The HTTP communication protocol is also used
among NOS and the data sources for the data transmission.
Since received data is highly heterogeneous, NOSs initially
store them in the Raw Data collection, and, periodically,
elaborate them according to the two-phase process shown
in Fig. 1 (including Data Normalization and Analyzers) in
order to obtain an uniform representation and, as specified
in the next section, enriching it with relevant metadata