The goal of this paper is to study timed requirements on distributed real time data. More precisely, we want to ensure that values used for computation are valid considering timed requirements. For that purpose, we model relations and interactions between data and define timed properties and requirements on those relations.

The possibility is given to express different requirements on data by considering the update times of variables. For example, we expect a value to be fresh when used or we filter transient values or sporadic values. Moreover we generally characterize the behaviour of a variable depending on the properties of any of its values.

Communication in distributed systems introduce a latency and a timed indeterminism incompatible with real time systems requirements. We define an abstract communication mechanism as a relation between a couple of variables: a source and an image. To introduce timed properties, we characterize the communication delay by binding the time shift between the source and the image.

The properties of the model are then used to check that, during any execution, timely values are always available (safety) or available in enough states (liveness).