Databases Reference
In-Depth Information
Databases
Architecture
Data models
Reference
models
(ISO, ANSI)
Relational
Object-oriented
Standardization
Theoretical
foundations
Practical
applications
Figure 1.1
Foundations of DB advances.
was always an important objective in DB evolution, and the three-level
architecture, together with the relational data model, was a major step in that
direction.
In terms of data models, the relational model has influenced research
agendas for many years and is supported by most of the current products.
Recently, other DBMSs have appeared that implement other models, most
of which are based on object-oriented principles.
2
Three key factors can be identified in the evolution of DBs: theoretical
basis (resulting from researchers work), products (developed by vendors),
and practical applications (requested by users). Those three factors have been
present throughout the history of DB, but the equilibrium among them
has changed. What began as a product technology demanded by users needs
in the 1960s became a vendor industry during the 1970s and 1980s. In the
1970s, the relational model marked the consideration of DB as a research
technology, a consideration that still persists. In general, users needs have
always influenced the evolution of DB technology, but especially so in the
last decade.
Today, we are witnessing an extraordinary development of DB tech-
nology. Areas that were exclusive of research laboratories and centers are
appearing in DBMSs latest releases: World Wide Web, multimedia, active,
object-oriented,
secure,
temporal,
parallel,
and
multidimensional
DBs.
2.
An IDC forecast in 1997 denoted that object-oriented DBMSs would not overcome 5%
of the whole DB market.
