harmonize the disjoint person schemas of the participating countries in order to have a common way for expressing data about persons, exchanged between educational organizations. SCHAC, as are other person schemas, is designed to ease the sharing of information about a given individual between parties, mostly, but not limited to, educational and research institutions. The main aims of this sharing are to provide resources to individuals and to allow said individuals to move, virtually and physically, between such institutions. Thus, the SCHAC schema was defined with input from all participants' national person schemas [7].

SCHAC does not supplant other person schemas such as organizationalPerson [8], inetOrgPerson [9], or eduPerson [10]; it extends those where needed for the purposes of Higher Education outside the United States. This characteristic has made SCHAC, originally a European effort, useful for groups outside Europe.

2. Requirements Language

The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in RFC 2119 [1].

3. Specification Template

Namespace ID:


Registration Information:

Registration Version Number 1

      Registration Date: 2011-06-22

Registrant of the namespace:

European Committee for Academic Middleware (ECAM) Trans-European Research and Education Networking Association (TERENA)
The Netherlands

Designated contacts:

Contact: Licia Florio
Affiliation: TERENA
Singel 468 D
Amsterdam, 1017 AW
The Netherlands

      Phone: +31(0)20 5304488

Contact: Victoriano Giralt
Affiliation: University of Malaga
Central ICT Services
Blvd. Louis Pasteur, 33
Campus de Teatinos
29071 Malaga

      Phone: +34 95 213 1415

Syntactic structure:

The Namespace Specific Strings (NSSs) of all URNs assigned by SCHAC will conform to the syntax defined in Section 2.2 of RFC 2141, "URN Syntax" [11]. In addition, all SCHAC URN NSSs will consist of a left-to-right series of tokens delimited by colons. The left-to-right sequence of colon-delimited tokens corresponds to descending nodes in a tree. To the right of the lowest naming authority node, there may be zero, one, or more levels of hierarchical naming nodes terminating in a rightmost leaf node. See the "Identifier assignment" section below for more on the semantics of NSSs. This syntax convention is captured in the following normative ABNF rules for SCHAC NSSs (see RFC 5234 [2]):

SCHAC-NSS = 1*subStChar *( ":" 1*subStChar )

           subStChar    =   trans / "%" HEXDIG HEXDIG

trans = ALPHA / DIGIT / other / reserved

           other        =   "(" / ")" / "+" / "," / "-" / "." /
                            "=" / "@" / ";" / "$" /
                            "_" / "!" / "*" / "'"
           reserved     =   "/" / "?" / "#"

The exclusion of the colon from the list of "other" characters means that the colon can only occur as a delimiter between string tokens. Note that this ABNF rule set guarantees that any valid SCHAC NSS is also a valid RFC 2141 NSS.

Relevant ancillary documentation:


Identifier uniqueness:

It is the responsibility of TERENA to guarantee uniqueness of the names of immediately subordinate naming authorities. Each lower- level naming authority in turn inherits the responsibility of guaranteeing uniqueness of names in its branch of the naming tree.

Identifier persistence:

TERENA bears ultimate responsibility for maintaining the usability of SCHAC URNs over time. This responsibility MAY be delegated to subordinate naming authorities per the discussion in the section below on identifier assignment. That section provides a mechanism for the delegation to be revoked in the case where a subordinate naming authority ceases to function.

Identifier assignment:

TERENA will create an initial series of immediately subordinate naming authorities, and will define a process for adding to that list of authorities. Such a list, and the policy for adding to it, will be published at the root registry page. Each country with a representative in SCHAC will be invited to designate a naming authority. Country-specific namespaces based on the country Internet Top-Level Domain (TLD) [12] will then be assigned to the designated authority. The subordinated namespaces int and eu will remain under TERENA authority, controlled by the SCHAC activity members, for entities of global, international, or European interest. There is also the possibility of granting subordinate namespaces to multi-country organizations; in this case, the organizational Internet Fully Qualified Domain Name (FQDN) will be used as the prefix.

As an example, a European-level interest entity would be any value related to information used in the Higher Education European Space, or the so-called Bologna process. Such entities will belong in the eu subordinate namespace.

Global international entities could encompass values related to the Grid community or values useful both for some European and for some Australian universities. Such entities would belong in the int subordinate namespace.

