I'm using the boundary-control-entity model for my sequence diagram, but in the alt fragment I'm confused about the interactions between the control and the entity in case the entity I'm adding contains duplicated fields.
shoudl I put select() before entering the alt fragment to show that the control is checking whether the informations are duplicated or no ?
My diagram:
5.Select() is the message I'm asking about
It's correct that way. The test condition is executed first. The alt fragment evaluates the existing conditions via the guards. These guards can contain anything and relate to something that happened any time (and not only directly) before.
Personal note: graphical programming is not really the silver bullet as it was praised in the 90s. SDs are fine to give an overview of collaborating objects. But when you try to go into details (like when using fragments) you soon recognize its shortcomings.
Related
I want to create a very basic sequence diagram for the first iteration of my app. I have a database of exercises, and I have a use case for creating, another for editing, and another for deleting an exercise. They are all very simple, and use the same elements and actors, like User, DAO, and Database. What I want to do is to create a single SD, that begins with the user asking to create an exercise, followed by the user asking to edit that exercise, and then asking to delete it. My question is: is this considered correct in a sequence diagram? I don't want to create 3 SDs almost identical to one another, and this seems like a simple way to represent all the information, but I don't know if this is correct by UML standards. Thanks.
From a standards conformance point of view, there is nothing in the UML standard, that imposes a relationship between your use case models and sequence diagramme models. So, no matter how many use cases you want to reflect in a sequence diagramme, it would be neither "correct" nor "incorrect".
From a personal point of view : What you are asking about is a question of modeling style, not conformity. As long as the people who are reading your models understand them, you can do whatever you want. So, something like this would be perfectly fine :
Hi, I would like to have the receptionist and the manager to be able to view work type and rates and subsequently update it. However, tech personnel can only view but not update. Is the diagram valid?
I read that extended use-case are initiated by actors that initiated the base case. How should I differentiate that tech personnel can only initiate the base case and not the extended case? Should I not place the extension association? What about included use-case?
Sorry if this question has been asked before.
You should neither «include» nor «extend»
View work type and rates and Edit work type and rates are perfectly valid independent use cases.
In general it is a bad idea to chain use cases together just because you usually do one after the other.
You should not try to model the sequence of activities with use cases. Use your business process analysis for that.
You can use the post- and preconditions to constrain the execution of use case. In fact your Edit use case doesn't really require the View use case in particular to be executed does it?. It probably only needs a work type to be selected. So it can be executed right after any use case that has a postcondition stating that work type is selected.
Which use case does that is irrelevant to the Edit use case, as long as a work type is selected before the use case starts. There might be 10 different use cases that result in a work type being selected.
The «extend» I consider to be simply wrong. Extending use cases are usually incomplete use cases that insert their behavior into a complete use case are a particular extension point defined in the extended use case. The extended use case in does not have any knowledge about the extending use case and does not need or use the results of this behavior.
The few cases I which I found «extend» use cases to be applicable were things like monitoring use case. For example a use case that monitors the number of open tickets in the system and sends an alert to an admin in case a certain threshold is surpassed.
If you still insist on linking the use cases together, for example in case you really mean that you can only edit rates after executing the use case View work type and rates I would do it the other way around. Include the use case View work type and rates from the use case Edit work type and rates, probably as the first step.
Both solutions (separate use cases, or include from Edit to View) solve your issue regarding the rights of different users as it is now clear beyond any doubt who can do what.
I'd model it this way:
Manager and Receptionist have the same roles in this context which is why I used a generalization. Without knowing the domain this seems okay, but it's just a proposal.
The <<extend>> is constrained by {not allowed for actor Tech} which clearly excludes this actor from entering this (optional) use case.
There is no need to also associate Receptionist with Update... since it's an extension of View..., except you want to be able to Update without Viewing first.
N.B. about <<include>>/<<extend>>: They are not meant as chaining use cases. The UML spec states (pp. 638):
Extend is intended to be used when there is some additional behavior that should be added, possibly conditionally, to the behavior defined in one or more UseCases.
and
The Include relationship is intended to be used when there are common parts of the behavior of two or more UseCases. This common part is then extracted to a separate UseCase, to be included by all the base UseCases having this part in common.
Now that <<include>> just looks like a bastard. A use case is about a unique added value. And this uniqueness can be questioned if there were behavioral recurrence in more than one use case. In any case these relations are often just taken as functional decomposition. And that would be plain wrong. From my POV the UML spec would be better without these relations.
In context of the above diagram it represent a pattern where you view something and only then can make it editable. It would well be perfect to have two individual bubbles without <<extend>> where you place a constraint in Update telling { can only be reached after View... }.
I would change extend by include. To update the work, you have to view it. It is mandatory to view it.
In your diagram, Manager and Receptionnist are equivalent, with this schema only, you can define one actor only. Or model that Manager inherits from Receptionnist.
And to avoid mistake, if you do that, you have to be sure that Receptionist and Manager can also activate the view use case without the update. Otherwise some associations have to be remove.
For example, the user can perform action A, action B or action C in a tool. Whether they choose A, B or C, the order of these actions and how many times they are repeated is up to the user and the reason why they choose A,B or C and why they are chosen in a particular order isn't clear. Also any action can be repeated again after another action has been done by the user.
EDIT: A more concrete example would be the creation of an image. The user can draw a shape, choose a new shape, choose a new colour and save the image. While drawing these 4 actions can be performed intertwined in any random order and in any random quantity, only guided by the whims of the user.
