- From: Seaborne, Andy <andy.seaborne@hp.com>
- Date: Fri, 13 Jan 2006 12:17:29 +0000
- To: Bijan Parsia <bparsia@isr.umd.edu>
- CC: Dan Connolly <connolly@w3.org>, RDF Data Access Working Group <public-rdf-dawg@w3.org>
Bijan Parsia wrote: > On Jan 12, 2006, at 7:05 PM, Dan Connolly wrote: > >> I don't think there's any WG decision that I can cite >> in response to this comment; I don't think we considered >> identifier length, except inasmuch as we OK'd the grammar. >> >> I suppose it might be useful to specify that identifiers >> longer than, say, 1024 characters aren't guaranteed >> to work. > > I don't see that that's particularly useful. I mean, what' more likely > to be an issue in an implementation is total number of variables in a > query. 1024^nrofqueryvariablenamecharacters is a frickin lot of > variables ;) > > Also, I don't think that we should limit the number of variables in a > query. > > I searched around for some limits: > > http://www.oracle.com/technology/support/tech/sql_plus/htdocs/ > sub_var6.html > http://web.njit.edu/info/limpid/DOC/server.920/a90842/apa.htm > http://publib.boulder.ibm.com/infocenter/iseries/v5r3/index.jsp? > topic=/db2/rbafzmstlimtabs.htm > > I mean, 128 chars....if we are talkin 1024 we should just say arbitrary > :) > >> On the other hand, Java seems to get away with silence >> on this issue... >> >> http://java.sun.com/docs/books/jls/third_edition/html/lexical.html#3.8 >> >> Does anybody have implementation-defined limits in their code? > > Since you already have to parse arbitrarily sized bits of data > (including identifiers such as URIs), I think length of identifier > doesn't matter *except* insofar as it constrains number of variables. > And the kinds of constraints we are talking about (e.g., 1024) doesn't > constraint *that* very effectively...so...why bother? > > Cheers, > Bijan. Today's systems don't seem to have limits or have quite large limits so we'd end up with a high limit. IRIs aren't limited (and a degree of pain that causes to handle both long and short in a database). As not all variables are used in a single query, if necessary, a subsitution to shorter names can be done (hasing, incremental allocation). Less readable but teh app writer will not see them. (The SQL identifiers I use are not the ones in the query.) So, without a framework for making a reasoned choice of length, we might be just arbitrarily picking one (like 256 or 1024). I'd want to see a concrete case where it is causing difficulty. Andy
Received on Friday, 13 January 2006 12:17:41 UTC