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<div class="alert-warning">NOTE: The text in this section is extracted from ETSI TS 103 410-10 (V2.1.1) <a href="#[0]">[0]</a>, and therefore falls inside the <a href="https://www.etsi.org/intellectual-property-rights">ETSI IPR Policy</a></div>

The present document is a technical specification of SAREF4WATR, an OWL-DL ontology that extends SAREF for the Water domain. 

SAREF4WATR V2.1.1 is a major revision of SAREF4WATR, using updated reference ontology patterns specified in ETSI TS 103 548 <a href="#[3]">[3]</a>  to solve the harmonization needs identified in ETSI TR 103 781 <a href="#[i.9]">[i.9]</a> , with updated development framework and tools defined in ETSI TS 103 673 <a href="#[i.10]">[i.10]</a> .

This extension has been created by investigating resources from potential stakeholders of the ontology, such as standardization initiatives, associations, European projects, EC directives, existing ontologies, and data repositories, as reported in ETSI TR 103 547 <a href="#[i.1]">[i.1]</a> . In addition, the use cases defined in <a href="#[i.1]">[i.1]</a>  were also taken into account, namely:

* Use case 1: Remote reading of metrological registers

* Use case 2: Advanced meter reading and configuration

* Use case 3: Risk management over water critical infrastructure

* Use case 4: Interaction of cross-domain variables and models for policy-making

Taking into account ontologies, data models, standards and datasets provided by the identified stakeholders, a set of requirements were identified and grouped in the following categories: Water infrastructure, Water meter, Meter observations, Infrastructure observations, Water observations, Indicators, and Tariff. Such requirements and categories were validated during the "SAREF4WATR Validation Workshop" at the ICT4Water Cluster annual event in Brussels on 11th June 2019. During the workshop, attendees validated the use cases proposed above and the list of requirements for the above-mentioned categories. According to the feedback and outcomes of the workshop, some actions were taken such as to better define the geolocation of meters or to allow connecting information from the water domain to other domains. The concrete decisions were reported in ETSI TR 103 547 <a href="#[i.1]">[i.1]</a> . The requirements listed in ETSI TR 103 547 <a href="#[i.1]">[i.1]</a>  were taken as input for the ontology development. 

SAREF4WATR is an OWL-DL ontology that extends SAREF and reuses six other ontologies. SAREF4WATR includes 54 classes (40 defined in SAREF4WATR and 14 reused from the SAREF, SAREF4CITY, SAREF4SYST, time, geo, and sf), 34 object properties (8 defined in SAREF4WATR and 26 reused from SAREF, SAREF4CITY, SAREF4SYST, and geo), 19 data type properties (12 defined in SAREF4WATR and 7 reused from SAREF and SAREF4CITY), and 65 individuals. 

SAREF4WATR focuses on extending SAREF in order to create a common core of general concepts for water data oriented to the IoT field. The main idea is to identify the core components, as mentioned, that could be extended for particular water subdomains, for example, for water supply.

The prefixes and namespaces used in SAREF4WATR and in the present document are listed in [the Namespace Declarations section](#namespacedeclarations).

<p>This document presents the implementation of the SAREF extension for the water domain (SAREF4WATR) which based on a limited set of use cases and from available existing data models. This work has been developed in the context of the <a href="https://portal.etsi.org/STF/STFs/STF-HomePages/STF566">STF 566</a> which was established with the goal to create SAREF extensions for the domains of automotive, eHealth and ageing well, wearables, and water.</p>

<h3>General overview</h3>

<p><a href="#Figure_1">Figure 1</a> and <a href="#Figure_2">Figure 2</a> present an overview of the classes and the properties included in the SAREF4WATR extension.</p>

<figure>

  <a href="diagrams/SAREF4WATR Overview 1.png"><img src="diagrams/SAREF4WATR Overview 1.png" alt="SAREF4WATR overview. Observations and KPIs"/></a>

  <figcaption id="Figure_1">Figure 1: SAREF4WATR overview. Observations and KPIs</figcaption>

</figure>

<figure>

  <a href="diagrams/SAREF4WATR Overview 2.png"><img src="diagrams/SAREF4WATR Overview 2.png" alt="SAREF4WATR overview. Water-related terms"/></a>

  <figcaption id="Figure_1">Figure 2: SAREF4WATR overview. Water-related terms</figcaption>

