Following is a safety controller with input and output
Condition given below for designing a state machine:
Here SignalOk, SignalWeak and SignalLost are measurements signal quality of steering angle. SteeringAngle signal itself contains the original steering data. In case of 3 consecutive SignalOk, system controller will output ValidSignal with the steering angle data. In other cases, signal will be considered as CorrputSignal. I am using UML 2 state charts(Harel charts). This is so far what I have done:
N.B.:Parallel states and broadcasting is not supported yet, but nested states are supported.
I don't know how to model this stream of inputs in state machine, any kind of help will be appreciated.
First I would recommend renaming the states, so that they don't resemble actions. I suggest to name them First Ok received, Second Ok received and Ok confirmed.
Since the SteeringAngle shall be ignored the first two times, the only transition triggered by it should be an internal transition in Ok confirmed. This transition will also invoke ValidSignal.
Nothing is specified about the order of SteeringAngle and SignalOk. Therefore, SteeringAngle should be deferred in Second Ok received. This way, even it it comes first, it will stay in the event pool.
Any reception of SignalWeak or SignalLost should return to Ready. You could do this with a local transition of Operational to Ready.
One additional recommendation: Define an Initial state in Operational and target the SystemOk transition to Operational. The effect is the same, but it results in a better separation of the two top level states.
Related
how would you drow diagram - example A or Example B or both are fine? In Example A there is an event, one extra task and process is back in the main flow. Example B - if the event occurs process is not back in main flow. Is it correct to draw process like in example A? Examples enclosed. Thank you in advance for help.
I draw examples (enclosed) and checked in BPMN specification but still have doubs.
I would go a step further and put a gateway in front of "Application Analysis" and then draw the arrow from the message event to that gateway (so the gateway is only used to join, doesn't need a condition, it is best practice, you could draw the arrow from the message event directly back on the task itself and it would express the same thing).
The basic reasoning is that you shouldn't have multiple tasks for the same thing in the diagram unless it is really at a different stage in the workflow.
However it isn't exactly the same as your workflow, because like this the customer could change the loan amount multiple times and not just once.
There are some problems:
I think you want to make the message event interrupting, otherwise you grant both loans, the original one and the changed one.
After "Application Analysis" there should probably be a gateway that checks the result of the analysis and only if it was ok you grant the loan.
I'm struggling to understand how timed games work together with (broadcast) synchronization in UPPAAL (TiGa / Stratego). Imagine the following example:
Forcing the environment
Here, the edge receiving an event over the broadcast channel a is controlled by the environment. From what I understand, the semantics of broadcast synchronization enforce a transition in P2 from the initial state to P2.F as soon as the event is sent in P1 (assuming edge P2.<init> -> P2.F is enabled).
So naturally I would expect a strategy to exist for the controller to force the environment to transition to P2.F. This strategy would simply tell the controller to take the transition P1.<init> -> P1.F.
However, when calling the query control: A<> P2.F, UPPAL TiGa and Stratego tell me that there is no such strategy and that the counter-strategy for the environment is to stay in P2.<init> is simply wait forever.
Being forced by the environment:
When controller and environment switch sides, it looks a little different.
In that case, the query control: A[] (not P2.F) is not satisfied, indicating that there is no chance for the controller to prevent the environment from forcing a transition to P2.F.
In both examples A[] P1.F imply P2.F and E<> P1.F hold.
I'm curious about why the environment seems to be able to evade a transition that a controller can't, or if anyone can point me to some place where the timed game semantics of UPPAAL TiGa or Stratego are explained in detail.
Thank you all!
I have a BPMN diagram (see below) with some errors that I can't seem to figure out. The diagram depicts the Produce Magazine Article Process, where the writer and Researcher are freelancers who work together to write articles for various publications.
Bigger version: BPMN diagram
There is a bunch of errors here, three of them are logical (two are related), one is BPMN syntax.
Let's start with the syntax.
The message is always a communication between two separate pools s it has to cross pool boundaries. In your case, you have depicted Freelancers as a single pool, so Send information, being between lanes but not pools is a syntax error. Before suggesting a solution though, I will focus on logical errors.
Time event is not used to show the fact that some time goes by between the activities. That is actually something natural in the process It is used to indicate that the flow of time is a trigger of the next action(s). For instance, 7 days after choosing a topic the Publication might contact the Researcher to check on the progress. That would be indicated by timed event. In your case, it seems that the flow continuation is triggered by passing messages so you should indicate it as an Incoming message event. You actually do that in 2 places, one that is obvious (Get article as a "result" of time event) and the second that correlates to a second problem.
