Databases Reference
In-Depth Information
ENTITY:
BILLING ACCOUNT
DATA ELEMENTS:
BILLING_ACCT_NBR
BILLING_COMP_CD
One problem with externally controlled business information is that the
same entity in two Organizations may not be consistently defined or have
consistent entity identifiers. This occurs when the data models for each
organization are constructed independently, with no overall coordination
and resolution of differences by an impartial third party. TMs is less of an
issue when the organizations are in the same industry, because of the estab-
lishment of data administration, which performs this coordination function.
It is always an issue when crossing corporate boundaries, however, because
each organization has its own version of the industry's vernacular.
An organization must understand what the business information that
originates from an external organization actually represents. Only a subset
of business information may be received based on some prespecified crite-
ria. For example, the relevant business information from an external billing
system are bills with a final status, all other statuses are not relevant. In
addition, an aggregate level of the business information is of concern
instead of a detailed level. For example, the relevant billing information for
time-sharing computer services is the number of minutes used during each
rate period, the applicable rate per minute, and the associated cost, not the
detail on each individual access to the time-sharing system. By under-
standing the business information, the data modeler can create entities
that capture these relationships in the data model, which improves its clar-
ity and understandability. The determination of the specific business infor-
mation that is received, as well as its derivation algorithm, can be docu-
mented in the repository.
The same entity identifier that the originating organization uses should
be implemented whenever possible. The external organization has already
determined an entity identifier and it should be used as long as it has all the
properties of a proper identifier. This ensures that the same object is iden-
tified consistently across organizations. Unfortunately, entity identifiers
under the control of an external organization are not always proper identi-
fiers. The entity identifier may not be unique, always present, not null, and
stable. In this case, a surrogate key may be used as the entity identifier and
the original entity identifier data elements can be included as nonkey data
elements in the entity. TMs resolves the entity identifier problem and main-
tains the ability to track entity occurrences across organizations.
Another consideration when dealing with externally controlled business
information is how to physically define the data elements. The originating
organization may define data elements as having a numeric physical domain.
This is a problem when the business information is physically implemented
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