[DFDL-WG] Reducing the number of DFDL properties.

Mon Mar 2 12:27:29 CST 2009

Suman,

In regards to your point that not having the specialized annotation
elements will mean that the user has to go through and understand when
and where representation properties are applicable - doesn't this hold
true one way or the other? For example, when annotating an xs:sequence
element, whether the user is using a dfdl:format element or a
dfdl:sequence element, they still must understand which of the superset
of representation properties can be applied to the annotation element.
The fact that it's called "dfdl:format" or "dfdl:sequence" doesn't make
it easier to understand which representation properties are valid for
xs:sequence elements.

In general, the following points are what led me to recommend the
special annotation elements be removed:

- Because a special annotation element can be used interchangeably with
dfdl:format, it is up to the DFDL parser to eventually validate defined
representation properties based on the XML Schema element to which to
annotation applies, regardless of whether the annotation element is a
dfdl:format or one of the special annotation elements (in other words,
the parser can never just trust that the user only defined valid
representation properties simply because they used a special annotation
element such as dfdl:sequence).

- Parsers must recognize and validate both conventions, thus adding an
extra burden on implementations.

- The explanation of the representation properties and where they are
valid gets awkward and confusing. For example, right now a
representation property is said to apply to "dfdl:sequence," and it is
up to the reader to understand that that also means dfdl:format when
used to annotate a xs:sequence element (and understand they must because
using a dfdl:format is equally valid).

- A reader of a DFDL schema must know that the special annotation
elements are really just dfdl:format annotation elements, thus given
them one more syntactic convention to remember. 

- The introduction of two syntactically different ways to mean exactly
the same thing creates a situation where the use of one method over the
other becomes a preference of an individual DFDL schema developer and
could make DFDL schemas more difficult to read and understand by someone
used to the alternate method.

- Multiple types of annotation elements for the description of
representation makes it more difficult to parse a DFDL Schema using XML
technologies. For example, someone may wish to use XSLT to pull out all
the representations defined in a DFDL Schema - if more than one element
for defining representations is used, this stylesheet would be much more
complicated because it would have to deal with all possibilities.

I think my heartburn can be summed up by saying that they seem to me to
add a disproportionate amount of complication compared to the limited
benefit. In fact, it would seem to me that having the concept in the
standard doesn't actually add anything of value - what is it exactly
that an implementation or DFDL Schema developer can do or do easier with
them that they couldn't do without?

Dave

---
David Glick  |  dglick at dracorp.com  |  703.299.0700 x212
Data Research and Analysis Corp.  |  www.dracorp.com

________________________________

From: Suman Kalia [mailto:kalia at ca.ibm.com] 
Sent: Monday, March 02, 2009 11:25 AM
To: Dave Glick
Cc: Alan Powell; dfdl-wg at ogf.org; dfdl-wg-bounces at ogf.org;
mbeckerle.dfdl at gmail.com
Subject: Re: [DFDL-WG] Reducing the number of DFDL properties.

I am not sure what kind of confusion or redundancy is caused by these
specialized annotations.  In the absence of these specialized
annotations, you will have to go through plethora of  annotations and
determine which ones are applicable for sequence , choice, all, elements
etc.. 

The danger is we don't have these levels of abstractions, then number of
folks (specifically implementers) would build them anyway and then we
will have to contend with incompatible abstractions.. 

Suman Kalia
IBM Toronto Lab
WMB Toolkit Architect and Development Lead
WebSphere Business Integration Application Connectivity Tools 

http://www.ibm.com/developerworks/websphere/zones/businessintegration/wm
b.html
<http://www.ibm.com/developerworks/websphere/zones/businessintegration/w
mb.html> 

Tel : 905-413-3923  T/L  969-3923
Fax : 905-413-4850 T/L  969-4850
Internet ID : kalia at ca.ibm.com 

From: 

"Dave Glick" <dglick at dracorp.com> 

To: 

"Alan Powell" <alan_powell at uk.ibm.com>, <mbeckerle.dfdl at gmail.com> 

Cc: 

dfdl-wg at ogf.org 

Date: 

03/02/2009 11:16 AM 

Subject: 

Re: [DFDL-WG] Reducing the number of DFDL properties.

