Re: [office-metadata] Rough Proposal for RDFa + RDF/XML/XForms + xml:id

["Bruce D'Arcus" <bdarcus@gmail.com>]

On Feb 7, 2007, at 10:35 AM, Michael Brauer wrote:

>> I agree that there is little time left. Believe me I try to focus  
>> with my questions on this list on the remaining problems.
>> We might split the RDF metadata problematic into two general  
>> areas, which affect ODF
>>   1. The subject is in the content
>>   2. The object is a literal and in the content.
>
> I agree to Svante regarding these two general cases, but would like to
> know if this a common understanding of the SC, or just Svante's and my
> understanding.

I guess, but I'd maybe just want to say for 1 "one wants to make  
statements about arbitrary content in the document".

> The first use case is the case where a document contains some text, an
> image, a table cell, etc., and where the user wants to add additional
> information about this text (for instance an annotation, author
> information, whether it is important, and so on). It is also the use
> case where a document is converted from other document formats, and
> where additional information about the text, etc. that does not have a
> counterpart in ODF should be preserved.
>
> My understanding is that one possibility to store these metadata is
> - to add an id to an appropriate element that contains the text, table
> cell, etc., and
> - to use the either relative or absolute URI of the content.xml  
> with the
> id attached as fragment identifier as subject in the RDF triples that
> are stored in a RDF-XML stream next to the content.xml.
>
> Is that correct?

Yes.

> Bruce, am I right that this is exactly what you propose in your Image
> and Table examples?

Yes, though the wiki examples there do not reflect the more recent  
discussion of absolute vs. relative, global vs. local URIs. For the  
case Svante presented, using a global absolute URI may be important.

> This first use case is actually the case where I think subjects may be
> splitted: The user may select some text regardless of paragraph or
> boundaries and the like, and may then attach author information to it.

Yes, but it's not the subject that gets split. The subject is just a  
URI. It's the object literal of a property of that subject.

> However, the only extension to the above we would need in this case is
> the possibility to identify these selection with a singe id. That's
> something we have to add at the ODF content level, not at the meta  
> data
> level. There are many option how to do that. One is the start- and
> end-element solution we use for bookmarks already, that we may want to
> reuse in order to remain consistent with the remaining  
> specification. But that's an issue we may work on in detail if we  
> agree that RDF-XML + ids is the right solution for this use case.

Right.

> Regarding the 2nd use case: This is the use case where the literal
> object of an RDF triple is either in the content, or displayed there.
>
> The task to display such content is not new in ODF. ODF therefore
> already has concepts that we may use as basis.
>
> The first one are text fields. They display some text content, and
> contain a description where this text content comes from. On the XML
> level they are just XML elements, whose text content is the text to be
> displayed, and that have some attributes that specify what shall be
> displayed.
>
> We therefore could add a meta data field. There are two options for
> this: First we may add attributes for the RDF subject and  
> predicates, and may define that the text content of the field is  
> the literal RDF object. I think that is very similar to a subset  
> RDFa, except that the meta data attributes are not attached to  
> arbitrary elements, but that there is a specific element that  
> carries the meta data attributes, and that these elements cannot  
> nested.

OK, that might be fine. It at least includes the attributes.

> The other option is to have the meta data in separate stream  
> (including
> the literal object), and to have attributes that specify what RDF
> literal objects shall be displayed. This takes us directly to XForms,
> the 2nd feature that we may reuse, as Svante is pointing out:  
> XForms can
> be used to bind controls and text fields (although we don't have the
> later right now) to RDF objects in an RDF-XML stream. This works  
> already in ODF 1.1 (but for controls only). It therefore seems to  
> be reasonable to reuse XForms for all those cases where the metadata
> is in a separate stream in the package, and where we want to display
> some of the RDF objects in the content.
>
> If we want to reuse existing concepts, we therefore have two options:
> 1. Some kind of RDFa-text-field as descibed above.
> 2. RDF/XML+XForms
>
> Actually, I think an RDFa based text field and RDF/XML + XForms
> supplement each other. The RDFa text field is a good choice if the  
> data
> duplication of literal objects is a concern, or if there is no RDF/XML
> instance already existing. The XForms solution is a good choice if one
> already has an RDF/XML document that should be included, if the meta
> data is very complex, or if a strict separation between meta data and
> office content is requested.
>
> I therefore propose that we support both options, and additionally of
> cause what is required for the "subject is in the content" case.

I haven't had a lot of time to think about this, but it seems  
reasonable. But XForms is just one way to bind a GUI to the RDF  
content (an implementation detail); is it really something we have to  
worry about at the ODF level?

Bruce