Constraint Programming (CP) is a powerful declarative programming paradigm where inference and search are interleaved to find feasible and optimal solutions to various type of constraint systems. However, handling logical connectors with constructive information in CP is notoriously difficult. This paper presents If Then Else (ITE), a lightweight implementation of stratified constructive reasoning for logical connectives. Stratification is introduced to cope with the risk of combinatorial explosion of constructing information from nested and combined logical operators. ITE is an open-source library built on top of SICStus Prolog clpfd, which proposes various operators, including constructive disjunction and negation, constructive implication and conditional. These operators can be used to express global constraints and to benefit from constructive reasoning for more domain pruning during constraint filtering. Even though ITE is not competitive with specialized filtering algorithms available in some global constraints implementations, its expressiveness allows users to easily define well-tuned constraints with powerful deduction capabilities. Our extended experimental results show that ITE is more efficient than available generic approaches that handle logical constraint systems over finite domains.

中文翻译：

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ITE：构造逻辑运算符的分层推理的轻量级实现

约束编程 (CP) 是一种功能强大的声明性编程范式，其中推理和搜索交错，以找到各种类型约束系统的可行和最佳解决方案。然而，在 CP 中处理具有建设性信息的逻辑连接器是非常困难的。本文介绍了 If Then Else (ITE)，这是一种用于逻辑连接词的分层建设性推理的轻量级实现。引入分层以应对从嵌套和组合逻辑运算符构造信息的组合爆炸风险。ITE 是建立在 SICStus Prolog clpfd 之上的开源库，它提出了各种运算符，包括建设性析取和否定、建设性蕴涵和条件。这些运算符可用于表达全局约束，并受益于在约束过滤期间进行更多域修剪的建设性推理。尽管 ITE 无法与某些全局约束实现中可用的专用过滤算法竞争，但它的表现力允许用户轻松定义具有强大推导功能的调整良好的约束。我们扩展的实验结果表明，ITE 比处理有限域上的逻辑约束系统的可用通用方法更有效。