Workshop on Hierarchical Planning (HPlan)

6th ICAPS Workshop on Hierarchical Planning (HPlan 2023)
Prague, Czech Republic
Monday, July 10, 2023 (room N5)

Aim and Scope of the Workshop

The motivation for using hierarchical planning formalisms is manifold. It ranges from an explicit and predefined guidance of the plan generation process and the ability to represent complex problem solving and behavior patterns to the option of having different abstraction layers when communicating with a human user or when planning co-operatively. The best-known formalism in the field is Hierarchical Task Network (HTN) planning. In addition, there are several other hierarchical planning formalisms, e.g., hybrid planning (incorporating aspects from POCL planning), Hierarchical Goal Network (HGN) planning (incorporating a hierarchy on goals), or formalisms that combine task hierarchies with timeline planning (e.g. ANML). Hierarchies induce fundamental differences from classical planning, creating distinct computational properties and requiring separate algorithms from non-hierarchical planners. Many of these aspects of hierarchical planning are still unexplored. Thus, we encourage any contribution, independent of the underlying hierarchical planning formalism, and want to provide a forum for researchers to discuss the various aspects of hierarchical planning.

Topics of Interest

Topics of interests include but are not limited to:

  • theoretical foundations, e.g., complexity results
  • heuristics, search, and other solving techniques for plan generation
  • techniques and foundations for providing modeling support
  • challenges and lessons learned from modeling systems (using hierarchical models)
  • applications of hierarchical planning
  • plan explanation for hierarchical models
  • hierarchical plan repair techniques
  • techniques for verifying solutions of hierarchical planning problems
  • techniques for automated learning and synthesis of hierarchical models

Important Dates

  • Submission Deadline: March 24, 2023 March 31, 2023 (AoE), also see note below!
  • Author Notification: April 28, 2023
  • Camera-Ready Deadline: June 3, 2023
  • Workshops Day: Monday, July 10 (room N5), 2023

Note that at the date of the submission deadline, all papers need to be registered, which includes all relevant information such as title, abstract, authors, and kind of paper (long, short, etc.). You will still be able to upload/update your paper until April 3 (AoE).

Submission Details

The formatting guidelines (author kit, etc.) are the same as for ICAPS 2023. Like at the main conference, there will be a high quality double-blind review process against the standard ICAPS criteria of significance, soundness, scholarship, clarity, and reproducibility. However, submissions may be less evolved than at the main conference.

We have two categories:

  1. Technical research papers (short or long) and
  2. Challenge papers (short).

Technical research papers are standard conference papers, but may be less evolved. The purpose of challenge papers is to report on or to make aware of interesting/important problems in Hierarchical Planning and to encourage discussion at the workshop – not to present some significant contribution.

Authors may submit long papers (up to 8 pages plus up to one page of references) or short papers (up to 4 pages plus up to one page of references). The purpose of short papers is to encourage publications of more preliminary results; challenge papers need to be short papers.

In case of acceptance, the full 9, resp. 5, pages can be used for the paper.

Submissions will be done via easychair.

Workshop Proceedings

Please be aware that we put all accepted papers into a single proceedings that we will make publicly available (check out previous years’ editions if interested:

Our proceedings are non-archival meaning that you will keep all copyrights.

Policy on Previously Published Materials

Despite our proceedings being non-archival we will strictly not include any paper where at the time of putting the proceedings online, portions of that paper are under the copyright of some other publisher. The reason is that normally the rights granted to the authors are rather restricted; they might be allowed to upload the specific entire paper on their own institution’s webpage, but this does not include allowing others (like us workshop organizers) to distribute that material or parts of it. This means that all submitted work must be entirely original – just as at any conference. If in doubt, contact the organizers.

We do allow and also explicitly encourage the submission of papers that at the time of submission are under review at another conference. Note that other conferences usually allow material that is under review at a workshop in parallel, but do not allow papers currently being under review at another archival conference or journal (HPlan is non-archival). If however the paper is also accepted at the respective conference, it will not be included in our proceedings to prevent any possible copyright infringements. We will still mention the paper as being accepted at the workshop and expect the paper be part of the program (and thus presented like all other papers), but no final paper can be submitted for our workshop/proceedings. Instead, the proceedings will include links to the respective conference paper version. Please check out websites and proceedings of the previous years ( to see examples of how this looks.

