- From: Henry Story <henry.story@bblfish.net>
- Date: Sun, 26 Feb 2012 11:02:45 +0100
- To: public-rdf-comments@w3.org
Further down in the examples it says: [[ As indicated by the grammar, a collection can be either a subject or an object. This subject or object will be the novel blank node for the first object, if the collection has one or more objects, or rdf:nil if the collection is empty. ]] It is true that the grammar does say NIL ::= "(" (WS)* ")" but NIL is not used anywhere. Currently one finds collection ::= "(" object* ")" I think what was meant was collection ::= "(" object+ ")" | NIL And I can see how an attempt at simplification would have lead from one to the other. But as a result the NIL case is missing a description in the documentation. And it seems a bit odd that it is hiding in an example. On 26 Feb 2012, at 10:43, Henry Story wrote: > In section 5.3 of the latest Turtle editors draft [1] I read > > [[ > Beginning the collection production records the curSubject and curPredicate, sets curSubject to a novel blank node Bhead and sets curSubject and curPredicate to Bhead and rdf:first respectively. Each object O in collection allocates a novel blank node Bn, creates an additional triple curSubject rdf:rest Bn . and sets curSubject to Bn. Finishing the collection production creates an additional triple curSubject rdf:rest rdf:nil . and restores curSubject and curPredicate The node produced by matchingcollection is the blank node Bhead. > ]] > > Is this correct? In most programming languages one thinks of Nil as itself a list (just the empty one). > So one thinks that > > :tasks todo () . > > as equivalent to > > :tasks todo rdf:nil . > > Things are a bit odd, as otherwise it is not clear what the rdf:first of () is . > This seems wrong: > > :tasks todo _:t1 . > :t1 rdf:first ? . > :t2 rdf:next rdf:nil . > > I see that this is tricky to describe correctly. Lists are usually described recursively. > > Henry > > > [1] http://dvcs.w3.org/hg/rdf/raw-file/default/rdf-turtle/index.html#sec-parsing-triples > > Social Web Architect > http://bblfish.net/ > Social Web Architect http://bblfish.net/
Received on Sunday, 26 February 2012 10:03:16 UTC