Specifying ubiquitous systems through the algebra of contextualized ontologies - Leitura de Artigo

The Knowledge Engineering Review, Vol. 29:2, 171–185. & Cambridge University Press, 2014 doi:10.1017/S0269888914000046

Specifying ubiquitous systems through the algebra of contextualized ontologies

ISABEL CAFEZEIRO, JOSE´ VITERBO , ALEXANDRE RADEMAKER , EDWARD HERMANN HAEUSLER and MARKUS ENDLER

Abstract
In order to be able to specify and design ubiquitous applications, it is necessary to rely on a precise and formal representation of context. Aiming at reducing the gap between the formal specification and the design of a concrete ubiquitous application, we have proposed an approach to specify a context-aware system at three levels of abstraction.

[Sistemas ubíquos que utilizam contexto, no exemplo, de localização do usuário com dispositivo móvel]

1 Introduction

Ubiquitous computing is normally associated with a large set of electronic devices—either embedded into physical environments or in form of portable, wireless devices— that compute, sense and interact with each other to collectively enable the seamless services to mobile users. These ubiquitous services aim at supporting the users in their daily activities in a way that their presence becomes unnoticed, while their absence may cause some inconvenience.

[Busca Exploratória não é ubíqua e também não me parece querer não ser notada]

This algebra, named Algebra of Contextualized Ontologies, has as central principles a homogeneous and independent description of entities and contexts, and a representation of their semantics through a net of relationships. By homogeneous description of entities and contexts, we mean the use of a uniform representation of the knowledge pertaining to these elements, that is, we use ontologies to describe both entities and contexts. The homogeneous description not only facilitates a uniform mapping between entities and contexts, but also allows to regard an entity both as a single component of a system, or as a complete system. 

[O contexto está associado as entidades e ambos são representados por ontologias]

Finally, by semantics through a net of relationships we mean that it is just through the semantic links (connections) that one determines which ontology represents an entity (i.e. the domain of the link) and which represents the context (i.e. the codomain of the link) in each situation. Since links compose associatively, one context can act as an entity of a different context, for example, a meta-context of the first context. In addition, it is also possible for an entity to have several contexts (represented by several links with the same domain), or for a context to contextualize several entities (represented by several links with the same codomain).

[Um entidade pode estar associada a um ou vários contextos. Uma entidade pode ser o contexto de outra entidade.]

[O mesmo acontece na modelagem do CKG com a diferença de que não exige que o contexto ou a entidade seja modelado como uma Ontologia mas pode ser ... ]

1.2 Motivating scenario

Context-aware applications that interact with Silva in such different situations have to be able to identify the different contexts that must be used to trigger the system’s behaviors. To set the ring mode to silent, an application running on Silva’s smartphone has to consider different contexts if he is at PUC-Rio or participating in a meeting at UFF. In the latter case, this application must concomitantly take into account contexts that describe Silva’s personal preferences and his role and activity at UFF, or his private situation (e.g. father-to-be). On the other hand, in the same situation, a service running in the ambient infrastructure at UFF, would also have to take into account the contexts related to Silva whenever he is visiting that institution. In both cases, there is the need of a methodology to support the modeling and specification of such entities and contexts at different levels of abstraction.

[A aplicação identifica automaticamente o contexto de Localização e se comporta de acordo com este contexto]

[Na busca exploratória com o CKG a melhor resposta ira identificar o tipo de contexto, caso esteja mapeado no modelo. Mas o comportamento do usuário no sentido de avaliar se a alegação é Verdadeira e Útil não compete ao sistema de busca ]

2 The algebra of contextualized ontologies

Contextualized ontologies are composed of three parts: an entity and a context, which are both ontologies, and a link between them. 

[CKG é composto por (1) um KG, (2) o mapeamento deste KG em relação ao esquema contextual para contexto explícito e (3) as regras de inferência para contexto implícito e default] 

When referring to ubiquitous computing, we can think about the entity, for example, as being a mobile device. The context can be thought of as the environment where the entity operates, which, in this case, could be a physical environment where this mobile device is located. The link is the immersion of the entity into its context. Under this model, information concerning either the physical or computational environment is treated as a relevant part of the application, deserving its own representation.

[A definição de contexto para a Busca Exploratória está relacionada com a noção de Verdade e Utilidade]

DEFINITION 3 (Contextualized Ontologies). A contextualized ontology is a triple (e, l, c), also represented by e -l-> c, where l is a link between the ontologies e (domain ontology) and c, codomain ontology.

 

2.1 Operations on contextualized ontologies

The operations have the general purpose of manipulating information of ontologies in order to produce a coherent and concise body of information. For that sake, to play the role of establishing binary relations between contexts or between entities, we define alignment and coalignment operations. We define also context integration, collapsed union, entity integration and relative intersection operations, which are devoted to produce new entities, contexts or contextualized entities according to the related information. The composition operations are alignment, context integration and collapsed union. Decomposition operations are coalignment, entity integration andrelative intersection.

Alignment. It is a situation where an entity has more than one context

[Exemplo Location + Temporal. O filme X foi lançado em "dd/mm/yyyy" em "Tal Lugar"]

[Não consegui aplicar as outras operações]

3 Specifying context-aware applications

[Detectar mudança de contexto de Localização do usuário]

4 Algorithms and complexities

The contextualization of an entity is the definition of a link between ontologies, where the source is the  entity and the target is the context. According to Definition 2, a link preserves hierarchy, relations and logical properties, enabling, thus, a consistent and coherent mapping of meanings of the entity into the context. Contextualization is not an automatic process, as it reflects the intended semantics for the entity. 

[A contextualização do conhecimento contido no KG se torna explícita através do mapeamento entre os predicados, alegações e entidades com as respectivas dimensões contextuais. Além disso regras semânticas permitem tornar explícito o contexto que ainda estiver implícito. ]

5 Related work

There are several other works that deal with formalization of context modeling using different theoretical approaches. In Cafezeiro et al. (2008b), we presented a detailed comparison between our approach and Context UNITY (Julien et al., 2003; Roman et al., 2004), Context-Aware Action System (Yan & Sere, 2004) and Bigraphical Reactive System (BRS) Models (Birkedal et al., 2005). Beside these, we cite CommUnity (Lopes & Fiadeiro, 2005) who as well as our approach uses Category Theory as theoretical basis to express integration and contexts.

It also emphazises the separation between systems behavior and context modeling. As it evolved from a previous work on distribution and mobility in software architectures, it adopts concepts of communication by channels and location variables. We believe our approach is more general than it, since CommUnity context mappings happen always via channels and location variables while ours is based on any conceptual piece of the ontology.

[A Busca Exploratória no CKG irá usar os mapeamentos do esquema contextual para o contexto explícito e as regras semânticas para extrair contexto implícito. O comportamento do sistema de busca não muda de acordo com o contexto mas a contextualização do KG, através do mapeamento e regras, pode ser reusado em outros tipos de aplicação.]

Conclusion

In this paper, we propose a formal approach to support the specification of context modeling of context-aware systems (e.g. mobile or ubiquitous systems). We follow the direction of much of the works (Julien & Roman, 2002; Lopes & Fiadeiro, 2005) in context-aware computing, where the application logic is independent of the informational infrastructure, what results in a high degree of reuse and facilitates easy program development.

[A associação do contexto as alegações realizada a nível de KG remove da aplicação a lógica de identificação dos predicados que atendem as perguntas contextuais]