Imagine there are two statuses that an application is operating with, e.g. order status and shipment status.
When the order status is placed, the shipment status is blank.
When the order status is "paid", the shipment status is "ready to ship".
Then the shipment status is being changed to "assigned" through "shipped", "on delivery" and "delivered".
Should the order status be set to "Cancelled" the "shipped" or "on delivery" shipment status is changed to "being returned" and then "received at the warehouse".
What is the best way to describe the interaction between the two statuses on a diagram?
I know two types of diagrams that could be utilized here, but both have drawbacks for the task:
Activity Diagram - will perfectly describe the use cases, but is hard to read
State Machine Diagram - can only describe one status, so there can be two state diagrams, but it won't be clear how the statuses interact with each other.
What would you recommend?
Your UML model contains two state machines. A UML model can be visualized by one or more UML diagrams. A UML diagram may visualize any subset of the UML model, or even the whole model (see UML specification version 2.5.1, Annex A). Therefore, it is allowed to show both state machines in one diagram.
The dependencies between two state machines can be modeled in two ways:
Using 'signal send symbols' in one state machine to send a message to the other state machine. The other state machine uses these messages by means of 'signal receipt symbols'. See figure 14.32 of UML spec 2.5.1.
Using actions in one state machine and corresponding triggers in the other. This is the most convenient technique for your problem, as illustrated by the diagram fragment below. Actions are written behind a slash.
Related
What are the differences and similarities between the state machine diagram and flowchart?
So far I found that the state diagram shows us the actual change in the state, not the process or commands like in the flowchart.
In a state diagram, the nodes are states and the arrows correspond to something that happens that triggers a change of state.
In a flow chart, the nodes are actions or decisions, and the arrows correspond to the flow of control, i.e. what happens next. Flow chart are not UML. The closest UML diagram is an activity diagram that allows you to meodell more precisely everything you can model with a flow-chart and more (since the arrows can also represent an object flow).
Both can be complementary: an action/decision in a flow-chart could trigger events that cause changes of state. But it's not necessarily one for one: an action may cause several state changes without any evidence in the flow-chart that these may happen.
Short and simplified example:
Imagine an Order object. It may have the state received, delivey in preparation, delivery complete, invoiced. Each of these state tells what can happen next with the order. That'll be a topic for astate diagram.
Imagine a flowchart. These are different actions happening in sequence: Get an order from customer, Pick items of the orders from the inventory, Send items to the customer, Are all items sent?, if yes, Prepare and send invoice, if no, Find missing items and then go back to Pick items ... and continue from there.
As you see: both can tell the same story, but from a different angle with different details.
As you mentioned, a State Machine Diagram focus on display from which state to which state the execution goes based on the input.
Although a State Machine can be handled as a specialized form of a flow chart / activity chart.
Im new in UML,
I am recently in charge of a web application, this application manages projects through a flow of states. There are multiple users within the application and each of them can intervene in the flow in a certain state.
Therefore I want to represent this information through a state diagram for me and for future developers do not have to ask the same question again.
My question is: How do I represent the different actors in the state diagram and their intervention in each of them?
Do I need to create a different state diagram for each actor?
Is there a diagram to do this that you do not know?
Thanks.
This is my example diagram and how an actor can pass from stateX to stateY
You try to oversimplify your model.
Each actor has certain system functionality that they can run. These single functionalities are called Use Cases (UC) and you present them on a Use Case diagram. This diagram shows which Actor can perform what Use Case but it does not show a relation to a state. While each Use Case can have pre-conditions defining what has to be true before the UC can be performed and post-conditions declaring what will be true if the UC ends successfully (which in your case would both probably be something like "System is in State A"), UC diagram does not support showing pre- and post-conditions. You can always add them in the notes attached to a UC.
To have a clear view of the system State Machine you can use two diagrams. One will be UC diagram, the other one will be State Machine Diagram or to be more specific Protocol State Machine. Then on State Machine you depict which UC causes what system State change while UC diagram provides information which Actor is eligible for running specific UC.
Finally you can use Sequence Diagram if you want to model how specific flow of interactions in the system impact changes of the system state. You can present states and actors on a single diagram here, but it is not designed, cannot and should not be used to depict all possibilities on a single diagram.
Disclaimer
Next part of my answer is opinion based
/Disclaimer
Most probably I would use UC diagram and SM diagram together according to information you've provided.
On the notation
A side note to your diagram - ovals are used only on UC diagram and represent Use Cases. They are not associated with each other, only with Actors.
States are presented as rectangles with rounded corners (both in State Machine Diagram and Sequence Diagram).
My requirement : I want to come up with a suitable UML diagram based on the case which is described below. I need to know which UML will best suit this condition.
The case : Two object A and B in the form of "Application Forms" interacts with each other.Certain event in object A triggers a state change of object B.Both object interacts with each other for a Use Case.
I tried using State Diagram but it fails as here 2 object interact with each other to change the state of one object, whereas State diagram is suitable to depict state change of one object only without showing interaction with another object which is causing state change.
My requirement is to show both interaction and state change together in the same diagram.Is it possible?
Any suggestion on this which UML diagram is suitable for this?
UML uses two different diagrams for each behavior, one for State (State Machine Diagram) and one for Interaction (could be the communication diagram or the sequence diagram).
Since the Interface of a class doesn't change when it's state changes (by applying the State Pattern for example), the interaction should not really change from the perspective of the caller, sure, internally all kinds of things might be going on, but that should not really matter.
The way I'd model this is to describe which states your objects are in and which scenario will play out. That will result in a few interactions and possibly state changes. Then pick a new scenario, either using the end-state of the previous one as a starting point, or describing a new starting state.
