Measurement and Operating properties for actuators

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Discussions

Kerry: What is the impact on SSN?

- Maxime: should we decide which of the MeasurementProperty can also apply to Actuators? As a first guess, I would say Accuracy, ActuationLimit, Drift, Frequency, Latency, Precision, Resolution, ResponseTime, all apply to Actuation

- Maxime: I believe all of the OperatingProperties also apply to Actuators.

Measurement Properties

SSN defines Measurement properties:

a ssn:Sensor can be linked to a ssn:MeasurementCapability through property ssn:hasMeasurementCapability, a ssn:MeasurementCapability can be linked:

  • to zero or more ssn:Property to which it applies through property ssn:forProperty ;
  • to zero or more ssn:Condition in which this capability is true using ssn:inCondition ;
  • to zero or more ssn:MeasurementProperty through property ssn:hasMeasurementProperty .

Then the hierarchy of measurement properties is:

 ssn:MeasurementProperty 
 |- ssn:MeasurementRange
 |- ssn:Accuracy
 |- ssn:DetectionLimit
 |- ssn:Drift
 |- ssn:Frequency
 |- ssn:Latency
 |- ssn:Precision
 |- ssn:Resolution
 |- ssn:ResponseTime
 |- ssn:Selectivity
 |- ssn:Sensitivity

I'm not an expert in sensors and actuators, but I guess some of these properties can also apply to actuators. As a first guess, I would say Accuracy, Drift, Frequency, Latency, Precision, Resolution, ResponseTime. Then I'd propose to introduce ActuationLimit for instance.

Question: What should we do ? This is some of the options I can propose:

Option 1: do nothing

pros: simple to implement

cons: users might wonder why these properties only applies to Sensors, or worse, they will add MeasurementCapabilities to Actuators

Option 2: make so that these properties can also be applied for actuators

pros:

  • simple to implement

cons: there are a lot of side effects:

  • change the documentation for all of the MeasurementProperties so that they can be applied to actuators as well.
  • change the name MeasurementProperty?
  • change the name MeasurementCapability?
  • deprecate oldssn:MeasurementProperty, deprecate ssn:hasMeasurementProperty?
  • deprecate oldssn:MeasurementProperty, keep ssn:hasMeasurementProperty, introduce ssn:hasActuationProperty?

Proposed Implementation

a ssn:System can be linked to a ssn:SystemCapability through property ssn:hasSystemCapability, a ssn:SystemCapability can be linked:

  • to zero or more ssn:Property to which it applies through property ssn:forProperty ;
  • to zero or more ssn:Condition in which this capability is true using ssn:inCondition ;
  • to zero or more ssn:SystemProperty through property ssn:hasSystemProperty .

Then the hierarchy of system properties is:

 ssn:SystemProperty 
 |- ssn:MeasurementRange
 |- ssn:Accuracy
 |- ssn:DetectionLimit
 |- ssn:Drift
 |- ssn:Frequency
 |- ssn:Latency
 |- ssn:Precision
 |- ssn:Resolution
 |- ssn:ResponseTime
 |- ssn:Selectivity
 |- ssn:Sensitivity

solving the side effects:

  • definition of ssn:hasSystemCapability : "Relation from a System to a SystemCapability describing the capabilities of the system."
  • definition of ssn:SystemCapability : "Collects together measurement or actuation properties (accuracy, range, precision, etc) and the environmental conditions in which those properties hold, representing a specification of a system capability in those conditions. The conditions specified here are those that affect the measurement or actuation properties, while those in OperatingRange represent the system's standard operating conditions, including conditions that don't affect the observations or the actuations."
  • definition of ssn:SystemProperty : "An identifiable and observable characteristic of a sensor's observations or ability to make observations, or of an actuator's actuations or ability to make actuations."
  • definition of ssn:Accuracy: "The closeness of agreement between the result of an observation (resp. the command of an actuation) and the true value of the observed quality (resp. of the actuated quality)."
  • definition of ssn:Drift: "As a sensor property: a continuous or incremental change in the reported values of observations over time for an unchanging quality. As an actuator property: a continuous or incremental change in the true value of the actuated quality over time for an unchanging command."
  • definition of ssn:Frequency: "The smallest possible time between one observation or actuation and the next."
  • definition of ssn:Latency: "The time between a request for an observation (resp. actuation) and the sensor providing a result (resp. the actuator operating the actuation)."
  • definition of ssn:Precision: unchanged
  • new term: ssn:Repeatability: "The closeness of agreement between replicate actuations for an unchanged or similar command: i.e., a measure of an actuator's ability to consistently reproduce an actuation."
  • definition of ssn:ResponseTime: "As a sensor property: the time between a (step) change in the value of an observed quality and a sensor (possibly with specified error) 'settling' on an observed value. As an actuator property: the time between a (step) change in the command of an actuator and a change in the actuated quality."
  • definition of ssn:Selectivity: "As a sensor property: Selectivity is a property of a sensor whereby it provides observed values for one or more qualities such that the values of each quality are independent of other qualities in the phenomenon, body, or substance being investigated. As an actuator property: Selectivity is a property of an actuator whereby it actuates one or more qualities such as the values of each quality are independent of other qualities in the feature of interest being actuated."
  • definition of ssn:Sensitivity: unchanged
  • oldssn:MeasurementCapability owl:deprecated true ; rdfs:subClassOf ssn:SystemCapability .
  • oldssn:hasMeasurementCapability owl:deprecated true ; rdfs:subPropertyOf ssn:hasSystemCapability
  • oldssn:MeasurementProperty owl:deprecated true ; rdfs:subPropertyOf ssn:SystemProperty .

Option 3: deprecate all this part of the old SSN ontology, and potentially re-introduce them in a future version of the SSN ontology?

pros:

  • simple to implement,
  • save us some time, can be re-introduced in a future version of the SSN ontology.

cons:

  • ...


MeasurementRange is at odds with OperatingRange and SurvivalRange

How to solve isse in https://lists.w3.org/Archives/Public/public-sdw-wg/2017Mar/0233.html

Option 1: deprecate ssn:MeasurementRange

pros:

  • ...

cons:

  • ...