>> 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@ca.ibm.com

From:	"Dave Glick" <dglick@dracorp.com>
To:	Suman Kalia/Toronto/IBM@IBMCA
Cc:	"Alan Powell" <alan_powell@uk.ibm.com>, <dfdl-wg@ogf.org>, <dfdl-wg-bounces@ogf.org>, <mbeckerle.dfdl@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@dracorp.com | 703.299.0700 x212
Data Research and Analysis Corp. | www.dracorp.com

From: Suman Kalia [mailto:kalia@ca.ibm.com]
Sent: Monday, March 02, 2009 11:25 AM
To: Dave Glick
Cc: Alan Powell; dfdl-wg@ogf.org; dfdl-wg-bounces@ogf.org; mbeckerle.dfdl@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@ca.ibm.com

From: "Dave Glick" <dglick@dracorp.com>
To: "Alan Powell" <alan_powell@uk.ibm.com>, <mbeckerle.dfdl@gmail.com>
Cc: dfdl-wg@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@dracorp.com | 703.299.0700 x212
Data Research and Analysis Corp. | www.dracorp.com

From: dfdl-wg-bounces@ogf.org [mailto:dfdl-wg-bounces@ogf.org] On Behalf Of Alan Powell
Sent: Monday, March 02, 2009 11:03 AM
To: mbeckerle.dfdl@gmail.com
Cc: dfdl-wg@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@uk.ibm.com
Tel: +44 (0)1962 815073 Fax: +44 (0)1962 816898

From: "Mike Beckerle" <mbeckerle.dfdl@gmail.com>
To: Alan Powell/UK/IBM@IBMGB
Cc: <dfdl-wg@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"/> 
<xs:element name="anotherElem" type="xs:float"/> 

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@uk.ibm.com]
Sent: Thursday, February 26, 2009 12:22 PM
To: mbeckerle.dfdl@gmail.com
Cc: dfdl-wg@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@uk.ibm.com
Tel: +44 (0)1962 815073 Fax: +44 (0)1962 816898

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From:	"Mike Beckerle" <mbeckerle.dfdl@gmail.com>
To:	Alan Powell/UK/IBM@IBMGB
Cc:	<dfdl-wg@ogf.org>
Date:	28/02/2009 19:38
Subject:	RE: Reducing the number of DFDL properties.