</figure>

<h3>Observation</h3>

<p>As it appears in <a href="#Figure_3">Figure 3</a>, the modelling of observations in the SAREF4WATR ontology mostly relies on the observation model proposed in SAREF.</p>

<p>SAREF allows to define the temporal extent of an observation by defining the timestamp for it (using the <a href="https://saref.etsi.org/core/hasResultTime">saref:hasResultTime</a> property) and to define the temporal interval to which an observation applies, apart from the temporal instant defined by the timestamp (using the <a href="#saref:hasPhenomenonTime">saref:hasPhenomenonTime</a> property).</p>

<p>Besides, the extension requires to be able to represent those devices that measure a certain feature of interest (and those features of interest that are measured by a device) independently of having measures from which this relationship could be inferred. This can be represented with two properties of SAREF that relate <a href="https://saref.etsi.org/core/Device">saref:Device</a> and <a href="https://saref.etsi.org/core/FeatureOfInterest">saref:FeatureOfInterest</a>: <a href="https://saref.etsi.org/core/actsUpon">saref:actsUpon</a> and <a href="https://saref.etsi.org/core/isActedUponBy">saref:isActedUponBy</a>.</p>

<figure>

  <a href="diagrams/SAREF4WATR Observation.png"><img src="diagrams/SAREF4WATR Observation.png" alt="Observation model"/></a>

  <figcaption id="Figure_3">Figure 3: Observation model</figcaption>

</figure>

<h3>Water meter</h3>

<p><a href="#Figure_4">Figure 4</a> provides an overview of how to represent a water meter using the <a href="#s4watr:WaterMeter">s4watr:WaterMeter</a> class. The representation of water meters and their properties has been extracted from the European M-Bus standard (EN 13757).</p>

<p>A water meter may be defined by the properties inherited from SAREF (e.g., <a href="https://saref.etsi.org/core/hasManufacturer">saref:hasManufacturer</a> or <a href="https://saref.etsi.org/core/hasModel">saref:hasModel</a>) and also by a set of properties defined in SAREF4WATR to indicate: its fabrication number (<a href="#s4watr:hasFabricationNumber">s4watr:hasFabricationNumber</a>), its firmware version (<a href="#s4watr:hasFirmwareVersion">s4watr:hasFirmwareVersion</a>), its hardware version (<a href="#s4watr:hasHardwareVersion">s4watr:hasHardwareVersion</a>), its version (<a href="https://saref.etsi.org/core/hasVersion">saref:hasVersion</a>), the radio frequency in which it operates (<a href="#s4watr:operatesAtRadioFrequency">s4watr:operatesAtRadioFrequency</a>), and its required power (<a href="#s4watr:requiresPower">s4watr:requiresPower</a>).</p>

<p>Observations may be taken from the water meter themselves. To enable the representation of such observations, water meters are defined as features of interest (<a href="https://saref.etsi.org/core/FeatureOfInterest">saref:FeatureOfInterest</a>) and a non-exhaustive list of properties has been defined based on the M-Bus standard to allow measuring: on time (<a href="#s4watr:MeterOnTime">s4watr:MeterOnTime</a>), operating time (<a href="#s4watr:MeterOperatingTime">s4watr:MeterOperatingTime</a>), battery operating time (<a href="#s4watr:BatteryOperatingTime">s4watr:BatteryOperatingTime</a>), battery last change (<a href="#s4watr:BatteryLastChange">s4watr:BatteryLastChange</a>), and battery remaining time (<a href="#s4watr:BatteryRemainingTime">s4watr:BatteryRemainingTime</a>).</p>

<figure>

  <a href="diagrams/SAREF4WATR Water meter.png"><img src="diagrams/SAREF4WATR Water meter.png" alt="Water meter model"/></a>

  <figcaption id="Figure_4">Figure 4: Water meter model</figcaption>

</figure>

<h3>Water flow</h3>

<p>Water meters are mainly intended to measure water flows. SAREF4WATR defines the main properties related to the water flow that are defined in the European M-Bus standard (EN 13757): pressure (<a href="#s4watr:FlowPressure">s4watr:FlowPressure</a>), rate (<a href="#s4watr:FlowRate">s4watr:FlowRate</a>), temperature(<a href="#s4watr:FlowTemperature">s4watr:FlowTemperature</a>), and volume(<a href="#s4watr:FlowVolume">s4watr:FlowVolume</a>). These properties are depicted in <a href="#Figure_5">Figure 5</a>.</p>

