- From: Gregg Kellogg <gregg@greggkellogg.net>
- Date: Mon, 10 Sep 2012 18:44:06 -0400
- To: Hugh Glaser <hugh.glaser@seme4.com>
- CC: "public-rdf-comments@w3.org" <public-rdf-comments@w3.org>, Sandro Hawke <sandro@w3.org>, SW-forum Web <semantic-web@w3.org>, Tim Berners-Lee <timbl@w3.org>
\On Sep 10, 2012, at 9:59 AM, Hugh Glaser <hugh.glaser@seme4.com> wrote: > Hi, > Sandro has asked on the SemWeb list if there are any comments on Turtle syntax. > I raised an issue (forwarded below) a few years ago, but it looks to me like the syntax is still the same. > > I would like the syntax to allow comma and semicolon as a terminator (and thus also to be compatible with N3). Production 7 does allow a statement to end with a semicolon: [7] predicateObjectList ::= verb objectList (';' predicateObjectList?)* However, production 8 does not allow this: [8] objectList ::= object (',' object)* It would be fairly easy, and would allow exactly the same form as 7, to just make it objectList ::= object (',' object?)*, or even objectList ::= object (',' objectList?)*. Either of these would create more recursive parser states and are certainly not optimal, but that's not really the standard for publishing normative grammars. I could go either way on making this change. Gregg > Hopefully the message is still sufficiently explanatory, but please ask if you need elaboration. > Best > Hugh > > On 10 Jan 2008, at 02:25, Tim Berners-Lee <timbl@w3.org> wrote: > >> Oh, I completely understand why -- that's indeed why N3 has it. >> (I have sed files for generating N3 -- very practical. Don't tell anyone.) >> Mind you, I have always been generating pred-object pairs, >> so I have used the ability to end in a semicolon, not a comma. >> >> Tim >> >> PS: IIRC Pascal and Algol has the same problem. See e.g.http://www.lysator.liu.se/c/bwk-on-pascal.html "Pascal, in common with most other Algol-inspired languages, uses the semicolon as a statement separator rather than a terminator". Just because I shave it off doesn't mean it ain't grey ;-) Ee bah gum, when I were a lad, were would be lucky to even *have* semicolons, ... ;-) >> >> On 2008-01 -09, at 14:33, Hugh Glaser wrote: >> >>> >>> This was going to be a quick confirmation on N3 and turtle syntax for ';' >>> and ',', but seems to have got a bit complicated. >>> >>> I want to write >>> >>> @prefix owl: <http://www.w3.org/2002/07/owl#> . >>> <http://southampton.rkbexplorer.com/id/person-00021> >>> owl:sameAs <http://citeseer.rkbexplorer.com/id/resource-CSP109020> ; >>> owl:sameAs >>> <http://dblp.rkbexplorer.com/id/people-1726e6ee8fb20c8704f47285949b39b3-d101 >>> 32da488b7179a8b1844f88470032> ; >>> . >>> >>> Similarily: >>> @prefix owl: <http://www.w3.org/2002/07/owl#> . >>> <http://southampton.rkbexplorer.com/id/person-00021> owl:sameAs >>> <http://citeseer.rkbexplorer.com/id/resource-CSP109020> , >>> <http://dblp.rkbexplorer.com/id/people-1726e6ee8fb20c8704f47285949b39b3-d101 >>> 32da488b7179a8b1844f88470032> , >>> . >>> >>> That is: >>> <#pat> <#age> 24; <#eyecolor> "blue"; . >>> and >>> <#pat> <#child> [ <#age> 4 ], [ <#age> 3 ], . >>> >>> Looking at the syntagmata in (1) and (2), my reading is that I can do this >>> for ';', although they have different structures: >>> N3 seems to do it by the possibility of () for propertylist. >>> Turtle seems to have an explicit optional ';' (in rule 7). >>> >>> On the other hand, for ',': >>> N3 seems to do it by the possibility of () for objecttail. >>> However, I don't think I can do the same in turtle, as rule 8 in (2) lacks >>> the extra (',')? >>> >>> (I would have downloaded the yacc grammar for N3 and tried it for real, but >>> the link on (3) to the yacc grammar gives 404, by the way.) >>> >>> So the question is: have I got something wrong? >>> If not, then to use the second, ',', construct, I need to use N3, not >>> turtle. >>> So some questions are: >>> Is this what is intended, rather than an omission? >>> If so, why? >>> It seems a bit strange that such simple N3 is not compatible with turtle. >>> >>> (1) http://www.w3.org/2000/10/swap/grammar/n3.n3 >>> (2) http://www.dajobe.org/2004/01/turtle/#sec-tutorial >>> (3) http://www.w3.org/DesignIssues/Notation3.html >>> >>> PS >>> And if you want to know why, it is because I want to generate a load of >>> sameAs triples. It is a common problem for program (and other) generators >>> not to want to know you are generating the last item in a list, and simply >>> treat the ';' or ',' as terminator, rather than separator. This can be >>> achieved by allowing null productions (as N3 above), or an explicit optional >>> (as turtle ';'), or by actually making it a terminator, although then you >>> tend to end up with ';;;' in the code. >>> And you can't put it at the front of each output either, otherwise you need >>> to treat the first item in the list specially. >>> (For the grey beards among us, this is why generating something like Algol68 >>> was more of a pain than generating Pascal!) >>> >>> Best >>> Hugh >>> -- >>> Hugh Glaser, Reader >>> Dependable Systems & Software Engineering >>> School of Electronics and Computer Science, >>> University of Southampton, >>> Southampton SO17 1BJ >>> Work: +44 (0)23 8059 3670, Fax: +44 (0)23 8059 3045 >>> Mobile: +44 (0)78 9422 3822, Home: +44 (0)23 8061 5652 >>> http://www.ecs.soton.ac.uk/~hg/ >>> >>> >>> >> > > -- > Hugh Glaser > Chief Architect > Seme4 Limited > 18 Soho Square > LONDON > W1D 3QL > Mobile: +44 7595334155 > Main: +44 2070601590 > > hugh.glaser@seme4.com > www.seme4.com > > Seme4 - the experts in semantic web and linked data applications > > Notice of Confidentiality. 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Received on Monday, 10 September 2012 22:45:27 UTC