The KB paradigm and its application to interactive configuration

The knowledge base paradigm aims to express domain knowledge in a rich formal language, and to use this domain knowledge as a knowledge base to solve various problems and tasks that arise in the domain by applying multiple forms of inference. As such, the paradigm applies a strict separation of concerns between information and problem solving. In this paper, we analyze the principles and feasibility of the knowledge base paradigm in the context of an important class of applications: interactive configuration problems. In interactive configuration problems, a configuration of interrelated objects under constraints is searched, where the system assists the user in reaching an intended configuration. It is widely recognized in industry that good software solutions for these problems are very difficult to develop. We investigate such problems from the perspective of the KB paradigm. We show that multiple functionalities in this domain can be achieved by applying different forms of logical inferences on a formal specification of the configuration domain. We report on a proof of concept of this approach in a real-life application with a banking company. To appear in Theory and Practice of Logic Programming (TPLP).Comment: To appear in Theory and Practice of Logic Programming (TPLP

FO(FD): Extending classical logic with rule-based fixpoint definitions

We introduce fixpoint definitions, a rule-based reformulation of fixpoint constructs. The logic FO(FD), an extension of classical logic with fixpoint definitions, is defined. We illustrate the relation between FO(FD) and FO(ID), which is developed as an integration of two knowledge representation paradigms. The satisfiability problem for FO(FD) is investigated by first reducing FO(FD) to difference logic and then using solvers for difference logic. These reductions are evaluated in the computation of models for FO(FD) theories representing fairness conditions and we provide potential applications of FO(FD).Comment: Presented at ICLP 2010. 16 pages, 1 figur

Hsc70-4 Deforms Membranes to Promote Synaptic Protein Turnover by Endosomal Microautophagy

SummarySynapses are often far from their cell bodies and must largely independently cope with dysfunctional proteins resulting from synaptic activity and stress. To identify membrane-associated machines that can engulf synaptic targets destined for degradation, we performed a large-scale in vitro liposome-based screen followed by functional studies. We identified a presynaptically enriched chaperone Hsc70-4 that bends membranes based on its ability to oligomerize. This activity promotes endosomal microautophagy and the turnover of specific synaptic proteins. Loss of microautophagy slows down neurotransmission while gain of microautophagy increases neurotransmission. Interestingly, Sgt, a cochaperone of Hsc70-4, is able to switch the activity of Hsc70-4 from synaptic endosomal microautophagy toward chaperone activity. Hence, Hsc70-4 controls rejuvenation of the synaptic protein pool in a dual way: either by refolding proteins together with Sgt, or by targeting them for degradation by facilitating endosomal microautophagy based on its membrane deforming activity

Finite domain and symbolic inference methods for extensions of first-order logic

In this dissertation, we investigate various sorts of reasoning on finite structures and theories in the logic FO(.), a rich extension of classical logic with, amongst others, inductive definitions and aggregates. In particular, we study the tasks of constraint propagation, grounding, model revision, and debugging for FO(.).status: publishe

Grounding FO(ID) with bounds

Grounding is the task of reducing a given first-order theory T and finite domain to an equivalent propositional theory. It is used as preprocessing step in many logic-based reasoning systems. In this paper, we present a method to improve grounding for FO(ID), the extension of first-order logic with inductive definitions. The method consists of computing bounds for subformulas of T, indicating for which part of the given domain, the truth value of their subformula is the same in every model of T. Bounds can be used to efficiently produce compact groundings. We present both theoretical results and experiments to support this claim.status: publishe

The IDP system

This paper presents the IDP system, a finite model generator for extended first-order logic theories. IDP can be used as a didactic tool in courses on (first-order) logic. It can also be applied to solve various constraint problems and for lightweight verification tasks.status: publishe

Constraint propagation for first-order logic and inductive definitions

In Constraint Programming, constraint propagation is a basic component of constraint satisfaction solvers. Here we study constraint propagation as a basic form of inference in the context of first-order logic (FO) and extensions with inductive definitions (\foid) and aggregates (\foagg). In a first, semantic approach, a theory of propagators and constraint propagation is developed for theories in the context of three-valued interpretations. We present an algorithm with polynomial-time data complexity. We show that constraint propagation in this manner can be represented by a datalog program. In a second, symbolic approach, the semantic algorithm is lifted to a constraint propagation algorithm in {\em symbolic structures}, symbolic representations of classes of structures. The third part of the paper is an overview of existing and potential applications of constraint propagation for model generation, grounding, interactive search problems, approximate methods for exists/forall Second Order problems, and approximate query answering in incomplete databases.43 pages, 1 figure submitted to ACM Transactions on Computational Logicstatus: publishe