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286 6 Structural Pattern Recoenition

6.5 Improve the set of primitives and relations indicated in section 6.2.2 (Figure 6.4) in
order to describe all capital letters by digraphs.

6.6 In section 6.3.2 two different PDL descriptions were given for the pattern "R,
according to the traversing direction of the description. Develop a general rule that will
generate a PDL description based on the description of the inverse traversing direction.

6.7 Consider "standard" prototype drawings of the decimal digits.
a) Develop a PDL grammar that will generate the prototypes for each digit class.
b) Perform string matching experiments (use StrMatch.xls) in order to determine which
digit class an unknown PDL sequence can be assigned to. Also set a threshold for the
matching score in order to establish a reject class.

6.8 An FHR spike (see Figure 6.1 1) has amplitude that is approximately half (negative
spike) or double (positive spike) of its onset value.
a) Determine the attributed grammar that will detect FHR spikes.
b) Perform experiments with this grammar using the FHR Signals dataset, adjusting the
appropriate attribute rules.

6.9 An upward FHR wave is considered an acceleration if it lasts for more than 15 s,
reaching an amplitude of at least 15 bpm. Write the appropriate rules for the attributed
grammar describing FHR accelerations (see rules (6- 14)).
6.10 A downward FHR wave is considered a deceleration if it lasts for more than 15 s,
reaching an amplitude of at least 10 bpm.
a) Draw the state diagram describing decelerations, analogous to the one describing
accelerations shown in Figure 6.12.
b) Write the appropriate rules for the attribute vectors of this grammar, studying its
behaviour by experimenting with the FHR Signals dataset.

6.1 1 Develop the grammar rules that will recognize the P. Q, R, S and T waves of ECG
signals (see description in A.4). Use the ECG Signals dataset to carry out experiments
with these rules.

6.12 A human expert has assigned the waves described by the following strings of T=(h, u,
d) to a certain class:

hudh
huudh
huhuhddh
huhudh
huhuuddh

Use the successor method in order to determine the state diagram that will recognize
these strings.

6.13 Repeat the tank classification experiments, described in section 6.4.1, using other views
of tanks available in the Tanks dataset. Determine whether an improvement of
matching scores can be obtained by using scale and angular normalizations derived