application/xtm+xml Media Type Registration

Abstract

This document describes a media type (application/xtm+xml) for serialization of Topic Maps into Extensible Markup Language (XML). Topic Maps is a technology for encoding knowledge and connecting this encoded knowledge to relevant information resources. Topic maps are organized around topics, which represent subjects of discourse; associations, representing relationships between the subjects; and occurrences, which connect the subjects to pertinent information resources. Topic Maps is an ISO standard (ISO 13250).

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1. Introduction

Topic Maps is a technology for encoding knowledge and connecting this encoded knowledge to relevant information resources. Topic Maps has a common structure defined by [ISO13250-2] that can be used for interoperable data interchange.

Many formats exist for the interchange of Topic Maps, but ISO has defined the XTM syntax [ISO13250-3] as the main interchange syntax, in order to allow topic map to be serialized in an XML format. The application/xtm+xml media type allows consumers of Topic Maps information to identify XTM documents so they can be processed properly.

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 BCP 14, RFC 2119 [RFC2119].

2. application/xtm+xml Registration

This is a media type registration as defined in RFC 4288, "Media Type Specifications and Registration Procedures" [RFC4288].

MIME media type name: application

MIME subtype name: xtm+xml

Required parameters: none

Optional parameters: charset

Same as charset parameter of application/xml, defined in RFC 3023 [RFC3023].

Encoding considerations: Same as encoding considerations of application/xml, defined in RFC 3023 [RFC3023].

Security considerations: See Section 5.

Interoperability considerations: It is RECOMMENDED that XTM documents use the new XTM 2.0 syntax [ISO13250-3] as opposed to the older XTM 1.0 syntax [XTM1.0]. In general use of features of XML which XML processors may choose not to support should be avoided.

Published specification: See the Topic Maps Data Model [ISO13250-2] and the XTM specification [ISO13250-3].

Applications which use this media type: Any tool which can process or produce data according to the Topic Maps Data Model [ISO13250-2]. This has included in the past generic Topic Maps tools, web portals, product configuration tools, e-learning systems, and a variety of web services and web service clients.

Magic number(s): none

Although no byte sequences can be counted on to consistently identify XTM, XTM documents will have the sequence "http://www.topicmaps.org/xtm/" to identify the XTM namespace. This will usually be near the top of the document.

File extensions(s): .xtm

Macintosh File Type Code(s): "xtm "

Person & email address to contact for further information:For further information: Lars Marius Garshol <larsga@garshol.priv.no>

Intended usage: COMMON

Author: Lars Marius Garshol <larsga@garshol.priv.no>

Change controller: The IESG.

3. Fragment Identifiers

The id attribute can be used to define fragments in an XTM document. So given an XTM document with the URL someurl the URL reference someurl#frag is taken to refer to the topic element in the XTM document whose id attribute value is "frag". Such URLs commonly occur in XTM documents to refer to topics defined either in the same XTM document or a different XTM document.

4. IANA Considerations

This document calls for registration of a new MIME media type, according to the registration in Section 2.

5. Security Considerations

XTM is a generic format for exchanging application information, but application designers must not assume that it provides generic protection against security threats. RFC 3023 [RFC3023], section 10, discusses security concerns for generic XML, which are also applicable to XTM.

XTM documents can be secured for integrity, authenticity and confidentiality using any of the mechanisms available for MIME and XML data, including XML signature, XML encryption, S/MIME, OpenPGP or transport or session level security (e.g., see [RFC3631], especially sections 3.4, 3.5, 3.10, [RFC2818], [RFC3275], [xmlenc-core]).

XTM is intended to be used to combine information from disparate sources into a coherent whole, but it is entirely possible for sources outside the control of the receiver to provide information that is false, misleading, unclear, or inappropriately structured. The use of Topic Maps schemas may guard against inappropriate structure, but as far as the other concerns go, caution and careful engineering are required.

XTM documents may contain references to other XTM documents via the mergeMap element, and XTM processors are required to dereference and process these references. This can be a source of insecurity, by means either subtle or obvious, such denial of service attacks by automatically generated never-ending chains of mergeMap references or infinitely sized documents.

6. References

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