There is also the choice of creating a new image from scratch or editing an existing image to create a new image.
Very simple solution to you question is below.
Please do not omit the guards after decision node if you don't want to have an undeterministic behaviour of your activity. Decision node offers a token to the first flow that have true guard whereas the order of evaluating of the guards is not defined.
When modelling anything using any notation, it is important to remember what the purpose of is in creating the model, and who is going to use it.
If you simply omit the guards on arcs, then the model has no information describing how the system behaves. It cannot guide another developer to create the software, it does not record the intent of the designer.
The user is outside the system boundary, so the decision as to what action to perform is elsewhere. The system behaviour should be modelled as a condition of its state, inputs or events - these are what the system can operate on, and what developers expect to find in the UML model to guide them.
The exact UML construct used will depend on how that choice is communicated across the system boundary - an activity diagram may well not be the best way of communicating that, or you might use multiple diagrams for each interaction
The software being modelled does not make an unconditional choice, and the information in the model should reflect that with enough detail to be useful to the next person viewing it.
Normally a loop node should help you to solve your problem. If the flag isTestedFirst, the loop node is a while-do loop.
However this is not the easiest node of activity diagram.
It has three part : the setup part, the test part which is test at each iteration and the body part.
Maybe this image extracted from sparx documentation may help you :
Hope this help and maybe someone else may provide more details.
Well, you just leave away the guard:
Now the path can take any way. However, since there is a choice, it's the user taking the action and choosing the path he likes.
Edit Thinking a bit about the "natural" control flow it seems obvious, that preceding the ConditionalNode you find an action like Offer choice (e.g. in the concrete example of the OP: "draw", "choose shape", "choose color", etc.). So the outcome of the ConditionalNode is one of the users choices which in turn should have an appropriate guard. So the above is merely a sketch and can be regarded as incomplete. However, presenting this sketch to a reader would either make him "aha" or ask the question that came up my mind after thinking a while. Regardless of this, there will be just one path been taken after the ConditionalNode.
I have a class (let's call it "CLASS") in two different EA diagrams.
CLASS is the same object in both diagrams.
I want to change the attributes order in one diagram without it automatically changed in the other diagram too.
Any ideas?
Thanks.
That depends on what you want. Do you want to show different aspects of the same element in the two diagrams then you can play with the Feature and Compartment Visibility (Ctrl-Shift-Y)
If you want to show different elements, but one starting as a copy of the other then you can Copy the element (Ctrl-C) and Paste as duplicate (Ctrl-Shift-V)
You can not do that. And it does not make much sense to hide single attributes or methods of a class in specific diagrams. Either all or nothing (to show just the class). EA has a way to hide single stereotyped element parts for a whole diagram. But that's not what you're looking for.
Maybe you can explain WHY you want to do that.
No, you can't do that. As you note, it is the same element (avoid using the term "object" here; object is actually a type of element in UML, just like class, component, use case, etc).
Attributes can either be sorted alphabetically (by default) or in some custom order which you set manually, but EA stores this order with the class, not with the diagram. In other words, the attributes of one particular class will always be displayed in the same order in all diagrams.
New users often find this type of issue confusing or even frustrating, until they realize that a diagram is only a visualization of the underlying model data -- it is not a drawing. This is why you don't do search-and-replace in models: you make a change to an element in one place and it is immediately reflected wherever else that element is shown.
The only way to show two different attribute sort orders is to make a copy of the class, but then of course it's not the same element anymore.
Imagine that you have a simplistic GUI application. When you open it, there is an input box and a button placed on the application window. When you press the button you should see the entered value displayed in a popup message box. Of course, the button can be clicked without entering the value into the input box. Another possibility is that user exits the application right after opening it.
How-do you model this in UML activity diagram?
The typical UML elements like
a) decision node
b) fork/join node
do not seem appropriate to me.
According to my understanding a) is used when a check on certain set property is made and according to the outcome, the flow is routed somewhere; this is not appropriate since no checks are made
b) is not appropriate since it assumes parallel execution (?) which is not the case in the modeled situation.
There is a similar question here on SO though I don't understand what is meant by the suggested "Event element" in the accepted answer.
This seems not appropriate for a useful activity diagram:
Of course, the button can be clicked without entering the value into the input box.
Then there was no noteworthy activity, so nothing to model.
Another possibility is that user exits the application right after opening it.
Same here.
Most aspects of UML are rather GUI-unaware. You want to not spend your time modeling trivial cases but instead focus on actual workflows. Such diagrams will add way more value.
Nevertheless if you were to model something for your example, your assumption is basically right. The input validation is not bound to the willing user decision of leaving an input blank, though. You gotta do it anyway.
It is possible.
Use call operation for operation invocation on classes instance which represent GUI elements and also use Accpet Event Actions to receive events from GUI elements.GUI elements should be defined as standard classes. See Action Model part in UML Superstructure document. UML Website
It's a very interesting question. As already said in the previous post, a UI typically receive events and send informations in a visual form.
So, the particular UML actions (activity diagram) like "accept event" and "signal sending" are appropriate when the UI can receive different s events in no predefine order. Activity diagram are generally based on a "scenario" point of view, showing some scenarios but not all. Make events oriented activity diagram is more difficult; sometimes, "interruption region" have to be used.