Meta-interpretive learning of higher-order dyadic datalog: predicate invention revisited

Since the late 1990s predicate invention has been under-explored within inductive logic programming due to difficulties in formulating efficient search mechanisms. However, a recent paper demonstrated that both predicate invention and the learning of recursion can be efficiently implemented for regular and context-free grammars, by way of metalogical substitutions with respect to a modified Prolog meta-interpreter which acts as the learning engine. New predicate symbols are introduced as constants representing existentially quantified higher-order variables. The approach demonstrates that predicate invention can be treated as a form of higher-order logical reasoning. In this paper we generalise the approach of meta-interpretive learning (MIL) to that of learning higher-order dyadic datalog programs. We show that with an infinite signature the higher-order dyadic datalog class$$H^2_2$$H22has universal Turing expressivity though$$H^2_2$$H22is decidable given a finite signature. Additionally we show that Knuth–Bendix ordering of the hypothesis space together with logarithmic clause bounding allows our MIL implementation Metagol$$_{D}$$Dto PAC-learn minimal cardinality$$H^2_2$$H22definitions. This result is consistent with our experiments which indicate that Metagol$$_{D}$$Defficiently learns compact$$H^2_2$$H22definitions involving predicate invention for learning robotic strategies, the East–West train challenge and NELL. Additionally higher-order concepts were learned in the NELL language learning domain. The Metagol code and datasets described in this paper have been made publicly available on a website to allow reproduction of results in this paper

A voluntary logbook scheme as a method of monitoring the by-catch of seals in Swedish coastal fisheries

Abstract Monitoring by-catches of marine mammals in fisheries is notoriously difficult. An alternative to observer programs or direct interviews with fishermen could be a detailed logbook system. In 1997 such a system was launched by the Swedish Fisheries Board, whereby fishermen were contracted to keep a detailed daily log of fish catches, seal disturbance (damage to gear and to fish and catch losses) and by-caught seals. In total, nearly 38,000 fishing records have been collected to date from a participating group of over 100 fishermen. The fishermen are compensated for their trouble with a small payment. To ensure that the information is properly recorded, all fishermen are contacted personally on a regular basis, and their entries are checked during site visits and by statistical means. In 2004, 22 grey seals, 4 ringed seals and 15 harbour seals were reported by-caught. The fishing effort represented by the participants in the logbook scheme is approximately 5 % of the total fishing effort in the Swedish coastal fisheries. These figures indicate that the total by-catch of seals in the Swedish fishing industry would be in the region of 900 animals annually. This figure tallies closely with the results from a telephone survey of 220 randomly selected fishermen in 2002. From that it was estimated that over 400 grey seals and harbour seals and 50 ringed seals were by-caught during the year 2001. By-catches as a relative proportion of the seal populations seem to be decreasing

Baltic Salmon and Trout Assessment Working Group (WGBAST)

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{SLD}-Resolution Reduction of Second-Order {H}orn Fragments

We present the derivation reduction problem for SLD-resolution, the undecidable problem of finding a finite subset of a set of clauses from which the whole set can be derived using SLD-resolution. We study the reducibility of various fragments of second-order Horn logic with particular applications in Inductive Logic Programming. We also discuss how these results extend to standard resolution