Announcing the Logical Contracts Server


November 14, 2017 6:25 PM
The Logical Contracts Server incorporates extensions of LPS (Logic Production System) to facilitate deployment of smart contracts. Its website http://logicalcontracts.com/server/ contains a link to a preliminary version, now available for trial. It also contains a short, three minute video, illustrating an application to the paper-rock-scissor game, with an interface to the Ethereum blockchain.
Logical Contracts is an upcoming spinoff, which builds upon decades of research at Imperial College London in AI, logic programming, the event calculus and legal reasoning. The Logical Contracts Server extends the logic and computer language LPS http://lps.doc.ic.ac.uk/ with web services and other features, to facilitate the development of self-executing contracts. It includes:

· Logic programs, which serve as constitutive rules, defining abstract legal concepts in terms of raw facts. They are like the beliefs of an intelligent agent.
· Reactive or regulatory rules, which prescribe and prohibit actions and states of affairs. They are like an agent’s goals.
· Domain-dependent causal laws, which define the effects of actions and external events on states of affairs. Together with the logic programs, they specify the space of candidate models of the world.

Logical contracts represented in LPS have both a declarative, logical interpretation and an imperative, computational implementation. In their logical interpretation, they specify goals that must be satisfied by executing actions to generate a model that makes the goals true. In their computational implementation, they execute programs in a manner that resembles the agent cycle of BDI (Belief Desire Intention) agent programming languages.

The basic ontology of LPS builds upon that of the event calculus, but without frame axioms, which are computationally infeasible for large applications. However, the event calculus ontology of LPS facilitates the representation of natural language notions of time, events and states of affairs. The Logical Contracts Server exploits this link with natural language by including a preliminary Formal English syntax. More refined improvements of the syntax are under development.