在过度规划问题(over-subscribed planning,简称OSP)研究中,如果目标之间不是相互独立的,那么目标间的效益依赖比单个目标效益更能提高规划解的质量。但是已有的描述模型不符合标准规划描述语言(planning domam description language,简称PDDL)的语法规范,不能在一般的OSP规划系统上进行推广。提出了用派生谓词规则和目标偏好描述效益依赖的方法,这二者均为PDDL语言的基本要素。实质上,将已有的GAI模型转换为派生谓词规则和目标偏好,其中派生谓词规则显式描述目标子集的存在条件,偏好机制用来表示目标子集的效益,二者缺一不可。该转换算法既可以保持在描述依赖关系时GAI模型的易用性和直观性上,又可以扩展一般的OSP规划系统处理目标效益依赖的能力。从理论上可以证明该算法在转换过程中的语义不变性,在基准领域的实验结果表明其可行性和对规划解质量的改善能力。提出符合PDDL语言规范的目标效益依赖关系的描述形式,克服了已有模型不通用的缺点。
In the field of over-subscribed planning (OSP), goal utility dependencies are more useful than a single goal utility used to improve the plan quality, if goals are not independent. However, existing description models do not follow the grammatical specification of standard planning domain description language (PDDL), so they cannot be used in other OSP planning systems yet. To solve this, this paper presents a new way of describing goal utilitydependencies with derived predicate rules and goal preferences, both of which are essential elements of PDDL. The goal of the process is to transform GAI (general additive independence) models into these two elements, where a derived predicate rule is used to describe the explicitly triggering conditions of a goal sub-set. A preference is usedto depict explicitly its utility or value and both are indispensable. This compilation mechanism can not only maintain the characteristic of ease-of-use and straightness of GAI models in describing utility dependencies, but can also expend the ability of handling utility dependencies for general OSP planning systems. Also, this paper provesthe semantic conservation in the compilation process. Experimental results in some OSP benchmark domains show that the algorithm is feasible and useful for improving the plan quality. It is the first time to describe goal utility dependency with PDDL elements in order to overcome the limitations of existing models.