Basics to get started with HTN Planning

You do understand the basics of planning already? Great! Then you can move on studying Hierarchical Task Network (HTN) planning. :)

Some recommendations, again listed in order of recommended reading:

• Start with our IJCAI survey paper from 2019 on HTN planning, since it is written for non-experts, i.e., without much technical content. Disregard all contents about HGN or GTN planning, i.e., read until (including) chapter 3.1.
• After that, for more technical definitions, read the paper which introduced the simplistic HTN formalism, i.e., my IJCAI 2011 paper, but only until section 2 (inclusive) to get the full technical definitions. If you know the basics of complexity theory, also read section 3.
• By this point you should have understood the problem class of HTN planning, i.e., how is the problem defined, which includes which task networks are considered solutions and which are not. You should now be able to follow the following material:
  • Tutorial on HTN planning, which explains all that in a bit more detail (though only slides are available) and also explains some search algorithms for solving such problems.
  • My course at Ulm University, Germany on Hierarchical Planning. Website.
• You may now read until (including) page 10 (Def. 4) of our JAIR 2020 article, after which you will understand the standard (progression) algorithm for solving HTN problems.