Build state machines from type definition

[SanobLuj]

To simplify the creation of a state machine I added an initial implementation to build a state machine based on its type definition. Currently an existing node of a state machine type needs to be passed to the constructor. The StateMachineClass will then browse the type definition of this node to add the states, transitions, and causes defined by the type.

For executing a state, each State object provides an on_entry and on_exit method. These are executed on each state change for the current state and the next one. These methods can be overwritten to execute a certain behaviour.

Base classes for the ProgramStateMachine, FileTransferStateMachine, and ExclusiveLimitStateMachine have been added. However, none of these are fully implemented. The ProgramStateMachine is missing some functionality as it is described by the specification but can be used in a simple form (see example). About the FileTransferStateMachine and the ExclusiveLimitStateMachine I'm not sure how these are intenden to be used. At least there are some references missing, I guess coming from the TemporaryFileTransferType and a ConditoinAlarmType.

In addition to the state machine a ParameterSet implementation has been added. A parameter set is a flat list of parameters/variables. These are used e.g. within the device specification to organize the parameters of a device. Optionally the values of the parameters in the set can be subscribed.

There is the example server_typed_state_machine.py using a custom nodeset with several predefined state machines and parameter sets.

There is still some more work needed. However, would be glad if you guys can tell me what you think.

[oroulet]

I have no ideas what that stuff is about. @AndreasHeine isn'it the kind of things you are working on?

[AndreasHeine]

empty print?

[SanobLuj]

Better not? It's just for prettier prtinting ^^

[AndreasHeine]

f-string would be better!

[AndreasHeine]

@oroulet sure i implemented them as far as i needed them ... the rest i left open for reference! @SanobLuj is probably the first one using it else then me ^^

on the first look it appearance fine, the only thing i am not sure about is that internal/serverside subscription

[SanobLuj]

The original intention was to use this for implementing skills. Here are a few references describing the skill concept:

• Plattform I40 - Describing Capabilities of I40 Components
• OPC UA skills based on the program type using open62541
• SkillUp framework with skills based on the PackML state machine using milo

However, I thought it could be helpful for implementing all kinds of state machines that are defined by its type. I will make additional changes and give some more explanation soon.

@AndreasHeine the parameter set class could be used with a server or a client (source). That is why I have used the subscription there. Probably not the best idea to be used with the server ^^

[AndreasHeine]

@oroulet after a while and recap what i did ^^ the FiniteStatmachineType is abstract... so it should not be possible to instantiate it only subtypes... maybe we need to add a check for that in instantiate-method!? some refactoring is required as well...