<div dir="ltr">





<p class="gmail-p1" style="margin:0px;font-style:normal;font-variant:normal;font-size-adjust:none;font-kerning:auto;font-feature-settings:normal;font-stretch:normal;font-size:14px;line-height:normal;font-family:Arial;color:rgb(26,26,26)"><span class="gmail-s1" style="font-kerning:none">Peter</span></p><p class="gmail-p1" style="margin:0px;font-style:normal;font-variant:normal;font-size-adjust:none;font-kerning:auto;font-feature-settings:normal;font-stretch:normal;font-size:14px;line-height:normal;font-family:Arial;color:rgb(26,26,26)"><span class="gmail-s1" style="font-kerning:none">Re your comments:</span></p>
<p class="gmail-p2" style="margin:0px;font-style:normal;font-variant:normal;font-size-adjust:none;font-kerning:auto;font-feature-settings:normal;font-stretch:normal;font-size:18px;line-height:normal;font-family:Arial;color:rgb(26,26,26)"><span class="gmail-s1" style="font-kerning:none">1.</span></p>
<p class="gmail-p1" style="margin:0px;font-style:normal;font-variant:normal;font-size-adjust:none;font-kerning:auto;font-feature-settings:normal;font-stretch:normal;font-size:14px;line-height:normal;font-family:Arial;color:rgb(26,26,26)"><span class="gmail-s1" style="font-kerning:none">You have a machine which takes inputs and computes on those inputs, and makes decisions based on</span></p>
<p class="gmail-p1" style="margin:0px;font-style:normal;font-variant:normal;font-size-adjust:none;font-kerning:auto;font-feature-settings:normal;font-stretch:normal;font-size:14px;line-height:normal;font-family:Arial;color:rgb(26,26,26)"><span class="gmail-s1" style="font-kerning:none">that data. It's a state machine. Obviously. But there is more than one state machine it implements.</span></p>
<p class="gmail-p1" style="margin:0px;font-style:normal;font-variant:normal;font-size-adjust:none;font-kerning:auto;font-feature-settings:normal;font-stretch:normal;font-size:14px;line-height:normal;font-family:Arial;color:rgb(26,26,26)"><span class="gmail-s1" style="font-kerning:none">It also implements the qualitative state machine which doesn't work with the numbers but works with</span></p>
<p class="gmail-p1" style="margin:0px;font-style:normal;font-variant:normal;font-size-adjust:none;font-kerning:auto;font-feature-settings:normal;font-stretch:normal;font-size:14px;line-height:normal;font-family:Arial;color:rgb(26,26,26)"><span class="gmail-s1" style="font-kerning:none">the categorisation. This state machine is non-deterministic: from "Normal", performing a "withdraw"</span></p>
<p class="gmail-p1" style="margin:0px;font-style:normal;font-variant:normal;font-size-adjust:none;font-kerning:auto;font-feature-settings:normal;font-stretch:normal;font-size:14px;line-height:normal;font-family:Arial;color:rgb(26,26,26)"><span class="gmail-s1" style="font-kerning:none">action could lead you to "Normal" or to "Overdrawn". I agree with you that, in any given context,</span></p>
<p class="gmail-p1" style="margin:0px;font-style:normal;font-variant:normal;font-size-adjust:none;font-kerning:auto;font-feature-settings:normal;font-stretch:normal;font-size:14px;line-height:normal;font-family:Arial;color:rgb(26,26,26)"><span class="gmail-s1" style="font-kerning:none">you need to be clear which of these state machines you are talking about.</span></p>
<p class="gmail-p2" style="margin:0px;font-style:normal;font-variant:normal;font-size-adjust:none;font-kerning:auto;font-feature-settings:normal;font-stretch:normal;font-size:18px;line-height:normal;font-family:Arial;color:rgb(26,26,26)"><span class="gmail-s1" style="font-kerning:none">2.</span></p>
<p class="gmail-p1" style="margin:0px;font-style:normal;font-variant:normal;font-size-adjust:none;font-kerning:auto;font-feature-settings:normal;font-stretch:normal;font-size:14px;line-height:normal;font-family:Arial;color:rgb(26,26,26)"><span class="gmail-s1" style="font-kerning:none">I don't see what you can't have two different words for the same thing. They are usually called</span></p>
