W3C home > Mailing lists > Public > w3c-rdfcore-wg@w3.org > September 2002

decision time: semantics of non-datatyped literals

From: Brian McBride <bwm@hplb.hpl.hp.com>
Date: Mon, 16 Sep 2002 12:48:48 +0100
Message-Id: <5.1.0.14.0.20020916115141.0233fbf0@0-mail-1.hpl.hp.com>
To: RDF Core <w3c-rdfcore-wg@w3.org>

I indicated last week my intention that the WG should decide on the 
semantics of non-datatyped, i.e. old style, literals, at this weeks 
telecon.  I ask for the WG's support in keeping to that schedule.

The decision we have to make is to choose whether literals of the form:

   <rdf:Description>
     <foo:age>10</foo:age>
   </rdf:Description>

have tidy or untidy semantics, or indeed whether we are not saying one way 
or the other.  Note: I like the terms introduced by Patrick, "value based 
semantics" and "string based semantics".

This debate has raged for many months, with committed proponents of each 
position arguing at length and failing to convince each other.  After all 
this, I think we have to conclude that we have failed to find a decisive 
flaw or advantage in either approach.  We have, in fact, to assume that we 
have two self consistent positions and we must make a choice between them, 
or choose not to decide.

I think it is the role of the chair to assist the WG to reach a 
decision.  We have been stuck on this for ages.  In the light of this, I am 
going to introduce a bias in the way I frame the decision.

I note that all of the implementations of RDF with which I am familiar have 
implemented M&S with the assumption that literals have string semantics, 
i.e. literal("foo").equals(literal("foo")).

Our charter is to clarify M&S, not to go rewriting it.  We have in the past 
allowed ourselves some leeway in this regard, but we have set the bar 
higher for justifying a "change" than for more straight forward clarifications.

If we are going to ask implementations to change to remain conformant, I 
suggest the WG has a duty to justify that decision.  There must be a strong 
and clear benefit from such a change and it must be one we can clearly 
articulate to the developer community and expect them to support.

The issue here is not whether the developer community is willing to 
change.  I expect the Jena team will implement what the WG decides as no 
doubt will others.  But if the WG are going to ask folks to spend time and 
money making these changes, it ought to have a good reason for doing so.

I am suggesting therefore that the default decision is that non-datatyped 
literals have string based semantics (tidy) unless there is good reason to 
change.  I invite those who advocate value based semantics (untidy) to 
advance a rationale for such a change and we will determine at Fridays 
telecon whether this convinces the WG.

I suggest that we have debated this issue to death and that further debate 
is pointless.  We are at the stage where we need to summarize the argument 
and have the WG decide whether it finds it convincing.  As chair, I could 
try that summary myself, but I have decided that it would be best done by 
the advocates themselves, though I'll try to help out if it looks like that 
would be useful.

Brian

ps: summaries are short and clear
Received on Monday, 16 September 2002 07:51:23 EDT

This archive was generated by hypermail pre-2.1.9 : Wednesday, 3 September 2003 09:51:00 EDT