I have different Types of ECU states
ECU_STATE_1
ECU_STATE_2
ECU_STATE_3
Currently I have a scenario where I need to transmit different PDU for Different States, how can I send?
Related
In my UML model I have a system and its subcomponents that talk to each other. For Example, I have a computer and a RC robot where they talk via Bluetooth. Currently in the diagrams the flow is something like:
"Computer" triggers "setVelocity()" function of "RC car".
At this point, I want to refine the communication by saying that
computer sends "Movement" message
with velocity field is set to 100 and direction field is set to 0
which is acknowledged by RC car by sending ACK message
with message id "Movement" and sequence number X.
How do I do that?
EDIT: Clarification
Normally this is what my diagram looks like without protocol details:
But when I tried to add messages, there are at least 2 problems:
It seems like Computer first triggered the setVelocity() funciton and then sendBluetoothMessage() sequentially which are not sequential . The followings of setVelocity() are actually what happens inside that.
sendBluetoothMessage() is actually a function of Computer. But here it belongs to RC Car. (or am I wrong?) And the same things for ACK.
Thanks for the responses. You are gold!
Communication protocols in general
There are two main ways of representing the sending of a movement message between two devices:
A movement() operation on the target device, with parameters for the velocity and direction. You would typically show the exchange in a sequence diagram, with a call arrow from the sender to the receiver. The return message could just be label as ACK.
A «signal» Movement: Signals correspond to event messages. In a class diagram, they are represented like a class but with the «signal» keyword: velocity and direction would be attributes of that signal. ACK would be another signal. The classes that are able to receive the signals show it as reception (looks like an operation, but again with «signal» keyword).
In both cases, you would show the interactions of your communication protocol with an almost identical sequence diagram. But signals are meant for asynchronous communication and better reflect imho the nature of the communication. It's semantic is more suitable for your needs.
If you prefer communication diagram over interaction diagrams, the signal approach would be clearer, since communication diagrams don't show return messages.
Why signals is what you need (your edit)
With the diagrams, your edited question is much clearer. My position about the use of signals is unchanged: signals would correspond to the information exchanged between the computer and the car. So in a class diagram, you could document the «signal»Movement as having attributes id, velocity and direction:
In your sequence diagram, you'd then send and arrow with Movement (X,100,0). Signal allows to show the high level view of the protocol exchanges, without getting lost on the practical implementation details:
The implementation details could then be shown in a separate diagram. There are certainly several classes involved on the side of the computer (one diagram, the final action being some kind of sending) and on the side of the car (another diagram: how to receive and dispatch the message, and decode its content). I do not provide examples because it would very much look like your current diagram, but the send functions would probably be implemented by a communication controller.
If you try to put the protocol and its implementation in the same diagram, as in your second diagram, it gets confusing because of the lack of separation of concerns: here you say the computer is calling a send function on the car, which is not at all what you want. The reader has then difficulty to see what's really required by the protocol, and what's the implementation details. For instance, I still don't know according to your diagram, if setVelocity is supposed to directly send something to the car, or if its a preparatory step for sending the movement message with a velocity.
Last but not least, keep in mind that the sequence diagram represents just a specific scenario. If you want to formally define a protocol in UML, you'd need to create as well a protocol state machine that tells the valid succession of messages. When you use signals, you can use their name directly as state transition trigger/event.
If you really want to display this level of detail in a sequence diagram, it would look like this:
Notes:
For an asynchronous call, use an open arrowhead.
Use stacked bars to represent the call stack.
In the operation's argument list, write "argumentName=argumentValue" or just "argumentValue".
For messages for which the exact operation name is unknown or irrelevant, I use just a description without an argument list.
But be careful about which level of detail you want to show. Often, a sequence diagram becomes too complex if you display every operation in the call stack.
I was dealing with the same issue. I searched online and couldn't find something that I like. Hence I come up with this solution.
I show the communication ports on the sequence diagram and I draw communication dependent steps among port lines.
Here is a screenshot: my version of your problem.
Note: I haven't used bluetooth before so I am not sure about the acknowledge step. If this is something done automatically by the hardware( Like in the CAN Bus) I wouldn't draw it like this. I probabily wouldn't show it or I wouldn't add the function acknowledge(); and just draw the line between bluetooth port life lines.
I am working on representing interactions of a system that pulls conversations using webhook events in a system sequence diagram.
The actors of User, The system and the External System that sends webhook events that i have registered too already.
Is there a way to represent that or should i don't represent it at all since it's a system - system interaction only and it's not fired by the user?
A Webhook is usually an HTTP call. HTTP calls are synchronous. Synchronous messages are represented in a sequence diagram by an arrow with a filled triangular arrowhead (as opposed to asynchronous messages, which have an open arrowhead).
If you want to represent a Webhook event in a sequence diagram, you must draw the sending system and the receiving system as lifelines and draw an arrow from the sending system to the receiving system.
You may also choose not to represent this message at all. It depends on the audience. Who is using your sequence diagram? If they may be interested in the Webhook, then draw it. Otherwise, don't draw it.
