[sae-aadl] 2013-01-23 Error annex questions

[Peter Feiler]

Hi Myron,

Regarding E8 occurrence:
I have defined a property to express this probability distribution using a record.

(1)   An occurrence probability property indicates the probability with which the entity occurs, with which the property is associated. For example, as a property associated with an error source and optionally an error type token it indicates the probability with which a component is an error source.

OccurrenceProbability : record (

   ProbabilityValue : aadlreal;

   Distribution : EMV2::Distribution;

   )



Distribution : type enumeration (Poisson,Fixed);

I could have done it as  Occurrence: aadlreal units (poisson, fixed => poisson *1) applies to (all);
Using poisson or fixed as units literals requires a conversion factor as shown.

The concept of a type token is useful in the context of an instance model, e.g., as AADL model or as a Petrinet. In the context of AADL a type token represents an error event instance or an error propagation instance.
In the context of a representation such as Petrinet, the type token would represent a (colored) token.

Peter

From: Myron Hecht [mailto:myron.hecht at sbcglobal.net]
Sent: Tuesday, February 05, 2013 8:44 AM
To: Peter Feiler; Bruce Lewis External
Cc: sae-aadl at lists.sei.cmu.edu; 'Don Ward'; 'Boydston Alex K AMRDEC'; 'Hall Brendan \(MN65\'; 'Mike Whalen'; 'Silvia Abrahao'; 'Jean-Pierre Talpin'; 'Emilio Insfran'; 'John Hatcliff'; 'May Michael J Dr OSD ATL'; 'Preston John CIV (US'; nbrock at draper.com
Subject: 2013-01-23 Error annex questions

Hello Peter, Bruce, et. al.
Good morning all

First of all, thanks for the continuing improvment on the error annex.  I hope to be successful in making contact via Skype and LIve Meeting at 2:30 Valencia time (5:30 AM Pacifc Time).  However, in the interim, I have four questions (which could be interpreted as comments):

Section E.5:  Error type tokens:  The text says it is a token is an instance of a type, but it's not clear to me how they are used or why they are necessary.  An example might help.

Section E.8:

1. I couldn't find the concept of stochastic distributions for  as occurrence properties for error events in state machines (e.g.,

Fail: error event {Occurrence => poisson lambda  };  This concept is extremely important for quantitative modeling (note that it is related to but distinct from the notion of a duration and branch probability).  Did I miss something?



2.  Error states can be working or non-working.  Can more properties be specified (e.g., "hazardous", etc.)?



3.  As was the case in section E.5, I'm afraid I don't understand the role of tokens and how they are to be used in state machine model definitions (as opposed to how the models are analyzed).



I apologize for the lateness of these remarks, but I hope they are correct and useful nonetheless.



Regards





Myron Hecht









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