Does sequence diagrams involves actor?

[Ajay Xavier]

hi,

i am in the learning phase of sequence diagrams.My queries are

1.Does sequence diagarms involves any actor to initiate the action?

if there is no actor then who will initiate the action or how the control reaches the first class?

2. consider this scenario
i am having an webpage which has four radio buttons. based on this selection of the radio buttons i decide the next webpage to be displayed . how to express this selection in sequence diagrams?

please let me know the solutions.

[Scott Ambler]

1.Does sequence diagarms involves any actor to initiate the action?

if there is no actor then who will initiate the action or how the control reaches the first class?

Depends on what you're modeling. If you're modeling something which is initiated by an actor, or simply evolving an actor, then one or more actors will appear on your diagram. See Simple Example, Complex Example, and Stereotyped Example.

2. consider this scenario
i am having an webpage which has four radio buttons. based on this selection of the radio buttons i decide the next webpage to be displayed . how to express this selection in sequence diagrams?

Several ways:
1. You could model four different diagrams, one for each selection.
2. You could use a frame to model a switch statement. There would be four sections, one for each choice.
3. You could use a UI Flow Diagram instead, because they're better at modeling UI stuff than sequence diagrams (e.g. Apply the Right Artifact).
4. You could make the incredibly wild assumption that the person programing this logic isn't a complete moron and actually has the ability to code this based on the screen sketch/specication/verbal description.

Personally, I lean towards #4.

- Scott

[Ajay Xavier]

Thanks scott

[Ilja Preuss]

Originally posted by Scott Ambler:
4. You could make the incredibly wild assumption that the person programing this logic isn't a complete moron and actually has the ability to code this based on the screen sketch/specication/verbal description.

Personally, I lean towards #4.

[Kishore Dandu]

If there is a actor in the sequence diagram, it is mostly in the left end of the diagram.

I consider sequence diagram as the top 1/2/3 concept in a UML diagram of a module or system during development/implementation phase.

[Ilja Preuss]

Originally posted by Kishore Dandu:
If there is a actor in the sequence diagram, it is mostly in the left end of the diagram.

That's of course because in english, which most UML books are probably written in, is read from left to right, and the actor initiates an action (by definition).

I consider sequence diagram as the top 1/2/3 concept in a UML diagram of a module or system during development/implementation phase.

Sorry, the whole concept of distinct phases is a red rag to me - don't do that! Besides that, I'm not sure what you are getting at here - care to elaborate? (What does "the top 1/2/3 concept" mean? :confused

[Kishore Dandu]

Originally posted by Ilja Preuss:


Sorry, the whole concept of distinct phases is a red rag to me - don't do that! Besides that, I'm not sure what you are getting at here - care to elaborate? (What does "the top 1/2/3 concept" mean? :confused

I meant top 3 aspects(when I said top 1/2/3). Referring to different phases is a personal choice. If I do that or not is my own business

[Ilja Preuss]

Originally posted by Kishore Dandu:
I meant top 3 aspects(when I said top 1/2/3).

I see. Personally, I don't draw a lot of sequence diagrams. Can you explain *why* you draw them?

Referring to different phases is a personal choice. If I do that or not is my own business

Well, OK. You will just have to live with me pointing out that dividing software development into distinct phases based on activities like analysis, design, implementation and testing is today being seen as being responsible for many of the problems encountered in our industry.

[Kishore Dandu]

Originally posted by Ilja Preuss:


Well, OK. You will just have to live with me pointing out that dividing software development into distinct phases based on activities like analysis, design, implementation and testing is today being seen as being responsible for many of the problems encountered in our industry.

I presently work in a environment where IT is part of the organization(not the whole organization). In this kind of setup, phases in a system are more understood better by different players that participate in realizing the over-all system.

If I were working in a pure IT shop, i can understand what you are going towards.

[Ilja Preuss]

Originally posted by Kishore Dandu:
I presently work in a environment where IT is part of the organization(not the whole organization). In this kind of setup, phases in a system are more understood better by different players that participate in realizing the over-all system.

So you are saying that seperating your work in phases of, say, analysis, design, implementation and testing somehow helps with the communication of your non-it team members? Care to elaborate?

[Scott Ambler]

You might find Use Case Modeling Style Guidelines interesting. The usual approach, in Western cultures that read left to right, is to put people actors on the left and system actors on the right.

The page above summarizes techniques described in detail in my newly released Elements of UML 2.0 Style.

- Scott

[Kishore Dandu]

Originally posted by Scott Ambler:
The usual approach, in Western cultures that read left to right, is to put people actors on the left and system actors on the right.

- Scott

That is very funny(at least for me) I didn't know that going from left to right is a western thing. We in India(which is more closer to the east than west), we do write stuff from left to right(hindi, telugu and many other popular languages in India)

[Ilja Preuss]

Originally posted by Kishore Dandu:
That is very funny(at least for me) I didn't know that going from left to right is a western thing.

I didn't read Scott to mean that *only* Western cultures read from left to right.