Database Reference
In-Depth Information
Logical data modeling is the process of capturing the detailed business solution. The logical
data model looks the same regardless of whether we are implementing in MongoDB or
Oracle.
During conceptual data modeling we might learn, for example, what the terms, business
rules, and scope would be for a new order entry system. Logical data modeling is taking
these findings down to the next level and understanding all of the data requirements for the
order entry system. For example, conceptual data modeling will reveal that a
Customer
may place many
Orders
. Logical data modeling will uncover all of the details behind
Cus-
tomer
and
Order
, such as the customer's name, their address, the order number, and what
is being ordered. During logical data modeling, questions or issues may arise having to do
with specific hardware or software such as:
•
What should the collections look like?
•
What is the optimal way to do sharding?
•
How can we make this information secure?
•
How should we store history?
•
How can we answer this business question in less than 300 milliseconds?
These questions focus on technology concerns such as performance, data structure, and
how to implement security and history. These are all physical considerations, and therefore
are important to address during the physical data modeling stage, and not during logical
data modeling. It is OK to document questions like these if they come up during logical
data modeling, just make sure no time is spent addressing these questions until after the lo-
gical data modeling process is complete. Once the logical data modeling phase is complete,
you will have more knowledge about what is needed, and will be able to make intelligent
physical data modeling decisions including answering questions like these correctly.
The logical data model is also a great mapping point when multiple technologies exist. The
logical data model will show one technology-independent perspective, and then we can
map this business perspective to each of the various technology perspectives, similar to a
hub in a bicycle tire:
