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INTERNET-DRAFT                                              Ralf Dorfner
Intended Status:  Proposed Standard
Expires: September 25, 2019                               March 24, 2019


      SimpleMetadata: An interoperable format for sharing metadata
                  draft-dorfner-core-simplemetadata-01

Abstract

   This document describes a  standardized container format for storing
   serializable metadata. It does not describe any additional new
   format, but provides a shell for the exchange of arbitrary,
   structured data. It shall provide the possibility to store and share
   any kind of metadata, including encryption support. The idea is to
   create an open, universal and interoperable standard for storing and
   distributing every kind of metadata independent from media type or
   file format.

Status of This Memo

   This is an Internet Standards Track document.

   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).  Further information on
   Internet Standards is available in Section 2 of RFC 7841.

   Information about the current status of this document, any errata,
   and how to provide feedback on it may be obtained at https://www.rfc-
   editor.org/info/rfc8335.

   This Internet-Draft is submitted in full conformance with the
   provisions of BCP 78 and BCP 79.

   Internet-Drafts are working documents of the Internet Engineering
   Task Force (IETF), its areas, and its working groups.  Note that
   other groups may also distribute working documents as Internet-
   Drafts.

   Internet-Drafts are draft documents valid for a maximum of six months
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   time.  It is inappropriate to use Internet-Drafts as reference
   material or to cite them other than as "work in progress."

   The list of current Internet-Drafts can be accessed at
   http://www.ietf.org/1id-abstracts.html



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Copyright and License Notice

   Copyright (c) 2019 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

   This document is subject to BCP 78 and the IETF Trust's Legal
   Provisions Relating to IETF Documents
   (https://trustee.ietf.org/license-info) in effect on the date of
   publication of this document.  Please review these documents
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   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.


































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Table of Contents

   1  Introduction  . . . . . . . . . . . . . . . . . . . . . . . . .  3
     1.1  Terminology . . . . . . . . . . . . . . . . . . . . . . . .  3
   2. Structure . . . . . . . . . . . . . . . . . . . . . . . . . . .  4
     2.1 Header Definition  . . . . . . . . . . . . . . . . . . . . .  4
     2.2 Identifier . . . . . . . . . . . . . . . . . . . . . . . . .  4
     2.3 Version  . . . . . . . . . . . . . . . . . . . . . . . . . .  4
     2.4  Serialization . . . . . . . . . . . . . . . . . . . . . . .  4
     2.5 Crypto . . . . . . . . . . . . . . . . . . . . . . . . . . .  4
     2.6 Schema URI length  . . . . . . . . . . . . . . . . . . . . .  5
     2.6 Content Length . . . . . . . . . . . . . . . . . . . . . . .  5
   3  Schema information  . . . . . . . . . . . . . . . . . . . . . .  5
   4 Metadata Content . . . . . . . . . . . . . . . . . . . . . . . .  5
   5 Notes  . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  5
   6 Security Considerations  . . . . . . . . . . . . . . . . . . . .  6
   7  IANA Considerations . . . . . . . . . . . . . . . . . . . . . .  6
   8  References  . . . . . . . . . . . . . . . . . . . . . . . . . .  6
     8.1  Informative References  . . . . . . . . . . . . . . . . . .  6
   Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . .  6

1  Introduction

   Nowadays a variety of media file are shared and published all over
   the world. Information about the origin, purpose or copyright of
   these files getting more and more important. There are already
   different standards which enhance files with metadata, like ID3
   <http://id3.org/>, Exif <https://www.exif.org/> or Dublin Core
   [RFC5013]. SimpleMetadata shall create the foundation to unite these
   standards and provide an universal and open container format. The
   idea is not to describe any additional new format, but provides a
   shell for the exchange of arbitrary, structured data. Any metadata
   payload shall be created, stored and shared with an open standard,
   like JavaScript Object Notation (JSON)  [RFC7159] in combination with
   schema validation <https://tools.ietf.org/id/draft-handrews-json-
   schema-00.txt>. Every data structure of metadata can be defined and
   distributed within schema definitions. Furthermore, SimpleMetadata
   can be extended by additional formatters or crypto standards.