<p class="gmail-p1" style="margin:0px;font-style:normal;font-variant:normal;font-size-adjust:none;font-kerning:auto;font-feature-settings:normal;font-stretch:normal;font-size:14px;line-height:normal;font-family:Arial;color:rgb(26,26,26)"><span class="gmail-s1" style="font-kerning:none">synonyms. Synonyms are explicitly allowed for in the International Electrotechnical Vocabulary IEV).</span></p>
<p class="gmail-p3" style="margin:0px;font-style:normal;font-variant:normal;font-size-adjust:none;font-kerning:auto;font-feature-settings:normal;font-stretch:normal;font-size:10px;line-height:normal;font-family:Arial;color:rgb(26,26,26)"><span class="gmail-s1" style="font-kerning:none">———</span></p>
<p class="gmail-p4" style="margin:0px;font-style:normal;font-variant:normal;font-size-adjust:none;font-kerning:auto;font-feature-settings:normal;font-stretch:normal;font-size:10px;line-height:normal;font-family:Arial;color:rgb(26,26,26);min-height:11px"><span class="gmail-s1" style="font-kerning:none"></span><br></p>
<p class="gmail-p1" style="margin:0px;font-style:normal;font-variant:normal;font-size-adjust:none;font-kerning:auto;font-feature-settings:normal;font-stretch:normal;font-size:14px;line-height:normal;font-family:Arial;color:rgb(26,26,26)"><span class="gmail-s1" style="font-kerning:none">As you may have sensed by now, I view any confusion over the definition of terms in a Safety-Critical system as a serious safety issue.</span></p>
<p class="gmail-p1" style="margin:0px;font-style:normal;font-variant:normal;font-size-adjust:none;font-kerning:auto;font-feature-settings:normal;font-stretch:normal;font-size:14px;line-height:normal;font-family:Arial;color:rgb(26,26,26)"><span class="gmail-s1" style="font-kerning:none">In some contexts, synonyms are harmless. In others, they can kill.<span class="gmail-Apple-converted-space"> </span></span></p>
<p class="gmail-p5" style="margin:0px;font-style:normal;font-variant:normal;font-size-adjust:none;font-kerning:auto;font-feature-settings:normal;font-stretch:normal;font-size:14px;line-height:normal;font-family:"Helvetica Neue";color:rgb(10,10,10)"><span class="gmail-s2" style="font-variant:normal;font-size-adjust:none;font-feature-settings:normal;font-stretch:normal;line-height:normal;font-family:Arial;font-kerning:none;color:rgb(26,26,26)">When the </span><span class="gmail-s3" style="font-variant:normal;font-size-adjust:none;font-feature-settings:normal;font-stretch:normal;line-height:normal;font-family:".SF NS";font-kerning:none">Pilot Monitoring (PM) calls V1, the takeoff decision speed, the Pilot Flying (PF) </span><span class="gmail-s1" style="font-kerning:none">knows he/she is committed to take off; any attempt to abort takeoff after this point stands a high probability of injury and death.<span class="gmail-Apple-converted-space"> </span></span></p>
<p class="gmail-p5" style="margin:0px;font-style:normal;font-variant:normal;font-size-adjust:none;font-kerning:auto;font-feature-settings:normal;font-stretch:normal;font-size:14px;line-height:normal;font-family:"Helvetica Neue";color:rgb(10,10,10)"><span class="gmail-s1" style="font-kerning:none">Analogous conditions were redolent in every chemical reactor control project I ever participated in. For example, in a reactor with ethylene oxide as a feedstock, an excess of unreacted oxide meant you were cooking a bomb that could explode and kill everyone in the plant and the local neighbourhood to quite a large radius. Ethylene oxide vapour clouds are used in hyperbaric bombs.<span class="gmail-Apple-converted-space">  </span>In this case, the audible and visual alarms and ensuring state changes need to be unambiguous.<span class="gmail-Apple-converted-space"> </span></span></p>
