A Device-Oriented Defi nition of Functions of Artifacts and Its Perspectives 213
effect context, we can defi ne subtypes of the goal-oriented role as a categorization of more
general functions, as shown in fi gure 12.3. Note that fi gure 12.3 shows only an is-a hier-
archy for the sake of readability, because some distinctions are independent of each other.
These differences represent different perspectives for capturing functions. When a behav-
ior is captured from a different perspective it is recognized as a different function. To some
extent it might be possible to account for the perspectivity of function ascriptions. However,
this is beyond the scope of this chapter.
12.3.2 Teleological Context
The teleological context is a generalized type of the functional context discussed in section
12.2.3 and is categorized into a function context and an unintended context. The function
context represents that the effect (behavior) is “intended” by a user. With the function
context, we can defi ne a general function as a subtype of the goal-oriented role, as shown
in fi gure 12.3. On the other hand, unintended phenomena such as faults can be defi ned a
Goal-oriented role
Effect function Quasi-function
General function Unintended phenomena
Device
function
Environmental
function
Capability
function
Effect-on-state
function
Flowing-
object
function
Essential-part
function
Effect-on-
process
function
Interpretative
function
Physical
environmental
function
Supplementary-
part function
Causal-meta
function
Partial-achievement
function
Property
enabling
function
Effect-on-
function
(meta) function
Inter-device
function
Functional
property
Function-with
way-of-
achievement
Figure 12.3
Categories of functions.