Is it possible to leave provided interface without connecting to the required interface?

Question

I've drawn component diagram for the following scenario. User comes to the system and download content. (This is a part of my whole system). I wanna check whether the User has permission to download that content. Therefore I've used Access controller component. Access controller takes information of user from the database and it takes content from the database. After that it provides content to the user. That's how I've modelled this.

Can I leave provided interface without connecting to any required interface (like in Access controller. That is the content provided to the user after checking permission)?

Is there any better way to do this?

Any guidance would be most helpful. Thanks!!!

Answer 1

A component represents a replaceable self-contained part of a system that offers and requires interfaces to interact with the other parts of the system.

Can an unused interface be represented in the component diagram?

In a component diagram, we are free to chose which component we want to represent, and which interfaces may be relevant for the readers. It's perfectly legitimate to show call the interfaces that a component requires or offers, even if some are left unused. There are even good explanations for that:

• It could be a reused component with an interface that is provided but not yet needed elsewhere
• Your diagram may not show all the components, and for example not the component that requires exactly this interface.
• Your diagram may represent the internals of an enclosing component and the interface provided would document which of the internal components provide the interface that the enclosing component offers to the outside world.

But are you sure about the access control interfaces?

Are you sure that the user should provide the interface DownloadRequest? Shouldn't it be the Access controller that offer the interface DownloadRequest, and the User uses this interface to submit its requests?

Also, according to your narrative, the user requires content to be provided:

User comes to the system and download content.

Wouldn't a socket that requires Content be missing on the User side? And would the Access control provided Content be connected to exactly this socket? (i.e. no unused provided interface anymore)