To illustrate the concepts, we use a small example from the supermarket domain. The set of items is I = { m i l k , b r e a d , b u t t e r , b e e r , d i a p e r s } {\displaystyle I=\{\mathrm {milk,bread,butter,beer,diapers} \}} and in the table is shown a small database containing the items, where, in each entry, the value 1 means the presence of the item in the corresponding transaction, and the value 0 represents the absence of an item in that transaction.