Informatica Tutorials

Big Data Analytics

Creating a Logical Design

A logical design is conceptual and abstract. You do not deal with the physical
implementation details yet. You deal only with defining the types of information that
you need.
One technique you can use to model your organization's logical information
requirements is entity-relationship modeling. Entity-relationship modeling involves
identifying the things of importance (entities), the properties of these things
(attributes), and how they are related to one another (relationships).
The process of logical design involves arranging data into a series of logical
relationships called entities and attributes. An entity represents a chunk of
information. In relational databases, an entity often maps to a table. An attribute is a component of an entity that helps define the uniqueness of the entity. In relational databases, an attribute maps to a column.

To be sure that your data is consistent, you need to use unique identifiers. A unique
identifier is something you add to tables so that you can differentiate between the
same item when it appears in different places. In a physical design, this is usually a primary key.

While entity-relationship diagramming has traditionally been associated with highly
normalized models such as OLTP applications, the technique is still useful for data
warehouse design in the form of dimensional modeling. In dimensional modeling,
instead of seeking to discover atomic units of information (such as entities and
attributes) and all of the relationships between them, you identify which information
belongs to a central fact table and which information belongs to its associated
dimension tables. You identify business subjects or fields of data, define relationships between business subjects, and name the attributes for each subject.

Your logical design should result in (1) a set of entities and attributes corresponding to fact tables and dimension tables and (2) a model of operational data from your source into subject-oriented information in your target data warehouse schema.

You can create the logical design using a pen and paper, or you can use a design tool
such as Oracle Warehouse Builder (specifically designed to support modeling the ETL

Related Posts Plugin for WordPress, Blogger...

Please Share

Twitter Delicious Facebook Digg Stumbleupon Favorites More

Follow TutorialBlogs
Share on Facebook
Tweet this Blog
Add Blog to Technorati