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

Mon Mar 2 15:51:02 CST 2009

>> 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.

That is not exactly true for specialized annotations.. dfdl:format can 
have any of the annotation specified in the spec.. but dfdl:sequence will 
have only the set of annotations that are applicable to sequence..  This 
will be enforced through DFDL model. As an example, in the DFDL model we 
would define a dfdl:sequence element and add only dfdl attribute specific 
to sequence.  It should save time while validating DFDL schema and  there 
should be savings in DFDL runtime parser also as it would have  to look 
for restricted set of annotations. 

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/wmb.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:
Suman Kalia/Toronto/IBM at IBMCA
Cc:
"Alan Powell" <alan_powell at uk.ibm.com>, <dfdl-wg at ogf.org>, 
<dfdl-wg-bounces at ogf.org>, <mbeckerle.dfdl at gmail.com>
Date:
03/02/2009 01:34 PM
Subject:
RE: [DFDL-WG] Reducing the number of DFDL properties.

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/wmb.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  |  703.299.0700 x212
Data Research and Analysis Corp.  |  www.dracorp.com 

From: 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. 
Mike Beckerle | OGF DFDL WG Co-Chair | CTO | Oco, Inc.
Tel:  781-810-2100  | 100 Fifth Ave., 4th Floor, Waltham MA 02451 | 
mbeckerle.dfdl at gmail.com 

From: Alan Powell [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

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