We start the framework description with the data layer since it is the core element in data
management. Understanding where and how data is stored is essential to subsequent updates, queries,
and access to the data. There are two main issues to be addressed in IoT data management with regard to the data itself: the placement of storage facilities (the where), and the format to be used for data
storage (the how). In our framework, we opt for a hybrid approach to data storage—with temporal,
real-time data stored near at the objects’ generating this data, and persistent, long-term data that is to
be used for analysis catalogued and stored at dedicated facilities—is expected to yield a beneficial
trade-off between the costs of storage space and data transmission on one hand and the availability of
data for sophisticated analysis and queries on the other hand. The data layer is concerned with the
storage of persistent data, while the things layer is concerned with the storage of transient data, among
other things to be discussed at later sections.