Global Technical Committee
User Defined Field Range Proposal
December 17, 2009
0.3
Proposal Status: Approved for Public Comment
For Global Technical Committee Governance Internal Use Only
Submission Date: Dec. 17, 2009
Control Number:
Submission Status Approved for Public
Ratified Date
Comment
Primary Contact Person: GTC Governance
Release Identifier:
 Copyright, 2009, FIX Protocol, Limited
N/A
N/A
User Defined Field Range Proposal
81895168
December 17, 2009 - 0.3
DISCLAIMER
THE INFORMATION CONTAINED HEREIN AND THE FINANCIAL INFORMATION EXCHANGE
PROTOCOL (COLLECTIVELY, THE "FIX PROTOCOL") ARE PROVIDED "AS IS" AND NO PERSON OR
ENTITY ASSOCIATED WITH THE FIX PROTOCOL MAKES ANY REPRESENTATION OR WARRANTY,
EXPRESS OR IMPLIED, AS TO THE FIX PROTOCOL (OR THE RESULTS TO BE OBTAINED BY THE USE
THEREOF) OR ANY OTHER MATTER AND EACH SUCH PERSON AND ENTITY SPECIFICALLY
DISCLAIMS ANY WARRANTY OF ORIGINALITY, ACCURACY, COMPLETENESS, MERCHANTABILITY
OR FITNESS FOR A PARTICULAR PURPOSE. SUCH PERSONS AND ENTITIES DO NOT WARRANT
THAT THE FIX PROTOCOL WILL CONFORM TO ANY DESCRIPTION THEREOF OR BE FREE OF
ERRORS. THE ENTIRE RISK OF ANY USE OF THE FIX PROTOCOL IS ASSUMED BY THE USER.
NO PERSON OR ENTITY ASSOCIATED WITH THE FIX PROTOCOL SHALL HAVE ANY LIABILITY FOR
DAMAGES OF ANY KIND ARISING IN ANY MANNER OUT OF OR IN CONNECTION WITH ANY USER'S
USE OF (OR ANY INABILITY TO USE) THE FIX PROTOCOL, WHETHER DIRECT, INDIRECT,
INCIDENTAL, SPECIAL OR CONSEQUENTIAL (INCLUDING, WITHOUT LIMITATION, LOSS OF DATA,
LOSS OF USE, CLAIMS OF THIRD PARTIES OR LOST PROFITS OR REVENUES OR OTHER ECONOMIC
LOSS), WHETHER IN TORT (INCLUDING NEGLIGENCE AND STRICT LIABILITY), CONTRACT OR
OTHERWISE, WHETHER OR NOT ANY SUCH PERSON OR ENTITY HAS BEEN ADVISED OF, OR
OTHERWISE MIGHT HAVE ANTICIPATED THE POSSIBILITY OF, SUCH DAMAGES.
DRAFT OR NOT RATIFIED PROPOSALS (REFER TO PROPOSAL STATUS AND/OR SUBMISSION
STATUS ON COVER PAGE) ARE PROVIDED "AS-IS" TO INTERESTED PARTIES FOR DISCUSSION
ONLY. PARTIES THAT CHOOSE TO IMPLEMENT THIS DRAFT PROPOSAL DO SO AT THEIR OWN
RISK. IT IS A DRAFT DOCUMENT AND MAY BE UPDATED, REPLACED, OR MADE OBSOLETE BY
OTHER DOCUMENTS AT ANY TIME. THE FPL GLOBAL TECHNICAL COMMITTEE WILL NOT ALLOW
EARLY IMPLEMENTATION TO CONSTRAIN ITS ABILITY TO MAKE CHANGES TO THIS
SPECIFICATION PRIOR TO FINAL RELEASE. IT IS INAPPROPRIATE TO USE FPL WORKING DRAFTS
AS REFERENCE MATERIAL OR TO CITE THEM AS OTHER THAN “WORKS IN PROGRESS”. THE FPL
GLOBAL TECHNICAL COMMITTEE WILL ISSUE, UPON COMPLETION OF REVIEW AND
RATIFICATION, AN OFFICIAL STATUS ("APPROVED") TO THE PROPOSAL AND A RELEASE NUMBER.
No proprietary or ownership interest of any kind is granted with respect to the FIX Protocol (or any rights therein).
