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. @en