Another important index type is the patterned index. A patterned index is created when a common pattern is found and recognized. On occasion, the type of word is recognized merely by looking at its format. Some simple examples are:
· (American) telephone number – 999-999-9999
· Email address – firstname.lastname@example.org
· Social security number – 999-99-9999
When the pattern is recognized, the index value and the type of pattern are created in the index table. Figure 7.9 shows a patterned index.
Figure 7.9 Patterned index