I was searching around for a simple example depiction on how it would look if class Professor and Class Student would both implement and interface from Class Person in a communication diagram or System sequence diagram.
I think its depicted as this a class diagram:
But i am curious if it can be depicted in a communication diagram or System sequence diagram ?
You can show anything in any diagram type. Citing p. 683 of UML 2.5:
NOTE. This taxonomy provides a logical organization for the various major kinds of diagrams. However, it does not preclude mixing different kinds of diagram types, as one might do when one combines structural and behavioral elements (e.g., showing a state machine nested inside an internal structure). Consequently, the boundaries between the various kinds of diagram types are not strictly enforced.
I think, that's more than clear.
I've been struggling to understand the transition from a UML Class Design Diagram to a UML Sequence Diagram for a school assignment. My design class diagram contains a central DataManager class that connects the use case control classes to the data table classes (ie. user, product, employee), however, do I need to include the data table classes in my use cases' sequence diagrams?
Design Class Diagram
My Sequence Diagram Attempt
So, in the end, I didn't phrase my question as I wanted to. I was asking if communications between the database tables and the data manager class should also appear in the sequence diagram. The answer is, they should. The whole point of having a sequence diagram is to guide a developer in the "development" of a class. For my diagrams, all messages I used for this communication had a standard sql() operation for each message.
I know that I can build a Class diagram from a database E-R Diagram (tables become classes, tables properties are the classes properties...)
But I'm looking for informations (or step by step like) to create a class diagram from a use case description (or even a sequence diagram).
(All I found now is that the sequence diagram objects becomes classes and the stimuli messages methodes)
Any idea ?
I used to TA in software engineering, and both create a class diagram from a textual definition as well as create a class diagram from a sequence diagram were regular exam questions.
Creating class diagrams from a specification should be covered in your lectures since its one of the most important things to learn. This site explains the workflow quite well in my opinion.
It is important to note, that in software engineering there never is just one solution. You can tackle problems in multiple ways each with their own benefits and problems. The most important step to learning is doing it yourself, just looking at solutions won't help you.
For creating class diagrams from a sequence diagram:
Objects are instance of classes, in most sequence diagrams there is only one instance of any given class. Therefore "objects become classes" is not technically correct but the right intention.
Messages represent method calls on the receiving object, ergo you need to add these methods to the class of the receiving object.
Any communicating classes need to be associated, else they could not call their methods.
We put focus on only modelling the information you can derive from the sequence diagram, e.g. in most cases you do not know multiplicities of associations.
Can someone give me an example of when is better to use State Diagram and when Class Diagram. Tnx in advance!
For what type of software system would you use state machine diagrams to model functional requirements?
For what type of software system is data modeling via UML class diagrams suitable?
A class diagram shows classes in their relation and their properties and methods.
A state diagram visualizes a class's states and how they can change over time.
In both cases you are talking about diagrams which are only a window into the model. The class relations define how the single classes relate to each other. A state machine can be defined for each class to show its states. In embedded systems you use state machines almost all the time but there are also state machines for business applications (you can do this if that).
This question reveals a very common misunderstanding. There are only thirteen types of diagram in UML. They're not used to describe different types of system, but to describe different aspects of the system you are documenting. Which you pick in any given situation is more a question of style, what you want to emphasize.
It is better to use state diagrams if you want to focus on how the system can go into different states in response to various events. Activity diagrams are better if you want to focus on activities being carried out in some order, sequence diagrams are better if you want to show messages being sent between entities.
The above are all types of diagram which show behaviour. Class diagrams are a different type of beast altogether, and show how structures of things fit together (as do package diagrams and component diagrams).
It might be worth pointing out that while UML does not include a "requirement" element type, the related modelling language SysML does. If you want to express a number of functional requirements on the form "the system shall" in a model, SysML is a better fit.
A state diagram shows the behavior of the class. A class model shows the relationship between two or more classes. It includes its properties/attributes...
A state is an allowable sequence of changes of objects of a class model.
I've had this discussion with my professor at college about UML diagrams .
He believes that sequence diagrams should be drawn before getting to class diagrams, but I think the opposite . I think after finishing the usecase diagram , the next diagram should be class diagram and after that we should get to sequence diagram.
Rational rose requires us to use the classes in sequence diagram, which are already in class diagram.
Can anyone help me with this?
I think you're both wrong. They should be drawn at the same time. As you're drawing your sequence diagram, you will undoubtedly come up with properties that you will need to keep track of the state, or that you hadn't thought of if you do the class diagram in a vacuum.
Of course, this is highly subjective and personal, but years of real-world experience (as opposed to academic theory) have taught me to work on both at the same time. MAYBE starting with the class diagram, but the class diagram invariably changes when you start going through process flows.
Well it depends a lot on how you plan to do things. I think it's a subjective matter. If you rather explain the actions performed for your usecases and after this has been done write the classes based on what you need to perform the sequences your professor is right.
But if you prefer to determine what the structure of your classes are and then adapt the action sequence to this then you would do the class diagram first and later the sequence.
In my experience I do them concurrently. I put the fundamental attributes to the class diagram but not the actions, and while I do the sequence diagram I add the methods and attributes that I need to the class diagram.
There is no one standard answer. There are several opinions, approaches and methods. In Unified Process I believe you first identify use case and then make realizations for them, e.g. sequence diagrams. As in use cases, there are actors and the systems and/or its parts interacting ina sequence. Actually this interactions should help you decompose your design and get to classes. Once you have classes on the analysis level, you can go further to design classess and design interactions. However these are quite a lot to draw in a diagram, most of the times code is the best documentation on this level, even generated diagrams are too large and more difficult to understand then code itself.
To prepare sequence diagram you need classes not the class diagram
You can prepare empty classes on the fly while in process of preparing sequence diagram....
Identification class objects in be part of preparing sequence or you can try to identify your objects before hand....
sequence is logical process while class diagram is end output
I don't think there is an order for creating diagrams since both are two different views of a system: class diagram structural (static) and sequence is behavioral (dynamic). I would start with sequence diagrams since you will discover more classes to create as you go through sequences. Do whatever makes sense for you at the time. If your doing more object oriented programming, I would consider doing classes before sequences.
Structural and behavioural models for all but the very simplest systems are naturally created simultaneously and iteratively, refining both over time.
You may have some method of "object discovery" such as CRC cards, which will yield a set of initial classes, with collaborations (the classes they interact with) and responsibilities, which informs both the methods they will need, and internal behaviour/state/activity.
You may then want to explore the use cases and scenarios using sequence or communication diagrams, this will expose the details of the required object communication and therefore inform the generation of public methods and relationships to refine the class diagram while at the same exploring the system behaviour which may yield further objects and classes to be created.
You may also want to explore the internal behaviour of classes, especially if they have stateful and/or active behaviour; activity ans state-machine diagrams are useful for this.
Either way I doubt that the use of Rational Rose is really the determinant of diagram creation order. Rational may require the classes on a sequence diagram to exist, but I imagine that they need not actually appear on a class diagram; they can probably equally be created on the sequence diagram and then later placed on a class diagram, or even created in the project explorer or whatever the equivalent is in that tool. Even if the only method of creating a class is to place it on a class diagram, that does not require you to refine and complete the class or its relationships before exploring interactions on a sequence diagram.
You need to buy some clothes, how you will proceed. You start choosing clothes first or you will decide first where to go? At the same time, will you go to shoe store if you want to buy shirt.
So both are iterative, but definitely first step is sequence on very high (component) level then drill down to class level sequence
You should first decide your application flow,means you should first draw a sequence diagram. It will show the flow of your application after this you should go for class diagram.