A Theoretical Framework for the Declarative Debugging of Datalog Programs

Abstract

Abstract. The logic programming language Datalog has been extensively researched as a query language for deductive databases. Although similar to Prolog, the Datalog operational mechanisms are more intricate, leading to computations quite hard to debug by traditional approaches. In this paper, we present a theoretical framework for debugging Datalog programs based on the ideas of declarative debugging. In our setting, a debugging session starts when the user detects an unexpected answer for some query, and ends with the debugger pointing to either an erroneous predicate or to a set of mutually recursive predicates as the cause of the unexpected answer. Instead of representing the computations by means of trees, as usual in declarative debugging, we propose graphs as a more convenient structure in the case of Datalog, proving formally the soundness and completeness of the debugging technique. We also present a debugging tool implemented in the publicly available deductive database system DES following this theoretical framework.

VIDEAS: A Development Tool for Answer-Set Programs Based on Model-Driven Engineering Technology

“…VIDEAS has been implemented on top of the Eclipse platform. 5 In particular, technologies provided by the Eclipse Modeling Framework (EMF) 6 and the Graphical Modeling Framework (GMF) 7 projects have been used. The meta-model representing the ER diagram modelling language has been created using the Ecore modelling language which is specified within the EMF project.…”

“…However, practice has shown that the development of answer-set programs is not always straightforward and that programs are, as all human-made artifacts, prone to errors. In fact, debugging in ASP is currently a quite active research field [1][2][3][4][5][6][7][8][9].…”

Declarative Debugging of Wrong and Missing Answers for SQL Views

“…Some tools as [2,13] allow the user to trace and analyze the stored SQL procedures and user defined functions, but they are of little help when debugging systems of correlated views. Declarative Debugging, also known as algorithmic debugging, is a technique applied successfully in (constraint) logic programming [16], functional programming [12], functional-logic programming [5], and in deductive database languages [3]. The technique can be described as a general debugging schema [11] which starts when an initial error symptom is detected by the user, which in our case corresponds to an unexpected result produced by a view.…”

On the Chase for All Provenance Paths with Existential Rules

“…Unlike existing work that focuses on obtaining only one provenance path, the novelty of this work consists in obtaining all provenance paths to a ground query. This problem is relevant in many practical applications such as explanation [9], abduction [13], debugging [4] and notably, defeasible reasoning. In [11], the authors have stumbled upon this problem as query answering in defeasible reasoning with existential rules became unsound due to provenance path loss (not all provenance paths could be extracted).…”

“…Extracting the provenance paths for the query q using backward chaining [4] is not possible as it is infinite. To extract provenance paths using forward chaining the state of the art uses a chase graph [6] (also called derivation tree [1]).…”