Thursday, 26 March 2009

S88 Part 1 update progress

The Update to Part 1 is apparently late, it has taken so far 3 years when it should have been done in 2, and there is still a lot of disagreement.

S88 defines hierarchical recipe management and process segmentation frameworks, which separate products from the equipment that they are made in, we all know that don't we?

But I am starting to wonder if the people working on the new version actually understand what that means.

Why do I say this? Well they are persisting with  their extension of the Procedural Model into the Equipment, so now they propose, for example, that the Recipe Procedure and Equipment Requirements can be passed to the equipment and that the equipment can contain the procedural hierarchy. 

In my opinion this is completely the wrong approach, and it will ruin Part 1.

 I really believe that they are confusing Controllers such as PLC's in packages with Equipment. And I can understand that, but I think there is a way round it.

I know that the team has been working hard to improve part 1 and there are no doubt some good things they have done. But that will all be undermined if they continue to follow their present path.

I got some good background from Lynn who was the one who managed to get the original Part 1 published, I won't quote all that he said, but here are a couple of points

I think the basic mistake we made in “part one – the original” was that we drew the diagrams that show interaction of the recipe with equipment control at multiple levels wrong.  We took the correct base case (recipe phase references equipment phase) and simply expanded it without coming to grips with what those things we offhandedly labeled “equipment operation” or “equipment unit procedure” above the equipment phase really are.  Once we all accepted the flawed diagrams we were stuck with that mode of thought and have been trying to explain how that works conceptually – and when we really try to do that it seem we really can’t. 

How did we get into this twisted solution?  It was pretty easy.  We knew we had a master recipe and that it needed to turn into a control recipe to make a batch.  So far, so good.  

We also knew that the master recipe needed to be able to direct the equipment at more than one level.  

Why?  Well there are two pretty good reasons why this flexibility could be needed.  First it is possible that someone has invented an operation or a unit procedure that doesn’t subdivide as Paul has pointed out. Secondly, we may just want to create the master recipe based on higher level procedural elements even though the equipment procedural elements the control recipe needs to address is an equipment phase.

 Lynn has much more to say, such as

 we were so taken with the genius of our hierarchy (it really is pretty neat) that we thought everyone should really use all levels of the model if they want to do the job right.  In most cases that is still not a bad idea.  But forgive us, we couldn’t stop there.  We – in our zeal – had to indicate to folks building packaged equipment that they really need to build these things in a modular way even if we don’t need to actually see anything below the operation or unit procedure level.  Thence cometh the diagram that shows the control recipe interacting with the procedural control of an equipment entity at the unit procedure level (or whatever) and – again in our zeal – we included the lower level parts of the hierarchy that we really thought people ought to know we thought they ought to build in

The huge mistake we all bought into and that has affected our thinking ever since is  that the diagram showed the control recipe connecting to an EPE at the unit procedure (or other) level when it was the master recipe that was really our concern

So it looks to me like like the update is just compounding rather than fixing a mistake.

I think they should make it absolutely clear that Equipment Control involves only the logic etc that actually connects to equipment. This of course means basic control but also the phase(+) logic that directly speaks to basic control.

As ever comments are welcome.

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