Despite
the sometimes religious wars of dimensional
modeling vs. third normal form, the
truth is that you need both in order
to answer the business needs of real
world.
Dimensional Modeling (DM) is a
favorite modeling technique in data
warehousing. In DM, a model of tables
and relations is constituted with
the purpose of optimizing decision
support query performance in relational
databases, relative to a measurement
or set of measurements of the outcome(s)
of the business process being modeled.
Practitioners of DM have approached
developing a logical data model
by selecting the business process
to be modeled and then deciding
what each individual low level record
in the "fact table" (the
grain of the fact table) will mean.
The fact table is the focus of dimensional
analysis.
It is the table dimensional queries
segment in the process of producing
solution sets. The criteria for
segmentation are contained in one
or more "dimension tables"
whose single part primary keys become
foreign keys of the related fact
table in DM designs. The foreign
keys in a related fact table constitute
a multi-part primary key for that
fact table, which, in turn, expresses
a many-to-many relationship.
In a DM further, the grain of the
fact table is usually a quantitative
measurement of the outcome of the
business process being analyzed.
Dimension tables are generally composed
of attributes, measured on some
discrete category scale that describe,
qualify, locate, or constrain the
fact table quantitative measurements.
In contrast, conventional E-R (3nf)
models are constituted to
(a) Remove redundancy in the data
model
(b) Facilitate retrieval of individual
records having certain critical
identifiers and
(c) Therefore, optimize On-line
Transaction Processing (OLTP) performance.
Third normal form is a model of
entities, relationships, and attributes.
It usually represents our world
in a logical, mathematical sort
of way, like the "who, what,
when, and where" approach to
journalism. Any departure from this
"normal" model is called
de-normalization.
We have deep expertise of above
modeling techniques which gives
you choices by letting you physically
implement either or mixed logical
model.