Many of the currently available sensors do not provide simple, numericalvalues but more complex data like a list of other devices in range.Although these sensors can, in the general case, not be transformedto numerical values, they nonetheless provide valuable informationabout the device or user context. For exploiting all available contextinformation, it is thus important to also regard ordinal and nominalsensor values. In this paper, we propose to jointly develop a metadata format for the evaluation and assessment of context recognitionand prediction methods.