- From: David Allsopp <dallsopp@signal.dera.gov.uk>
- Date: Wed, 15 Aug 2001 16:10:33 +0100
- CC: www-rdf-logic@w3.org, www-rdf-interest@w3.org
Patrick.Stickler@nokia.com wrote: > > > >For those who are convinced that anonymous nodes are a good > > thing, please > > >think about the implementational burden and > > portability/interoperability > > >issues they may introduce. > > > > What burdens and issues? . > > Specifically the need to refer to resources as a template of > property values (i.e. [X namespace '...', X name '...']) > rather than a single opaque URI identifier. But this is just querying - you have to do that anyway to find out what the "opaque URI" actually is. And as I said previously, you have to keep generating long pseudo-unique IDs, which may clash occasionally. Finally, this hinders you in identifying equivalent resources when you merge data from two sources, because the two sources have to assign a pseudo-unique URI to the resource; a third party can't then determine that the nodes really refer to the same thing, e.g: John --hasFather--> [] --age--> 84 John --hasFather--> [] --age--> 84 compared with John --hasFather--> randomgenid0123456789 --age--> 84 John --hasFather--> randomgenid9876543210 --age--> 84 where [] represents an anonymous node. The point is that we don't know the name of John's father, so assigning him a random name makes our life harder, not easier, since everybody necessarily assigns him a _different_ random name. > Another is not knowing whether I will get back from a > query an anonymous node constituting the root of a collection, > containing resource nodes (or other collections) rather than > an actual resource node -- or possibly getting a set of results > having both resource nodes *and* collection root nodes -- because > in one case in the *serialization* the values of a property were > defined as a bag in the "same" statement and in another case > each was defined as a separate statement! Yuck! I don't see how removing anonymous nodes assists here - the data can always be structured in different ways, and you have to know that in advance, or perform cleverness to deduce the structure. I agree the RDF collections are rather awkward though. Regards, David Allsopp. -- /d{def}def/u{dup}d[0 -185 u 0 300 u]concat/q 5e-3 d/m{mul}d/z{A u m B u m}d/r{rlineto}d/X -2 q 1{d/Y -2 q 2{d/A 0 d/B 0 d 64 -1 1{/f exch d/B A/A z sub X add d B 2 m m Y add d z add 4 gt{exit}if/f 64 d}for f 64 div setgray X Y moveto 0 q neg u 0 0 q u 0 r r r r fill/Y}for/X}for showpage
Received on Wednesday, 15 August 2001 11:10:43 UTC