About Overlay GHC

Overlay GHC is an overlay network programming language based on concurrent logic language GHC.

>>About GHC (Guarded Horn Clauses)
>>Overlay GHC
- Overview of Overlay GHC
- Scripting Language OG

>>About GHC (Guarded Horn Clauses)

Overview of GHC

GHC was designed in 1985 at Institute for new generation COmputer Technology (ICOT; so-called Fifth Generation Computer Project). It is based on concurrent¹ logic programming² paradigm, and is designed as a concurrent programming language for symbol processing.

GHC and KL1 (Kernel Language One)

KL1 (Kernel Langauge One) was desigend as the system description language for parallel inference machines, based on GHC. By removing pragmas (directives to the runtime) from a KL1 program, you obtain the corresponding GHC program. The GHC program is naturally a logic formula, so that it is considered easy to reason with.

References

Concurrent Logic Programming Language GHC/KL1 (in Japanese)
- Introduction by Prof. Ueda, the designer of GHC
KLIC
- A KL1 to C compiler developed in ICOT.

>>Overlay GHC

Overview of Overlay GHC

Overlay GHC is basically an extension of GHC for distributed real-time applications. It is designed as the Shell Language (as opposed to Kernel Language) for Global OS.

Just like KL1, a language for parallel inference machines, the semantics of GHC programs in the distributed real-time settings is described by pragmas, and the GHC language itself is to be maintained unchanged.

Please refer to Overlay GHC Language Reference for the detail of the language specification of Overlay GHC.

Scripting Language OG

We have been testing how easy or difficult it is for students to write Overlay GHC programs, using occasions such as lectures and workshops at Shonan Fujisawa Campus, Keio University. As a result, we are planning to develop a scripting language OG (provisional) that corresponds one to one with Overlay GHC.

In OG, GHC primitives such as predicates or functions will also be describable. Our goal is that a wija plug-in can be developed solely in OG.

¹	[concurrency] Being happening at the same time. Parallelism is how to realize concurrency.
²	[concurrent logic programming] Characterized by commitment to a clause whose conditions specified as a guard are satisfied. For this reason, this type of language is also called committed-choice language.