What can be said about extending entities?

Entity extensions are defined in etx files, which are essential in the process of extending the functionality of existing entities within Guidewire applications. This capability allows developers to add custom behavior or fields to an entity without modifying the underlying entity itself, preserving the integrity of the base code and simplifying future upgrades.

The etx file serves as a blueprint for the extension, detailing how the new fields or functionalities will integrate with the existing entity. By using these files, developers ensure that any changes made during the extension process are structured and manageable.

The other statements do not hold true within the context of extending entities. For example, extensions are permitted, and there are established conventions regarding naming. While extensions have specific naming conventions, they do not necessarily have to end with _Add, nor must fields be removed when extending an entity; instead, new fields can be added to enhance functionality.