Attribute affinity in Distributed Database System

Attribute affinity

Vertical Fragmentation

Each site may not need all the attributes of a relation.

Thus we use vertical fragmentation which divides a relation vertically by columns.

It is a subset of a relation which is created by a subset of columns.

Basic idea of VF is access efficiency

Information Requirement is application based

Attribute affinities:  obtained from more primitive usage data

Example

Attribute Usage Matrix

Access Frequency Matrix

             .

Attribute Affinity Matrix