Re: MALT: A Multiway Alternation

[Adrian Lawrence <adrian.lawrence@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx>]

Gerald H. Hilderink writes:
> 
> At the WoTUG-21 conference, held at the University of Kent on 5-8 April 
> 1998, Adam K.L.Wong and Francis C.M.Lau wrote a paper titled "MALT: A 
> Multiway Alternation Construct for occam". They proposed a multiway guarded 
> ALT construct, called MALT, which can solve several problems, such as the 


> 
> Is there a notation in CSP that supports the multiway alternative 
> composition? Is the MALT really necessary or are there better solutions?

As I said at the time, MALT is not necessary if we introduce the event
merging operation "<*>" of HCSP. So e1 <*> e2 is the joint event consisting
of e1 and e2 happening "simultaneously". {"Simultaneously" because this needs
care in a timed version.} Adam did not disagree, although I am 
not sure that he really understood. HCSP|CSPP seems to me to be a necessary
extension of CSP if we are to handle codesign. But it also naturally includes
both priority and things like MALT as special cases. And gives them all a
precise (denotational) semantics. We *must* apply occam's strimmer: so
perhaps MALT can be included as an abbreviation, but not as a new primitive.
On 2nd thoughts, the razor is sharper than the strimmer.

Adrian

PS. BTW, `strimmer' is the sort garden power tool which cuts by a high speed
    rotating plastic string. Just in case it is unfamiliar word outside uk?
     


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Adrian Lawrence.
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