A scalechart is a species of statechart1 which communicates by means of signals' Scalecharts have a

1
ScalechartsRichard BosworthVisual Modelling
Group, Brightonhttp//www.cmis.brighton.ac.uk/Res
earch/vmg/
DrinksMachine
Signal start,deliver,empty
t,cIngredient
Ingredient
CoinBox
Main
p,a,xint
qint
A
/start
start a'0?p'50
paid
J
q'100
/enter(p-a)
K
pay(x) a'ax
/select
0.1 sec this.deliver q'q-1
0.1 sec qgt0
tea ?t.empty
coffee ?c.empty
C
altp
a?p
L
q0
/paid
ap
10 sec /c.deliver
10 sec /t.deliver
agtp
/this.empty
/change(a-p)

• A scalechart is a species of statechart1 which
  communicates by means of signals. Scalecharts
  have a formally defined semantics.

2
Specifying scalechart behaviour

• We obtain relationships between occurrences of
  signals. Occurrence i of signal s is expressed as
  si.
• lt means happened before 2
• co means happens concurrently with 3
• e.g.within orthogonal component Main
• starti lt selecti lt starti1 for all igt0
• this relationship is independent of the other
  orthogonal components - the semantics scales.

3
Specifying scalechart behaviour
a1
t
b1
a1 lt b1
a1
t
b1
a1 co b1
where a1,b1 are signal-occurrences
4
Automatic extraction of behaviour
/start
paid
/select
tea ?t.empty
coffee ?c.empty
10 sec /c.deliver
10 sec /t.deliver

• we grow all the trails from the root of the
  equivalent directed graph, until they mature
  (form a cycle) or terminate
• (F)
• (F,G)
• (F,G,H)
• (F,G,I)
• (F,G,H,F)
• (F,G,I,F)

5
Generation of partial orders

• from the trails, we automatically identify the
  cycles and parallel trails
• cycles (F,G,H,F), (F,G,I,F)
• parallel trails (G,H,F), (G,I,F)
• we mark the nodes which are inside parallel
  trails and also contained in a cycle (H and I)
• signal-occurrences from these nodes cannot be
  ordered
• we generate the partial-order relationships from
  the remaining nodes
• starti lt selecti lt starti1 for all igt0

6
Conclusions and future work

• given a formal semantics, it is possible to
  generate some behavioural specifications
  automatically from a scalechart
• the next step is to write a drawing tool which
  would automatically generate behavioural
  specifications as designs are drawn
• References
• 1. Harel, D. Statecharts a Visual Formalism for
  Complex Systems. Science of Computer Programming
  8 (1987) 231-274
• 2. Lamport, L. Time, Clocks and the Ordering of
  Events in a Distributed System. Comm.A.C.M. 21
  (1978) 558-565
• 3. Shields, M.W. Semantics of Parallelism.
  Springer-Verlag, Berlin Heidelberg New York (1997)