<p class="gmail-p5" style="margin:0px;font-style:normal;font-variant:normal;font-size-adjust:none;font-kerning:auto;font-feature-settings:normal;font-stretch:normal;font-size:14px;line-height:normal;font-family:"Helvetica Neue";color:rgb(10,10,10)"><span class="gmail-s1" style="font-kerning:none">In these contexts, synonyms abominate the functional Safety countryside. They must be hunted down and eliminated with extreme prejudice - along with the “</span><span class="gmail-s4" style="font-variant:normal;font-size-adjust:none;font-feature-settings:normal;font-stretch:normal;line-height:normal;font-family:Arial;font-kerning:none;color:rgb(26,26,26)">qualitative state machine(s)</span><span class="gmail-s1" style="font-kerning:none">” they rode in on. Nature does not reward Humpty Dumpty engineering.</span></p>
<p class="gmail-p6" style="margin:0px;font-style:normal;font-variant:normal;font-size-adjust:none;font-kerning:auto;font-feature-settings:normal;font-stretch:normal;font-size:14px;line-height:normal;font-family:Arial;color:rgb(26,26,26);min-height:16px"><span class="gmail-s1" style="font-kerning:none"></span><br></p>
<p class="gmail-p7" style="margin:0px;font-style:normal;font-variant:normal;font-size-adjust:none;font-kerning:auto;font-feature-settings:normal;font-stretch:normal;font-size:14px;line-height:normal;font-family:"Helvetica Neue";color:rgb(0,0,0)"><span class="gmail-s1" style="font-kerning:none">My remedy is as follows:</span></p>
<p class="gmail-p8" style="margin:0px;font-style:normal;font-variant:normal;font-size-adjust:none;font-kerning:auto;font-feature-settings:normal;font-stretch:normal;font-size:14px;line-height:normal;font-family:Helvetica"><span class="gmail-s5" style="font-variant:normal;font-size-adjust:none;font-feature-settings:normal;font-stretch:normal;line-height:normal;font-family:"Helvetica Neue";font-kerning:none;color:rgb(0,0,0)">Let us abandon “qualitative” and pursue determinism with vigour. The labels state and mode qualify as “Design Entitles” </span><span class="gmail-s1" style="font-kerning:none">as defined in detail in IEEE Standard 1016 1998, the standard for Software Design Descriptions (para 5.2 Design entities), which states “</span><i>A design entity is an element (component) of a design that is structurally and functionally distinct from other elements and that is separately named and referenced.<span class="gmail-Apple-converted-space"> </span></i></p>
<p class="gmail-p9" style="margin:0px;font-style:normal;font-variant:normal;font-size-adjust:none;font-kerning:auto;font-feature-settings:normal;font-stretch:normal;font-size:14px;line-height:normal;font-family:Arial;color:rgb(26,26,26)"><span class="gmail-s6" style="font-style:normal;font-variant:normal;font-size-adjust:none;font-kerning:auto;font-feature-settings:normal;font-stretch:normal;font-size:14px;line-height:normal;font-family:Helvetica;color:rgb(0,0,0)"><i>The standard (bless its cotton socks) goes on to describe 10 attributes of a design entity in glorious detail. Here is our path to the forms of pure truth.</i></span><span class="gmail-s7" style="font-kerning:none"> So come with me back down the rabbit hole to Wonderland (where the inhabitants freely admit they are all mad - could the Cheshire Cat on a standards committee be a<span class="gmail-Apple-converted-space">  </span>benefit?)<span class="gmail-Apple-converted-space"> </span></span></p>
<p class="gmail-p1" style="margin:0px;font-style:normal;font-variant:normal;font-size-adjust:none;font-kerning:auto;font-feature-settings:normal;font-stretch:normal;font-size:14px;line-height:normal;font-family:Arial;color:rgb(26,26,26)"><span class="gmail-s1" style="font-kerning:none">See:</span></p>