1.1  Terminology

   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 [RFC2119].







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2. Structure

   The SimpleMetadata format consists of the three parts, Header, Schema
   URI and Metadata payload.
   +-------------------------------------------------------------------+
   |            Header (12 bytes)  (fixed length)                      |
   +-------------------------------------------------------------------+
   |            Schema URI  (variable length, optional)            |
   +-------------------------------------------------------------------+
   |            Serialized Metadata   (variable length)              |
   +-------------------------------------------------------------------+

2.1 Header Definition

   +----------------------------------------------------------------+
   |         Identifier "SMD"           3 Bytes / string              |
   +----------------------------------------------------------------+
   |         Version                        1 Byte / number            |
   +----------------------------------------------------------------+
   |         Serialization                1 Byte / number            |
   +----------------------------------------------------------------+
   |         Crypto                         1 Byte / number            |
   +----------------------------------------------------------------+
   |         Schema URI Length    2 Bytes / number          |
   +----------------------------------------------------------------+
   |        Content Length            4 Bytes / number          |
   +----------------------------------------------------------------+

2.2 Identifier

   The first three bytes of the header are always "SMD" to check if
   SimpleMetadata is present.

2.3 Version

   Defines the used  version of the SimpleMetadata format.
   1 = Current version

2.4  Serialization

   Defines the used formatter for the metadata. A formatter serializes
   or deserializes the metadata with the corresponding procedure. The
   standard formatter uses Binary JSON (BSON) <http://bsonspec.org/>
   with the JavaScript Object Notation (JSON)  [RFC7159].

   0 = BSON

2.5 Crypto



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   Defines the used crypto standard for en/decrypting metadata.

   0 = None encryption
   1 = Advanced Encryption Standard (AES)

2.6 Schema URI length

   Defines the string length of a schema or type. If no schema is
   defined the schema length is 0. The schema information is described
   in chapter 3.

2.6 Content Length

   Defines the length of the serialized metadata, based on the selected
   formatter (Chapter 2.3). If the content is encrypted, the length is
   calculated over the encrypted string.

3  Schema information

   The schema information can be used to validate the metadata against a
   schema or type. A schema information is an optional string with
   variable length encoded with UTF-8. It is recommended to use an URI ,
   e.g. "http://exampleschemas.org/Person". Moreover a local file path
   or even a type definition (AssemblyQualifiedName) can be used. For
   interoperability,  metadata should be based on public schema.

   The length of the schema is stored in the header (See chapter 2.6).

4 Metadata Content

   Basically every serializable content can be stored as metadata. It is
   highly recommended to use for interoperability and compatibility the
   JavaScript Object Notation (JSON) [RFC7159] for metadata and the
   according schema definition.

5 Notes

   Adding SimpleMetadata to a file will damage it under circumstances,
   unless there is a suitable parser to handle the format!












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6 Security Considerations

   Sensitive metadata can be encrypted within a supported crypto
   standard (Chapter 2.4).

7  IANA Considerations

   All data must be stored in UTF-8 [RFC2044].

8  References

8.1  Informative References

   [RFC7159]  Bray , Tim
                      The JavaScript Object Notation (JSON) Data
                      Interchange Format, March 2014,
                      <https://www.rfc-editor.org/info/rfc7159>.

   [RFC5013]  Kunze J., Baker T.
                      The Dublin Core Metadata Element Set,
                      August 2007
                      <https://www.rfc-editor.org/info/rfc5013>

   [RFC2044]  Francois, Yergeau
                      UTF-8, a transformation format of Unicode
                      and ISO 10646, October 1996
                      <https://www.rfc-editor.org/info/rfc2044>.

   [Internet-Draft]  Wright, A.
                      JSON Schema: A Media Type for Describing
                      JSON Documents, November 19, 2017
                      <https://tools.ietf.org/id/
                      draft-handrews-json-schema-00.txt>

Authors' Addresses

   Ralf Dorfner
   Muensterplatz 8
   88250 Weingarten
   Germany

   EMail: smd@simplemetadata.org









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