Capabilities of the datalog reasoner?

[jubax]

Hi, nice new language! I'm always happy when new projects use Datalog :-)

I could not find a description of the capabilities of the reasoning engine:

• Is stratified negation supported?
• Do you execute bottom-up or top-down?
• Are there optimizers like rule unfolding or magic sets?

Thank you!

[EvgSkv]

These are great questions, I'll post response soon.

[EvgSkv]

Since the language is written as a compilation from Datalog-like syntax to SQL I didn't have a chance to dive into the classical art of Datalog execution, so I needed to read a little to even give a rough answer to your questions.

• Is stratified negation supported?

Please correct me if I'm wrong, but as far as I understood, the notion of stratified negation is introduced for compilation of recursive programs and recursion is not supported in Logica yet. Some problems that are usually solved via recursion can be solved with tricks in Logica. Support of recursion is intended in the future.

• Do you execute bottom-up or top-down?
  I believe that compilation to SQL with further SQL execution corresponds to bottom-up.

• Are there optimizers like rule unfolding or magic sets?
  No, there are no such optimizations, but they could be considered in the future.

[EvgSkv]

Thanks for the link! Looks very powerful.

I wonder how much of the reasoning power could be expressed as transformation of the propositional formula to a logically equivalent, but computationally simpler form. It is would be easy to enable custom Logica plug-ins for this kind of transforms.

[kamahen]

You might be interested in SYLLOG by Adrian Walker. It's described in Knowledge systems and prolog: A logical approach to expert systems and natural language processing byAdrian Walker (Ed.), Michael McCord, John F. Sowa and Walter G. Wilson. It appears that the Syllog section is available as a separate reprint. See also https://www.complang.tuwien.ac.at/ulrich/syllog.html

Syllog handles stratification and negation, and also features a simplified English syntax. There are a few articles giving examples of its use.

[EvgSkv]

Thanks Peter! Looks interesting, I'll read more about SYLLOG.

[jubax]

Our reasoner was based on the IRIS reasoner from DERI Innsbruck, but over the years the whole code was basically re-written. In particular we added scalable DB integration, zero-allocation in-memory reasoning and a top-down engine.

The original website (iris-reasoner.org) seems to be down, but on this GitHub page a clone seems to exist:

https://github.com/NICTA/iris-reasoner

I found the new website: http://iris-reasoner.sti2.at/

Has some additional info.

[EvgSkv]

This is great! Thanks, @jubax.