1.5.2 Entities
Entities can be anything that a user works with in their business. For example, in an order entry application, a Product, a Customer or an Order may be entities.
Entities contain elements that describe their characteristics. For example, a Customer entity may have elements such as Customer Code and Customer Name.
Each entity is assigned a type. This is very important in determining how entities interact with each other via relationships, and how they are implemented in the repository when the model is built. The four types of entity are:
For more details, refer to 5. Entities.
A Data Entity stores information, and is the most commonly used type of entity. For example, a Customer is a data entity.
Data entities are implemented as database tables in the LANSA Repository.
A Conceptual Entity describes information but does not store information. For example, Address information might be modeled as a Conceptual Entity.
Conceptual entities are implemented as fields in the LANSA Repository.
A Variant Entity is similar to a Data Entity in that it stores information. It is used in situations where elements are dependant on the value of another element. For example, there may be a type of Product called a Manufactured Product. Associated with a Manufactured Product may be information such as Drawing Number. There may be another type of Product called Supplied Product, which contains the Vendor who supplied the product.
Variant Entities are implemented as database tables in the LANSA Repository.
An external entity is used to define a physical or logical file which already exists in the LANSA repository. The key structure of this definition can be used in relationships with logical entities in order to extend the existing database.
No database tables are implemented from External Entity definitions.