That way each scenario is clearly defined, the interaction diagram shows how the objects interact, and multiple State Diagrams with the active state highlighted can show the changes in state and thus behavior of the different objects.
There is no diagram that gracefully combines both, since one (the state machine) is a static diagram, showing all possible options, while the other describes the interaction.
Sure you could play around with creative naming, as suggested (ObjectA/State) as your different objects in the interaction type diagrams, but it would not result in a very clear picture. What you're trying to describe here is a story, a sequence of events and how those events impact the different states of the objects. So your scenario's are the story on a high level, the communication diagrams the stories on a much more detailed level and the state machine diagram the snapshots of specific situations.
Model your states in the state diagram as such: (Object / ObjectState).
For example:
States (A/uninitialized) , (A/initialized), ...
Should work then.
State diagram, sequence diagram, communication diagram and the whole answer by #jessehouwing is fine, but I think there is an easier and more natural way:
(1) http://agilemodeling.com/style/activityDiagram.htm, Figure 3. Submitting expenses
Note that this is UML 1.4 activity diagram. Current UML notation is slightly diferent. Dashed lines represent Object flow : Chapter 3.90.2.2 Object flow ...Objects that are input to or output from an action may be shown as object symbols. A
dashed arrow is drawn from an action state to an output object, and a dashed arrow is drawn from an input object to an action state. The same object may be (and usually is) the output of one action and the input of one or more subsequent actions...
and (2) http://www.uml-diagrams.org/document-management-uml-activity-diagram-example.html
show an examples of how you can combine object states and UML activity diagram. The pictures are activity diagrams and the orange rectangles highlight points where objects with states (the part in [some state]) are shown. The purple rectangles show authors who were robbed.
Considering this situation:
...when an order is placed there is a check for availability, if is passed the preparation will start else the order is refused.
If the customer decides to pay with a credit card before starting the preparation the price of the order is locked on the credit card.
When the preparation is completed the order is delivered and if more than 30 minutes from the placement of the order have passed there is a discount of 50%.
My doubt is how to model the if condition in a state machine diagram, I would model it in the following way but I'm not sure it's the right way:
How should I model if conditions in a state machine diagram?
On a UML state machine diagram, conditionals are associated with transitions. The transition has a 3-part label in the form of "trigger-signature [guard]/activity". Guard is the conditional and must evaluate to true in order for the transition to be taken. All 3 parts of the transition label are optional.
From your problem description, I might define 3 states named "Waiting for Order", "Preparing Order", and "Delivering Order". There is a transition from "Waiting for Order" to "Preparing Order" and that transition could be labeled "order placed [order is available] /". I opted to leave off the activity because, from the problem description, I don't see any activity associated with this transition. You could maybe draw another transition labeled "order placed [order is unavailable] / refuse order". However, this transition would start from "Waiting for Order" and return to "Waiting for Order" because we don't change states when the order is refused. In this transition I included the refuse order activity because I assume there is some actual activity associated with refusing an order.
Alternately, I have seen transitions drawn which include a decision diamond where the arrow leading into the diamond is labeled with the trigger, one arrow out of the diamond is labeled with [guard] / activity and the other arrow out of the diamond is labeled with [else] / activity. I'm not sure whether this is technically correct UML though.
I think that the conditionals that you put in the entry activities for your Preparation and Delivery states are pretty good the way they are. Because those conditionals seem like they are associated with the activity that occurs upon entry into those states rather than any state transition.
In an UML state diagram, an if-condition should be modeled as a choice element, represented by a diamond-shaped symbol. The outgoing transitions must be marked with the corresponding conditions ("guards" in UML terminology) in square brackets. A trigger (event) and a behaviour (action) may be additionally given as described by kkrambo.
Example:
This and this gives some good advice on choices (and state diagrams in general).
This diagram (taken from here) might help:
So to answer your question, you didn't do it wrong, it's just a matter of style and readability. As far as I know, UML doesn't really define a standard way to represent conditionals. So just go with what looks best and makes sense.
It is not possible to define conditions inside of state element of state machine. Review you diagram. I think , you should some information put on diagram. For example, use choice element to define alternative transition paths. Or draw detailed diagram for "prepare order" and "payment" behaviors from Preparation and Delivery states.
It is not always possible to put all information on the exactly one diagram.
I am really unable to understand the real difference between these 2 diagrams. I mean both of these deal is "states" but I am not sure what deals with what?
It might seems so, but the difference is, activity diagrams describe activities and state charts describe states. So those models are orthogonal - you might imagine there is an activity between two states (something that occurs during the transition) and you might say there is a state between two activities. This is rather a simplification, but I think it might suffice to explain the difference, which is primarily focus, both diagrams are for describing behaviours.
An activity diagram is a special case of a state chart diagram in which states are activities (“functions”).
Two types of states:
– Action state:
-- Cannot be decomposed any further.
-- Happens “instantaneously” with respect to the level of abstraction used in the model
– Activity state:
--Can be decomposed further
--The activity is modeled by another activity diagram
For examle an elevator ride.
State chart could contain states such as: entering, standing still, exit, arrived.
These state transitions are caused by activity diagram events.
And events in activity diagram could be:
Walk in to the elevator, push button to correct floor, walk out of the elevator.
I would say these two diagrams overlaps each other.
Activity diagram is used to document the logic of a single operation/method, a single use case or the flow of logic of a business process. It is equivalent to flowchart and data flow diagram from structured development.
The state diagram depict (show)the state of objects as their attributes change from state to the other state. State chart modeling is used to show the sequence of states that an object goes through, the cause the transition from one state to other and the action that result from a state change.
Activity diagram is flow of functions without trigger (event) mechanism, state machine is consist of triggered states.