by I. D. Zaharakis and A. D. Kameas

This document describes the indispensability of the ontologies in an awareness application installed in a ubiquitous computing environment and their role in the user involvement in such types of applications. The document, also, presents an incremental development of a layered scheme of specific ontologies based on well-established theories of both philosophical and application-oriented points of view. Although, the described application specific ontologies deal with the requirements of ASTRA project, they can support a wide range of home/office awareness applications.

Awareness applications and ASTRA specific requirements

The study treats the term awareness application as a software application that aims at helping people to construct and maintain levels of awareness of each others’ activities, context, or status, even when the participants are not co-located. This means that several heterogeneous devices, installed in the activity space of the participants must be employed and integrated into a common framework. Apparently, these devices have to exchange information and, as ordinary people use them, to be configurable either automatically or somehow by simple commonsense ways. As the heterogeneity of these devices varies greatly between activity spaces, there is a need to make feasible their physical connection, logical co-operation and semantical negotiation.

On the other hand, the physical and unobstructive human-device interaction, the employment of pervasive awareness services, the distinction between implicit and explicit input of awareness information, and the retention of privacy when sharing information are issues that must be addressed. Undoubtedly, there are techniques that deal with these issues but this is done either by centralize models or by (computational) resource demanding approaches.

ASTRA project has already developed a service oriented platform to support both the development and the composition of awareness applications by end-users; furthermore, a first stage evaluation of the platform has been made by both end-users and the development team. The feedback from the evaluation made clear the need for a more physical and advanced way to compose applications in terms of user interaction with the development tools and detailed configuration of the participating devices and providing services, respectively.

In order to meet the requirements of the awareness applications, to address the results of the evaluation and to move further coping with research issues, we design and develop a multi-layer ontology that provides the necessary terms and semantics not only for ASTRA applications but for a wider range of indoors awareness applications.

Approaches

The research in the scientific area of ontology is roughly carrying onto two perspectives, the philosophical and the informatics ones.

In a recent article, Poli¹ defends that the theories of causation, time and space, and levels of reality are mutually interrelated can be understood better, and perhaps dealt with, in a categorial context. Thus, he integrates causal and spatio-temporal phenomena into a modified model of the levels of reality. Initially, he distinguishes the three broad realms of material, psychological and social phenomena and argues that these are categorially orthogonal domains. Then, he provides a bilateral dependence between them into a triangular scheme. According to this approach, the psychological and the social level are characterized by the presence of a twofold form of existential dependency: on the one hand, both depend on appropriate material bearers; on the other, the psychological level depends on the social one, and the social level on the psychological one.

On the other hand, in their study on context awareness systems, Abowd et al.² distinguish four primary types of context: location, identity, activity and time. These context types not only answer the questions of who, what, when, and where (primary context), but also act as indices into other sources of contextual information (secondary information). Based on this argument, they use a two-level approach where the primary context elements are in the first level while any other context elements are in the second level. This helps designers to choose context to use in their applications, structure the context they use, and search out other relevant context.

Amalgamating the above perspectives and projecting them into a realistic ontological scheme that could, not only, satisfy the requirements of the awareness applications but, in general, to facilitate the development of Ubiquitous Computing applications, we define and develop a set of inter-connected ontologies described in more detail in the next section.

Layered architecture

The proposed set of ontologies is classified into two types: invariable to the applications and depended on the applications. The first type of ontologies is populated with an ontology that describes temporal notions, such as before, after, meanwhile, etc, and with an ontology that describes spatial notions, such as near, far, behind, etc. As we deal with applications that employ everyday devices and take place mostly in home or in office locations, we also define and develop an ontology that describes the most common attributes of the digital and analog devices as well as an ontology that describes the basic components of a building, such as room, stairs, etc (Figure 2).

The second type of ontologies includes ontologies that describe individual activities of several types (awareness activities, pleasure activities, professional activities, etc) or social activities that mostly involve other persons.

The Figure 1 illustrates the interconnection between the employed by ASTRA ontologies and their correspondence to the theories that were described in the previous section.

Figure 1. Ontologies for ASTRA system.

Figure 2. Building architecture class diagram

1 Poli, R., (2007), Three obstructions: forms of causation, chronotopoids, and levels of reality, Axiomaths, 17(1):1-18, Springer Netherlands.

2 Abowd, G. D., Dey, A. K., Brown, P. J., Davies, N., Smith, M., Steggles, P., (1999), Towards a Better Understanding of Context and Context-Awareness, LNCS 1707, pp.304-307, Springer Berlin/Heidelberg