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Re: First steps on SPARQL Update formal model

From: Andy Seaborne <andy.seaborne@epimorphics.com>
Date: Tue, 31 Aug 2010 14:46:53 +0100
Message-ID: <4C7D07CD.9020407@epimorphics.com>
To: Alexandre Passant <alexandre.passant@deri.org>
CC: SPARQL Working Group <public-rdf-dawg@w3.org>


On 31/08/10 12:39, Alexandre Passant wrote:
>> >  [[
>> >  Definition: CreateOperation
>> >
>> >  A CreateOperation OpC is an UpdateOperation in which (1) a new named slot<j>  and (2) a new graph are created in the GraphStore. The new graph is held in the new slot. Other slots and graphs are not affected.
>> >
>> >  OpC(GSS(GS, t)) = (S(DG, t), {(<i>, S(G_i, t)}, (<j>, S(G_j, t+1))
>> >  ]]
>> >
>> >  I think OpC needs to take some argument so we can talk about them on the RHS.
> Makes sense, I've added the following the the update operation definition:
>
> ""It can accept some arguments""
>

some arguments for the defintional line.

Writing as:

OpC(<IRI>, silent, GSS(GS, t)) = GSS(GS, t) UNION (<IRI>, {}_t+1)

Gives opC arguments IRI and silent as well as the graph store.  The 
introduction of <IRI> means it's appearance on the RHS is connected to 
the operation.

> Should silent be in the formal model ?
> To me, it's more from the implementation pov, as it having it or not does not make any change to the graph state after the operation.

Could do it that way.

SILENT affects whether further operations in the request are processed 
or not.  If the definitions say "this is an error", even if by not 
defining a particular set of parameters, then SILENT is having a 
semantic effect of don't generate this error.  That can be handled in 
the operation or the glue for the request.  It makes more sense to me to 
add to the operations but that is a style matter, not a requirement.

> If keeping the timestamp, I'd rather use t on the left side, and got t+1 as a result on the right side
> So OpC(<IRI>, silent, GSS(GS, t)) = something_at_t+1
> But t might indeed be not needed anymore

Agreed.  Further observation: requests are the unit of atomicity.  A 
sequence of operations leads to t being incremented several times but 
it's the overall effect on the GS that matters going from stare at time 
t, to state at time t-visble-next.

	Andy
Received on Tuesday, 31 August 2010 13:47:31 GMT

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