W3C home > Mailing lists > Public > www-rdf-interest@w3.org > February 2001

RE: Decentralized RDF Distribution

From: Danny Ayers <danny@panlanka.net>
Date: Mon, 19 Feb 2001 23:21:31 +0600
To: <fmanola@mitre.org>, <www-rdf-interest@w3.org>
Message-ID: <EBEPLGMHCDOJJJPCFHEFEEIHCMAA.danny@panlanka.net>
Hi,

<out of touch ramblings>
Some form of bracketing will be needed as Frank suggests - otherwise you
could have a scenario very comparable to the transaction classic of debiting
one bank account and crediting another - if you stop halfway you've got an
invalid (or at least undesirable) state. Some form of imposing ACID on a
group of triples? Ideally some form of existing grouping (or one that could
be easily produced using an existing tool) - but what about putting the set
of triples (or even URIs) that should behave together atomically in a bag?
Or is there a neater way of grouping (potentially distributed) items?

The transaction itself shouldn't be too problematic - the relevant part of
the database made read-only for the duration of the transaction (snapshot
taken), all (grouped) changes made, read-write reinstated - I see problems
with queueing where the sequence of the transactions is important, maybe
better to reject an incoming update (return to sender?) if an update is
already in progress.
</out of touch ramblings>

This is obviously quite a crucial problem - does anyone happen know how
Linda/Javaspaces handles it?

Cheers,
Danny.

---
Danny Ayers
http://www.isacat.net

<- -----Original Message-----
<- From: www-rdf-interest-request@w3.org
<- [mailto:www-rdf-interest-request@w3.org]On Behalf Of Frank Manola
<- Sent: 19 February 2001 22:38
<- To: www-rdf-interest@w3.org
<- Cc: RDF Interest
<- Subject: Re: Decentralized RDF Distribution
<-
<-
<- Inserts may have been solved as far as the simple mechanics of
<- publishing them is concerned, but the semantic aspects are essentially
<- the same as those of updates and deletes:  you have to deal with
<- temporal (or nonmonotonic) effects:  specifically, the idea that the set
<- of assertions has now changed, and that may change what you now conclude
<- from the set of assertions (a subsequent email has pointed out that an
<- update can be considered a combined delete-and-add operation).  The
<- whole issue of transactions (in the database sense) comes in too, since
<- you may want to make what is a semantically-consistent modification to
<- the "database" that consists of several distinct operations (inserts,
<- deletes, modifys), and want somehow to bracket that set of operations.
<-
<- --Frank
<-
<- Aaron Swartz wrote:
<- >
<- snip
<- >
<- > ***Inserts
<- >
<- > Inserts (adding triples) has been already solved. To insert data to
<- > the decentralized database, you simply publish it to the Web at a
<- > well-known location.
<- >
<- > ***Updates and Deletes
<- >
<- > Updates (modifying triples) and deletes (removing triples) are more
<- > difficult, and require entering an area that RDF has been afraid to
<- > touch: time. Most RDF systems do not factor time into the equation, or
<- > at least, they do it in a simplistic way.
<- >
<-
<- --
<- Frank Manola                   The MITRE Corporation
<- 202 Burlington Road, MS A345   Bedford, MA 01730-1420
<- mailto:fmanola@mitre.org       voice: 781-271-8147   FAX: 781-271-8752
<-
Received on Monday, 19 February 2001 12:24:00 GMT

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