It's the first time I draw an UML sequence diagram and I am not sure about few things.
I have a beacon which is a raspberry pi with bluetooth dongle. The server asks the beacon to start to change it's ID periodically(startIDRotation). The beacon broadcast and change them after each interval. When the smartphone wants to make a request, it includes the detected IDs, that the beacon is broadcasting in the request, with the requested file and send the request to the server. The server uses a logic represented in another activity diagram to decide if the user has access or not to the file and send back a response to the smartphone.
The first question is, is it correct to draw the line between the beacon and the smartphone? Because the beacon is not sending the IDs specifically to the beacon, it's just broadcasting them over bluetooth.
Is it possible to make a reference to another diagram type as the decision diagram is an activity diagram?
The server sends a post request to the beacon to start the rotation once, but it keep the state of the beacon and know that it's rotating its IDs. Shall this be represented as synchronous as I did or asynchronous?
If you have any other remark please feel free to correct me.
is it correct to draw the line between the beacon and the smartphone?
Yes. The line represents a message. And the life line represent an individual instance. When the phone receives the broadcast, this is the message sent. Since you did draw an open arrow, it indicates an asynchronous call. So that's perfect.
Is it possible to make a reference to another diagram type ? as the decision diagram is an activity diagram.
Yes. And you will do it the way you did, by adding a diagram reference. This represents details at the covered area. You can as well add arbitrary diagram references as shown below.
shall this be represented as synchronous as I did or asynchronous ?
It depends. Most likely you will have a synchronous communacation (closed triangle) here, because the server want's to know whether the message has arrived and the beacon acknowledges the start of the activity.
Yes, Beacon sends (broadcasts) an asynchronous signal to a Smartphone so there should be a message line depicting it.
By Ref you reference another sequence diagram. If you want to represent some behaviour (activity that is described with some activity diagram), use a synchronous request that pings back to the same lifeline (from Server to Server) with the call to activity responsible to perform privileges check. You can also put name of executed action inside the execution specification (make the thin rectangle somewhat wider to squeeze it in - see 17.2.4.4 in UML specification).
All your lines represent asynchronous messages. To show synchronous message use a solid line with a filled triangle as an arrowhead. To present response use dashed line with an open arrowhead. If your specific message should be synchronous or asynchronous depends on your needs. Broadcast is asynchronous all other can be either synchronous or asynchronous.
Considering the following block diagram:
I would like to model a continuous flow from PressureSensor.pressure to LPF.input.
Is it compliant to the SysML 1.4 specification to model this flow without using ports like in the following diagram?
Or do I have to use ports like in the following diagram?
From the SysML spec (1.3):
The main motivation for specifying ports and flows is to enable design
of modular, reusable blocks with clearly defined ways of connecting
and interacting with their context of use.
In other words: you can of course use direct connectors, but you will loose the ability to specify more details about what is going on along those connectors.
There is a difference between a non-abstract block and a port typed with an interface. A non-abstract block cannot be substituted. In contrast, something with a matching interface is easily substituted.
Think about two analogies:
One brand of HDTV will only work with one brand of cable TV box. If you want to use another brand of HDTV, you would have to emulate the original brand of HDTV completely because of some undocumented inter-dependency.
Any brand of HDTV that has an HDMI interface will work with any brand of cable TV box that has an HDMI interface.
Which situation would you rather have in your living room?
I am currently Designing UML Diagrams for a distributed backed made up of 8 nodes, which handle specific operations depending on the message received from the web Client.
The problem I have is that, the initial node which acts as the "Gate of Entry" to all messages and interactions generated from the Client-end, does not contain concrete operations that could be denoted as "Standard Use cases" but only a multitude of message flows pertaining to client-end use cases operations that flow throw this point.
But I also desperately require a method to show a process mapping between the client-end Use Case and initial node Use Case processes for consistency sake. If these messages are not mapped, the following the flow of operations from the Client-end to Server-end will be somewhat complicated.
Unfortunately due to the complexity of the system I have a problem of designing the whole System in a single diagram too.
Some Possible Improvisations considered
• To create "Place holder" like Use Case Ext. notation to indicate an extension.
E.g. The client-end has a place new order Use Case from which a message flows through initial node to the back-end nodes. In order to create connectivity indicate a Use Case which would read Place new order Ext. and this would signify a connectivity but would only point to a message flow.(But I am not sure if this practice is largely excepted in UML.)
• Only rely on Sequence and communication diagrams aim to show how "things" interact, each lifeline designating one of the system components. But I feel is that the correlation between Client-end and Back-end Use Case will not be very clear.
I also checked for similar problems on this forum and there were a few but did not explicitly answer my question.so I thought of posting this question.
Can someone please suggest what would be the best option in showing information flow in this highly event-driven distributed information system such as this - One of the above mentioned or any other options that I may have overlooked?
Have you considered using component diagrams, where the components have ports and the ports accept (and produce) signals instead of operations? A signal is basically a message / event.
You can also model signals as classes at the high level, or in as much detail as you need. You could model some of the properties of an application-level signal such that you can show how a component demultiplexes based on some property before forwarding the message along to an output port.