On 12/4/11 2:11 PM, Pat Hayes wrote:
> On Dec 4, 2011, at 12:34 PM, Kingsley Idehen wrote:
>
>> On 12/4/11 12:23 PM, Pat Hayes wrote:
>>> Many in the RDF world would agree. However, RDF is quite independent of
>RDF/XML. Much of the world's RDF is written using other notations, and the RDF
>standard was written using an 'abstract' (graph) syntax precisely to allow a
>variety of surface notations. Just like ISO Common Logic, in fact.
>> All,
>>
>> I think we continue to miss a fundamental issue that is the root of so much
>confusion. Personally, I believe positioning RDF as both a data model and a
>collection of syntaxes is the root of the problem.
> And what do you see "the problem" as being, exactly? Seems to me that RDF has
>(a whole host of tedious small problems, but) no really big, central problem.
>
> Still I agree that there is a muddle in the RDF world having to do with how
>best to "layer" more expressive notations (such as OWL) onto RDF. This was
>clear (and gave rise to much heated discussion) when the RDF and OWL specs
>were being written, before 2004. I think we have all learned to live with the
>awkwardnesses that it caused, however. Certainly none of the extremely dire
>consequences that were predicted have come to pass. OWL and RDF do get used
>together, and applications do actually work. OWL2 and RIF have been published
>and both layered onto RDF syntax, although admittedly in both cases
>alternative notations are more elegant and will likely get used in dedicated
>applications.
>
>> A very simple question. How is RDF (the model) different from the long
>established Entity-Attribute-Value model?
> Very abstractly and formally, perhaps not very different. In practice,
>however, and in intention and design, very different. Chiefly, RDF allows (and
>is mostly comprised by) data in which the 'value' is itself also an 'entity',
>so that one finds 'chains' or even (!!) graphs of links, which can get quite
>dense. This is not even contemplated in most EVA approaches. Second, the RDF
>identifiers are URIs (IRIs), as you know, which are globally unique and are
>links that can be followed using HTTP. This is hugely important and alone is
>enough to make RDF/OWL quite different in design from previous data models.
>And third, at least according to Wikipedia, EVA assumes that the entities are
>sparse in the overall attribute space, which is not part of the RDF design or
>assumptions. (01)
Pat, (02)
Thanks for the reply, as I hoped, the discussion if veering towards the
heart of what I believe the problem is. To answer your question to me, I
believe the problem re. RDF model lies in lack of genealogy in its
narrative, compounded by the conflation with RDF/XML syntax in its very
early days. (03)
When I discuss Linked Data, especially at InterWeb scales, I try to
outline the following re. the underlying graph based models that make
the aforementioned feasible: (04)
1. EAV -- basic model thats familiar to many developers working with
ASN.1, XML, and most recently JSON based syntaxes
2. EAV + URIs -- this is what RDF as a model adds to the mix, it is
unambiguous about the use of URIs but remains ambiguous about
de-referencable URIs
3. EAV + de-referencable URIs -- this is what Linked Data mandates
explicitly, since it is very explicit about de-reference and address-of
operation aspects of URIs i.e, a Name is distinct from an Address even
though URIs are used to denote either. (05)
Linked Data is still fundamentally about high fidelity structured data
at InterWeb scale, more than anything else. (06)
RDF gets into trouble when its supporters infer that RDF is the only
route to Linked Data at InterWeb scale. You know this is a slippery
slope, and I even know you've tried to curb this tendency. Basically,
RDF can be used to construct graphs that deliver InterWeb scale Linked
Data, but that isn't something you would clearly discern from RDF specs
due to ambiguity that remains about URI de-reference and disambiguation
of names and address denoted by URIs. (07)
When people "gut react" to the letters R-D-F, I tend to orient the
conversation to what's outlined above, and it works most of the time
because I can always identity: (08)
1. the 3-tuple pattern
2. the use or potential incorporation of URIs -- albeit rarely since the
name / address ambiguity issue lingers persistently. (09)
To conclude, there is also another major RDF unique selling/value point
that is often lost in the R-D-F arguments, and this it the issue of
typed literals fidelity, language tags, and i18n in general. Trouble is,
only when people get going with EAV + URIs (whether they call it RDF of
not) will the real power come to the fore. (010)
Anyway, I think we are making progress :-) (011)
Kingsley
>
> Pat
>
>
>> What does it bring to the table that differentiates it?
>>
>> I have some answers to the above, but I would like to see if responses to
>what's posed above (from others) could lead to clarity that's desperately
>needed re. RDF.
>>
>>
>> Links:
>>
>> 1. http://en.wikipedia.org/wiki/Entity%E2%80%93attribute%E2%80%93value_model
>- EAV model
>> 2. http://ycmi.med.yale.edu/nadkarni/eav_cr_frame.htm -- EAV/CR .
>>
>> --
>>
>> Regards,
>>
>> Kingsley Idehen
>> Founder& CEO
>> OpenLink Software
>> Company Web: http://www.openlinksw.com
>> Personal Weblog: http://www.openlinksw.com/blog/~kidehen
>> Twitter/Identi.ca handle: @kidehen
>> Google+ Profile: https://plus.google.com/112399767740508618350/about
>> LinkedIn Profile: http://www.linkedin.com/in/kidehen
>>
>>
>>
>>
>>
>>
>>
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> (012)
-- (013)
Regards, (014)
Kingsley Idehen
Founder& CEO
OpenLink Software
Company Web: http://www.openlinksw.com
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