Database Reference
In-Depth Information
you collect requirements for the outputs and the processes and then determine the
inputs. Determination of the inputs leads to the design of the data files.
In the data-driven method, you gather requirements about the business objects
that are pertinent to the business. You collect the data required to be included about
these objects. Then you design the database to support the business. After this, the
design of the initial processes follows.
Right away, you can see the advantage of the data-driven approach. Although
you are interested in supporting the initial processes, because you have designed
the database to contain all data relevant to the business, you will find it easy to
add further processes later on. Data-driven approach provides enormous flexibility
to provide for new and additional processing requirements at a later time. In
practice, companies adopting the database approach use a combination of both
methods, although the data-driven method dominates the application development
phases.
Basic Concepts
You are now beginning to appreciate the significance of the database approach. You
are discerning the major benefits of developing and using applications in a database
environment. Before proceeding further, let us review a few fundamental concepts
and become familiar with some key terminology.
Data Repository All data in the database reside in a data repository. This is the
data storage unit where physical data files are kept. The data repository contains
the physical data. Mostly, it is a central place of storage for the data content.
Data Dictionary The data repository contains the actual data. Let us say that you
want to keep data about the customers of your company in your database. The struc-
ture of a customer's data could include fields such as customer name, customer
address, city, state, zip code, phone number, and so on. Data about a particular
customer could be as follows in the respective fields: Jane Smith/1234 Main
Street/Piscataway/NJ/08820. There are two aspects of the data about customers. One
aspect is the structure of the data consisting of the field names, field sizes, data types,
and so on. This part is the structure of the data for customers. The other part is the
actual data for each customer consisting of the actual data values in the various
fields.
The first part relating to the structure resides separately in storage, and this is
called the data dictionary or data catalog. A data dictionary contains the structures
of the various data elements in the database. It also contains the relationships
among data elements. The other part relating to the actual data about individual
customers resides in the data repository. The data dictionary and the data reposi-
tory work together to provide information to users.
Database Software Are Oracle and Informix databases? Oracle and Informix
are really the software that manages data. These are database software or database
management systems. Database software supports the storing, retrieving, and updat-
ing of data in a database. Database software is not the database itself. The software
helps you store, manage, and protect the data in a database.
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