The most basic unit of information in the repetitive structured environment is a block of
data. Inside each block of data are records of data.
Fig. 1.2.3 shows a simple record of data.
Fig. 1.2.3 Records inside a block.Each record of data is (normally!) representative of a transaction. For example, there are
records of data representing the sale of a product. Each record is representative of a
single sale.
Inside each record are keys, attributes, and indexes. Fig. 1.2.4 shows the anatomy of a
record.
Fig. 1.2.4 Attributes, keys, and indexes.If a record is representative of a sale, the attributes might be information about the date
of the sale, the item sold, the cost of the item, any tax on the item, who bought the item,
and so forth. The key of the record is one or more attributes that uniquely define the
record. The key for a sale might be the date of sale, item sold, and location of the sale.
The indexes that are attached to the record are on the attributes that are needed when
there is a desire to have quick access to the record.
Chapter 1.2: The Data Infrastructure