Is it fair to say that a definition for a "Named Graph" may
be as follows?
In short, my interpretation is that a Named Graph is nothing
more than a "collection" that has an identifier and a set of
traits.
On 6/13/14 12:15 PM, David Price wrote:
We've found in this and previous projects is that
RDF/OWL named graphs
are usually better used as the "bucket of triples" for
more
practical/bookkeeping tasks like access control,
caching, managing
automated update of background facts, deleting data when
a new version
of the same report data needs to be uploaded to fix
errors, versioning
schemas, etc. There are, of course, times when things
are just too
complex (e.g. like very complex access control rule
requirements) to
be handled using named graphs. In those cases, you just
have to model
your way out of trouble ... at least that's what we've
found.
Changing the topic so as to focus on the important issues
that David and
Ed have brought to the surface in regards to Named Graphs,
Statements,
and Triples.
I think its really important to get a handle on
understanding what each
of those terms denote. In our world view (at OpenLink
Software) where
see the following:
1. Named Graph IRIs denote distinct RDF data sources which
may be local
or external to a DBMS -- basically, they are
Document/Database
identifiers (e.g., a piece of paper provides a writing
surface and it is
an example of a real-world named graph, ditto any other
medium for
durable and reusable capture of data).
2. Reified Statements (i..e., Statements denoted by an IRI)
are
instances of rdf:Statment meaning they are the domainOf
rdf:subject,
rdf:predicate, rdf:object properties
3. Triples being the content (in the form of subject,
predicate, object
patterns) of RDF documents which are denoted by IRIs
(typically HTTP
URLs when external to the DBMS).
As David indicates, you need these items (properly
described and loosely
coupled) to handle accounting, attribute based access
controls and data
access policies, version control etc.. These issue are
obvious and
natural in the enterprise realm.
Some other anecdotes from the real-world:
We have documents comprised of words and phrase. We also
have contracts
(a kind of document) comprised of terms (explicit
combination of
denotation and connotation) and clauses (reified
statements) .
At some point in time we've all signed one part of a
contract.
At some point in time we've all signed one part of a
contract an
initialed each clause.
This is an interesting and important topic that will
contribute to bring
much needed clarity to these matters, in the digital realm
provided by
the likes of HTTP networks etc..
--
Regards,
Kingsley Idehen
Founder & CEO
OpenLink Software
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