JEP-xxxx: File Transfer Preview

This JEP provides documentation for showing a preview image of the file before a file transfer


WARNING: This document has not yet been accepted for consideration or approved in any official manner by the Jabber Software Foundation, and this document must not be referred to as a Jabber Enhancement Proposal (JEP). If this document is accepted as a JEP by the Jabber Council, it will be published at <http://www.jabber.org/jeps/> and announced on the <standards-jig@jabber.org> mailing list.


JEP Information

Status: ProtoJEP
Type: Standards Track
Number: xxxx
Version: 0.0.2
Last Updated: 2006-09-04
JIG: Standards JIG
Approving Body: Jabber Council
Dependencies: XMPP Core, JEP-0096: File Transfer <http://www.jabber.org/jeps/jep-0096.html>
Supersedes: None
Superseded By: None
Short Name: File Transfer Preview

Author Information

Olivier Goffart

Email: ogoffart@kde.org
JID: ogoffart@kde.org

Legal Notice

This Jabber Enhancement Proposal is copyright 1999 - 2006 by the Jabber Software Foundation (JSF) and is in full conformance with the JSF's Intellectual Property Rights Policy <http://www.jabber.org/jsf/ipr-policy.shtml>. This material may be distributed only subject to the terms and conditions set forth in the Creative Commons Attribution License (<http://creativecommons.org/licenses/by/2.5/>).

Discussion Venue

The preferred venue for discussion of this document is the Standards-JIG discussion list: <http://mail.jabber.org/mailman/listinfo/standards-jig>.

Relation to XMPP

The Extensible Messaging and Presence Protocol (XMPP) is defined in the XMPP Core (RFC 3920) and XMPP IM (RFC 3921) specifications contributed by the Jabber Software Foundation to the Internet Standards Process, which is managed by the Internet Engineering Task Force in accordance with RFC 2026. Any protocol defined in this JEP has been developed outside the Internet Standards Process and is to be understood as an extension to XMPP rather than as an evolution, development, or modification of XMPP itself.

Conformance Terms

The following keywords as used in this document are to be interpreted as described in RFC 2119: "MUST", "SHALL", "REQUIRED"; "MUST NOT", "SHALL NOT"; "SHOULD", "RECOMMENDED"; "SHOULD NOT", "NOT RECOMMENDED"; "MAY", "OPTIONAL".


Table of Contents

1. Introduction
2. Requirements
3. Service Discovery
4. Picture
5. Example
6. Buisness rules
7. Security Considerations
8. IANA Considerations
9. XML Schema
Notes
Revision History


1. Introduction

In the File Transfer [1] there are few metadata about the file, but there are no possibility to add a preview image like some legacy protocol already does.

This JEP add support for image preview meta-data

2. Requirements

Add the possibility to have a picture metadata for preview.

3. Service Discovery

Since the preview element may be big in size, before sending a file with a preview, one entity MUST do service discovery as defined in Service Discovery [2]

Entity that support, and desire receive preview MUST include <feature var='http://kopete.kde.org/protocol/file-preview'/> in their reply

Example 1. Service Discovery Information Request

 <iq from='romeo@montague.net/orchard'
      id='disco1'
      to='juliet@capulet.com/balcony'
      type='get'>
    <query xmlns='http://jabber.org/protocol/disco#info'/>
  </iq>

Example 2. Service Discovery Information Response

  <iq from='juliet@capulet.com/balcony'
      id='disco1'
      to='romeo@montague.net/orchard'
      type='result'>
    <query xmlns='http://jabber.org/protocol/disco#info'>
      ...
	  <feature var='http://kopete.kde.org/protocol/file-preview'/>
      ...
    </query>
  </iq>
  

4. Picture

The picture will be embed ed into a <preview/> element placed in the <file/> element of the invitation.

It consist in a base64 encoded string of the PNG, GIF or JPEG data of the image

The image SHOIULD not exceed 128x128 pixel

The <preview/> element MUST have the type attribute with the mimetype of the preview

5. Example

Example 3. Offer a file with a preview

<iq type='set' to='juliet@capulet.com/balcony' id='offer1' >
  <si xmlns='http://jabber.org/protocol/si' 
      profile='http://jabber.org/protocol/si/profile/file-transfer' 
      id='s5b_46e78e4a0ddacc74' >
    <file xmlns='http://jabber.org/protocol/si/profile/file-transfer' 
          size='330527' 
          name='image.png' >
      <preview xmlns='http://kopete.kde.org/protocol/file-preview' type='image/png'>
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      </preview>
      <range/>
    </file>
    <feature xmlns='http://jabber.org/protocol/feature-neg'>
      ...
    </feature>
  </si>
</iq>
	

6. Buisness rules

The image SHOULD represend a thumbmail of the file. It MAY be a small representation of an image, a representation of the first page of a text document or even the CD cover of a musical track. However, it SHOULD NOT be a representation of the mime-type of the document. It is better to not provide a preview if it is not possible to have a drawn representation of the file.

7. Security Considerations

The client should take care that the preview cannot replace normal element of the GUI. Exemple, if the client show the mime-type icon when there is no preview, a malicious user could make his executable file looks like a multimedia file with his preview

8. IANA Considerations

This JEP requires no interaction with the Internet Assigned Numbers Authority (IANA) [3].

9. XML Schema

<?xml version='1.0' encoding='UTF-8'?>

<xs:schema
    xmlns:xs='http://www.w3.org/2001/XMLSchema'
    targetNamespace='http://kopete.kde.org/protocol/file-preview'
    xmlns='http://kopete.kde.org/protocol/file-preview'
    elementFormDefault='qualified'>

  <xs:element name='preview' type='xs:base64Binary' >
    <xs:complexType>
      <xs:attribute name='type' type='xs:string' use='required'/>
    </xs:complexType>
  </xs:element>

</xs:schema>


Notes

1. JEP-0096: File Transfer <http://www.jabber.org/jeps/jep-0096.html>.

2. JEP-0030: Service Discovery <http://www.jabber.org/jeps/jep-0030.html>.

3. The Internet Assigned Numbers Authority (IANA) is the central coordinator for the assignment of unique parameter values for Internet protocols, such as port numbers and URI schemes. For further information, see <http://www.iana.org/>.


Revision History

Version 0.0.2 (2006-09-04)

Added type attribute. Added the discovery section. Added the support for GIF. Changed the size recomandations (ogoffart)

Version 0.0.1 (2006-08-01)

Initial version. (ogoffart)


END