[Versa] Issue 3

[Uche Ogbuji]

On Mon, 2005-08-15 at 12:13 -0400, Chimezie Ogbuji wrote:
> I'll assume by #1 - #3 you are referring to (Uche's points on SPFs):
> 
> 1. If the SPF is *, it is resolved into a pattern that matches anything
> 2. If the SPF is a primitive scalar, datatyped literal or resource, it is
> resolved into a pattern that must match that string or resource exactly
> 3. If the SPF is a list or set, it is resolved into a pattern that must
> match one of the items in the list or set exactly
> 4. If the SPF is a function, f, then it is a special filtering function
> pattern, and the pattern is equivalent to the resulting list from
> filter(<all possible values>, f).  (This means that the function must
> take each item to be filtered as its first parameter)
> 
> > I wonder what we need to change so much syntactically?
> > 
> > Why can't  "all() - B -> we("'foo') return statements.  Then use
> > "object(expression)" or "subject (expression)" to filter the results.
> 
> (Just thinking out loud) would that make traversal expessions even
> more verbose?:
> 
> Consider the query from Versa by Example (to get the labels of all
> rdfs:Classes):
> 
> (rdfs:Class <- rdf:type - *) - rdfs:label -> *
> 
> If traversal operators returned statements (instead of their parts)
> you would have to write this as:
> 
> objects(subjects(rdfs:Class <- rdf:type - *) - rdfs:label -> *)
> 
> > As far is "SPF"s.  Isn't "all()" equivalent to "*" already? 
> 
> '*' is a synonym for true.

Yes.  It's a predicate rather than a function (that returns a list).


> > qname("foo",union("a",b")) - map(properties(<rdfs:class>),{. -
> > rdfs:subPropertyOf *}), gt("1"^^"xsd:int")
> > 
> > So, using many new ideas
> > 
> > "Give me, all _statements_ where the subject us the URI from the
> > expanded prefix "foo" and the local name of "a" or "b". 
> 
> I'm not sure how your suggesting the qname function would work, but do you mean:
> 
> qname(prefix,localNameSet ) => set(prefix:localName1,prefix:localName2,..)
> 
> That is, it builds a resource from a single prefix and a *set* of
> localNames? That would also be very useful (although I'm not sure why
> you are using union in that part of the example)

OK.  You got more out of it than I did.  If you're right, I suspect Mike
meant "set", not "union".

Side note: we're talking about using { ... } in various ways.  It's the
mathematical notation for set, so we'd want a note to make sure there is
no confusion over this.


> > The predicate
> > is one of the subProperties of any property that is used on the
> > resource "rdfs:Class" and the object is the integer value greater then
> > one.
> 
> If we adopted the way Notation3/Turtle addresses uri's then you
> wouldn't need to surround the rdfs:Class with '<' .. '>'  since qnames
> work the same in both Versa and Notation3/Turtle.
> 
> So, assuming we also adopted '>' as syntactic shorthand for gt (which
> *might* clash with using '<' .. '>'  for explicit Uris - I'm not
> comfortable enough with the grammer to know if thihs would be the case
> if we adopted both) the query would be?:
> 
> qname("foo",set("a",b")) - map(properties(rdfs:Class),{. -
> rdfs:subPropertyOf *}) -> > "1"^^xsd:int
> 
> To return the 'statements' that match that criteria?

Well a grammar could probably handle that, especially with () around the
object part.  I'm more worried about *people* trying to avoid adjusting
their spectacles :-)


-- 
Uche Ogbuji                               Fourthought, Inc.
http://uche.ogbuji.net                    http://fourthought.com
http://copia.ogbuji.net                   http://4Suite.org
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