Database Reference
In-Depth Information
a letter, motion words and sentences are shown in Figures 4, 5, and 6 using the concept of
partita, a measure used in music. Note the complex expression shown in Figure 6 describ-
ing the motion of two links (arm and forearm) moving in parallel and coordination. The
equivalent description in verbal language would hardly reach that level of effi ciency.
We illustrate a simple sign language for forearm direction. Two expressions are defi ned,
HALT and SLOW, by means of a single limb motion in the vertical plane only (e.g., right
forearm). A 3-bit building block is needed to defi ne this rudimentary language, where:
Bit 1 defi nes motion (1), and rest (0)
Bits 2+3 defi nes increase (10), decrease (01), and no change (00) in forearm angle.
Given a base position in which the forearm is at rest, hanging down along the side of
the body, we assume:
A sampling frequency of two samples per second.
•
A basic measuring unit of 90 degrees, i.e., a motion change of 90 degrees takes ½
sec.
•
H = a HALT message is discharged by a motion of 180 degrees (decrease angle rela-
tive to arm), and staying at this position for at least ½ second.
•
S = a SLOW message is given by moving the arm 90 degrees (decreasing angle rela-
tive to arm), and staying at this position for at least ½ second.
•
B = back to base position takes place either from H or S (increasing angle).
•
SH = moving the forearm from SLOW to HALT (decrease angle relative to arm).
•
Remaining at a certain position (S, H, or Base position) is denoted by a (.).
•
There is no meaning to any other motion, e.g., transition from HALT to SLOW.
Table 4 depicts the different levels of the forearm motion language.
Time Scale -
Sets the time in elapsed seconds.
Bit Level -
Describes the binary building blocks stored in the database.
Motion Level -
Shows motion quantities and directions (increase/decrease).
Pattern Level -
Shows information patterns in the motion database.
Language Level -
Gives a linguistic meaning to the motion patterns.
Given a motion language and database, we can begin to look at a “motion query lan-
guage” (MQL) by defi ning a two-term component of the movement message (H, S, base)
and a number that represents motion duration in time units. The data in Table 4 may be
viewed as:
Slow-5
Halt-3
Base-1
And queries may take the form:
Select “Slow”
From database-name
Where time is between 0 and 8.
