The observedProperty of an OGC Observations & Measurements Observation is the property of the featureOfInterest that is observed during the act of observation. For example, if the temperature of the featureOfInterest is measured, then the observedProperty is 'temperature'.
The observedProperty in O&M must be a reference to some definition of that property. So typically this would be to an item in a published vocabulary. However, it is quite common in practice that definitions of observed properties in published vocabularies are not specific enough to allow end users to interpret exactly which property was observed.
For example, the observedProperty may be 'radiance', and this may be defined in a vocabulary. However the actual property observed is radiance at a particular wavelength or wavelength range e.g. between 300-400 nm. Another example is temperature. It may not be sufficient to simply state that an Observation has the observedProperty 'temperature'. It may be important to know that it is 'Daily Maximum Temperature'.
The Complex Property Model provides a framework for extending a pre-defined term in a vocabulary with additional information, such as constraints (e.g. the earlier wavelength example), or statistical measures (e.g. the earlier temperature example).
This repository presents an OWL representaion of the Complex Property Model.
The OWL ontology file can be accessed via a PURL at http://purl.org/voc/cpm, with a preferred namespace URI of http://purl.org/voc/cpm# and a preferred namespace prefix of cpm
The Complex Property Model ontology defines many of its classes as subclassess of SKOS Concwepts in order to allow the use of vocabulary entries from SKOS Concept Schemes or Collections as instances of the CPM ontology classes.
An enumeration of comparison operators
In order to provide other constraints on ObservableProperties, the type Constraint has been created and can be associated with an ObservableProperty. A constaraint may be specialised or the simple description attribute may be used to provide a free text description of the constraint.
The AbstractObservableProperty class is the root of the ObservableProperty model. It is implemented by two specialisations: ObservableProperty and CompositeObservableProperty.
Usually, when performing multiple observations on one featureOfInterest, one provides a separate ObservableProperty element for each Phenomenon being observed. However, in certain cases where either:
- there is a strong link between the Phenomena or
- the multiple phenomena are clearly observed as part of the same Observation,
these Phenomena may be provided together in one Observation. In this case a CompositeObservableProperty can be defined that groups together multiple Phenomena (ObservableProperty) into one CompositeObservableProperty element.
An example of a strongly linked pair of Phenomena is wind speed and wind direction
At its simplest an ObservableProperty simply carries a reference to a phenomenon definition in a codelist with optional units of measure. However an ObservableProperty definition may be augmented using Constraints and/or Statistical Measures to create a more full definition of the observed property.
A description of some statistical measure e.g. "daily maximum". The measure is usually some function over some time (e.g. an hour, a day) or space (e.g. a length, area or volume). Other aggregation types can be supported by the 'otherAggregation' extension point.
The matrix is a special case of a feature-of-interest that provides the context (container feeaure or medium) for an observable property.
The substance, taxon or other physical/chemical phenomenon of the Feature Of Interest that is being observed. E.g. Waves, Rainfall, Calluna Vulgaris, Aluminium.
A specialisation of ObjectOfInterest for use where the Object of Interest is a physical phenomen, such as "throughfall" or "waves".
A specialisation of ObjectOfInterest for use where the Object of Interest is a chemical substance
A specialisation of ObjectOfInterest for use where the Object of Interest is an organism with a binomial classification
The property of the environment which the ObservableProperty is describing.