Programming languages and software engineering - The Computing Universe: A Journey through a Revolution - page 80

The relational data model that forms the basis of modern data-
bases is undoubtedly one of the great abstractions of the twentieth cen-
tury. Historically, there were approaches for handling large volumes of
data based on hierarchical, treelike structures or more general network
structures. An early example of the hierarchical approach was the IBM's
Information Management System. One difficulty with this approach is
that not all data relationships fit well into a tree structure. A more gen-
eral network structure can provide a more flexible solution, but now
the user has to know the exact path leading to the data item in order
to access or update it. This approach also did not scale well - with the
growth of data, programmers found it difficult to navigate through a
complicated web of data relationships.
The real breakthrough for database software came with the idea
of the relational data model, suggested by a British mathematician Edgar
“Ted” Codd ( B.4.14 ). In 1970 he published his groundbreaking paper
“A Relational Model of Data for Large Shared Data Banks.” The ideas
described in this paper became the foundation of modern databases.
Ironically, his own company, IBM, was initially not very supportive of
his ideas. There were many skeptics and a strong resistance toward rela-
tional databases even in professional circles. In the dedication of his topic The Relational Model for Database
Management he refers to this struggle:

B.4.14. Edgar “Ted” Codd (1923-2003)
graduated from Oxford with a degree in
mathematics and chemistry and was an
RAF fighter pilot during the war. After
the war he joined IBM and moved to the
United States. In 1981 he received the
Turing Award for his contribution to the
development of relational databases.

To fellow pilots and aircrew in the Royal Air Force during World War II and the dons at Oxford. These people
were the source of my determination to fight for what I believed was right during the ten or more years in
which government, industry and commerce were strongly opposed to the relational approach to database
management. 29

The idea of a relational database is simple, yet very powerful. All the data, including the relations between
data, is stored in tables that are linked together. The link is established when the same column of data is
shared between two or more tables. This column is called a key. The main advantage of the relational data
model is that it provides a systematic way to create the interconnections between tables. It is much easier to
access data and there is no need to know the path leading to the data ( B.4.15 ). This model is also supported
by a powerful mathematical set theory and a declarative programming language called SQL - structured query
language .

B.4.15. Jim Gray (1944-2007) on board his boat Tenacious . In 1988 Gray received the Turing Award
for his contributions to database design and transaction processing. After gaining a PhD in com-
puter science from Berkeley, he worked for IBM, Tandem Computers, and DEC. From 1995 Gray
was a Technical Fellow at Microsoft Research. He was first to develop a website that displayed
geographic data - the Terraserver - and that could deliver data to users using a web service. Gray
spent the last decade of his life working with scientists with “Big Data” problems. With astron-
omer Alex Szalay, he pioneered the hosting of the Sloan Digital Survey astronomical data by
creating the SkyServer website. Gray also coined the term Fourth Paradigm to reflect the increase
in importance of data-intensive science. He was lost at sea, west of San Francisco Bay, in January
2007. Despite a massive collaborative effort by the emergency services and the computer science
community, in searching for signs of Tenacious , no trace was ever found.