Invited Talk

Hector Munoz-Avila

Dr. Munoz-Avila is a Program Director at NSF's Information and Intelligent Systems (IIS) Division, where he is cluster lead for the Information Integration and Informatics (III) program. Prior to joining NSF, Dr. Muñoz-Avila was a (tenured) professor of Computer Science and Engineering and of Cognitive Science at Lehigh University. He was founding co-director of Lehigh's Institute for Data, Intelligent Systems, and Computation (I-DISC). Dr. Muñoz-Avila is recipient of a National Science Foundation (NSF) CAREER and held a Lehigh Class of 1961 Professorship. He has been chair for various international scientific meetings including the Sixth International Conference on Case-Based Reasoning (ICCBR-05) and the twenty-fifth Innovative Applications of AI Conference (IAAI-13). He was funded by the Office of Naval Research (ONR), the National Science Foundation (NSF), the Defense Advanced Research Projects Agency (DARPA), the Naval Research Laboratory (NRL) and the Air Force Research Laboratory (AFRL).

Automated Learning of Hierarchical Knowledge for Planning and Acting

In this talk I will cover a variety of algorithms for learning hierarchical knowledge for planning developed together with collaborators over the years. This will include a variety of formalisms ranging from hierarchical task networks (HTNs) to hierarchical reinforcement learning. I will also present our studies on a variety of planning settings including deterministic planning, nondeterministic planning and planning and acting with a two-level architecture of feedforward neural networks. I will show results of empirical evaluation versus various baselines as well as theoretical analysis regarding the expressiveness of the resulting algorithms and architectures. This work has been published in AAAI, IJCAI, AAMAS and ACS conferences, among others.

Workshop Committee

Organizing Committee

  • Pascal Bercher, pascal.bercher at, webpage
  • Daniel Höller, hoeller at, webpage
  • Julia Wichlacz, wichlacz at, webpage
  • Ron Alford, ronwalf at, webpage

Program Committee

  • Ron Alford, The MITRE Corporation
  • Pascal Bercher, the Australian National University
  • Susanne Biundo, Ulm University
  • Pascal Lauer, Saarland University
  • Rouxi Li, University of Maryland, College Park
  • Jane Jean Kiam, Universität der Bundeswehr München
  • Songtuan Lin, the Australian National University
  • Ugur Kuter, Smart Information Flow Technologies (SIFT)
  • Damien Pellier, Laboratoire d’Informatique de Grenoble
  • Julia Wichlacz, Saarland University
  • Gregor Behnke, University of Amsterdam
  • Xing Tan, Lakehead University
  • Daniel Höller, Saarland University
  • Sunandita Patra, IIT Kharagpur
  • Robert Goldman, Smart Information Flow Technologies (SIFT)
  • Kutluhan Erol, Izmir University of Economics
  • Felipe Meneguzzi, University of Aberdeen
  • Simona Ondrčková, Charles University
  • Conny Olz, Ulm University

If you’d like to be part of our team in any of the future years, please reach out to the organizers!

List of Accepted Papers

Accepted at HPlan and included in proceedings

The following publications will be included in the proceedings once it’s ready.

Accepted at HPlan and another venue

The following publications will be excluded from the proceedings to preven copyright issues. We will provide a link instead.

Workshop Schedule

If you are interested in presenting work on hierarchical planning that was accepted or published at some other conference or journal (to promote your work to the hierarchical planning community), please contact the organizers. We will not include such a paper into our proceedings, but we are happy to discuss options for presenting such work.

  • 2:00 – 2:05      Welcome!
  • 2:05 – 2:45      Teaser Talks (all 8 presentations, 5 mins each)
  • 2:45 – 3:30      Poster Session
  • 3:30 – 4:00      afternoon coffee (break)
  • 4:00 – 5:00      Invited talk by Hector Munoz-Avila (see above) + Q&A

Further Information

  • On the HPlan website you find (among other things) a list of bibtex entries for all accepted papers in all HPlan editions. Individual workshop pages of past editions are available by adding the respective year, e.g., you may use for last year’s edition.
  • Note that this year the second IPC on Hierarchical Planning will take place! See The link to the first IPC as well as any future ones can be found on
  • We have a mailing list (via google groups) for hierarchical planning with currently approx. 70 subscribers. The list is almost zero traffic, moderated, and only allows mails related to hierarchical planning! Interested? Drop Pascal an email.