Bio-medical Ontologies Maintenance and Change Management

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Fig. 2. SCOP (top) and CATH (bottom) hierarchical trees
The CATH database is a hierarchical classification of protein domain structures
in the Protein Data Bank (http://www.rcsb.org/pdb/). Protein structures are classified
using a combination of automated and manual procedures. There are four
major levels in this hierarchy: Class, Architecture, Topology and Homologous
superfamily, as shown in Fig. 2. Domains within each Homologous superfamily
level are subclustered into sequence families using multi-linkage clustering, identifying
five family levels (named S, O, L, I, D). Thus, the complete classification
hierarchy consists of nine levels (CATHSOLID).
5.2 Extracting Association Rules
The first step in finding association rules is to look for attribute values that appear
in the same tuple. Every attribute-value couple is an item. A group of items is