IDEF1
Information Modeling Method
Overview
IDEF1 was designed as a method for both analysis and
communication in the establishment of requirements. IDEF1 is generally
used to 1) identify what information is currently managed in the
organization, 2) determine which of the problems identified during
the needs analysis are caused by lack of management of appropriate
information, and 3) specify what information will be managed in
the TO-BE implementation.
IDEF1 captures the information that exists about objects
within the scope of an enterprise. The IDEF1 perspective of an information
system includes not only the automated system components, but also
non-automated objects such as people, filing cabinets, telephones,
etc. IDEF1 was designed as a method for organizations to analyze
and clearly state their information resource management needs and
requirements. Rather than a database design method, IDEF1 is an
analysis method used to identify the following:
The results of information analysis can be used by
strategic and tactical planners within the enterprise to leverage
their information assets to achieve competitive advantage. Their
plans may include the design and implementation of automated systems
which can more efficiently take advantage of the information available
to the enterprise. IDEF1 models provide the basis for those design
decisions, furnishing managers with the insight and knowledge required
to establish good information management policy.
IDEF1 Principles
IDEF1 uses simple graphical conventions to express
a powerful set of rules that help the modeler distinguish between
1) real-world objects, 2) physical or abstract associations maintained
between real-world objects, 3) the information managed about a real-world
object, and 4) the data structure used to represent that information
for acquiring, applying, and managing that information. IDEF1 provides
a set of rules and procedures for guiding the development of information
models. One of the IDEF1 goals is to provide a structured and disciplined
process for analyzing information managed by an organization. This
goal is accomplished by the evolutionary process defined in the
method and by the measurable results and specific products required
by the method. IDEF1 enforces a modularity that eliminates the incompleteness,
imprecision, inconsistencies, and inaccuracies found in the modeling
process.
IDEF1 Concepts
There are two important realms for modelers to consider
in determining information requirements. The first realm is the
real world as perceived by people in an organization. It is comprised
of the physical and conceptual objects (e.g., people, places, things,
ideas, etc.), the properties of those objects, and the relations
associated with those objects. The second realm is the information
realm. It includes information images of those objects found in
the real-world. An information image is not the real-world object,
but the information collected, stored, and managed about real-world
objects. IDEF1 is designed to assist in discovering, organizing,
and documenting this information image, and thus is restricted to
the information realm.
An IDEF1 entity represents the information maintained
in a specific organization about physical or conceptual objects.
An IDEF1 entity class refers to a collection of entities or the
class of information kept about objects in the real-world. There
are two basic concepts that distinguish entities:
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They are persistent. The organization expends resources
to observe, encode, record, organize, and store the existence
of individual entities. |
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They can be individuated. They can be identified uniquely from other entities. |
Entities have characteristic attributes associated
with them. Attributes record values of properties of the real-world
objects. The term attribute class refers to the set of attribute-value
pairs formed by grouping the name of the attribute and the values
of that attribute for individual entity class members (entities).
A collection of one or more attribute classes which distinguishes
one member of an entity class from another is called a key class.
A relation in IDEF1 is an association between two individual information
images. The existence of a relation is discovered or verified by
noting that the attribute classes of one entity class contain the
attribute classes of the key class of the referenced entity class
member. A relation class can be thought of as the template for associations
that exist between entity classes. An example of a relation in IDEF1
is the label "works for" on the link between the information
entity called "Employee" and the information entity called
"Department." If no information is kept about an association
between two or more objects in the real-world, then, from an IDEF1
point of view, no relation exists. Relation classes are represented
by links between the entity class boxes on an IDEF1 diagram. The
diamonds on the end of the links and the half diamonds in the middle
of the links encode additional information about the relation class
(i.e., cardinality and dependency). The figure below illustrates
the manner in which IDEF1 diagrams are drawn.
Figure
1: An IDEF1 Diagram
Strengths of IDEF1
IDEF1 is an effective method for documenting the informational
requirements of an enterprise. The IDEF1 modeling exercise provides
a foundation for database design, gives a definition of the information
structure, and provides a requirements statement reflecting the
basic information needs. IDEF1 uses a disciplined, structured technique
to uncover the information and business rules used by an organization.
This gives needed rigor to the method for untangling the complex
challenge of modeling the information of the organization. IDEF1
requires the active participation of the information users. This
serves to accurately model the organization by forcing the users
to think about how and where the information is being used and managed.
Finally, information models are useful throughout the life-cycle
of the enterprise.
KBSI has developed an automated Information and Data
Modeling tool, SMARTER®,
to support the IDEF1 and IDEF1X methods. |
