Dey, A.K. (2001) Understanding and Using Context, Personal Ubiquitous Computing, 5 (1), pp.4-7
I was looking for a definition of context information, and what I found was definition on context that includes the information in it:
“Context is any information that can be used to characterize the situation of the entity”
Some of the important features of context-aware applications are possibility to store and access historical data and aggregate the collected context information. For my research the focus was little bit off since it was in context-aware applications, but the definition itself is in such a general level that it can be used as a base for more precise definitions. And other researchers have done exactly that, see for example, Zimmermann et al. “An Operational Definition of Context” (2007).