RE: the <meta> tag

Yes, syntactically one needs an <object>, and in Example 5 on the
wiki page, instead of a variable (interpreted existentially) there
should really be a bNode (cf. DaveR's remark), a Skolem constant
(http://www.ai.sri.com/~yang/papers/jods2003.pdf), or some kind
of anonymous-object symbol. But we don't have any of these yet.

However, usually we would want to give such descriptions an IRI,
so in the IRC today I gave a modified, named-object example.
For instance, with the IRI http://sample.org we can use this:
<object><Const type="rif:iri">http://sample.org</Const></object>

Instead of a named-argument Expression variant

<Ruleset>
 <id><Const type="rif:iri">http://sample.org</Const></id>
 <meta>
   <Expr>
     <op><Const type="rif:iri">rif:description</Const></op>
     <slot>
       <Prop>
         <key><Const type="rif:iri">dc:publisher</Const></key>
         <val><Const type="rif:iri">w3:W3C</Const></val>
       </Prop>
     </slot>
     <slot>
       <Prop>
         <key><Const type="rif:iri">dc:date</Const></key>
         <val><Const type="xsd:date">2008-04-04</Const></val>
       </Prop>
     </slot>
   </Expr>
 </meta>
 <rule>
 ...
 </rule>
 . . .
 <rule>
 ...
 </rule>
</Ruleset>

with a standard function symbol, say, rif:description,
we propose the Frame variant

<Ruleset>
 <meta>
   <Frame>
     <object>
       <Const type="rif:iri">http://sample.org</Const>
     </object>
     <slot>
       <Prop>
         <key><Const type="rif:iri">dc:publisher</Const></key>
         <val><Const type="rif:iri">w3:W3C</Const></val>
       </Prop>
     </slot>
     <slot>
       <Prop>
         <key><Const type="rif:iri">dc:date</Const></key>
         <val><Const type="xsd:date">2008-04-04</Const></val>
       </Prop>
     </slot>
   </Frame>
 </meta>
 <rule>
 ...
 </rule>
 . . .
 <rule>
 ...
 </rule>
</Ruleset>

keeping the object id and its descriptive named arguments together
as a single term, in the spirit of an rdf:Description about a
resource.

In both variants, the Ruleset is the item being annotated,
by virtue of its <meta> role tag.

-- Harold


-----Original Message-----
From: public-rif-wg-request@w3.org [mailto:public-rif-wg-request@w3.org]
On Behalf Of Sandro Hawke
Sent: April 1, 2008 6:22 PM
To: Michael Kifer
Cc: RIF WG
Subject: the <meta> tag



I'm fairly comfortable with the meta tag as in

  http://www.w3.org/2005/rules/wiki/BLD#XML_for_RIF-BLD_Rule_Language

but it has some odd bits.

Syntactically, one needs an <object>, right?   And the example makes it
a variable, because it doesn't want to give it a URI.   We have to do
that every time?

Also, you said one could easily put a formula there, but how would you
refer to the item being annotated?  You'd need to give it a name, right?

  <Ruleset>
     <id><Var>M</Var></id>
     <meta>
         ... formula about M ...

Just trying to understand.

     -- Sandro

Received on Wednesday, 2 April 2008 01:48:17 UTC