Examples of multi-country organizations include TERENA itself or an association like the Educational Policy Institute (EPI) ( that has members from Australia, Canada, and the US.

URNs intended for values of SCHAC attributes will include the attribute name immediately after the NSS prefix, before any geographical namespace delegation, such that any string can convey information about the attribute for which it is a value. For example, values for schacUserStatus will be of the form:

                urn:schac:userStatus:au or

If at all possible, automated registry publication mechanisms will be provided, based on the work on distributed URN registries done by the TF-EMC2 task force members.

Institutions and communities affiliated with SCHAC participants may request that they be granted subordinate naming authority status. Uniqueness of these namespaces under country authority will be based on the requestor's Internet FQDN. This subordination procedure SHOULD be carried along the delegation chain; i.e., if at all possible, all entities that receive a delegated namespace MUST have a valid FQDN and MUST publish an Internet accessible URN value registry, based on the URN registry mechanisms designed by the TF-EMC2 task force members.

On at least an annual basis, TERENA will contact the liaisons or directors of each immediately subordinate naming authority. If there is no response, or if the respondent indicates that they wish to relinquish naming authority, the authority over that branch of the tree reverts to TERENA. This process will be enforced recursively by each naming authority on its subordinates. This process guarantees that responsibility for each branch of the tree will lapse for less than one year, at worst, before being reclaimed by a superior authority.

Lexical equivalence of two SCHAC Namespace Specific Strings (NSSs) is defined below as an exact, case-sensitive string match. TERENA will assign names of immediately subordinate naming authorities in lowercase only. This forestalls the registration of two SCHAC- subordinate naming authorities whose names differ only in case. Attribute names will use the same mixed-case format as in the schema definition.

Identifier resolution:

The namespace is not currently listed with a Resolution Discovery System (RDS), but nothing about the namespace prohibits the future definition of appropriate resolution methods or listing with an RDS.

TERENA will maintain a registry of all SCHAC-assigned URN values, both final and for delegation, on its web site:

Delegation entries will have a pointer to the registry of the subordinate naming authority. This SHOULD recurse down the delegation tree, but registries for several delegated namespaces MAY be maintained by a single naming authority.

All registries MUST publish their URNs over https links [3]. The https links MUST be secured by sites offering credentials signed by a SCHAC-community recognized Certification Authority (CA) using the latest secure methods for accessing a web site (which at present is the latest version of Transport Layer Security (TLS) [4]). Registries SHOULD consider the user interface implications of their choice of CA, taking into account issues like browser alerts and blind trust.

Lexical equivalence:

Lexical equivalence of two SCHAC Namespace Specific Strings (NSSs) is defined as an exact, case-sensitive string match.

Conformance with URN syntax:

All SCHAC NSSs fully conform to RFC 2141 syntax rules for NSSs.

Validation mechanism:

As specified in the "Identifier resolution" section above, TERENA will maintain an index of all SCHAC-assigned URNs on its web site: Presence in that registry or in any subordinate registry implies that a given URN is valid. Delegated naming authorities MUST guarantee that values are valid in their assigned spaces.



4. Examples

The following examples are not guaranteed to be real. They are listed for pedagogical reasons only.


5. Security Considerations

There are no additional security considerations beyond those normally associated with the use and resolution of URNs in general.

In order to guarantee the validity and origin of SCHAC-NSS URN values, they MUST be published over https links [3]. The https links MUST be secured by sites offering credentials signed by a SCHAC- community recognized Certification Authority (CA) using the latest secure methods for accessing a web site (which at present is the latest version of TLS [4]).

6. Namespace Considerations

Registration of a Namespace Identifier (NID) specific to SCHAC is reasonable given the following considerations:

SCHAC would like to assign URNs to some very fine-grained objects. This does not seem to be the primary intended use of the namespace (RFC 3120) [13], or the more tightly controlled Organization for the Advancement of Structured Information Standards (OASIS) [14] namespace (RFC 3121) [15].

SCHAC seeks naming autonomy. SCHAC is not a member of OASIS, so becoming a subordinate naming authority under the OASIS URN space is not an option. There is the MACE (Middleware Architecture Committee for Education) (RFC 3613) [16] namespace, but the SCHAC development is done outside of the MACE activity scope; thus, the attributes and values do not belong in the MACE namespace. Using the MACE namespace requires that the SCHAC namespace be placed under one of the SCHAC participants' namespaces, which hinders its global scope.

