Database Reference
In-Depth Information
model IMS. IMS was released in 1968, and subsequently enjoyed success in Customer Informa-
tion Control System (CICS) and other applications. It is still used today.
But in the years following the invention of IMS, the new model, the disruptive model, the threat-
ening model, was the relational database.
In his 1970 paper “A Relational Model of Data for Large Shared Data Banks,” Dr. Edgar F.
Codd, also at IBM, advanced his theory of the relational model for data while working at IBM's
San Jose research laboratory. This paper, still available at
http://www.seas.upenn.edu/~zives/03f/
cis550/codd.pdf
,
became the foundational work for relational database management systems.
Codd's work was antithetical to the hierarchical structure of IMS. Understanding and working
with a relational database required learning new terms that must have sounded very strange in-
deed to users of IMS. It presented certain advantages over its predecessor, in part because giants
are almost always standing on the shoulders of other giants.
While these ideas and their application have evolved in four decades, the relational database still
is clearly one of the most successful software applications in history. It's used in the form of
Microsoft Access in sole proprietorships, and in giant multinational corporations with clusters of
hundreds of finely tuned instances representing multiterabyte data warehouses. Relational data-
bases store invoices, customer records, product catalogues, accounting ledgers, user authentica-
tion schemes—the very world, it might appear. There is no question that the relational database
is a key facet of the modern technology and business landscape, and one that will be with us in
its various forms for many years to come, as will IMS in its various forms. The relational model
presented an alternative to IMS, and each has its uses.
So the short answer to the question, “What's wrong with relational databases?” is “Nothing.”
There is, however, a rather longer answer that I gently encourage you to consider. This answer
takes the long view, which says that every once in a while an idea is born that ostensibly changes
things, and engenders a revolution of sorts. And yet, in another way, such revolutions, viewed
structurally, are simply history's business as usual. IMS, RDBMS, NoSQL. The horse, the car, the
plane. They each build on prior art, they each attempt to solve certain problems, and so they're
each good at certain things—and less good at others. They each coexist, even now.
So let's examine for a moment why, at this point, we might consider an alternative to the rela-
tional database, just as Codd himself four decades ago looked at the Information Management
System and thought that maybe it wasn't the only legitimate way of organizing information and
solving data problems, and that maybe, for certain problems, it might prove fruitful to consider
an alternative.
We encounter scalability problems when our relational applications become successful and usage
goes up. Joins are inherent in any relatively normalized relational database of even modest size,
