Develop Your First Java Application in 20 Minutes › Project Entity and Triples › Field Inheritance

Field Inheritance

You use inheritance to define the properties of fields. Inheritance in CA Plex is defined in a simple way—using the is a verb.

Following are the triples you enter in the next series of steps:

• Project ID is a FIELDS/Identifier
• Project Description is a FIELDS/ShortDescription
• Project Start Date is a DATE/CheckedDateISO
• Project End Date is a DATE/CheckedDateISO

The FIELDS and DATE prefixes indicate that the objects concerned belong to the FIELDS and DATE pattern libraries, respectively.

The fields you defined previously have two different data types: character and date. These represent different kinds of fields. The Project ID field holds code that uniquely identifies a project, the description holds text, and the start and end dates hold dates. Currently, your model only indicates that those fields exist, and that they belong to the Project entity, but has no information about what type of data they store.

Inheritance is the mechanism that enables an object to adopt the properties of another more general (or abstract) object. By inheriting from pattern library fields, you enable your application to do the following:

• Validate data entered in the fields (which ensures, for example, that an end user does not accidentally enter February 31)
• Display data on the screen appropriately (such as displaying dates according to your Windows settings)
• Store data appropriately in the database (creating a text field in the database for the Project Description field, and date fields for the Project Start Date and Project End Date fields)