Updated below as agreed on DFDL WG call
Jan 29th.
Regards
Steve Hanson
Programming Model Architect, WebSphere Message Broker,
OGF DFDL WG Co-Chair,
Hursley, UK,
Internet: smh@uk.ibm.com,
Phone (+44)/(0) 1962-815848
----- Forwarded by Steve
Hanson/UK/IBM on 29/01/2010 17:40 -----
| From:
| Steve Hanson/UK/IBM
|
| To:
| dfdl-wg@ogf.org
|
| Date:
| 26/01/2010 12:26
|
| Subject:
| DFDL: TLOG proposal |
TLOG
The individual fields are a mixture
of ASCII strings, proprietary packed decimals, and the occasional pure
binary data. All fields are delimited by a separator. Fields of all types
can be fixed length or variable length with a maximum. Pure binary data
is preceded by a field giving the actual length. All lengths in bytes.
Packed decimals. Like a packed decimal
in the IBM sense. These can carry negative numbers but use a leading xD
sign nibble. No sign nibble if positive or unsigned. Odd number of digits
(including sign if present) are padded with xF nibble. This is best illustrated
using examples.
1234 => x12x34
123 => xF1x23
-1234 => xFDx12x34
-123 => xD1x23
Proposal
1) The 'variable length with a maximum'
will be handled using a post-timing assertion. Note this only applies on
parsing. **
2) dfdl:lengthKind 'delimited' is permitted
for numbers when dfdl:representation is 'binary' and dfdl:binaryNumberRep
is 'packed' or 'bcd' because it is possible to know in advance the range
of bytes being used, and therefore to choose suitable delimiters.
3) Core DFDL 1.0 will not be
enhanced to handle the TLOG packed decimal type. A future version
of DFDL will provide an extensibility mechanism that allows user-defined
types to be handled. In the 1.0 timeframe IBM may implement its own
proprietary extension to handle this type.
** While this can result in output from
a DFDL unparser that can not be re-parsed, that is a problem general to
the use of assertions, and a future version of DFDL may choose to change
this by enhancements to the assertion annotation.
Regards
Steve Hanson
Programming Model Architect, WebSphere Message Broker,
OGF DFDL WG Co-Chair,
Hursley, UK,
Internet: smh@uk.ibm.com,
Phone (+44)/(0) 1962-815848
Unless stated otherwise above:
IBM United Kingdom Limited - Registered in England and Wales with number
741598.
Registered office: PO Box 41, North Harbour, Portsmouth, Hampshire PO6
3AU
Unless stated otherwise above:
IBM United Kingdom Limited - Registered in England and Wales with number
741598.
Registered office: PO Box 41, North Harbour, Portsmouth, Hampshire PO6
3AU