SANY D2.3.4 Specification of the Sensor Service Architecture V3 Doc.V3.1
Copyright © 2007-2009 SANY Consortium Page 101 of 233
7. Information Viewpoint
7.1. Overview
The Information Viewpoint of specifies rules and guidelines about how to define SensorSA meta-information models. These provide the structure of the information that is being
accessed and exchanged in a service network. Principal guidance is given by the meta-model for information defined in RM-OA, 2007 as an extension of the ISO 19109 General Feature
Model GFM.
The following sections define the information model that is specifically defined to be used for the services of the OGC Sensor Web Enablement initiative. These services are
described in the Service Viewpoint in section 7.
7.2. Information Model for Observations Measurements OM
The SensorSA basically adopts the specification of the Observations and Measurements OM model as defined in Cox, 2007. This information model is of core relevance for the
access and interpretation of the data provided through the Sensor Observation Service. It defines an observation
as “an act associated with a discrete time instant or period through which a number, term or other symbol is assigned to a phenomenon”.
The phenomenon is a property of an identifiable object, which is the feature of interest of the observation. The observation uses a procedure, which is often an instrument or sensor
but may be a process chain, human observer, algorithm, computation or simulator. The key idea is that the observation result is an estimate of the value of some property of the feature of
interest, and the other observation properties provide context or meta-information to support evaluation, interpretation and use of the result.
The model for OM describes the semantics of the observation and its related feature of interest from a user view point. In contrast, sensor-oriented models emphasise a process or
data provider viewpoint. The OM model is illustrated in Figure 7-1. It defines pre-defined feature types and their relationships, thus extending the ISO 19109 General Feature Model
GFM.
Note: The SANY Information Viewpoint also supports further extensions of the GFM as specified in the meta-model for information of RM-OA, 2007.
The key concept of the OM model is the pre-defined feature type observation and its related feature type process. These pre-defined feature types are to be used as building blocks
of project-specific application schemas. An observation has the following characteristics:
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An observation is modelled as a feature type whose instances are created at a specific time point or time period, the samplingTime. An observation may have been processed
after sampling. The resultTime reflects the time when the result of the observation was produced. Observations may be members of ObservationCollections.
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The key properties of an observation modelled as association roles in Figure 7-1 are its featureOfInterest, observedProperty, procedure and result:
SANY D2.3.4 Specification of the Sensor Service Architecture V3 Doc.V3.1
Copyright © 2007-2009 SANY Consortium Page 102 of 233
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The featureOfInterest FOI is a feature of any type ISO 19109, ISO 19101, which is a representation of the observation target, being the real-world object
regarding which the observation is made
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The observedProperty identifies or describes the phenomenon for which the observation result provides an estimated value. It must be a property associated
with the type of the feature of interest.
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The procedure is the description of a process used to generate the result. It must be suitable for the observed property.
-
The result contains the value generated by the procedure. Note:
The schema of the result data is not determined by the OM model. The SensorSA recommends a self-describing schema, e.g. by using the definitions
of the SWECommon specification.
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As further properties, an observation may have meta-information, e.g. the responsible actor for the observation and an indication of the event-specific quality.
«FeatureType»
Observ ation
+ metadata: MD_Metadata [0..1] + samplingTime: TM_Object
+ resultTime: TM_Object [0..1] + resultQuality: DQ_Element [0..1]
+ parameter: Any [0..]
constraints
{observedProperty must be member or component of member of featureOfInterest}
{procedure must be suitable for observedProperty} {result type must be suitable for observedProperty}
«FeatureType»
Process
«FeatureType»
AnyFeature
«type»
Any
{n}
PropertyType
«metaclass»
GF_FeatureType
{n} + definition: CharacterString
+ isAbstract: Boolean = false + typeName: LocalName [0..1]
«metaclass»
GF_PropertyType
{n} + definition: CharacterString
+ memberName: LocalName «FeatureType»
Observ ationCollection
member 1..
generatedObservation 0..
procedure 1
propertyValueProvider 0..
featureOfInterest 1
result observedProperty
1 «instanceOf»
1
carrierOfCharacteristics 0..
«instanceOf»
Figure 7-1: Information Model Observation Measurement from OGC 07-022
7.3. Information Model of the Sensor Observation Service