<figure>

  <a href="diagrams/SAREF4WATR Water flow.png"><img src="diagrams/SAREF4WATR Water flow.png" alt="Water flow model"/></a>

  <figcaption id="Figure_5">Figure 5: Water flow model</figcaption>

</figure>

<p>There are also other environmental factors that are relevant since they affect water and the infrastructures using it. Therefore, the following environmental properties, depicted in <a href="#Figure_6">Figure 6</a>, are defined: atmospheric pressure (<a href="#s4watr:AtmosphericPressure">s4watr:AtmosphericPressure</a>), humidity (<a href="#s4watr:Humidity">s4watr:Humidity</a>), precipitation (<a href="#s4watr:Precipitation">s4watr:Precipitation</a>) and temperature (<a href="#s4watr:ExternalTemperature">s4watr:ExternalTemperature</a>).</p>

<figure>

  <a href="diagrams/SAREF4WATR Environmental property.png"><img src="diagrams/SAREF4WATR Environmental property.png" alt="Environmental properties model"/></a>

  <figcaption id="Figure_6">Figure 6: Environmental properties model</figcaption>

</figure>

<h3>Tariff</h3>

<p>SAREF4WATR allows describing the tariff that is applied to a water meter by means of the <a href="#s4watr:Tariff">s4watr:Tariff</a> class, as presented in <a href="#Figure_7">Figure 7</a>. The representation of tariffs has been extracted from the CEN/TR 17167 technical report.</p>

<p>A tariff may be described using different properties to describe its: start timestamp (<a href="#s4watr:hasStartTimestamp">s4watr:hasStartTimestamp</a>), duration (<a href="#s4watr:hasDuration">s4watr:hasDuration</a>), period (<a href="#s4watr:hasPeriod">s4watr:hasPeriod</a>), billing date (<a href="#s4watr:hasBillingDate">s4watr:hasBillingDate</a>), and billing period (<a href="#s4watr:hasBillingPeriod">s4watr:hasBillingPeriod</a>). Besides, a tariff can be related to a water meter by means of the <a href="#s4watr:appliesTo">s4watr:appliesTo</a> property.

There are different types of tariffs, depending on whether they are based on thresholds (<a href="#s4watr:ThresholdBasedTariff">s4watr:ThresholdBasedTariff</a>), consumption (<a href="#s4watr:ConsumptionBasedTariff">s4watr:ConsumptionBasedTariff</a>), or time (<a href="#s4watr:TimeBasedTariff">s4watr:TimeBasedTariff</a>). Each of these types of tariffs has its own properties: for threshold-based ones their volume flow can be defined (<a href="#s4watr:forVolumeFlow">s4watr:forVolumeFlow</a>), for consumption-based ones their volume and financial consumption can be defined (<a href="#s4watr:forVolumeConsumption">s4watr:forVolumeConsumption</a> and <a href="#s4watr:forFinancialConsumption">s4watr:forFinancialConsumption</a>, respectively), and for time-based ones their absolute time at day, week day and day in month can be defined (<a href="#s4watr:forAbsoluteTimeAtDay">s4watr:forAbsoluteTimeAtDay</a>, <a href="#s4watr:forWeekDay">s4watr:forWeekDay</a> and <a href="#s4watr:forDayInMonth">s4watr:forDayInMonth</a>, respectively). It is also possible to define a combined tariff by making it an instance of more than one type of tariff.</p>

<figure>

  <a href="diagrams/SAREF4WATR Tariff.png"><img src="diagrams/SAREF4WATR Tariff.png" alt="Tariff model"/></a>

  <figcaption id="Figure_7">Figure 7: Tariff model</figcaption>

</figure>

<h3>Water kinds</h3>

<p>SAREF4WATR defines four kinds of water as instances of the <a href="#s4watr:WaterKind">s4watr:WaterKind</a> class: raw water (<a href="#s4watr:RawWater">s4watr:RawWater</a>), drinking water (<a href="#s4watr:DrinkingWater">s4watr:DrinkingWater</a>), storm water (<a href="#s4watr:StormWater">s4watr:StormWater</a>), and waste water (<a href="#s4watr:WasteWater">s4watr:WasteWater</a>). All these kinds of water, depicted in <a href="#Figure_8">Figure 8</a>, are defined as feature kinds (<a href="https://saref.etsi.org/core/FeatureKind">saref:FeatureKind</a>).</p>

<figure>

  <a href="diagrams/SAREF4WATR Water kinds.png"><img src="diagrams/SAREF4WATR Water kinds.png" alt="Water kinds model"/></a>

  <figcaption id="Figure_8">Figure 8: Water kinds model</figcaption>

</figure>

<h3>Water properties</h3>

<p>SAREF4WATR includes a classification of the different water properties based on the classification proposed by the World Health Organization, as shown in <a href="#Figure_9">Figure 9</a>. Water properties (<a href="#s4watr:WaterProperty">s4watr:WaterProperty</a>) are classified into acceptability (<a href="#s4watr:AcceptabilityProperty">s4watr:AcceptabilityProperty</a>), chemical (<a href="#s4watr:ChemicalProperty">s4watr:ChemicalProperty</a>), and microbial (<a href="#s4watr:MicrobialProperty">s4watr:MicrobialProperty</a>) ones, being bacterial (<a href="#s4watr:BacterialProperty">s4watr:BacterialProperty</a>) properties a subclass of microbial ones. 

The extension defines different individuals for each type of water property, based in different EC directives on the quality of drinking water, bathing water, and groundwater. This list of individuals does not aim to be exhaustive but to reflect the potential use of the ontology. Note, for example, that it is out of the scope to categorize chemical compounds according to their intended use (e.g., pesticide, fertilizer, etc.).</p>

<figure>

  <a href="diagrams/SAREF4WATR Water property.png"><img src="diagrams/SAREF4WATR Water property.png" alt="Water properties model"/></a>

  <figcaption id="Figure_9">Figure 9: Water properties model</figcaption>

</figure>

<h3>Water infrastructure</h3>

<p>In SAREF4WATR water infrastructures can be defined using the <a href="#s4watr:WaterInfrastructure">s4watr:WaterInfrastructure</a> class. Such infrastructures may be designed for one of the water kinds described above (through the <a href="#s4watr:isDesignedFor">s4watr:isDesignedFor</a> property), may have an intended use (through the <a href="#s4watr:isIntendedFor">s4watr:isIntendedFor</a> property), and may be classified into five different types, although others may be defined if needed: distribution systems (<a href="#s4watr:DistributionSystem">s4watr:DistributionSystem</a>), storage infrastructures (<a href="#s4watr:StorageInfrastructure">s4watr:StorageInfrastructure</a>), treatment plants (<a href="#s4watr:TreatmentPlant">s4watr:TreatmentPlant</a>), hydroelectric power plants (<a href="#s4watr:HydroelectricPowerPlant">s4watr:HydroelectricPowerPlant</a>), and monitoring infrastructures (<a href="#s4watr:MonitoringInfrastructure">s4watr:MonitoringInfrastructure</a>).</p>

<p>In order to represent the topology of a water infrastructure or its assets, the GeoSPARQL ontology has been reused and connected to the SARE4WATR terms. As shown in <a href="#Figure_10">Figure 10</a>, for representing spatial objects the geo:SpatialObject class from GeoSPARQL has been reused along with its subclasses that allow defining spatial features (geo:Feature) and geometries (geo:Geometry). Different properties from GeoSPARQL can be reused to define spatial relations among spatial objects (e.g., geo:sfContains, or geo:sfWithin)or to define the geometry of a feature (geo:hasGeometry). Two types of geometries from the GeoSPARQL Simple Features ontology are proposed to be used: points (sf:Point) and polygons (sf:Polygon), although others may also be used from that same ontology or from another one.

We refer to the GeoSPARQL standard for further details on how to define the topology of water infrastructures.</p>

<figure>

  <a href="diagrams/SAREF4WATR Water infrastructure.png"><img src="diagrams/SAREF4WATR Water infrastructure.png" alt="Water infrastructure model"/></a>

  <figcaption id="Figure_10">Figure 10: Water infrastructure model</figcaption>

</figure>

<p>By reusing the SAREF4SYST ontology, the different subsystems of a water infrastructure may be defined. A water infrastructure is a complex system (<a href="https://saref.etsi.org/saref4syst/System">s4syst:System</a>) and each of its subsystems may be defined (using the <a href="https://saref.etsi.org/saref4syst/hasSubSystem">s4syst:hasSubSystem</a> property) as a water asset (<a href="#s4watr:WaterAsset">s4watr:WaterAsset</a>).</p>

<p>As shown in <a href="#Figure_11">Figure 11</a>, SAREF4WATR defines the main types of water assets found in the literature in a hierarchy that is not intended to be exhaustive and that may be extended if needed. This hierarchy classifies water assets into source assets (<a href="#s4watr:SourceAsset">s4watr:SourceAsset</a>), sink assets (<a href="#s4watr:SinkAsset">s4watr:SinkAsset</a>), storage assets (<a href="#s4watr:StorageAsset">s4watr:StorageAsset</a>), and transport assets (<a href="#s4watr:TransportAsset">s4watr:TransportAsset</a>).</p>

<p>A dedicated class has been defined for water devices (<a href="#s4watr:WaterDevice">s4watr:WaterDevice</a>), which are those water assets that are also devices according to SAREF (<a href="https://saref.etsi.org/core/Device">saref:Device</a>). A water meter, described above, is one special type of water device, among other possible water-related sensors and actuators.</p>

<figure>

  <a href="diagrams/SAREF4WATR Water asset.png"><img src="diagrams/SAREF4WATR Water asset.png" alt="Water asset model"/></a>

  <figcaption id="Figure_11">Figure 11: Water asset model</figcaption>

</figure>

<h3>Key Performance Indicator</h3>

<p><a href="#Figure_12">Figure 12</a> provides an overview of the modelling of Key Performance Indicators (KPI). The KPI modelling involves two main concepts, namely <a href="https://saref.etsi.org/saref4city/KeyPerformanceIndicator">s4city:KeyPerformanceIndicator</a> and <a href="https://saref.etsi.org/saref4city/KeyPerformanceIndicatorAssessment">s4city:KeyPerformanceIndicatorAssessment</a>. As can be seen in the figure, the modelling of KPIs in SAREF4WATR totally relies on the KPI model proposed in SAREF4CITY.</p>

<p>In SAREF4WATR, KPIs are intended to be defined for water infrastructures (<a href="#s4watr:WaterInfrastructure">s4watr:WaterInfrastructure</a>). However, KPIs may also be defined for other features of interest.</p>

<figure>

  <a href="diagrams/SAREF4WATR Key Performance Indicator.png"><img src="diagrams/SAREF4WATR Key Performance Indicator.png" alt="Key Performance Indicator model"/></a>

  <figcaption id="Figure_12">Figure 12: Key Performance Indicator model</figcaption>

</figure>

<p>The example presented in <a href="#Figure_13">Figure 13</a> depicts a water meter (ex:Meter4837QW123). It can be described by a set of static properties either reused from SAREF (e.g., <a href="https://saref.etsi.org/core/hasModel">saref:hasModel</a>) or from SAREF4WATR (e.g., <a href="https://saref.etsi.org/saref4watr/hasFirmwareVersion">s4watr:hasFirmwareVersion</a>). The spatial extent of the meter is described by its geometry (ex:MeterGeom) that is represented as a point in space following its WKT representation. SAREF4WATR defines different measurable properties of a water meter, among them the battery remaining time (<a href="https://saref.etsi.org/saref4watr/BatteryRemainingTime">s4watr:BatteryRemainingTime</a>) that is the one used in the example. Observations of the meter for this property can be represented (ex:WMObservation200206) using for example the time instant of the observation and its value and the unit of measure in a property value.</p>

<figure>

  <a href="diagrams/SAREF4WATR Example water meter.png"><img src="diagrams/SAREF4WATR Example water meter.png" alt="Example of water meter"/></a>

  <figcaption id="Figure_13">Figure 13: Example of water meter</figcaption>

</figure>

<p>The main function of water meters is to measure water flow. <a href="#Figure_14">Figure 14</a> presents two examples of water flow observations (ex:WFObservation170206 and ex:WFObservation643234) for two different water flow properties (<a href="https://saref.etsi.org/saref4watr/FlowVolume">s4watr:FlowVolume</a> and <a href="https://saref.etsi.org/saref4watr/ExternalTemperature">s4watr:ExternalTemperature</a>, respectively). Notice how the flow volume observation is described with a time instant while the external temperature one is described with a time interval (ex:PT838452).</p>

<figure>

  <a href="diagrams/SAREF4WATR Example meter observations.png"><img src="diagrams/SAREF4WATR Example meter observations.png" alt="Example of water meter observations"/></a>

  <figcaption id="Figure_14">Figure 14: Example of water meter observations</figcaption>

</figure>

<p>Different tariffs can be applied to water meters. <a href="#Figure_15">Figure 15</a> presents an example of a consumption-based tariff (ex:Meter4837QW123Tariff) for a water meter (ex:Meter4837QW123). Different individuals are defined for describing the duration (ex:FiveYears), period (ex:OneYear) and billing period (ex:OneMonth) of the tariff. SAREF4WATR does not restrict how to define particular conditions of a tariff; in the example, for the consumption description a string literal is used.</p>

<figure>

  <a href="diagrams/SAREF4WATR Example tariff.png"><img src="diagrams/SAREF4WATR Example tariff.png" alt="Example of tariff"/></a>

  <figcaption id="Figure_15">Figure 15: Example of tariff</figcaption>

</figure>

<p>The observation of the different properties of the water itself is also of interest. <a href="#Figure_16">Figure 16</a> presents two observations (ex:DTSObservation106 and ex:DTSObservation107) of one chemical property (<a href="https://saref.etsi.org/saref4watr/Cadmium">s4watr:Cadmium</a>) and of one bacterial property (<a href="https://saref.etsi.org/saref4watr/EscherichiaColi">s4watr:EscherichiaColi</a>), along with their timestamps, values and units. Even if SAREF4WATR includes a set of predefined water properties, other properties could be defined by instantiating the corresponding <a href="https://saref.etsi.org/saref4watr/WaterProperty">s4watr:WaterProperty</a> subclass.</p>

<figure>

  <a href="diagrams/SAREF4WATR Example water observations.png"><img src="diagrams/SAREF4WATR Example water observations.png" alt="Example of water observations"/></a>

  <figcaption id="Figure_16">Figure 16: Example of water observations</figcaption>

</figure>

<p><a href="#Figure_17">Figure 17</a> depicts a water infrastructure (ex:DowntownDS) that represents a distribution system for drinking water (<a href="https://saref.etsi.org/saref4watr/DrinkingWater">s4watr:DrinkingWater</a>) intended for domestic use (<a href="https://saref.etsi.org/saref4watr/Domestic">s4watr:Domestic</a>). The spatial extent of the infrastructure is described by its geometry (ex:DSGeom) that is represented as a polygon in space following its WKT representation. The water distribution system has different subsystems: a water meter (ex:Meter4837QW123), a tank (ex:Tank38472) and a pump (ex:PumpRT73467). These subsystems can be represented through their geometries, as points in the example (ex:MeterGeom, ex:TankGeom, ex:PumpGeom), and different measures could be made of them such as the one depicted (ex:PObservation854306) that measures the flow rate (<a href="https://saref.etsi.org/saref4watr/FlowRate">s4watr:FlowRate</a>) of the pump.</p>

<figure>

  <a href="diagrams/SAREF4WATR Example water infrastructure.png"><img src="diagrams/SAREF4WATR Example water infrastructure.png" alt="Example of water infrastructure and water assets"/></a>

  <figcaption id="Figure_17">Figure 17: Example of water infrastructure and water assets</figcaption>

</figure>

<p><a href="#Figure_18">Figure 18</a> contains an example of a key performance indicator (ex:MinimumPressureLevel) defined for a water distribution system (ex:DowntownDS). The key performance indicator is defined with its name and calculation period (ex:OneWeek). Besides, an assessment is made for the KPI (ex:MPL2020020723), derived from existing observations (ex:PLObservation56206, ex:PLObservation56207 and ex:PLObservation56208), indicating the value of the assessment and its temporal properties.</p>

<figure>

  <a href="diagrams/SAREF4WATR Example KPI.png"><img src="diagrams/SAREF4WATR Example KPI.png" alt="Example of key performance indicator"/></a>

  <figcaption id="Figure_18">Figure 18: Example of key performance indicator</figcaption>

</figure>