Date: Tue, 5 Apr 2005 15:29:08 -0700 (PDT)
Message-ID: <20050405222908.85221.qmail@web52710.mail.yahoo.com>

```
Continuing where Bijan left off, I have a comment on
the formal definition of "Optional Matching".

Here's what the specs [1] say:
"Given graph pattern GP1, and graph pattern GP2,
Opt(GP1, GP2) is the optional match of GP2 of graph G,
given GP1.

Let GP = (GP1 union GP2) then S is a solution of
Opt(GP1, GP2) if"
[snip]
-----
I'm not sure which "union" is meant here? Obviously, I
assume we don't mean the 'union' keyword used for
pattern alternatives. In any case, "union" implies
logical disjunction whereas what we need here is a
conjunction, i.e.,  we need a group pattern, so we can
rewrite GP = {GP1, GP2}
----

..continuing with the defn..

"S is a solution for a match of GP on G, or else S is
a solution for GP1 and S is not a solution for GP.

S in R(Opt(GP1, GP2), G) if:
S in R(GP, G)
or
S not in R(GP,G) and S in R(GP1, G)."
------

I'm not sure if "S not in R(GP,G)" is required in the
second disjunct. As I understand Optional Matching, if
S is a solution to an optional match of GP2 on G given
GP1, it implies that S must match GP1 first (on G) and
then optionally match GP2 (on G), right? So in that
case, the definition should be:

S in R(Opt(GP1, GP2), G) if:

S in R(GP1, G)
or
S in R(GP, G), where GP = {GP1, GP2}
------

Cheers,

[1]
http://www.w3.org/2001/sw/DataAccess/rq23/defns.html

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Received on Tuesday, 5 April 2005 22:29:10 UTC

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