DESIGING THE DATA OF AN INFORMATION SYSTEM
The process of designing the data structure of an information system begins with
identifying the data entities and data attributes that comprise the data.
various pieces of data that have to be stored. For instance, an employee training
information system would need to store data (attributes) for employee name, training
class name, instructor, date of the class, etc.
Attributes can be grouped into
. Each data entity stores data attributes related to a
single kind of
. Generally you will have multiple
data entities in an information system, with each entity storing many data attributes about
a given class of persons, places, objects, events, or concepts. For instance, a college
enrollment information system might have an entity for
data, another entity for
information, and another entity for
data. Entities should be named with
a singular noun or a short singular noun phrase, such as those discussed above. Entities
correspond roughly to the tables in a relational database.
Why use the terms entities and attributes instead of the terms tables and fields? Tables
and fields are relational database terms. Though most information systems are
implemented using relational databases, not all are. Some information systems use non-
relational database systems. Some web-based information systems store data in XML, a
non-relational data format. Jumping too soon into any kind of implementation decision is
not a good idea. It limits how you think about the design and ultimately limits your
choices. So for now, we'll use the implementation-neutral terms data entities and data
Recognizing data entities and data attributes you need for your data is a skill that you will
develop with practice. In the next three labs, we will give you the conceptual tools for
designing basic data structures and implementing them in a database. In this lab, we will
concentrate on identifying data attributes and data entities. In the next lab we'll learn how
to correctly design the entity relationships. In the final data lab we will see how to
implement a data design in a database. But, like learning to play the piano, the only way
you will learn it is in actually working through data design on multiple systems.