Krohs_00_Pr.indd

A Device-Oriented Defi nition of Functions of Artifacts and Its Perspectives 205

use. For example, a heat exchanger can be used as a heater in a boiler in a power plant or
a radiator connected to an engine in a car.^2 The behavior is the same in any context; that
is, heat fl ows from the warmer fl uid to the colder one. As shown in fi gure 12.1, the func-
tions of the heater and the radiator can be to give heat and to remove heat, respectively.
This difference between the functions is dependent on the embedded system. Moreover,
a function can be performed (realized) by different behaviors. A function is associated
with specifi c constraints on some parts of behaviors to realize the function. A behavior
can perform multiple functions simultaneously. Thus a function here is rather separated
from a device.
On the basis of this discussion, we defi ne a (base-)function as follows (Kitamura et al.
2006):

A (base-)function performed by a device is a role played by a behavior of the device to
achieve a specifi c goal under a context of use, based on a certain capacity inherent in
the device.

By “role” we mean such a concept that an entity plays in a specifi c context and cannot
be defi ned without mentioning external concepts (Sunagawa et al. 2006). A role is anti-
rigid (i.e., contingent with respect to identity), dynamic (i.e., temporary and multiple), and
founded (i.e., is an extrinsic property defi ned with reference to an external concept)
(Masolo et al. 2004). Accordingly a function can be defi ned as a role. First, a function
(and a behavior as its basis) is founded, since a function of a device affects an entity other
than the device itself (operand) and causes temporal changes to it. Second, the property

Input port(s)

Function B

Function A

Device

Flowing operands

Behavior 1

e.g., remove heat

Operand 2

Operand 1

Functional

context B

Time/location

e.g., heat-flow behavior

Affecting Output port(s)

Functional

context A e.g., give heat

Input state 2

Input state 1

Operand 2

Operand 1

Output state 2

Output state 1

Figure 12.1
Device, operands, behavior, and function.