Fido, the domestic robot of the future, will encounter various sorts of active objects which move under their own power or using an external power source, some of them biological organisms, some of them artefacts designed and made by humans (or by humans and other machines), and some of them natural non-biological entities, such as rivers, volcanoes, and the wind. It will need to be given, or to develop an ontology, encompassig some subset of these, depending on where it is located (e.g. what sort of household, in what sort of external environment) and what its functions and responsibilities are (e.g. whether it functions only indoors or also outdoors).
We can distinguish various sorts of active objects according to their origins (e.g. biological or not), according to whether they have some internal energy source of not (in which case they are energetically purely passive), and according to whether they have control mechanisms that can determine how energy is deployed, so that they are to some extent autonomous (i.e. not purely passively controlled). An energetically passive, purely passively controlled object, like leaves blown in the wind is a degenerate type of active object (and might be better called 'mobile').
What is an active object?
I take an active object to be something that has either
A special case is a device powered by gravity, such as a clock driven by weights, or a river that flows downhill. Another special case would be an object that is powered by wind, e.g. a windmill, but also trees that move, or things blown about in the wind such as leaves, pieces of paper, and clouds.
Passive and self-controlled objects
We can describe mobile objects as passive if all their motions
and all changes in their motions are produced entirely by external
forces acting on them. Examples would be a ball rolling down a sloped
plane surface, something sliding or rolling down a helter skelter,
leaves and clouds blown in the wind (ignoring changes in the clouds
produced by their internal energy).
An active object is self-controlled to the extent that there are some parts of it, i.e. sensors, that can acquire information either about the environment or about internal states of the object, or both, and as a result of that go into a new state that causes the available energy to be directed in some new way.
A windmill is a simple case: all of its energy comes from an outside source (the wind) but it has a mechanism for sensing the direction of the wind which keeps it turning its sails so as to maximise the energy acquired from the wind. Birds that use gravity and air-currents as sources of energy also need an internal store of energy both when they need to travel against the external force (e.g. upwards, or into the wind), and when they have to force their control surfaces into special shapes in order to get an external force deployed in the required way (like a sailor holding a sail in a special position).
The kinds of motions an object is capable of, whether active or passive will depend on whether it is rigid or not, and if not rigid whether it is stretchable, compressable, bendable, twistable, etc. Different sorts of materials will support different kinds of non-rigid motion, e.g. cotton-wool, elastic bands, paper, cloth, water, mud, plasticene, etc.
Fido will meet many objects that are active in the sense described here, including many utensils and tools around the house, and if it is working for someone disabled, that could include things like powered wheel-chairs, stair-lifts, lifting gear in bedroom or bathroom, etc.
Some of the objects will be used regularly by Fido (e.g. kitchen and garden machines), whereas others will be used by other members of the household, e.g. children's toys and stair-lifts. Fido will need to know various things about them even if they are only used by other individuals, e.g. when something needs to be repaired, or has run out of charge.
Fido may need to know also about various kinds of active objects outside the house, including vehicles such as buses and cars, trains, street-cleaning machines, the wind, clouds, trees, and also humans and other animals.
Discussion of a subset of these capabilities for the end of project can be found here
A special subset of self-controlled active objects are those which we can call 'animate', described here.