UML Use Case Diagram: Access included or extending Use Cases

Question

I am currently refreshing/altering my knowledge in software development because I will work in this area soon. We have learned a lot about UML diagrams and coding at University, but I have never brought it all together in a real Project. Therefore, I started to create a test web-app in Grails, and I wanted to begin with a requirements analysis and use cases too keep it close to reality.

My web-app should allow users to share recipes, find recipes and review recipes by other users. Every recipe has many ingredients, which are not just strings but rather entities so that calories, fat, protein and carbs can be used to automatically calculate nutrition facts of a certain recipe.

An ingredient can be added to the database by either a consumer or nutrition expert. If it is created by a consumer, it is only a "prospective" ingredient, meaning that it has to be verified by an administrator to become a "proper" ingredient -- otherwise it is marked, e.g. red text color.

This is my current use case diagram:

http://ubuntuone.com/0zDw9kEbj1BwtXjnCtxdwC

My question here is:

• Can extending or included use cases be accessed independently? If I do it as in the screenshot, can AddProspectiveIngredient be used without going through the CreateRecipe use case? Same question for included use cases.

EDIT: I don't think this is a duplicate of this question. In the linked question (1), I ask if I have to use the same actor for extending and included use cases as in the extended or including use case. In this answer (2), however, I merely ask about reuse between use cases.

In (1) it is all about the actor, and I am very satsified with this answer, as I now understand that the primary actor of an extending use case will inevitably be a subclass of the primary actor of the extended use case.

(2) addresses reusability of extending and included use cases, but is not necessarily connected to actors. It is about reusing them in other use cases. So if I have two use case CreateRecipe (a) and AddIngredientToDatabase (b), where (b) extends (a), can I also extend a third use case with (b)? Here I also received my answer, that they can and should be reused.

Maybe the questions seem similar because I created them on the same day with the same example and the answers both mention actors, which make them seem as duplicates. As they are both answered and I am satisfied with both answers, why close the questions as "too broad" or "duplicates"? If it was answered succesfully with different answers, how can it be too broad or a duplicate?

I am also happy to rephrase them slightly to keep them open, if I am told what the core issues. More answers and comments on the topics are still interesting to me.

Answer 1

Can extending or included use cases be accessed independently?

They rather should be. It is a good and correct style. Use case is some activity conducted between one or more actors and system. You should try not to show here some inner operations, that are not connected to users. Nothing invisible to users can be shown here. USER cases, remember?

So, no inner structure here.

You can collect some cases in groups - subsystems. But it is not inner structure, they are not IT systems, they are simply common themes of activities, obvious for users. Such subsystems should get later at least common UI style.

As for logic that could be used by users, it can be shown on other diagrams. Many diagrams can exist on this level - State machines, Activities, Timing. But don't try to show processes on the Use case diagram, too.

So, I don't know how well have you interviewed the client, but you use case diagram looks almost correct. Only the AddProspectiveIngredient Use Case should get its user or more.