ContextElement
From MobiComp
Summary
A ContextElement takes the form of a subject-predicate-object triple with additional annotation. An element relates an entity to a, possibly complex, named context value. Additionally, elements carry a production timestamp, a default validity period, an optional observer identifier, and a privacy level indicating how they may be disseminated through the ContextService.
The object part of a context element may be arbitrarily complex, and different Trackers might produce elements with similar names but different semantics. Equally, similar information may be packaged in different forms. As a first step towards wider interoperability in MobiComp2, each Tracker will be required to supply XML Schema fragments for each element they may produce as part of their initial registration with the ContextService.
Element communication between infrastructure components takes the form of XML documents based on the ConteXtML schema which has been developed to support the infrastructure. Treatment of privacy is extremely limited. Indeed, the privacy attribute of a ContextElement is more correctly seen as a distribution control rather than any attempt to control access to the information. Elements marked as public may be distributed throughout the context service and are therefore visible to any user of the system. Those marked as local remain on the originating device.
See also:
Developer info
Source code:
