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The SEAS System ontology

The System Ontology defines Systems, Connections between systems, and Connection Points at which systems may be connected. This ontology is then specialized for multiple domains. For example:

  • In electric energy:
    • power systems consume, produce, store, and exchange electricity;
    • power connections are where electricity flows between systems;
    • power connection points are plugs, sockets, or power busses.
  • In the electricity market:
    • players and markets are systems;
    • connections are contracts or transactions between two players, or between a player and a market;
    • connection points include offers and bids.

Figure below provides an overwiew of the concepts in this ontology:

Overview of the System ontology

Classes

Connection

IRI: https://w3id.org/seas/Connection

The class of connections between systems.

This class qualifies property seas:connectedTo.

A connection describes potential interactions between systems.

For example, a power connection between power systems describes the fact that these systems may exchange electricity.

<connection> seas:connectsSystem <electric_vehicle> , <electric_vehicle_service_equipment> .
<electric_vehicle> seas:connectedThrough <connection> .
<electric_vehicle_service_equipment> seas:connectedThrough <connection> .

Any two connected systems are connected through a connection. If:

<system1> a seas:System .
<system2> a seas:System .
<system1> seas:connectedTo <system2> .

then there exists _:connection such that:

_:connection seas:connectsSystem <system1> , <system2> .

A connection can connect more than two systems at the same time.

Figure below illustrates connections of systems:

Connections of systems

Connection Point

IRI: https://w3id.org/seas/ConnectionPoint

The class of connection points of systems, at which they may be connected to other systems.

This class qualifies properties seas:connectsSystem and seas:connectedThrough.

A connection point belongs to exactly one system.

For example, an electric vehicle service equipment may have three power connection points: two different kinds of plugs that enable to charge electric vehicles, and a three phase power bus connection point to the grid:

<electric_vehicle> seas:connectsAt <plug_high_voltage> , <normal_plug> , <three_phase_connection_point> .

Any system connected through a connection is connected at one of its connection points to the connection: if:

<system> a seas:System .
<system> seas:connectedThrough <connection> .
<connection> a seas:Connection .

then there exists _:connectionPoint such that:

<system> seas:connectsAt _:connectionPoint .

_:connectionPoint seas:connectsSystemAt <connection> .

The system of a connection point that is connected through a connection is itself connected through the connection:. If:

<connection> a seas:Connection .
<system> a seas:System .
<connectionPoint> a seas:ConnectionPoint ;
<connectionPoint> seas:connectsSystemThrough <connection> .

then it is true that:

<connectionPoint> seas:connectionPointOf <system> .

Figure below illustrates connection points of systems:

Connection points of systems

System

IRI: https://w3id.org/seas/System

The class of systems, i.e., systems virtually isolated from the environment, whose behaviour and interactions with the environment are modeled.

Systems can be connected to other systems. Connected systems interact in some ways. For example:

<electric_vehicle> seas:connectedTo <electric_vehicle_service_equipment> .

Systems can also have subsystems. Properties of subsystems somehow contribute to the properties of the supersystem. For example:

<battery> seas:subSystemOf <electric_vehicle> .

Figure below illustrates systems and their connections:

Systems and their connections

Object Properties

connected through

IRI: https://w3id.org/seas/connectedThrough

Links a system to one of its connections to other systems.

connected to

IRI: https://w3id.org/seas/connectedTo

Links a system to a system it is connected to.

Connected systems interact in some way. The exact meaning of interact is defined by sub properties of seas:connectedTo.

For example, for the electricity to directly flow between an electric vehicle service equipment and an electric vehicle, then they must be linked by property seas:exchangesElectricityWith:

seas:exchangesElectricityWith rdfs:subPropertyOf seas:connectedTo .

<electric_vehicle> seas:exchangesElectricityWith <electric_vehicle_service_equipment> .

Property seas:connectedTo is symmetric:

if x seas:connectedTo y, then it is true that y seas:connectedTo x.

This property can be qualified using class seas:Connection, which connects the two systems.

If there is a connection between several systems, then one may infer these systems are pairwise connected.

connection point to

IRI: https://w3id.org/seas/connectionPointOf

Links a connection point to the one and only one system it belongs to.

connects at

IRI: https://w3id.org/seas/connectsAt

Links a system to one of the connection points at which it connects.

connects system

IRI: https://w3id.org/seas/connectsSystem

Links a connection to one of the systems it connects.

connects system at

IRI: https://w3id.org/seas/connectsSystemAt

Links a connection to one of the connection points at which it connects a system.

connects system through

IRI: https://w3id.org/seas/connectsSystemThrough

Links a connection point to one of the connections through which it connects its system.

has sub system

IRI: https://w3id.org/seas/hasSubSystem

Links a system to one of its sub systems.

sub system of

IRI: https://w3id.org/seas/subSystemOf

Links a system to its super system.

Properties of subsystems somehow contribute to the properties of the super system. The exact meaning of contribute is defined by sub properties of seas:subSystemOf.

For example, if a fridge is a subsystem of a kitchen, then its consumption power contributes to the consumption power of the kitchen.

Property seas:subSystemOf is functional, and should be asymmetric:

if x seas:subSystemOf y1 and x seas:subSystemOf y2, then y1 and y2 refer to the same resource.
if x seas:subSystemOf y, then it can't be the case that y seas:subSystemOf x.

The asymmetric aspect of property seas:subSystemOf would prevents a system from being its own sub-system. Unfortunately, OWL 2 DL disallow a non-simple property (e.g., a functional property) from being asymmetric, see OWL 2 Syntax section 11.

If it was possible that both the fridge and the kitchen be sub systems of a common super system, say, the house, then the consumption power of the fridge would contribute twice to the consumption power of the house. The functional aspect of property seas:subSystemOf prevents this undesired effect.

Due to the open world assumption of RDF, it is not possible to model the closed set of sub systems of a system using property seas:subSystemOf.