<p class="gmail-p1" style="margin:0px;font-style:normal;font-variant:normal;font-size-adjust:none;font-kerning:auto;font-feature-settings:normal;font-stretch:normal;font-size:14px;line-height:normal;font-family:Arial;color:rgb(26,26,26)"><span class="gmail-s1" style="font-kerning:none"><a href="https://bit.ly/4fvg8Ha">https://bit.ly/4fvg8Ha</a></span></p>
<p class="gmail-p10" style="margin:0px;font-style:normal;font-variant:normal;font-size-adjust:none;font-kerning:auto;font-feature-settings:normal;font-stretch:normal;font-size:14px;line-height:normal;font-family:"Helvetica Neue";color:rgb(0,0,0)"><span class="gmail-s8" style="font-variant:normal;font-size-adjust:none;font-feature-settings:normal;font-stretch:normal;line-height:normal;font-family:Arial;font-kerning:none;color:rgb(26,26,26)">{Search text: </span><span class="gmail-s7" style="font-kerning:none">The labels state and mode qualify as “Design Entitles” </span><span class="gmail-s8" style="font-variant:normal;font-size-adjust:none;font-feature-settings:normal;font-stretch:normal;line-height:normal;font-family:Arial;font-kerning:none;color:rgb(26,26,26)">}</span></p>
<p class="gmail-p11" style="margin:0px;font-style:normal;font-variant:normal;font-size-adjust:none;font-kerning:auto;font-feature-settings:normal;font-stretch:normal;font-size:14px;line-height:normal;font-family:"Helvetica Neue";color:rgb(0,0,0)"><span class="gmail-s1" style="font-kerning:none">Where I pose the question:</span></p>
<p class="gmail-p11" style="margin:0px;font-style:normal;font-variant:normal;font-size-adjust:none;font-kerning:auto;font-feature-settings:normal;font-stretch:normal;font-size:14px;line-height:normal;font-family:"Helvetica Neue";color:rgb(0,0,0)"><span class="gmail-s1" style="font-kerning:none">… does any entity that issues standards or guides to systems engineering (IEEE, IEC, CENELEC, DoD, NASA, INCOSE, Nuclear Regulatory Commission) attempt to provide a precise definition of both state and mode in these terms? If not with your knowledge of systems engineering, could you attempt such a definition that might differentiate a state from a mode?</span></p>
<p class="gmail-p12" style="margin:0px;font-style:normal;font-variant:normal;font-size-adjust:none;font-kerning:auto;font-feature-settings:normal;font-stretch:normal;font-size:14px;line-height:normal;font-family:Helvetica"><i><br></i></p><p class="gmail-p12" style="margin:0px;font-variant:normal;font-size-adjust:none;font-kerning:auto;font-feature-settings:normal;font-stretch:normal;line-height:normal;font-family:Helvetica"><i style="font-size:14px">I trust this dialogue indicates a path to clarification.</i></p><p class="gmail-p12" style="margin:0px;font-variant:normal;font-size-adjust:none;font-kerning:auto;font-feature-settings:normal;font-stretch:normal;font-size:14px;line-height:normal;font-family:Helvetica"><i>Seriously guys, this mess does need to be cleaned up.</i></p><p class="gmail-p12" style="margin:0px;font-style:normal;font-variant:normal;font-size-adjust:none;font-kerning:auto;font-feature-settings:normal;font-stretch:normal;font-size:14px;line-height:normal;font-family:Helvetica"><i><br></i></p><p class="gmail-p12" style="margin:0px;font-style:normal;font-variant:normal;font-size-adjust:none;font-kerning:auto;font-feature-settings:normal;font-stretch:normal;font-size:14px;line-height:normal;font-family:Helvetica"><i>Over to you all.<span class="gmail-Apple-converted-space"> </span></i></p>

<p class="gmail-p12" style="margin:0px;font-style:normal;font-variant:normal;font-size-adjust:none;font-kerning:auto;font-feature-settings:normal;font-stretch:normal;font-size:14px;line-height:normal;font-family:Helvetica"><i>Cheshire cat-like, I'll fade out on this issue with a verse I composed to give young control systems engineers pause when tempted to wander off the path of determinism towards qualitativeness.</i><i></i></p>
