[erlang-questions] idea: DB in Prolog application in Erlang

Robert Virding <>
Sun Dec 2 13:31:26 CET 2007


The obvious answer (obvious to me at least) is to use Erlog or a development
of it.

- You can do nice querying into a database. I did a simple Ets interface to
Erlog which takes a pattern (prolog term) and returns successive matches to
it over backtracking binding unbound variables.

- It  is integrated into Erlang concerning data.

- You don't define Erlog procedures as Erlang code, but this could be done
using parse transforms. Someone "just" has to do an interface to the "right"
database.

- It would be difficult to just directly call an Erlog procedure, even if it
was written in Erlang, as you need a context for it to work in which is not
the same as for normal Erlang code.

I never went further with Erlog as no-one came back with request/suggestions
for how it could be developed. But I am open to suggestion

On 30/11/2007, Joe Armstrong <> wrote:
>
> Question:
>
> A long time ago Erlang started as a extension to Prolog ...
>
> Now Prolog is a wonderful language for querying databases in -
> <<forget this SQL stuff it's horrendously verbose compared to Prolog
> queries>>
>
> So why when we talk about Erlang + an external data base do we
> automatically reach for an SQL data base?
>
> I haven't been actively following the Prolog world, so here's my
> questions:
>
> Are there any prolog data bases with ACID properties.
>
> I'd like something that is
>
>    - open source
>    - resident (is runs like mySQL as a resident task on my machine)
>    - can handle large amounts of data (meaning I could store several
> giga facts in the DB)
>    - has ACID properties
>
> Given the similarity between Erlang and Prolog data structures
> integration between the two languages
> could be very nice.
>
> Embedded prolog queries in Erlang would be *very* nice, just
> interpreting erlang variables
> as prolog logical variables.
>
> Comments anybody?
>
> /Joe Armstrong
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