SCHAC will want to assign URNs to non-XML objects as well. That is another reason that may not be an appropriate higher- level naming authority for SCHAC.

Some of the already defined SCHAC attribute values have been assigned URNs under the namespace. These values will enter a deprecation cycle, with a clear indication that they will be replaced by values under the new namespace once it is assigned. In any case, RFC 3406 [5] (which replaced RFC 2611) includes an explicit statement that two or more URNs may point to the same resource.

7. Community Considerations

The assignment and use of identifiers within the namespace are open, and the related rule is established by the SCHAC activity members. Registration agencies (the next-level naming authorities) will be the National Research and Education Networks (NRENs) and established organizational cross-border organizations that participate in SCHAC.

It is expected that the majority of the European NRENs, their constituencies, participants in the Australian Access Federation, and some other international activities will make use of the SCHAC namespace.

After the establishment of the SCHAC namespace, TERENA will establish a registry service (analogously to other distributed pan-European services, such as eduroam, PerfSONAR, etc.) for the namespace clients. This registry will be available via the root page of the namespace: The policy for registrations will be defined in documents available at the root page of the registry.

8. IANA Considerations

In accordance with BCP 66 [5], IANA has registered the Formal URN Namespace 'schac' in the Registry of URN Namespaces, using the registration template presented in Section 2 of this document.

9. Acknowledgments

SCHAC is the result of the TERENA TF-EMC2 task force and many others that have contributed ideas to the development of the schema.

This document was discussed on the URN-NID list, with the special help of Alfred Hoenes, who thoroughly reviewed the document, helped us correct errors, and suggested clarifications to the text.

Peter Saint-Andre has also provided comments that have improved the overall document quality, for which we herein thank him. We'd also like to thank Chris Lonvick for helping us express our security concerns in a better way. Finally, we thank other reviewers that have helped us to give the final touches to the text.

Special thanks should go to Dyonisius Visser from the TERENA technical team for taking the time and effort required to set up the root instance of the namespace registry.

10. References

10.1. Normative References

   [1]   Bradner, S., "Key words for use in RFCs to Indicate Requirement
         Levels", BCP 14, RFC 2119, March 1997.
   [2]   Crocker, D., Ed., and P. Overell, "Augmented BNF for Syntax
         Specifications: ABNF", STD 68, RFC 5234, January 2008.
   [3]   Rescorla, E., "HTTP Over TLS", RFC 2818, May 2000.
   [4]   Dierks, T. and E. Rescorla, "The Transport Layer Security (TLS)
         Protocol Version 1.2", RFC 5246, August 2008.
   [5]   Daigle, L., van Gulik, D., Iannella, R., and P. Faltstrom,
         "Uniform Resource Names (URN) Namespace Definition Mechanisms",
         BCP 66, RFC 3406, October 2002.

10.2. Informative References

   [6]   TERENA, "Trans-European Research and Education Networking
         Association", <>.
   [7]   TERENA TF-EMC2, "SCHAC activity web site",
   [8]   Sciberras, A., Ed., "Lightweight Directory Access Protocol
         (LDAP): Schema for User Applications", RFC 4519, June 2006.
   [9]   Smith, M., "Definition of the inetOrgPerson LDAP Object Class",
         RFC 2798, April 2000.
   [10]  MACE-Dir, "eduPerson Object Class Specification",
         December 2007, <
   [11]  Moats, R., "URN Syntax", RFC 2141, May 1997.
   [12]  IANA, "Country TLDs", <>.
   [13]  Best, K. and N. Walsh, "A URN Namespace for", RFC 3120,
         June 2001.
   [14]  OASIS, "Organization for the Advancement of Structured
         Information Standards: OASIS", <>.
   [15]  Best, K. and N. Walsh, "A URN Namespace for OASIS", RFC 3121,
         June 2001.
   [16]  Morgan, R. and K. Hazelton, "Definition of a Uniform Resource
         Name (URN) Namespace for the Middleware Architecture Committee
         for Education (MACE)", RFC 3613, October 2003.

Authors' Addresses

   Victoriano Giralt, M.D.
   University of Malaga
   Avd. Cervantes, 2
   Malaga, Malaga  E-29071
   Phone: +34-95-213-1415

Dr. Rodney McDuff
The University of Queensland