A data model is a conceptual representation of data structures (tables) required for a database and is very powerful in expressing and communicating the business requirements.
Data Modeling Basics
A data model visually represents the nature of data, business rules governing the data and how it will be organized in the database. A data model is comprised of two parts logical design and physical design. Data Models are created in Top-Down-Approach or Bottom-Up-Approach. In Top-Down, data models are created by understanding and analyzing the business requirements. In Bottom-Up-Mode, data models are created from existing databases, which has no data models.
Data Models for OLTP databases are created by normalizing the data and for OLAP databases, data models are created by de-normalizing the data. Data Models can be understood as blue prints or like a map. It is not an exact replica of the database and it will not contain all the objects or code present in the database. Usually Data Models contain key database objects like tables, columns, relationships, constraints and so on.
Data Models help developers and architects to design the database. A Data Model is acts like a map for business and technical employees, which both parties can use to discuss requirements and implementation methods. At the end, data modelers are responsible for designing the data model and communicate it to the business and technical people.
Logical versus Physical Data Modeling
To become a data modeler, you need to understand the concepts of a database and modeling techniques. There are two parts how a data model is created.
First, a logical data model is created. This is the business presentation of objects in a database which represents the business requirements of an organization. Usually, object names are very descriptive and relationships between different objects are shown. This makes it very easy for every one to understand the business of the organization.
Second, a physical data model is implemented and used by the business. It contains most of the objects present in the database. From developers perspective, it shows the table name, column name, data type, null not null and so which helps them to code.
When a data modeler works with the client, he creates the logical data model, which represents business information and defines business rules. When a data modeler works with a database designer, his task is to implement a physical representation of the model in the database. The logical data model is also known as semantic model and will be discussed in another blog.
Star-, Snowflake and Galaxy – Data model schemas
When it comes to an implementation of a data model for a data warehouse or data mart, the developer has to choose between a data model schema. Further details will be provided in another blog entry.
About Tobias Riedner
Tobias Riedner foundet WYCDWD.com in 2015. He works and worked as innovator, consultant, analyst and educator in the fields of business intelligence and data warehousing. He learned a lot from the best consultants, managers und educators in the past and shares his knowledge worldwide. He works for a steady growing traditional company which is a leader in industry 4.0.