Concepts and features
Concepts and features are often used and mentioned, but what exactly are they and when should you use them?
Concepts and features are the links between components (as seen in the image below) and are stored in a table on the appserver.
Concepts
A concept is a notion (comparable to a table, or an object in OOP) which is known to the appserver. Within the application a concept and a non-concept page cannot be told appart as they appear and act the same.
When do you need a concept?
A concept is always needed when 2 or more components need to know of the notion’s existence. This is done in order to prevent two components from creating two seperate instances of the same notion.
For example:
A component holds the basic product structure and contains a page called “Products”. On this page standard values such as the price, name and description are stored.
A customer asks for usefull actions related to the product which only apply to this specific customer. (say the customer wants to automatically decrease the price of a product by 3%, one year after it was first sold).
Since this seems to be a very customer specific question a second component is created. This component needs to know about the notion of “Product” in order to extend it.
Even if there is currently only one component which uses a new notion it can be worth making this new notion a concept. Most important is making sure that the concept does not already exist, is not in conflict with existing concepts and is fundamentally correct (A car even though it is a notion will most likely fit under the concept “product” or “system” depending on the context of the application). It ensures that other developers can find this concept and addapt it in their own work.
Features
A feature is a property of a concept (comparable to a column, or an attribute in OOP), which is known to the appserver. Similar to concepts the difference between a feature and a non-feature cannot be seen inside of the application. A feature always requires a concept and cannot exist without one.
When do you need a feature?
A feature is needed when 2 or more components need to know of the property’s existence. This ensures being able to use the value of the property in any component that is not the features origin (producer).