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Bio-medical Ontologies Maintenance and Change Management

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Classifying Patterns in <strong>Bio</strong>informatics Databases 191<br />

memories [6], morphological associative memories served as starter point for<br />

the creation <strong>and</strong> development of the alpha-beta associative memories.<br />

2.2.1 The α <strong>and</strong> β Operators<br />

Theheartofthemathematicaltoolsused in the alpha-beta model, are two<br />

binary operators designed specifically for these memories. These operators<br />

are defined in [22] as follows: First, we define the sets A = {0, 1} <strong>and</strong> B =<br />

{0, 1, 2}, then the operators α <strong>and</strong> β are defined in tabular form:<br />

Table 1. Definition of the Alpha <strong>and</strong> Beta operators<br />

α : A × A → B β : B × A → A<br />

xy α(x, y) xy β(x, y)<br />

00 1 00 0<br />

01 0 01 0<br />

10 2 10 0<br />

11 1 11 1<br />

20 1<br />

21 1<br />

The sets A <strong>and</strong> B,theα <strong>and</strong> β operators, along with the usual ∧ (minimum)<br />

<strong>and</strong> ∨ (maximum) operators, form the algebraic system (A, B, α, β, ∧, ∨)which<br />

is the mathematical basis for the alpha-beta associative memories.<br />

The ij-th entry of the matrix y ⊠x t is:[y ⊠ x t ] ij = α (yi,xj). If we consider<br />

the fundamental set of patterns: {(xμ ,yμ ) |μ =1, 2,...,p} then, the ij-th<br />

entry of the matrix yμ ⊠ (xμ ) t �<br />

is: yμ ⊠ (xμ ) t�<br />

ij = α � y μ<br />

i ,xμ<br />

�<br />

j<br />

2.2.2 The Learning <strong>and</strong> Recalling Phases<br />

Given that there are two kinds of alpha-beta associative memories, ∨ <strong>and</strong><br />

∧, if we consider that each of these kinds is able to operate in two different<br />

modes, heteroassociative <strong>and</strong> autoassociative, we have four different available<br />

choices.<br />

Due to expediency, we will only discuss here the alpha-beta autoassociative<br />

memories of kind ∨. Then, the input <strong>and</strong> output patterns have the same<br />

dimension n, <strong>and</strong> the memory is a square matrix V =[vij] n×n .Also,the<br />

fundamental set takes the form {(x μ ,x μ ) |μ =1, 2,...,p}.<br />

LEARNING PHASE<br />

For each μ =1, 2,...,p , <strong>and</strong> from each couple (x μ ,x μ ) build the matrix<br />

�<br />

x μ ⊠ (x μ ) t�<br />

. Then apply the binary ∨ operator to the matrices obtained<br />

n×n<br />

to get V as follows: V = p � �<br />

xμ ⊠ (xμ ) t�<br />

.<br />

μ=1

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