[dfdl-wg] More documents
Steve Hanson
smh at uk.ibm.com
Wed Feb 1 07:03:44 CST 2006
Martin, before I can review this properly, I would like to see how some
concrete instances of black-box extensibility appear with your conversions
proposal. That is, I would like to see actual, complete DFDL schema and not
just the odd snippet. The instances I have in mind are:
- A portion of the data is encrypted, with fields in the message prior to
the encrypted section providing the decryption keys etc. (X12 security
segment motivates this)
- Data where some XML is embedded in the middle
- Data where decimal fields (say) are in a wacky encoding not supported by
stock DFDL properties (TLOG retail standard motivates here)
Underlying this is a major concern I have with the consumability of the
DFDL standard, If we don't provide something that is fairly straightforward
for users to understand out-of-the-box so to speak then a lot of potential
users will simply not adopt DFDL. I would suggest that the way to address
this is by keeping the 'core' standard as simple as possible, then defining
'extensions'. We can discuss what these extensions might be, I would
suggest that support for non-essential XML schema constructs such as
attributes be one extension, also multiple input/output streams.
Extensibility is a big topic, my gut feel is that some extensibility will
appear in the core, some will be an extension. I would also suggest that it
be up to an implementor as to whether they support extensions - for some,
it might not make any sense, but that should not preclude them providing a
certifiable core implementation. Bottom line is that reading the core spec
should leave users thinking 'this is great' not 'this is complicated'.
None of what I say in the last paragraph invalidates your semantics
observations below. It's more on how we portray DFDL to consumers. If you
take W3C XML specifications as an example, whilst they are rigorous to the
nth degree, many are totally unreadable. While a primer obviously helps
things, on its own I don't think it goes far enough.
Regards, Steve
Steve Hanson
WebSphere Message Brokers,
IBM Hursley, England
Internet: smh at uk.ibm.com
Phone (+44)/(0) 1962-815848
"Westhead, Martin
(Martin)"
<westhead at avaya.c To
om> Steve Hanson/UK/IBM at IBMGB,
Sent by: <dfdl-wg at ggf.org>
owner-dfdl-wg at ggf cc
.org
Subject
RE: [dfdl-wg] More documents
01/02/2006 04:56
Hi Steve,
That is a good suggestion.
An important point that I can try to make, in the abstract is that both
cases you outline would have very similar annotations on the logical
model. That part of it would not need to change. The explicit
declarations are additional material that would (typically) be presented
to the compiler in advance.
I don't think its particularly important for us to get hung up on the
declaration of new conversions at this stage. After discussing this with
Mike, I think it makes sense to separate that section off into a new
document, that we could discuss separately.
At the heart of what I think is important in this conversions document
is the semantics for describing the conversions and how they are chosen.
In order for the standard to be comprehensible and comprehensive in its
description of DFDL I think we need to nail down these details. It is,
if you like a useful side effect, that doing so provides the hooks to
allow extensibility, but I think it is important in of itself to have a
clear description of how that all works. In principle we should be able
to hand this standards doc to two developers, lock them in separate
rooms and have them build two DFDL parsers that do the same thing for
all the many complex corner cases and I think we need a framework like
the one I have outlined to get that to work.
That said I think there are a lot of issues with what I laid out, Mike
identified many of them, which need attention and group discussion.
Talk to you tomorrow,
Martin
>-----Original Message-----
>From: owner-dfdl-wg at ggf.org [mailto:owner-dfdl-wg at ggf.org] On Behalf Of
>Steve Hanson
>Sent: Tuesday, January 31, 2006 1:41 AM
>To: dfdl-wg at ggf.org
>Subject: Re: [dfdl-wg] More documents
>
>I've read the Conversions document and to be honest I had a great deal
of
>trouble trying to work out what was going on. I'd like to see an
example of
>a DFDL schema that models a text stream that contains (say) a complex
type
>with string, integer and decimal children, with DFDL properties used to
>handle the implicit conversions from text to logical data type. Then
I'd
>like to see the same DFDL schema but with equivalent conversions
explicitly
>declared and used instead of the DFDL properties.
>
>Regards, Steve
>
>Steve Hanson
>WebSphere Message Brokers,
>IBM Hursley, England
>Internet: smh at uk.ibm.com
>Phone (+44)/(0) 1962-815848
>
>
>
> Mike Beckerle
> <beckerle at us.ibm.
> com>
To
> Sent by: Mike Beckerle
<beckerle at us.ibm.com>
> owner-dfdl-wg at ggf
cc
> .org dfdl-wg at ggf.org,
> owner-dfdl-wg at ggf.org,
"Westhead,
> Martin (Martin)"
> 28/01/2006 04:17 <westhead at avaya.com>
>
Subject
> Re: [dfdl-wg] More documents
>
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>
>Oh yeah, forgot the attachment.
>Mike Beckerle
>STSM, Architect, Scalable Computing
>IBM Software Group
>Information Integration Solutions
>Westborough, MA 01581
>voice and FAX 508-599-7148
>home/mobile office 508-915-4767
>
>
>
>
> Mike
> Beckerle/Worcester/IBM at IBMUS
> Sent by: owner-dfdl-wg at ggf.org
>
To
> "Westhead, Martin
(Martin)"
> 01/27/2006 07:50 PM <westhead at avaya.com>
>
cc
> dfdl-wg at ggf.org,
> owner-dfdl-wg at ggf.org
>
Subject
> Re: [dfdl-wg] More
documents
>
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>Sorry I missed the call this past week. Here are my comments and some
>in-line editing on the
>
>
>I actually think the primary reason to push this document forward is
NOT
>extensibility, but because it is needed to clarify the basic semantics
of
>DFDL. That is, it allows us to make very clear exactly what properties
in
>the annotations are guiding the selection of which conversion
functions.
>
>...mikeb
>
>Mike Beckerle
>STSM, Architect, Scalable Computing
>IBM Software Group
>Information Integration Solutions
>Westborough, MA 01581
>voice and FAX 508-599-7148
>home/mobile office 508-915-4767
>
>
>
> "Westhead, Martin (Martin)"
> <westhead at avaya.com>
> Sent by: owner-dfdl-wg at ggf.org
>
To
>
<dfdl-wg at ggf
> 01/23/2006 04:58 PM .org>
>
cc
>
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Subject
> [dfdl-wg]
> More
> documents
>
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>These are documents 3 and 4 of a set of 3 :).
>
>The documents are:
>- bundles - a reusable block of DFDL statements
>- Conversions - a proposal for the semantic details as to how
>conversions are chosen during the operation of a DFDL parser. These
>semantics include a description as to how the conversions can be
extended.
>
>These documents round off the current set of proposals from the
>extensibility design team. The team has reasonable consensus on these
>documents, with the (relatively trivial) exception of bundles where
there
>may be some outstanding issues. We believe that with these two
documents
>there is enough material to support the necessary extensibility.
However,
>we have not yet worked through enough examples of round tripping to
>understand whether that is sufficiently well covered and we are
expecting
>that all the ideas in these documents will require refining by the
group as
>a whole.
>
>I would like to discuss these two documents on Wednesday (if possible).
>
>Thanks,
>
>Martin[attachment "DFDL_Conversions_4.doc" deleted by Mike
>Beckerle/Worcester/IBM] [attachment "DFDL_Bundles_2.doc" deleted by
Mike
>Beckerle/Worcester/IBM]
>
>(See attached file: DFDL_Conversions_4.doc)
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