Course generation as a hierarchical task network planning problem

This thesis presents course generation based on Hierarchical Task Network planning (HTN planning). This course generation framework enables the formalization and application of complex and realistic pedagogical knowledge. Compared to previous course generation, this approach generates structured courses that are adapted to a variety of different learning goals and to the learners\u27; competencies. The thesis describes basic techniques for course generation, which are used to formalize seven different types of courses (for instance introducing the learner to previously unknown concepts and supporting him during rehearsal) and several elementary learning goals (e. g., selecting an appropriate example or exercise). The course generator developed in this thesis is service-oriented thus allowing the integration of learning supporting services into the generated course in a generic and pedagogically sensible way. Furthermore, learning environments can access the functionality of the course generator using a Web-service interface. Repositories are treated as services that can register at the course generator and make their content available for course generation. The registration is based on an ontology of instructional objects. Its classes allow categorizing learning objects according to their pedagogical purpose in a more precise way than existing metadata specifications; hence it can be used for intelligent pedagogical functionalities other than course generation. Course generation based on HTN planning is implemented in Paigos and was evaluated by technical, formative and summative evaluations. The technical evaluation primarily investigated the performance to Paigos; the formative and summative evaluations targeted the users\u27; acceptance of Paigos and of the generated courses.Diese Arbeit stellt Kursgenerierung vor, die auf Hierarchical Task Network Planung (HTN Planung) basiert. Der gewählte Rahmen erlaubt die Formalisierung von komplexem und realistischem pädagogischem Wissen und ermöglicht im Vergleich zu bisherigen Techniken die Generierung von strukturierten Kursen, die an eine Vielzahl von Lernzielen angepasst sind. Aufbauend auf allgemeinen Techniken zur Kursgenerierung wird das pädagogische Wissen für sieben verschiedene Kurstypen und für eine Reihe von elementaren Lernzielen formalisiert. Die in dieser Arbeit vorgestellte Kursgenerierung ist service-orientiert. Dadurch steht ein generischer Rahmen zu Verfügung, in dem externe Lernsysteme in die generierten Kurse eingebunden werden und dem Lernenden zur Verfügung gestellt werden können, wenn es pädagogisch sinnvoll ist. Weiterhin können andere Lernsysteme über eine Web-Service Schnittstelle auf die Funktionalitäten des Kursgenerators zugreifen: Datenbanken werden als Services betrachtet, die an dem Kursgenerator registriert werden können, und auf die während der Kurserstellung zugegriffen wird. Die Registrierung verwendet eine Ontologie, die verschiedene instruktionale Typen von Lernobjekten repräsentiert und es erlaubt, Lernobjekte nach ihrem pädagogischen Verwendungszweck zu klassifizieren. Sie geht dabei über existierende Metadatenspezifikationen hinaus und ermöglicht pädagogische komplexe Funktionalitäten, so wie beispielsweise Kursgenerierung und weitere. Die vorgestellte Kursgenerierung ist implementiert in Paigos und wurde durch technische, formative und summative Evaluationen untersucht. Die technische Evaluation analysierte in erster Linie die Performanz von Paigos; die formative und summative Evaluationen widmeten sich der Frage der Akzeptanz und Verständlichkeit der von Paigos erzeugten Kurse aus Benutzersicht

Combining a hierarchical task network planner with a constraint satisfaction solver for assembly operations involving routing problems in a multi-robot context

This work addresses the combination of a symbolic hierarchical task network planner and a constraint satisfaction solver for the vehicle routing problem in a multi-robot context for structure assembly operations. Each planner has its own problem domain and search space, and the article describes how both planners interact in a loop sharing information in order to improve the cost of the solutions. The vehicle routing problem solver gives an initial assignment of parts to robots, making the distribution based on the distance among parts and robots, trying also to maximize the parallelism of the future assembly operations evaluating during the process the dependencies among the parts assigned to each robot. Then, the hierarchical task network planner computes a scheduling for the given assignment and estimates the cost in terms of time spent on the structure assembly. This cost value is then given back to the vehicle routing problem solver as feedback to compute a better assignment, closing the loop and repeating again the whole process. This interaction scheme has been tested with different constraint satisfaction solvers for the vehicle routing problem. The article presents simulation results in a scenario with a team of aerial robots assembling a structure, comparing the results obtained with different configurations of the vehicle routing problem solver and showing the suitability of using this approach.Unión Europea ARCAS FP7-ICT-287617Unión Europea H2020-ICT-644271Unión europea H2020-ICT-73166

OCL Plus:Processes and Events in Object-Centred Planning

An important area in AI Planning is the expressiveness of planning domain specification languages such as PDDL, and their aptitude for modelling real applications. This paper presents OCLplus, an extension of a hierarchical object centred planning domain definition language, intended to support the representation of domains with continuous change. The main extension in OCLplus provides the capability of interconnection between the planners and the changes that are caused by other objects of the world. To this extent, the concept of event and process are introduced in the Hierarchical Task Network (HTN), object centred planning framework in which a process is responsible for either continuous or discrete changes, and an event is triggered if its precondition is met. We evaluate the use of OCLplus and compare it with a similar language, PDDL+

Progress in AI Planning Research and Applications

Planning has made significant progress since its inception in the 1970s, in terms both of the efficiency and sophistication of its algorithms and representations and its potential for application to real problems. In this paper we sketch the foundations of planning as a sub-field of Artificial Intelligence and the history of its development over the past three decades. Then some of the recent achievements within the field are discussed and provided some experimental data demonstrating the progress that has been made in the application of general planners to realistic and complex problems. The paper concludes by identifying some of the open issues that remain as important challenges for future research in planning

An Architectural Approach to Ensuring Consistency in Hierarchical Execution

Hierarchical task decomposition is a method used in many agent systems to organize agent knowledge. This work shows how the combination of a hierarchy and persistent assertions of knowledge can lead to difficulty in maintaining logical consistency in asserted knowledge. We explore the problematic consequences of persistent assumptions in the reasoning process and introduce novel potential solutions. Having implemented one of the possible solutions, Dynamic Hierarchical Justification, its effectiveness is demonstrated with an empirical analysis

Automatic validation of learning object compositions

Course construction using reusable learning objects is becoming ever more popular due to its’ efficiency. The course creator who uses this methodology may face problems due to the fact that he or she is not as intimately involved in the creation of every element of the course. In this paper we discuss one such problem faced by course creator known as “the competency gap”. Here, we define the competency gap, explain how it can be identified and suggest ways of correcting the problem