HP System Dictionary/XL General Reference Manual Vol 1 (32256-90004)

3- 15
3 Dictionary Architecture
Overview
The architecture of System Dictionary includes several major components (the E-R model and its
components, the core set, domains, versions, security, and the intrinsics) which are all interrelated and
work together to provide the benefits listed in Chapter 1. With the exception of the intrinsics, these
components are discussed individually in this and the following chapters.
This chapter provides a description of the Entity-Relationship Model, the structure on which System
Dictionary is based. It also includes information on the individual components that make up this model,
and tells how to use them. They are:
• Entities
• Relationships
• Entity types
• Relationship types
• Relationship classes
• Attributes
• Type-attribute associations
The main purpose of a data dictionary is to provide a mechanism for creating and accessing entities and
relationships. Entities and relationships are the definitions that are stored in the dictionary. The other
components of the E-R model (entity types, relationship types, attributes, and so on) are structures that
support the creation and retrieval of entity and relationship definitions.
The Entity-Relationship Model
System Dictionary is based on a structure called an Entity-Relationship model. The theoretical model
is composed of entities, that represent pieces of real-world data in an information network, and
relationships between entities. This model is general enough that it can describe most, if not all, of the
information processing done on a computer network.
A simple example of the E-R model might represent a data base called COMPANY, which contains a file
called PERSONNEL. In this example, the entities are COMPANY and PERSONNEL, and the relationship
between the two is contains. A standard illustration for this example is shown in Figure 3-1 below.