Addressing Information Processing Needs of Digital Agriculture with OpenIoT Platform - Interoperability and Open-Source Solutions for the Internet of Things - page 136

2.1 Data Model
The Phenonet logical data model is depicted in Fig. 2 . In Phenonet, a user is a log-
ical entity (e.g. a project or a research group), which owns a group of experiments.
An experiment has only one owner. Each experiment is a group of nodes and each
node belongs to a single experiment. A node can also have its location associated
with it, represented using latitude and longitude. A node itself is a group of streams
and a stream is a series of timestamps and real number pairs with a unit of mea-
surement. Phenonet allows metadata to be attached at every hierarchical layer of
the data model. The data model conforms to the following policies.
- Any user can have zero or more experiments
- Any experiment can have zero or more nodes
- Any node can have zero or more streams. Each node can also have latitude,
longitude and altitude values.
- Any stream is a set of (timestamp, value) pairs. Each stream has one unit of
measurement.
Fig. 2. Phenonet data model - logical
The mapping of a typical field experiment to the logical data model is illus-
trated in Fig. 3 . In this example, the experiment is an ordered arrangement of
2 m wide by 6 m length plots with each plot identified by a combination of physi-
cal Block, Row and Column number. The plots are subdivided into experimental
units and are mapped to the node level in Phenonet. The nodes are a collection
of physical sensor platforms assigned a specific location in using latitude and
longitude or plot location. E.g. a node is a soil moisture monitoring platform
with a base station as depicted in Fig. 3 . On some of these experiments, mea-
surements of soil moisture are made at multiple depths. A measurement of soil