Copyright 2003-2009 FIX Protocol Limited, all rights reserved
 Copyright, 2009, FIX Protocol, Limited
Page 2 of 8
User Defined Field Range Proposal
81895168
December 17, 2009 - 0.3
Table of Contents
Document History..........................................................................................................................................................4
1
Introduction ..........................................................................................................................................................5
2
Historical Analysis ...............................................................................................................................................5
3
Issues and Discussion Points ................................................................................................................................6
4
Proposal................................................................................................................................................................6
5
Appendix A - Data Dictionary .............................................................................................................................8
 Copyright, 2009, FIX Protocol, Limited
Page 3 of 8
User Defined Field Range Proposal
81895168
December 17, 2009 - 0.3
Document History
Revision
Date
Author
0.1
August 7, 2009
Ryan Pierce, FIX
Protocol Ltd.
Revision Comments
Jim Northey, LaSalle
Technology Group
0.2
Dec. 11, 2009
Lisa Taikitsadaporn
Editted for clarity
0.3
December 17,
2009
Ryan Pierce, FIX
Protocol Ltd.
Incorporated changes from December 17, 2009
GTC meeting. Removed issues for discussion, and
removed SessionRejectReason changes.
Removed references to SessionRejectReason from
Glossary.
 Copyright, 2009, FIX Protocol, Limited
Page 4 of 8
User Defined Field Range Proposal
81895168
December 17, 2009 - 0.3
1 Introduction
The popularity of FIX has much to do with its extensibility to meet new business needs. Since the beginning, the
FIX Protocol allowed for extensions to be made to the protocol to support new business functionality. The preferred
method for extending the FIX Protocol is by proposing changes to the protocol itself. FPL has now begun issuing
Extension Packs to the protocol which allow for immediate adoption. The time from completion of a Gap Analysis
document to an approved, usable Extension Pack can be as little as 2 months.
However, in some cases, firms do not wish to engage in standardizing their new business functionality, and wish to
keep these extensions proprietary. FIX supports this through the use of User Defined Fields (UDFs).
To allow for uniqueness among UDFs, FPL has maintained a registry of tags in the 5000-9999 range on its website.
Unfortunately, this range is now full.
Tags in the 10,000+ range were originally intended for use within a firm, but due to the lack of available sequential
UDFs, a desire not to make a public disclosure of tags used, or both, the use of the 10,000+ range for inter-firm
communication, especially among execution venues like Exchanges, ATS’s, and ECN’s, has become increasingly
popular. This poses a substantial problem to firms who use the tags in the 10,000+ range internally.
Further, the current allocation of tags places no upper bound on intra-firm tags in the 10,000+ range, and this
effectively limits FPL, giving FPL no ability to extend the standard tag range beyond 4999 and UDFs beyond 50009999.
The issue of managing the existing 5000-9999 range of tags is beyond the scope of this proposal. Rather, this
proposal seeks to address the issue of reserving additional tag space for private intra-firm usage, creating a new
range of tags for inter-firm usage, and capping these to a finite limit so that all remaining tag space is reserved for
future expansion as FPL sees fit.
2 Historical Analysis
FIX Version
UDF Usage
4.0 - 4.1
User Defined Fields:
In order to provide maximum flexibility for its users, the FIX protocol accommodates User
Defined Fields. These fields are intended to be implemented between consenting trading
partners and should be used with caution to avoid conflicts which will arise as multiple parties
begin implementation of the protocol. It is suggested that if trading partners find that particular
User Defined Fields add value, they should be recommended to the FIX Technical Committee
for inclusion in a future FIX version.
4.2 - 5.0SP2
The tag numbers 5000 to 9999 have been reserved for use with user defined fields.
User Defined Fields:
In order to provide maximum flexibility for its users, the FIX protocol accommodates User
Defined Fields. These fields are intended to be implemented between consenting trading
partners and should be used with caution to avoid conflicts, which will arise as multiple parties
begin implementation of the protocol. It is suggested that if trading partners find that particular
User Defined Fields add value, they should be recommended to the FIX Technical Committee
for inclusion in a future FIX version.
The tag numbers 5000 to 9999 have been reserved for use with user defined fields, which are
used as part of inter-firm communcation. These tags can be registered/reserved via the FIX
website.
The tag numbers greater than or equal to 10000 have been reserved for internal use (within a
single firm) and do not need to be registered/reserved via the FIX website.
 Copyright, 2009, FIX Protocol, Limited
Page 5 of 8
User Defined Field Range Proposal
81895168
December 17, 2009 - 0.3
3 Issues and Discussion Points
While FIX is used to pass messages between firms, it has become increasingly useful as a transport mechanism
within firms. For example, an external FIX gateway may communicate with external participants and then pass these
messages via an internal enterprise message bus to other components, such as OMS, EMS, algorithm, compliance,
risk, clearing, settlement, and database applications. Each of these components may need to enrich the messages
with internal data fields that are not seen by external parties, or are translated into existing FIX tags or UDFs before
being sent to external parties.
