OBJECT-BASED DATA MODEL: PRINCIPLES AND COMPONENTS - Database Design and Development: An Essential Guide for IT Professionals - page 173

PymntNo

PymntNo

Amount Amount

1

PATIENT PROVIDER

PAYMENT

PAYMENT *

pays

pays

InvNo

* *

PATIENT
STATEMENT

PROVIDER
INVOICE

StmtNo

*

receives

ProvID

StmtDate

1

1 1

InvAmt

PROVIDER

StmtAmt

bills invoices

* 1

ProvName

VISIT

DrID

PatientID

*

PATIENT DOCTOR

DrName

visits

*

Name

DrPhone

1

Address

VisitNo

includes

VisitDate

*

ServiceNo

SERVICE

SrvcAmt

PrcName

PROCEDURE TEST

TstName

Figure 6-3 Model diagram: medical practice.

This is an aggregate object. See the explanation of aggregate objects in a later sub-
section.

Attributes Review the ellipses attached to each object. These are the inherent or
intrinsic characteristics of the objects. Each attribute is a basic property of the object
to which it is connected. Note also that only the characteristics that are relevant to
the initial information requirements are included.

Identifiers Note the ellipses containing attribute names that are underlined. Each
such ellipse denotes the identifier for the particular object.

Relationships Look at all diamonds and the lines connecting pairs of objects.
These are the direct relationships. What are direct relationships? Consider the
object PROVIDER PAYMENT. Of course, this payment pertains to a visit by a
patient. Nevertheless, the payment is directly related only to invoice sent to the
third-party insurance provider. The relationship of a payment from a provider to
the patient is an indirect relationship. The model diagram only needs to show the
direct relationships. The indirect relationships may be derived from the direct rela-
tionships displayed in the diagram.

Cardinalities Note the numbers marked along the relationship lines. Number to
show cardinalities at either side of the diamonds for the above relationships. An