| | 24 | Presence is the fact, that an entity is physically there at a particular location at a particular time. This abstract construction covers even cases of explicit absence, i.e. when the entity is not present at that time at that location. |
| | 25 | |
| | 26 | A presence is established through a recognition event, that is when the entity is recognized by a dedicated observer (human or automatic). |
| | 27 | |
| | 28 | Recognition can happen implicitly, e.g. when other data are obtained directly from the entity. In these cases, the time and location of the observer are used to establish a presence. |
| | 29 | |
| | 30 | Recognition can happen explicitly, i.e. in response to observation requests. In these cases, the time and location as determined by the request are used to establish a presence. Explicit recognition events may lead to establishment of explicit absence (=this one not here now). |
