From bourassa@magma.ca Tue May 28 16:58:00 2002
From: Gregory Bourassa <bourassa@magma.ca>
To: ciao-users@cliplab.org
Subject: Re: forward-chaining/persistence
Date: Tue, 28 May 2002 16:56:53 +0200
Message-ID: <15603.39605.293916.744809@salmon.ls.fi.upm.es>
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Candide,

Regarding notifications, database connections and so on, you might consider t=
his strategy=20
which I have employed successfully to integrate Prolog with various other lan=
guages and=20
packages (like databases):

1) Define a little XML message protocol which maps easily between Prolog pred=
icates and=20
any structures or objects on the other side of the interface.   "MyJavaObject=
" with=20
instance variables "name" and "city" would become=20
<MyJavaObject><name>Gregory</name><city>Ottawa</city></MyJavaObject>.   On th=
e Prolog=20
side this would map to the fact, myJavaObject(name('Gregory'),city('Ottawa')).

2) Using a message middleware such as CORBA or MQSeries, or even something as=
 simple as=20
http or TCP/IP sockets, communicate with very small, simple programs that ins=
ert and=20
fetch from the data store using EJB or JDBC.

3) Notify users using this same XML inter-lingua.

If the Prolog you choose does not directly support the middleware you want to=
 use, it is=20
very simple to implement this scheme using the standard in and standard out s=
treams; this=20
way the Prolog program simply responds to the input stream as if to interacti=
ve Goals,=20
and makes requests to store or get data via the output stream.   Then a very =
simple=20
helper program in a language with bindings to the chosen middleware simply st=
arts the=20
Prolog program and attaches to its in and out streams -- all the helper progr=
am does=20
after that is provide strings from the Middleware to the Prolog and from the =
Prolog to=20
the Middleware.

Regards.

Gregory Bourassa

On May 28, Candide Kemmler <candide(a)urbanium.tv> wrote:
>=20
>=20
> Hi,
>=20
> I'm considering a number of options in trying to architect a distributed
> system in line with the semantic web's ambitions.
>=20
> I haven't yet given a try to ciao prolog, but I would like to know a
> number of things before I get into more details.
>=20
> First: I have read that prolog systems are generally backward-chaining
> systems. I would like to do forward-chaining so I can deal with
> notification of particular events to the users.
>=20
> Second: The user contributed libraries mention a utility to convert
> Prolog to SQL... Does that cover triggers ? :-) that would be too easy,
> wouldn't it ? More seriously, what does it cover ? It just sounds like
> magic !
>=20
> Finally: what kind of persistence does ciao prolog allow for ? In regard
> to XSB for example. I'm concerned about the convenience of writing
> triggered code to write things down to a database or an EJB,... Is such
> a thing possible ?
>=20
> Thanks in advance for taking the time to answer my naive questions,
>=20
> Candide Kemmler
> =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=
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