{"type":"ScholarlyArticle","title":"Cost-Optimal and Net-Benefit Planning - A Parameterised Complexity View","authors":[{"name":"Meysam Aghighi","slug":"meysam-aghighi","given":"Meysam","family":"Aghighi","affiliation":""},{"name":"Christer Bäckström","slug":"christer-backstrom","given":"Christer","family":"Bäckström","affiliation":""}],"abstract":"Cost-optimal planning (COP) uses action costs and asks for a minimum-cost plan. It is sometimes assumed that there is no harm in using actions with zero cost or rational cost. Classical complexity analysis does not contradict this assumption; planning is PSPACE-complete regardless of whether action costs are positive or non-negative, integer or rational. We thus apply parameterised complexity analysis to shed more light on this issue. Our main results are the following. COP is [W2]-complete for positive integer costs, i.e. it is no harder than finding a minimum-length plan, but it is paraNP-hard if the costs are non-negative integers or positive rationals. This is a very strong indication that the latter cases are substantially harder. Net-benefit planning (NBP) additionally assigns goal utilities and asks for a plan with maximum difference between its utility and its cost. NBP is paraNP-hard even when action costs and utilities are positive integers, suggesting that it is harder than COP. In addition, we also analyse a large number of subclasses, using both the PUBS restrictions and restricting the number of preconditions and effects.","doi":null,"url":"https://ijcai.org/proceedings/2015/213","pdf":"https://ijcai.org/proceedings/2015/0213.pdf","markdown":"https://ijcai.org/proceedings/2015/213.md","bibtex":"https://ijcai.org/proceedings/2015/bibtex/213","volume":{"slug":"2015","title":"Proceedings of the Twenty-Fourth International Joint Conference on Artificial Intelligence","short_title":"IJCAI 2015","url":"https://ijcai.org/proceedings/2015/","year":2015,"location":"Buenos Aires, Argentina","dates":"25–31 July 2015","editors":"Qiang Yang and Michael Wooldridge","isbn":"978-1-57735-738-4","publisher":"International Joint Conferences on Artificial Intelligence","doi_prefix":""},"section":"Planning","track":"Main Track","number":213,"pages":{"first":1487,"last":1492},"keywords":[],"videos":[],"references":[],"license_note":"Copyright International Joint Conferences on Artificial Intelligence."}