Without thinking to much, it seems to me that a large set of Prolog's functionality could be implemented as relational calculus (a.k.a. SQL).
Has anyone heard of any tools to automatically convert Prolog to SQL?
Asked
Active
Viewed 5,739 times
17
-
No, I don't know of any, but feel free to give it a shot :-) – paxdiablo Apr 07 '09 at 06:51
-
Wow. There sure is potential for discovery, still, in this world! :) – Lukas Eder Jun 06 '11 at 13:18
6 Answers
35
Yes, of course.
A premise for skeptics: any semi-decent book on database theory mentions Datalog (which is Prolog-like) and theorems which demonstrate that is possible to translate it to/from Relational Algebra (RA) (under specific restrictions).
SQL is not faithful to RA or relational calculi, but is enough to support Prolog:
- Christoph Draxler has developed a Prolog to SQL compiler (PL2SQL) for his thesis, available for download (.tgz) - also here at CMU Artificial Intelligence Repository (it was adapted and included in at least: Ciao Prolog and SWI-Prolog via Blipkit - Biomedical LogIc Programming Knowledge Integration Kit);
- Igor Wojnicki has developed for his PhD (A Rule-based Inference Engine Extending Knowledge Processing Capabilities of Relational Database Management Systems) a prototype system implementing his Jelly View technology called ReDaReS, but it seems not available for download;
- Relational Abstract Machine (RAM) translates Prolog to Relational Algebra, but it doesn't seems to have a SQL backend;
- Walter D. Potter has a couple of papers on Prolog/RDBMS integration;
- Kevin Boone's paper on Using SQL with Prolog to improve performance with large databases is also interesting;
- and so on...
MaD70
- 4,078
- 1
- 25
- 20
4
Recommending:
https://www.cs.cmu.edu/afs/cs/project/ai-repository/ai/lang/prolog/code/io/pl2sql/0.html
my advice- use Eclipse prolog (http://www.eclipseclp.org/) (not (here) to be confused with prolog in the eclipse IDE).
I spent hours trying to get the code to compile in 4 other prologs(!) and 4 minutes to compile in eclipse.
When it works, it's a thing of beauty.
Credit to Herr Draxler of course
Chrissy Flangé Allen
- 68
- 4
2
The mapping isn't very good. SQL, for example, doesn't do backtracking, unification, lists, or adhoc nested structures.
Prolog doesn't deal well with composite objects, indexes, etc.
I'd say it's a no-go.
MarkusQ
- 21,814
- 3
- 56
- 68
-
I don't think you would need backtracking or unification as thing would be generated from the other end (with joins) OTOH this would kill all arbitrary depth recursion – BCS Apr 07 '09 at 15:43
-
3Without backtracking, unification, recursion, and lists there isn't a whole lot left of prolog. And you can't generate the same class of things with joins, unless you're thinking of writing self modifying SQL (queries that build queries) which I suppose is _possible_ but... – MarkusQ Apr 07 '09 at 16:07
1
I wrote a translator that converts a subset of Prolog into SQL user-defined functions.
This predicate in Prolog can be translated into SQL:
is_between(A,B,C) :-
A<B,B<C.
This is the translator's output as a MySQL function:
CREATE FUNCTION is_between(A double,B double,C double) RETURNS BIT BEGIN
RETURN A>B and B>C;
END
Similarly, there is a Prolog-to-SQL compiler compiler for SWI-Prolog, and another translator that converts a non-recursive subset of Datalog into SQL.
Anderson Green
- 30,230
- 67
- 195
- 328
1
It makes more sense to do an sql query from prolog, which can then be translated into prolog facts. e.g. Prolog ODBC Library
This removes all restrictions and keeps the two languages separated into their proper places.
Timothy Allen
- 19
- 1
0
CQL, a SWI Prolog add-on pack, compiles Prolog, or rather a Prolog DSL, to SQL:
Erik Kaplun
- 37,128
- 15
- 99
- 111