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| author | version | line-number | content |
|---|---|---|---|
| 1 | ==== OWL file ==== | ||
| 2 | |||
| 3 | link to task ontology | ||
| 4 | |||
| 5 | ==== Authors ==== | ||
| 6 | |||
| 7 | Michael van Bekkum, Rifca Peters. Based on Task Ontology by Martijn van Welie | ||
| 8 | Short description of ontology | ||
| 9 | |||
| 10 | The task ontology provides a basis for a task world model that can be operationalized in the PAL software. It provides a structured model for task decomposition (tasks and goals), task world modeling (roles, groups and agents) and objects involved in the task (object). The ontology is an adapted version of van Welie's ontology for Task World Models . This ontology is further extended in the Pal Objectives Model (POM). | ||
| 11 | |||
| 12 | ==== Related work ==== | ||
| 13 | |||
| 14 | Welie, M. Van, Veer, G. C. Van Der, & Eliëns, A. (1998). An ontology for task world models. Design, Specification and Verification of Interactive Systems ’98, 57–70. | ||
| 15 | |||
| 16 | ==== Ontology design ==== | ||
| 17 | |||
| 18 | ====== **Ontology development** ====== | ||
| 19 | |||
| 20 | We have taken the ontology drafted by van Welie as a basis for a PAL task ontology. We have decided to adapt the model by applying the following changes: | ||
| 21 | |||
| 22 | We decided to remove the Event concept from the original ontology, as we had no need for it in the context of PAL. We assume that tasks in PAL are not triggered by external events, over which the agent (e.g. child) has no control. | ||
| 23 | We have decided to add a Group concept to the ontology. This provides the opportunity to assign tasks to group roles, consisting of several agents, instead of just individual agents. | ||
| 24 | |||
| 25 | The ontology is further extended in the PAL Objectives Model (POM), where tasks and goals are modeled in more detail and related to a.o. achievements. | ||
| 26 | |||
| 27 | ====== **Ontology structure** ====== | ||
| 28 | |||
| 29 | Agent - an agent is an entity that is considered active. Usually agents are humans but groups of humans or software components may also be considered agents. Agents are not specific individuals (like Chris) but always indicate classes of individuals with certain characteristics. Attributes of the agent can include skills, attitude and other miscellaneous. Agents perform tasks and always play certain roles within the task world (Welie 98). | ||
| 30 | |||
| 31 | [[image:task.jpg]] | ||
| 32 | |||
| 33 | **Goal** - A desired state in the task world or of the system. A goal can be reached by one or more tasks. Goals may also have sub-goals. | ||
| 34 | |||
| 35 | **Object** - An object refers to a physical or non-physical entity. A non-physical entity could be anything ranging from messages, passwords or addresses to gestures and stories. Objects have attributes consisting of attribute-name and value pairs. What can be done with an object is specified by actions, for instance move, change, turn off etc. Furthermore, objects may be in a type hierarchy and can also be contained in other objects, for example a form may contain an address field, and a cinema can contain a snack bar. Objects are typically used in tasks but they can also influence the task execution sequence when they cause events to occur. | ||
| 36 | |||
| 37 | **Role** - A role is a meaningful collection of tasks performed by one or more agents. The role is meaningful when it has a clear goal or when it distinguishes between groups of agents. A role is consequently responsible for the tasks that it encompasses. Roles can be hierarchically composed and are assigned to an agent in a certain way. The role can be obtained by assignment, delegation, mandate or because of a situational context. | ||
| 38 | |||
| 39 | **Task** - A task is an activity performed by agents to reach a certain goal. A task typically changes something in the task world and requires some period of time to complete. Complex tasks can be decomposed into smaller subtasks. Tasks are executed in a certain order and the completion of one task can trigger the execution of one or more other tasks. A task could also be started because of an event that has occurred in the task world. Important for the task concept is the distinction between unit tasks and basic tasks, where (ideally) a unit task should only be executed by performing one or more basic tasks. The relationship between the unit task and basic task is interesting because it can indicate the problems that an agent may have in reaching his goals. | ||
| 40 | |||
| 41 | ==== ==== | ||
| 42 | |||
| 43 | ==== Evaluation and results ==== | ||
| 44 | |||
| 45 | The ontology is implemented in the PAL software and tested as part of the evaluations of the PAL Objectives Model (POM). | ||
| 46 | |||
| 47 | ==== | ||
| 48 | References ==== |