||For a city, events might include
* an incident
* a measurement
* a change of a setting
* a transaction
* a use of a service
… and so on.
An EVENT will refer to a number of ITEMs which will take roles in the EVENT.
So, for example, a PERSON may take the role 'applicant', in one EVENT, and the same person may take the role 'patient', in another EVENT.
All types of ITEM can take roles in an EVENT, so for example
* a candlestick as an OBJECT could be the murder weapon in a crime EVENT.
* a tender as an ABSTRACT could be the subject of a contract signing EVENT.
EVENTs occur over a period of time, and might cause a change in the STATE of a number of ITEMs.
For example, a driver convicted of speeding might cause a change to the number of points on a driving licence, or to the eligibility to drive.