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the way a user understands a virtual world and the way a child understands our real
world. For Piaget, a schema is a structured set of characteristics of an action that can
be generalised, which helps to repeat the action or apply it to new contents (as in the
case of a user who operates his trolley in conditions similar to the real world).
A schema is thus the mental organisation of actions as they are transferred or
are generalised while repeating this action in similar circumstances. They correspond
to stabilised aspects of actions for various categories of situations. The schemas of
utilisation have a personal dimension which is peculiar to each individual; they are
recorded in the subject's personal memory as resources that can be called upon. They
also have a social dimension: They are common to a class or to a number of members
belonging to a social group, community, a work environment, etc. This is why it is
appropriate to consider them as social schemas of use, like resources registered in the
collective memory of a group (Rabardel, 1995).
It is on this concept that we base our approach to obtain behavioural interfaces,
offering a pseudo-natural immersion and interactivity. Behavioural interface is thus
a mixed entity including both an artefact (its hardware device) and a schema, which
we call “Imported Behavioural Schema'' (IBS). This schema is imported from the real
environment to be transferred and adapted to the virtual environment. This analysis
can be compared to that of the instrument, described by Rabardel. It involves explain-
ing the manner in which the users use the behavioural interface (or the instrument) and
the manner in which their skills are developed. It also includes describing the designing
process of these devices, to facilitate its consideration.
For the time being, let's consider Piaget's observations:
The schema is reproducible: It contains the conditions of recognising the situations
to which it is applicable;
The schema is assimilative: It can be applied to new situations;
The schema has a purpose and
The schema does not constitute declarative knowledge (it is used and assimilated
unconsciously).
To better understand these concepts, imagine that you are grasping an object. The
associated schema is not a particular sequence of movements and perceptions. It is the
general canvas that helps to reproduce them in different circumstances and to complete
various actions. When we grasp an object, we stretch our arm or open our hand more
or less depending on our distance from the object and its size. Whatever the object, the
schema of grasping does not change. Only the sensorimotor parameters are changed.
The Imported Behavioural Schema cannot be isolated. There is a relation of
interdependence between the schema and the artefact associated with it in a given
application. But the same schema can be used with different artefacts and vice versa.
For example, for operations in a 3D space, we can use the same schema with a six-
degrees-of-freedom tracker or a data glove. An Imported Behavioural Schema used in
a virtual environment is often altered compared to the schema in real environment.
The sensorimotor functions required can be partly different than those in the real
world. It's not just the sensorimotor parameters that vary. For example, the senso-
rimotor functions to grip and handle objects in a virtual shop are modified. Using a
six-degrees-of-freedom tracker, the user can virtually pick up the object and handle it.
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