According to the FIX specification, the tags in the 10,000+ range were reserved for this purpose. Firms could then
use these tags with confidence that external entities would not use them, transmit them, or expect the firm to
transmit data using these tags to the external entity, and any contrary behavior would not be in compliance with the
FIX specification. Defensive coding of applications is always recommended; even with this assurance, a FIX
implementation should never allow receipt of an internal tag from an external entity to trigger improper behavior.
But a FIX gateway could effectively “firewall” this tag range, either blocking transmission of tags using it, or
rejecting messages containing them.
However, a number of firms have begun using the 10,000+ range with external participants. This includes a number
of Exchanges, ATS’s, and/or ECN’s. Fortunately, many seem to recognize that the 10,000-19,999 range is likely one
which may conflict with internal tags, and as such have used the 20,000-39,000 range.
In the interest of preserving order, and in light of the relative lack of available UDFs in the 5000-9999 range, this
proposal seeks to redefining the usage of the 10,000+ range of tags with precise language to be included in the
Specification. This provides the best compromise. With the 10,000+ tag usage clarified, this proposal also
recommends imposing an upper limit on tag usage and reserving the rest of the tags for future expansion by FPL.
This compromise is not ideal. Some firms may be using tags in the 20,000-39,999 range for internal purposes and
some firms may be using 10,000-19,999 for external purposes. Other firms may be using tags in the 40,000+ range these firms would be inconvenienced by needing to move their tags to the allowed range or being considered noncompliant.
1.
4 Proposed Changes
The tag numbers including and above 10,000 are to be allocated as follows:

10,000-19,999 – Intra-Firm Private Tags

20,000-39,999 – Inter-Firm Private Tags

40,000+ - FPL Reserved Tags
Propose that the specification text in Volume 1's "User Defined Fields" section be amended as follows:
User Defined Fields:
In order to provide maximum flexibility for its users, the FIX protocol accommodates User Defined Fields. These
fields are intended to be implemented between consenting trading partners and should be used with caution to avoid
conflicts, which will arise as multiple parties begin implementation of the protocol. It is suggested that if trading
partners find that particular User Defined Fields add value, they should be recommended to the FIX Technical
Committee for inclusion in a future FIX version.
 Copyright, 2009, FIX Protocol, Limited
Page 6 of 8
User Defined Field Range Proposal
81895168
December 17, 2009 - 0.3
The tag numbers 5000 to 9999 have been reserved for use with user defined fields for Inter-Firm communication.
These tags can be registered/reserved via the FIX website.
The tag numbers 10,000 to 19,999 have been reserved for use with user defined fields for Intra-Firm
communication. These tags may be used within a firm, or between subsidiaries or other internal entities of a firm.
Usage of these tags to communicate with external firms is not allowed. Examples of prohibited usage include:
execution venues like Exchanges, ATS’s, and ECN’s using these tags to communicate with their members and
market participants, sell-sides using these tags to communicate with their clients, and vendors using these tags to
communicate with their clients. These tags will not be registered/reserved via the FIX website.
The tag numbers 20,000 to 39,999 have been reserved for use with user defined fields as part of inter-firm
communication. These tags will not be registered/reserved via the FIX website. No attempt will be made to
guarantee uniqueness of these tags, and firms must not assume that any such guarantee exists.
The tag numbers 40,000 and higher have been reserved by FPL for future use. No usage of these tags, either within a
firm or between firms, may be made until their usage is defined by FPL.
 Copyright, 2009, FIX Protocol, Limited
Page 7 of 8
User Defined Field Range Proposal
81895168
December 17, 2009 - 0.3
5 Appendix A - Data Dictionary
6 Appendix B - Glossary Entries
Term
Intra-Firm
Inter-Firm
Definition
Field where
used
Usage for communication within a firm, or between subsidiaries or
other internal entities of a firm. Note that communication between
execution venues like Exchanges, ATS’s, and ECN’s and their
members and market participants, between sell-sides and their
clients, and between vendors and their clients are not considered
Intra-Firm.
Usage for communication between firms. Communication between
execution venues like Exchanges, ATS’s, and ECN’s and their
members and market participants, between sell-sides and their
clients, and between vendors and their clients are all considered
Inter-Firm.
 Copyright, 2009, FIX Protocol, Limited
Page 8 of 8