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An -based Project.

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SCCharts are typically modeled using the textual SCT language defined as an Xtext grammar in KIELER. Generally, if you do not know which elements can be placed at a certain cursor position you are assisted by a content-assist that can be called pressing <Ctrl>+<Space>. It will display all possible valid elements also considering scoping of variables.

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[1] R. von Hanxleden, B. Duderstadt, C. Motika, S. Smyth, M. Mendler, J. Aguado, S. Mercer, and O. O’Brien. SCCharts: Sequentially Constructive Statecharts for Safety-Critical Applications. In Proc. ACM SIGPLAN Conference on Programming Language Design and Implementation (PLDI’14), Edinburgh, UK, June 2014. (pdf) 

ABRO Example

In the following we will describe some basic elements using the famous ABRO example:

@HVLayout
scchart ABRO {
  input bool A, B, R;
  output bool O = false; 
  region Main:
  initial state ABO "ABthenO" {
    entry / O = false;
    initial state WaitAandB {
      region HandleA: 
      initial state wA 
      --> dA with A;
      final state dA;
      region HandleB:
      initial state wB
      --> dB with B;
      final state dB;
    }
    >-> done with / O = true;
    final state done;
  }
  o-> ABO with R;
}           

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1. In the first line you see how an SCChart is defined using the scchart keyword where the ID of the SCChart will be ABRO. An optional label can be inserted after ABRO using "<LABEL>".
2. In the next three lines variables are declared, namely, A, B, R and O, where O is initialized with the value false. A, B, and R are inputs which must not be initialized and get there valued from the environment.
3. An SCChart typically contains concurrent regions which are introduced with the keyword region as shown in Line 69.
4. Every region must at least have one state, and every region must exactly have one initial state. An initial state ABO is defined for region Main in Line 76.
5. Every state is terminated by a ; as shown in line 11 for state HandleA.
6. If you like to specify internal behavior of a state, you can add concurrent regions to a state in { <regions> } as done for state ABO or state WaitAB.
7. Transitions outgoing from a state must be declared right before a state is terminated with ;. For example a transition from state WA wA to state DA dA is declared in Line 11.
8. Transitions can have triggers and effects which are separated by a dash: <trigger>/<effects>. Multiple sequential effects are separated by a ;. The transition in Line 11 declares just a trigger A (a dash is not necessary in this case), while the transition from line 18 declares only an effect O = true (here the dash is mandatory).
9. There are three types of transitions: 1. normal/weak abort transitions -->,  2. strong abort transitions o-> and 3. termination/join transitions >->.

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Detailed SCT Syntax of SCCharts Elements

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 scchart StateTransition {
  initial state A
  --> B;
  state B
  --> C;
  state C
  --> A immediate;
}

Variable

scchart Variable {
  int var1;
  bool var2;
  int var3 = 3;
  bool var4 = false;
  input int var5;
  output float var6;
  input output bool var7;
  initial state A
  --> B;
  state B;
}

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scchart MainSCChart {
  bool A[3];
  
  initial state S1 references InnerSCChart; 
}

scchart InnerSCChart  {
  input bool A[3];
  
  initial state S1
  --> S2 with A[0];
  
  final state S2;
} 

Annotations

The textual SCCharts language supports several annotations to influence the visual representation of the model.

Annotation are processed in sequential order.

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@synthesis[<key>] <value>

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Sets the synthesis option identified by <key> to the given value.

The available synthesis options for a diagram are displayed in the sidebar of the diagram view.

The values from the sidebar will be ignored if a corresponding annotation is present.

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Hostcode

You can also use you host language directly.

Function Calls

Call host code functions with dependency analysis. Use angle brackets to point to an extern function. You can also declare extern variables.

@hostcode "#include <stdio.h>"
@hostcode "#include <stdlib.h>"
scchart functionCall {
  output int i;
  extern int stdout;
  
  initial state getChar {
    entry / <printf("Enter an integer: ")>;
    entry / <fflush( stdout )>;
    entry / <scanf("%d", &i)>;
  }
  --> print with / <printf("The interger you entered: %d\\n", i)>; 
  				   <fflush( stdout )>;
  
  state print 
  --> getChar;
} 

Hostcode (inline)

Inline hostcode just as it is. Use the @hostcode annotation to add hostcode line before the tick function. Also use hostcode in single quotes as hostcode effects.

Important: Inline hostcode is not type-safe. Be careful.

@hostcode "#include <stdio.h>"
@hostcode "#include <stdlib.h>"
@hostcode "#include <unistd.h>"
@hostcode "#include <sys/time.h>"
@hostcode "struct timeval val;"
scchart hostcode {
  output int ms;
  
  initial state getChar {
    entry / 'gettimeofday(&val, NULL)'; 
    		ms = 'val.tv_sec'
  }
  --> print with / 'printf("Second: %d\\n", ms); fflush( stdout )';
  
  state print 
  --> getChar;
}

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Annotations

The textual SCCharts language supports several annotations to influence the visual representation of the model.

Annotation are processed in sequential order.

@diagram[<key>] <value>

@diagram[paper] true
scchart Testing {
  initial state A
  --> B;
  final state B;
}

@layout[<key>] <value>

direction

scchart Testing {
    @layout[algorithm] de.cau.cs.kieler.graphviz.circo
    region:
    initial final state A
    --> B;
    state B
    --> C;
    state C
    --> A;
}

scchart Testing {
    @layout[direction] UP
    region "up":
    initial state A
    --> B;
    final state B;
    @layout[direction] LEFT
    region "left":
    initial state A
    --> B;
    final state B;
}

@HVLayout
@VHLayout

@VHLayout
scchart Testing {
  initial state A
  --> B;
  final state B;
}

@collapse
@expand

scchart Testing {
  @collapse  
  region:
  initial state A
  --> B;
  final state B;
}

@hide

scchart Testing {

initial

 state A

  --> 

B;
  @hide
  

@HVLayout
@VHLayout

@VHLayout
scchart Testing {
  initial state A
  --> B;
  final state B;
}

@collapse
@expand

scchart Testing {
  initial state A
  --> B;
  final state B;
}

@hide

final state B;
}

Overview of Operators

The following briefly describes the operators that can be used in expressions.

Increment