<p class="gmail-p13" style="margin:0px;font-style:normal;font-variant:normal;font-size-adjust:none;font-kerning:auto;font-feature-settings:normal;font-stretch:normal;font-size:18px;line-height:normal;font-family:Helvetica;min-height:22px"><i></i><br></p>
<p class="gmail-p12" style="margin:0px;font-style:normal;font-variant:normal;font-size-adjust:none;font-kerning:auto;font-feature-settings:normal;font-stretch:normal;font-size:14px;line-height:normal;font-family:Helvetica"><i>A broken wing</i></p>
<p class="gmail-p12" style="margin:0px;font-style:normal;font-variant:normal;font-size-adjust:none;font-kerning:auto;font-feature-settings:normal;font-stretch:normal;font-size:14px;line-height:normal;font-family:Helvetica"><i>rocks on the sand</i></p>
<p class="gmail-p12" style="margin:0px;font-style:normal;font-variant:normal;font-size-adjust:none;font-kerning:auto;font-feature-settings:normal;font-stretch:normal;font-size:14px;line-height:normal;font-family:Helvetica"><i>beside a far</i><i>-</i><i>off sea.</i></p>
<p class="gmail-p12" style="margin:0px;font-style:normal;font-variant:normal;font-size-adjust:none;font-kerning:auto;font-feature-settings:normal;font-stretch:normal;font-size:14px;line-height:normal;font-family:Helvetica"><i>In pitch black<span class="gmail-Apple-converted-space"> </span></i></p>
<p class="gmail-p12" style="margin:0px;font-style:normal;font-variant:normal;font-size-adjust:none;font-kerning:auto;font-feature-settings:normal;font-stretch:normal;font-size:14px;line-height:normal;font-family:Helvetica"><i>faith was placed in men</i></p>
<p class="gmail-p12" style="margin:0px;font-style:normal;font-variant:normal;font-size-adjust:none;font-kerning:auto;font-feature-settings:normal;font-stretch:normal;font-size:14px;line-height:normal;font-family:Helvetica"><i>Christ!</i></p>
<p class="gmail-p12" style="margin:0px;font-style:normal;font-variant:normal;font-size-adjust:none;font-kerning:auto;font-feature-settings:normal;font-stretch:normal;font-size:14px;line-height:normal;font-family:Helvetica"><i>One of them was me.</i><i></i></p>
<p class="gmail-p13" style="margin:0px;font-style:normal;font-variant:normal;font-size-adjust:none;font-kerning:auto;font-feature-settings:normal;font-stretch:normal;font-size:18px;line-height:normal;font-family:Helvetica;min-height:22px"><i></i><br></p>
<p class="gmail-p12" style="margin:0px;font-style:normal;font-variant:normal;font-size-adjust:none;font-kerning:auto;font-feature-settings:normal;font-stretch:normal;font-size:14px;line-height:normal;font-family:Helvetica"><i>Cheers<span class="gmail-Apple-converted-space"> </span></i></p>
<p class="gmail-p12" style="margin:0px;font-style:normal;font-variant:normal;font-size-adjust:none;font-kerning:auto;font-feature-settings:normal;font-stretch:normal;font-size:14px;line-height:normal;font-family:Helvetica"><i>Les</i><i></i></p></div><br><div class="gmail_quote gmail_quote_container"><div dir="ltr" class="gmail_attr">On Thu, 21 May 2026 at 17:48, Prof. Dr. Peter Bernard Ladkin <<a href="mailto:ladkin@causalis.com">ladkin@causalis.com</a>> wrote:<br></div><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex">On 2026-05-21 03:10 , Les Chambers wrote:<br>
><br>
> Can I confirm that we agree the following statement is true?<br>
><br>
> In finite state modelling, the terms "mode" and "state" are synonymous.<br>
><br>
No, most definitely not.<br>
<br>
Mode and state for APs are two architecturally different things, but the (specification of) AP <br>
functioning is a finite state machine. i don't know why I need to repeat this.<br>
<br>
PBL<br>
<br>
Prof. Dr. Peter Bernard Ladkin<br>
Causalis Limited/Causalis IngenieurGmbH, Bielefeld, Germany<br>
Tel: +49 (0)521 3 29 31 00<br>
<br>
</blockquote></div>