95
Essences of Interaction
melting and evaporation. The hammer and the piece of wood are similar in
a functional manner, but their differences in properties result in different
performances for those functions. As objects, the piece of wood and hammer
have many common uses for humans (i.e., the wood and hammer present
nearly the same functions during interactions with people). If the shapes of
the hammer and piece of wood were similar, then the wood object could be
used to drive nails into wood. The density and hardness of the hammer
would seem to be greater than that of the wood, so driving nails would dent
the wood, whereas the hammer might not experience denting. The function
of ‘to hammer’ is carried out by a person with either the wood or the hammer, resulting in the nail being driven into a wallboard. The performance of
the function ‘to hammer’ is different for the hammer and wood.
From a user’s perspective, the object’s performances (due to properties,
traits, configuration, shape, size, etc.) distinguish the hammer and the piece
of wood. Many users recognize this distinction and will employ a 2 × 4* to
drive a nail, remove another piece of wood that is hinged by a nail, pry open
a door that is jammed, or prop open a box lid. Both the hammer and the piece
of wood offer mechanical properties supportive of these and many other
such functions. The enactment of an object’s function at the interface between
one object and another object signifies the functional boundary of two
objects. However, unlike the physical boundary which is the limit of the
interaction of an object’s matter, the functional boundary begins at the physical boundary and extends by the object’s EMMI to the furthest extent of the
influence of its EMMI. Integration is object to object, with emphasis on demonstration of functions.
From the perspective of a user, functions are expressed in part through
their use(s) and their performance(s). Uses are often thought of as performances, so uses and performances are dependent factors. Generally, there is
a mix of functional requirements and performance requirements that drive
a project’s development and integration processes. To achieve functional
performance(s), the sending object’s mechanism results in loss of EMMI and
the receiving object’s mechanism experiences a loss. Should that loss exceed
the output performance, the object’s function is said to “have degraded,”
“does not function,” or “does not have the function.” If the function’s performance ceases to be produced by either the sending or receiving objects’
mechanism, the function can also be said to not exist or to be degraded such
that the function is unavailable.
From an integration perspective, objects are connected to demonstrate
functions. Testing for functions is usually accomplished by measuring the
performance(s) that can be achieved by the connection between two objects.
Should an automobile not move because of not having a source of
energy from gasoline, diesel, electrically charged battery, compressed air,
* A “2 × 4” is an unspecified length of lumber that is nominally 4 cm thick by 9 cm length,
having been reduced in size from a historical sizing of 2 inches by 4 inches.