The second thing that most probably is a logical question is that since we are talking here about freelancers, most probably Researcher and Writer are two separate entities, not one organisation as your current diagram suggests. If that is the case, you should have them represented as two separate pools. Then your message would be judged, but still rather than "Wait for information" time event you should have "Receive information" incoming message event (that is BTW the starting event for the Writer pool - similarly receiving Article request by Researcher should be handled by Incoming message event).
If you prefer to depict the Freelancer as one "organisation", then you should completely abandon the time event (as again you have used it as an indication of time passing and as I have explained earlier that is not how it should be used). You have a simple flow, where once Researcher finishes their job, it is passed to Writer who carries it over from there. In such case, you should have a simple action flow (solid line) between the actions themselves.
It is also a good practice to be consistent in using End events (and at least recommended - some BPM engines verify that) to always have an End even for every branch of a process. You are missing one or two, depending on how are you going to approach the Freelancers part. Similarly, you should have a Start event for Publication.
Below are the two options shown in the form of diagrams. Note that I also did some minor changes to handle the insufficient information case by Publication. Otherwise, they will be stuck forever waiting for the article to come.
Option with Freelancers as separate pools:
Option with Freelancers considered as a single organisation
We have a situation where there are 2 modules, with one having a publisher and the other subscriber. The publisher is going to publish some samples using key attributes. Is it possible for the publisher to prevent the subscriber from reading certain samples? This case would arise when the module with the publisher is currently updating the sample, which it does not want anybody else to read till it is done. Something like a mutex.
We are planning on using Opensplice DDS but please give your inputs even if they are not specific to Opensplice.
Thanks.
RTI Connext DDS supplies an option to coordinate writes (in the documentation as "coherent write", see Section 6.3.10, and the PRESENTATION QoS.
myPublisher->begin_coherent_changes();
// (writers in that publisher do their writes) /* data captured at publisher */
myPublisher->end_coherent_changes(); /* all writes now leave */
Regards,
rip
If I understand your question properly, then there is no native DDS mechanism to achieve what you are looking for. You wrote:
This case would arise when the module with the publisher is currently updating the sample, which it does not want anybody else to read till it is done. Something like a mutex.
There is no such thing as a "global mutex" in DDS.
However, I suspect you can achieve your goal by adding some information to the data-model and adjust your application logics. For example, you could add an enumeration field to your data; let's say you add a field called status and it can take one of the values CALCULATING or READY.
On the publisher side, in stead of "taking a the mutex", your application could publish a sample with the status value set to CALCULATING. When the calculation is finished, the new sample can be written with the value of status set to READY.
On the subscriber side, you could use a QueryCondition with status=READY as its expression. Read or take actions should only be done through the QueryCondition, using read_w_condition() or take_w_condition(). Whenever the status is not equal to READY, the subscribing side will not see any samples. This approach takes advantage of the mechanism that newer samples overwrite older ones, assuming that your history depth is set to the default value of 1.
If this results in the behaviour that you are looking for, then there are two remaining disadvantages to this approach. First, the application logics get somewhat polluted by the use of the status field and the QueryCondition. This could easily be hidden by an abstraction layer though. It would even be possible to hide it behind some lock/unlock-like interface. The second disadvantage is due to the extra sample going over the wire when setting the status field to CALCULATING. But extra communications can not be avoided anyway if you want to implement a distributed mutex-like functionality. Only if your samples are pretty big and/or high-frequent, this is an issue. In that case, you might have to resort to a dedicated, small Topic for the single purpose of simulating the locking mechanism.
The PRESENTATION Qos is not specific RTI Connext DDS. It is part of the OMG DDS specification. That said the ability to write coherent changes on multiple DataWriters/Topics (as opposed to using a single DataWriter) is part of one of the optional profiles (object model profile), so no all DDS implementations necessariiy support it.
Gerardo
I have LV application, where user can specify input and output channels for connected DAQ device. I want to synchronise both channels using trigger on the input channel, with analog output start as a trigger source (image on this site shows part of what I am trying to do).
My problem is that user specifies only IO channels, but how can I switch from a DAQmx Physical Channel (e.g. cDAQ1Mod4/ao0) line into source for the DAQmx Start Trigger block (probably /cDAQ1Mod4/ao0/StartTrigger in this case, but I am not sure) ?
I've found an answer, but I am not really happy with this way of solving a problem. I have to scan whole devices tree and compare channel or module names available for each device with the name of my selected channel ... simple channel property would be easier, but haven,t found any property which could give me what I need.