http://dl.acm.org/citation.cfm?id=362534
This year the whole world celebrates the five-hundredth birthday of Nicolaus Copernicus, the famous Polish astronomer and mathematician. In 1543, Copernicus published his book, Concerning the Revolutions of Celestial Spheres, which described a new theory about the relative physical movements of the earth, the planets, and the sun.
I raise the example of Copernicus today to illustrate a parallel that I believe exists in the computing or, more properly, the information systems world.
In sequential file technology, search techniques are well established.
The availability of direct access storage devices laid the foundation for the Copernican-like change in viewpoint. The directions of “in” and “out” were reversed. Where the input notion of the sequential file world meant “into the computer from tape,” the new input notion became “into the database.” This revolution in thinking is changing the programmer from a stationary viewer of objects passing before him in core into a mobile navigator who is able to probe and traverse a database at will.
The programmer who has advanced from sequential file processing to either index sequential or randomized access processing has greatly reduced his access time because he can now probe for a record without sequentially passing all the intervening records in the file.
From this point, I want to begin the programmer’s training as a full-fledged navigator in an n-dimensional data space.
involves all aspects of storing, retrieving, modifying, and deleting data in the files on personnel and production, airline reservations, or laboratory experiments
inquiry or retrieval activity that reaccesses previously stored data
Let us now return to our story concerning the programmer as navigator. We left him using the randomizing or the index sequential technique to expedite either inquiry or update of a file based upon a primary data key.
There are many benefits gained in the conversion from several files, each with a single type of record, to a database with several types of records and database sets. One such benefit results from the significant improvement in performance that accrues from using the database sets in lieu of both primary and secondary indices to gain access to all the records with a particular data key value.