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Towards a Formal Model of Context Awareness

Towards a Formal Model of Context Awareness. Mikkel Baun Kjærgaard Jonathan Bunde-Pedersen Department of Computer Science University of Aarhus. Motivation. Pervasive computing vision: Move computation from the desktop computer to a number of devices embedded in the environment of the user.

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Towards a Formal Model of Context Awareness

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  1. Towards a Formal Model of Context Awareness Mikkel Baun Kjærgaard Jonathan Bunde-Pedersen Department of Computer Science University of Aarhus

  2. Motivation • Pervasive computing vision: • Move computation from the desktop computer to a number of devices embedded in the environment of the user. • Context-awareness • However the task of handling all these devices should not overwhelm the human user. • Therefore the devices and applications need to become aware of the context they are situated in. • The context of interest could here both be the physical, social and computational environment. • Modeling Context Information • Complex • A lot of different factors where some of them can only be described probabilistically. • Interwoven • The different types of information depend and relate to each other in many ways. Mikkel Baun Kjærgaard

  3. Example Pervasive Healthcare • Context information types • Personal Status • Activities • Location • Staff • Patients Mikkel Baun Kjærgaard

  4. Motivation • Context-aware applications • Contextual information Mikkel Baun Kjærgaard

  5. Motivation • Application areas • Healthcare, ... • A lot of the applications are critical in some way • At build time / online validation? • For interesting properties: consistency, privacy, … • Formal foundation • Should be expressive enough to model complex and interwoven context-information. • Goal • How can the Ambient Calculus be extended to allow us to model complex and interwoven sets of context information? Mikkel Baun Kjærgaard

  6. Ambient Calculus • The Ambient Calculus • deals with ambients which are tree-structured recursively defined entities. • An ambient may be situated in another ambient and itself contain ambients, and • Information between ambients may only flow between nearby ambients, i.e. parents or siblings. • Modeling Context using Ambients • If context-information should be made available for an ambient it must be positioned near the ambient in the tree. Mikkel Baun Kjærgaard

  7. Idea • Multiple Contexts • Ambients which can be present in one or more trees. • Two types of ambients • Context ambients vs. Reference ambients • New capabilities which enables the reference ambients to navigate in multiple contexts. Mikkel Baun Kjærgaard

  8. Example Mikkel Baun Kjærgaard

  9. Example Mikkel Baun Kjærgaard

  10. Example • 1: out{*} • 2: out{Person&Status&Entity} • 3: in{Person} Doctor • 4: in{Status} NotBusy • 5: in{Person&Status&Location&~Entity} ? Mikkel Baun Kjærgaard

  11. Extensions ambients • Context ambients • Context information is represented in trees. • Names of context trees are unmutable. • Context ambients have limited capabilities. • Reference ambients • Only one reference in a single context • Reference ambients must not contain references to other reference ambients. • Reference ambients are unique in the sense that all references to ambient n points to the same n. • Reference ambients cannot remove themselves directly from a context. Mikkel Baun Kjærgaard

  12. Extensions capabilities • Navigation • Multiple contexts • Simple Boolean expressions • Wildcard name • Observability • Coenter / Coexit Mikkel Baun Kjærgaard

  13. Defining semantics • Ambient like • Example of a simple in-rule Mikkel Baun Kjærgaard

  14. Discussion • Limitations • Restricts context information to a number of trees which limits the expressiveness but to a lesser degree than prior research. • Does not take probabilistic context information into account. It is important for a calculi to be able to handle such information because it is the typical output of most sensors of context information. • Is the above needed in practice? Mikkel Baun Kjærgaard

  15. Discussion • The present CONAWA calculus does not bridge the gap to a combined theory and systems building approach • base for simulation, verification and software prototyping • (i) Building a simulator which can interpret CONAWA descriptions • (ii) Defining a logic which make it possible to state properties which could be verified • “This awarephone must never reveal my location to other people than the ones I have explicitly granted this priviledge”? • (iii) Building a code generation facility that makes it possible to build skeleton code from the models. Mikkel Baun Kjærgaard

  16. Conclusion • Expressiveness of formal models of context awareness. • Here the models expressiveness should be sufficient to model complex and interwoven sets of context-information. • The CONAWA calculus was given as an example of a calculus that is a step in the direction of making such modeling possible. Mikkel Baun Kjærgaard

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