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Re: RDFa Last Call Comment: Better name than 'instanceof' is needed

From: Ivan Herman <ivan@w3.org>
Date: Tue, 18 Mar 2008 09:12:15 +0100
Message-ID: <47DF795F.6030600@w3.org>
To: Micah Dubinko <mdubinko@yahoo-inc.com>
CC: John Boyer <boyerj@ca.ibm.com>, public-rdf-in-xhtml-tf@w3.org

I think that one of the main reason for having instanceof is that in XML 
you cannot repeat attributes on the elements. Theoretically it is of 
course perfectly possible to use RDFa without instanceof but it would 
make life sometimes way more complicated by the necessity to include an 
additional nesting with <span> or <div>. I think the advantages 
outweight the extra difficulties.



Micah Dubinko wrote:
> Food for thought...
> If the instanceof attribute were completely removed from RDFa, would any 
> use cases be forclosed? Couldn't the same thing be done through rdf:type 
> properties on possibly blank nodes?
> In discussions about RDFa with non-RDF-familiar people, instanceof has 
> been harder for them to grasp.
> Thanks,
> -m
> John Boyer wrote:
>> RDFa is designed to provide a set of attributes for including RDF 
>> information into XHTML documents.
>> XHTML2 is designed to work with XForms.
>> Central to the operation of XForms is an "instance", which is a block 
>> of XML data over which the XForm operates.  This name for data was 
>> obtained from the XML Schema working group as the "standard" way to 
>> refer to an occurrence of XML conforming to a given schema as an 
>> "instance" of that schema.  In XForms, one can have an instance 
>> without physically associating a schema with it, or even having 
>> expressed the schema, but that is beside the point as one might 
>> reasonably regard such occurrences as an authoring convenience for an 
>> implied schema.
>> The main point is that these things are called "instances" because you 
>> can, in principle at least, *instantiate* a template description, much 
>> like creating a new object from a class definition.  The XForms 
>> instances can, in principle at least and often in practice, be viewed 
>> as an instantiation of a template defined by a schema.  In the future, 
>> I am hoping we get better at embedding the instantiation operation 
>> itself into XForms.
>> Instantiation does not appear to be what is happening in the case of 
>> RDFa.  Instead, the element to which you attach "instanceof" is 
>> something to which you simply seem to be attaching some RDF type 
>> information.  A name that more accurately reflects that behavior would 
>> be preferable.
>> Lest you think this is just picking a nit, a secondary reason for 
>> requesting a change here is that I would like to avoid any confusion 
>> between use of the word instance as it applies to XForms versus its 
>> use with RDFa.  Although the W3C will not always be able to see name 
>> conflicts coming in advance, we should at least take action when we do 
>> see a problem coming in advance.  We have been especially charged by 
>> W3 management with easing the authoring experience of XHTML and XForms 
>> going forward, and I notice to that end that the RDFa attributes are 
>> not namespace qualified.  The XForms syntax work being done in XForms 
>> 1.2 will likely allow adoption into XHTML without namespace 
>> qualification into the XForms namespace.  This eases authoring but 
>> accentuates the possibility of confusion when these vocabularies 
>> contain similar names, if not exact name conflicts, for different 
>> concepts.
>> Thank you,
>> John M. Boyer, Ph.D.
>> Senior Technical Staff Member
>> Lotus Forms Architect and Researcher
>> Chair, W3C Forms Working Group
>> Workplace, Portal and Collaboration Software
>> IBM Victoria Software Lab
>> E-Mail: boyerj@ca.ibm.com 
>> Blog: http://www.ibm.com/developerworks/blogs/page/JohnBoyer
>> Blog RSS feed: 
>> http://www.ibm.com/developerworks/blogs/rss/JohnBoyer?flavor=rssdw


Ivan Herman, W3C Semantic Web Activity Lead
Home: http://www.w3.org/People/Ivan/
PGP Key: http://www.ivan-herman.net/pgpkey.html
FOAF: http://www.ivan-herman.net/foaf.rdf

Received on Tuesday, 18 March 2008 08:14:05 UTC

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