[Tutor] class question

[ALAN GAULD]

> >>I'm not sure I follow that  bit.
> 
> Say you have a master part, # 3245671, this is sort of a "primary  machined 
>number".  
>
> On the blueprint for this part, there will be certain  features that don't have 
>any dimensional 
>
> information, but instead have a callout  of some kind, i.e., "Hole D", or 
>somesuch.  
>
> At the top of the blueprint is  a "tab block" that is a table of "alternate 
>part numbers", 
>

Ah OK, Yes I've seen that used in produccing similar but different printed 
circuit boards
(my background is in electronics not foundry work)

> This was originally a convenience/cost saving thing, I  suspect.  

Almost certainly, and it makes it much easier to add new variants since only 
the tab values need changing.

What it means for you is that you need in parallel to your main app a 
mechanism for managing the identities through these differeing ID values.
Effectively a lookup table and mechanism for tracing designs from raw 
pattern to finished item.

> >>You may also find it useful to think through the state  model for your 
> castings/workpieces. That may help to constrain the number of  
>Actions/operations required.
> 
> ummm...what's a "state model"?  

It defines what operations can be done on your objects at any given time 
depending on the "state" of the object. As a simple example a light can 
be switched on when it is off and off when it is on, but it cannot be 
switched off if it is already off. In your can you will have a sequence of 
operations with dependencies between them such that certain operations 
can only be done after others have completed. Others cannot be done 
after others have been done. State models can be table driven which 
makes them highly configurable so that a single object can be loaded by 
multiple state models and effectively act like different object types without 
having to change the code.

HTH,

Alan G.