Because if it does, then they are effectively equivalent.
Jim
On Wednesday, January 16, 2013, Peter Ansell <ansell.peter@gmail.com> wrote:
> On 17 January 2013 08:27, Jim McCusker <mccusj@rpi.edu> wrote:
>> http://www.hpl.hp.com/techreports/2003/HPL-2003-235R1.html
>
> That algorithm doesn't seem very clean, as it relies on all of the
> entities not changing the blank node identifiers for the simple
> version. The complex version relies on all parties modifying blank
> node identifiers to add extra statements to the graph to track the
> original blank node identifiers before they modified them, which you
> may not be able to rely on in general across an RDF pipeline. How can
> you be sure that there was never a real, pre-existing, RDF triple in
> the original graph with the _:blanknode hasLabel "xyz"? In order to
> use the algorithm it seems like you must substitute all of the
> "_:blanknode" references with "_:xyz" and discard all triples with
> hasLabel as the predicate before computing the digest. In controlled
> situations the "hasLabel" trick works well, but it isn't a general
> solution by any means. Having the blank node mapping triples
> independent of the original set at all times would be a better
> solution, but it wouldn't be compatible with typical RDF processing
> workflows that may still assume that all triples can be merged into a
> single RDF Graph.
>
> In addition, the main reason that people use blank nodes is to avoid
> having to create identifiers, or everyone would just use URIs. The
> main premise that all digestable statements will have unique
> serialisations assigned to them by the original RDF serialiser, and
> custom handling by any subsequent parsers and serialisers, would
> require tight control on the RDF serialisers and RDF parsers in use
> across a system.
>
>> But there's a faster way to compute bnode identities that was presented
at
>> ISWC this year, I still need to incorporate it:
>>
>> http://iswc2012.semanticweb.org/sites/default/files/paper_16.pdf
>
> That paper describes a mapping algorithm between two full sets of rdf
> statements. If you are not sure that what you have is the unmodified
> original set of RDF statements, and you only have the digest as a
> known, how can you utilise this algorithm to help with regenerating
> the digest to verify it?
>
> Cheers,
>
> Peter
>
--
Jim McCusker
Programmer Analyst
Krauthammer Lab, Pathology Informatics
Yale School of Medicine
james.mccusker@yale.edu | (203) 785-4436
http://krauthammerlab.med.yale.edu
PhD Student
Tetherless World Constellation
Rensselaer Polytechnic Institute
mccusj@cs.rpi.edu
http://tw.rpi.edu