Need an entity relationship
diagram for an information management requirements specification and
want practical timesaving suggestions?
objective of an entity relationship diagram is to show the business
apply to an organizations data. It contains entities, which are things
of interest to a company, and relationships, which are relationships
between entities. It also documents volumetric data so that we know
what the initial data storage requirements will be together with the
customer, product and order might be considered something of interest
to an organization. A simple relationship between these entities might
An attribute is something
that further describes an entity,
e.g. customer first name, customer last name, or product name.
- Customer places one or many orders;
- An order must be placed by one, and only one,
- An order must be for one or many products;
- A product may be ordered by one or many orders.
Why is a
- all entities of interest to a project;
- all attributes for each entity; and
- a definition of each entity and attribute
together with an example.
An entity relationship diagram is an excellent communications tool,
which can be
used to confirm business requirements and provide direction to the
architecture and design team as they move forward with physical
If we are building a data warehouse, it
provides the business rules that are needed to ensure data integrity
e.g. if an order is received from a source system and is not related to
a customer, then we have a data quality issue—We should not load this
data into the warehouse because it fails the business rules.
What is a
quick way to create an entity relationship diagram?
An information management project should use
the enterprise data model as a starting point.
a perfect world, the enterprise data model is a fully attributed model
but in reality, it may only include key entities and relationships.
data modeler should involve the business team in data modeling
sessions. There are data model resource books, which can also be used
as reference or as a starting point, if there is no enterprise
does the model provide?
Do we always
need a logical model?
- Confirms business rules;
- Is used as the “target” for data movement
mapping and helps ensure no data is overlooked;
- Provides direction to the architecture and
design team to start physical database design; and
- Helps make important decisions about facts and
dimensions required for business intelligence purposes.
- If the project is building a data warehouse,
than a model is required;
the project is extracting data from a source system and loading it
directly to a data mart (without using a data warehouse) then it is
desirable, but can be omitted; and
- If the project involves
extracting data from source systems and consolidating it into a data
a target system (without storing it a data warehouse or data mart),
then it may not be required.
An entity relationship diagram is a mandatory requirement for most
management projects. The enterprise model should serve as
the starting model and a data modeler needs to work with the business
team to finalize the model. A data model is not required for all
projects and may require an exception to the project management