Database Reference
In-Depth Information
of the ancillary technology available at the time of the model's introduction. Processing
speed, memory, and storage were simply insufficient to provide database software vendors
with a platform on which to build a full implementation of the relational database, so the
initial relational database software programs fell woefully short of their full potential. Ad-
vances in both hardware technology and software engineering over the past 20 years have
madeprocessingspeedaninsignificantissueandhaveallowedvendorstomakesignificant
gains in their efforts to support the model more fully.
You'll learn more about the relational database model as you work through the design pro-
cess presented in this topic. Some of the topics you'll encounter include creating tables,
establishing data integrity, working with relationships, and establishing business rules.
Relational Database Management Systems
A
relational database management system
(RDBMS) is a software application program
you use to create, maintain, modify, and manipulate a relational database. Many RDBMS
programs also provide the tools you need to create end-user applications that interact with
the data stored in the database. Of course, the quality of an RDBMS is a direct function of
theextenttowhichitsupportstherelationaldatabasemodel.Evenamong“true”RDBMSs,
supportfortherelationaldatabasevariesamongvendors,andthereisyettobea
full
imple-
mentation of the relational model's potential. Despite this, all RDBMS programs continue
to evolve and become more full-featured and powerful than ever before.
In the earliest days of the relational database, RDBMSs were written for use on mainframe
computers. (Didn't everything start on a mainframe?) Two RDBMS programs prevalent in
the early 1970s were System R, developed by IBM at its San Jose Research Laboratory
in California, and Interactive Graphics Retrieval System (INGRES), developed at the
UniversityofCaliforniaatBerkeley.Thesetwoprogramscontributedgreatlytothegeneral
appreciation of the relational model.
As the benefits of the relational database became more widely known, many companies
decided to make a slow move from hierarchical and network database models to the rela-
tional database model, thus creating a need for more and better mainframe RDBMS pro-
grams. The 1980s saw the development of various commercial RDBMSs for mainframe
computers by companies such as Oracle and IBM.
The early to mid-1980s saw the rise of the personal computer, and with it the development
ofPC-basedRDBMSprograms.Someoftheearlyentriesinthiscategory,fromcompanies
such as Ashton-Tate and Fox Software, were nothing more than elementary file-based
database management systems. True PC-based RDBMS programs began to emerge with
products developed by companies such as Microrim and Ansa Software. These companies