________________________________

Alan/Mike, 

I agree with this - one of my complaints with v033 was that these
specialized annotation elements just added confusion and redundancy. 

Dave 

---
David Glick  |  dglick at dracorp.com <mailto:dglick at dracorp.com>   |
703.299.0700 x212
Data Research and Analysis Corp.  |  www.dracorp.com
<http://www.dracorp.com/>  

________________________________

From: dfdl-wg-bounces at ogf.org [mailto:dfdl-wg-bounces at ogf.org
<mailto:dfdl-wg-bounces at ogf.org> ] On Behalf Of Alan Powell
Sent: Monday, March 02, 2009 11:03 AM
To: mbeckerle.dfdl at gmail.com
Cc: dfdl-wg at ogf.org
Subject: Re: [DFDL-WG] Reducing the number of DFDL properties. 

Mike 

Thanks 

Can I also suggest dropping the dfdl:sequence, dfdl:choice, dfdl:element
and dfdl:any specialized annotations and just have dfdl:format. 

Alan Powell

MP 211, IBM UK Labs, Hursley,  Winchester, SO21 2JN, England
Notes Id: Alan Powell/UK/IBM     email: alan_powell at uk.ibm.com  
Tel: +44 (0)1962 815073                  Fax: +44 (0)1962 816898

From: 

"Mike Beckerle" <mbeckerle.dfdl at gmail.com> 

To: 

Alan Powell/UK/IBM at IBMGB 

Cc: 

<dfdl-wg at ogf.org> 

Date: 

28/02/2009 19:38 

Subject: 

RE: Reducing the number of DFDL properties.

________________________________

If a property is redundant, I'm in favor of dropping it. 

If a property adds generality that we don't have a use case for, I'm in
favor of dropping it. 

I am happy to drop type substitution from v1.0. It's a convenience that
can be achieved a different way. 

E.g., if you really want "float" to mean "float in my particular binary
representation", then just put a type definition with DFDL annotations
in a different namespace, and when you write your DFDL schema, arrange
for the default namespace to pick it up from your namespace, and not
xs:float. 

<xs:element name="myElement" type="float"/> <!-- float here is
myNamespace:float which can have DFDL annotations on it --> 
<xs:element name="anotherElem" type="xs:float"/> <!-- explicitly
xs:float without further adornment --> 

If you want the XSD unadorned "float" type, be explicit and use
"xs:float". Voila - no loss of flexibility, equal textual convenience. 

I think that would satisfy the community that really wanted very compact
"slideware acceptable" schemas. This is the same group that wants
short-form annotations as well. 

________________________________

From: Alan Powell [mailto:alan_powell at uk.ibm.com
<mailto:alan_powell at uk.ibm.com> ] 
Sent: Thursday, February 26, 2009 12:22 PM
To: mbeckerle.dfdl at gmail.com
Cc: dfdl-wg at ogf.org
Subject: Reducing the number of DFDL properties.

Mike 

A number of people at IBM have become concerned at the number of
properties in DFDL and have identified a number of 'usability'
properties that could be dropped. They feel that we should be
simplifying the properties wherever possible and not introducing
multiple ways of doing the same function without very good reason. 

The following are offered for consideration. 
1.        lengthKind='nullterminated'
This is just shorthand for lengthKind=delimited and terminator='%Null'.
It was felt this this is not even the most common terminator so why have
a special case? 
2.        trimKind
It is felt that there aren't any cases when you would want to pad but
not trim and vice versa so make padKind control both. 
3.        typeSubstitution.
Is this needed in DFDL v1? 

Can you consider these before the call next week 

Alan Powell

MP 211, IBM UK Labs, Hursley,  Winchester, SO21 2JN, England
Notes Id: Alan Powell/UK/IBM     email: alan_powell at uk.ibm.com  
Tel: +44 (0)1962 815073                  Fax: +44 (0)1962 816898

________________________________

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 

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