DAXP Preamble Specification
Defines message-level metadata used for routing, decoding, and validation. The preamble always precedes the message body.
Purpose
The DAXP preamble is a compact header composed of key=value pairs separated by | (or SOH 0x01 in binary mode).
It enables receivers to interpret the message correctly before parsing payload tags.
| Tag | Required | Name | Description | Example |
|---|---|---|---|---|
DAXP |
Y | Protocol Version | Identifies the DAXP protocol name and version. Must be the first tag. | DAXP=1 |
TF |
Y | Tag Format | Format of tag identifiers: D=Decimal, H=Hexadecimal. |
TF=D |
EN |
Y | Encoding | Character encoding used in the message (full name). | EN=UTF8 |
MC |
N | Message Count | Number of messages following this preamble (batch size). | MC=5 |
CX |
N | Context | Logical or domain context (Subsystem or namespace) | CX=TRD |
TS |
N | Timestamp | UTC timestamp when the preamble was generated. | TS=20251105-18:45:11.123 |
SN |
N | Sender | Identifier of the sending component or system. | SN=RxGateway |
TG |
N | Target | Identifier of the target component or system. | TG=RxTrader |
TK |
N | Token | Authentication, session, or correlation token. | TK=abc123 |
Design Rules
- Two-letter uppercase tags are reserved for preamble metadata.
- Values may be compact (
D,H) or descriptive (UTF8,ASCII). - Recommended tag order:
DAXP → TF → EN → MC → CX → TS → SN → TG → TK - Unknown tags must be ignored gracefully by parsers.
- Pairs are separated by
|or SOH (0x01) in binary mode. - The two-letter tag convention is mandatory for future extensions.
Example Preamble with DD message
DAXP=1|TF=D|EN=UTF8|MC=2|CX=CRM
|9=DD|6=10|
7=1|209=Id customer|100=2001|110=?|
7=2|209=First name|100=2002|165=N|110=S|
7=3|209=Surname|100=2003|110=S|
7=4|209=Email|100=2004|110=S|
7=5|209=Town|100=2005|110=S|
7=6|209=Telephone|100=2006|110=S|
7=7|209=Id|100=2201|110=?|
7=8|209=Amount|100=2202|165=N|110=?|
7=9|209=Contract No|100=2203|165=N|166=20|167=2|110=S|
7=10|209=Status|100=2205|110=C|
99=123|
9=UCD|6=1|2001=2|2002=Anna|2004=This email address is being protected from spambots. You need JavaScript enabled to view it. |2006=+48 123 456 789|99=43|
Interpretation: DAXP v1, Decimal tag IDs, UTF-8 encoding, 3 messages in Trader context, timestamped, routed from