Author Topic: How to model logical structure alongside physical ones?  (Read 3199 times)

JoMa

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How to model logical structure alongside physical ones?
« on: July 19, 2016, 05:44:29 pm »
Hi,

I'm modelling physical structures using SysML. Naturally the "part of"/ composite association is the right association between two blocks. Now I need a kind of "logical structure" which I do not like to model fully in parallel. Idea is to use a different association to show a dependency of physical elements to the logical unit. The logical unit cannot be treated as a assembly or so, as its parts do not necessarily have a physical connection. It is more a collection of elements which together perform a function.
I thought about using the nesting, but I am not sure if this is correct.
Any ideas?

Thanx in advance,
JoMa

PeterHeintz

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Re: How to model logical structure alongside physical ones?
« Reply #1 on: July 20, 2016, 04:16:04 pm »
For the logical structure typically I use the same relationship kinds as for the physical stuff.

For relations between logical and physical items I use typically  “Dependeny”, “Trace”, “Realize” or “Allocate”.

From SysML Spec.:
“15 Allocations - Defines a basic allocation relationship that can be used to allocate a set of model elements to another, such as allocating behavior to structure or allocating logical to physical components.”
Best regards,

Peter Heintz

JoMa

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Re: How to model logical structure alongside physical ones?
« Reply #2 on: July 20, 2016, 09:44:22 pm »
Sure, I can use «allocate». For people familiar with SysML this might be easy to read, but I also consider "non SysML-speaker"  ;)
Additionally, I am thinking about exporting structures from EA to APIS IQ-FMEA for FMEA.
So there will be the question: How can I know what a logical-physical relationship is? Maybe I'll need to use the function tree and the elements allocated to the function ...

PeterHeintz

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Re: How to model logical structure alongside physical ones?
« Reply #3 on: July 20, 2016, 11:47:39 pm »
May be we move in future to the same direction.
The day will come when I have to support FMEDA and maybe FTA as well.

I have not jet thought deeply on that, but for FMEDA I thing logical stuff is not relevant at all; it is the physical stuff and the behavior what matters.

I think about writing a SQL query, to get out the data needed for that further processing.

If logical stuff is relevant for you and you need to know if a connection connects logical stuff to physical stuff, you have several options.
E.g.
1.   Stereotype you connector
2.   Stereotype you items connected
3.   Put your items under related packages (logical package, physical package)
4.   …

I currently use the third options just to avoid a stereotype flood.
Best regards,

Peter Heintz

JoMa

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Re: How to model logical structure alongside physical ones?
« Reply #4 on: July 21, 2016, 01:12:37 am »
I think you option is a good compromise.
Exploring my problem, I found allocate is a good way and my also suit my needs if some rules are applied. I think I use isAbstract=true to identify the logical component.
By the way, these logical components are relevant for my S-FMEA as a group of physical components with their functions building a new function while being assembled in bigger system.

Thanks!

PeterHeintz

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Re: How to model logical structure alongside physical ones?
« Reply #5 on: July 21, 2016, 06:04:05 am »
isAbstract could work as long as you do not have abstract physical components.
I get the feeling that your logical stuff is some kind of grouping your physical things. I remember that SysML 1.4 has introduced something for grouping (did not use that up to now).
In my models logical stuff is something more technology independent. So in my logical model you would find something like “sound recording medium” and in my physical model you would find something like tape, LP, CD,….
Best regards,

Peter Heintz