1. Chapter 5
SDL - Data
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2. Contents Data Simple data in SDL
Dynamic generation of process instances
SDL symbol summary
Example
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3. 5.1: What is Data?
The bytes of a computer normally play two different roles. Some bytes are parts of the program, while others are manipulated by the programs.  control and data
Data is usually used to represent spatial information whereas control is used for temporal information about behavior progress.
Data exists over time.
Abstract data types
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4. 5.2: Simple Data in SDL Cid (integer) Digit (integer)
DCL no_dig integer
DCL cardid integer
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5. Declaration of Variables
DCL is the keyword which precedes data declaration.
A list of names follows DCL and the line is terminated by a sort name.
The common predefined types: Boolean, Character, Charstring, Integer, Natural, and Real.
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6. Variable Declaration & Manipulation
A process may locally use and manipulate data stored in variables.
The variable may be initialized when it is created at interpretation time to a certain value.
During a transition the process can use and manipulate its own local variables, using the task construct.
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7. Task Symbol Used to set the values of data by assignments.
A task symbol may contain a list of assignments separated by commas.
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8. Task Symbol (II)
Variable occurrences on the right of an assignment operator means extracting the value from the variable.
Operations are associated with types.
Variables on the left of the assignment operator are modified to become the expression value of the right-hand side.
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9. Input Signal with Data
Values carried by input signals must be transferred to local variables
There is no way to access the input signal again after it has been consumed.
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10. Decision Symbol
Used to choose between different alternative courses of action upon a question.
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12. Output Signal with Data
Full expression can be in signal parameters, not only variables.
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13. Process PanelControl
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14. Process PanelControl (II)
A special initialization construct
DCL trial_no Integer := 0;
Output symbol where the destination is a process name
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15. TIME, Duration, and TIMERS
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16. TIME, Duration, and TIMER (II)
Time: data type
NOW is a predefined variable
Duration: data type
TIMER: a special type of object with operations
SETactive
RESETinactive
and sending a message when time period has elapsed
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17. TIMER Automata
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18. Process Identification (PId)
Each SDL process has a unique identifier, a value of data type PId.
Special value NULL (no process)
Predefined variables
SELF: the process itself
OFFSPRING: the most recent process created by SELF
PARENT: SELF is OFFSPRING of PARENT
SENDER: the process that sent the last signal received and processed by SELF
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19. Use of PId Variables
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20. Use of PId Variables (II)
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21. Output Symbols
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22. Save Symbol
Save symbol assures that a set of signals will be bypassed until the process has entered a different state.
Then the saved signals will be processed; they remain in the input queue in their original order.
Example below: in all states but Idle, Code will be saved.
Code signal will only be handled in the Idle state.
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23. 5.5: Dynamic Generation of Process Instances
In SDL, a process may create other processes.
The creation is shown by a dashed line from PARENT to OFFSPRING.
Blocks cannot be generated dynamically.
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24. Creation of Processes
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25. PROCESS CUControl
Create Symbol
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26. Dynamic Process Creation
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27. Stop Symbol Processes are created by their parent.
A processes terminates when it reaches a stop symbol. (Note: processes may not kill each other).
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28. Daemongame System
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29. Block Structure of Daemongame
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30. Process and Dynamic Process Creation
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31. 5.6: SDL Symbol Summary
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32. SDL Symbol Summary (II)
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33. SDL Data: Part 2 SDL data types Abstract data types
Shared variables and enabling conditions
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34. Operators Data types in SDL are
Predefined types, such as Integer, etc.
Programmer-defined types: They are defined using keywords Newtype or syntype. Examples are:
Subranges of Integer
Enumerations
Arrays
Record types (called structure in C, like objects with attributes)
Abstract data types (not much used)
For every data type defined in SDL, the following operators are always defined:
Assignment ‘:=’
Test for equality ‘=’
Test for non-equality ‘/=’
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35. Infix and Prefix Operators
“+” : Integer,Integer -> Integer;
num : Character -> Integer;
I := I+1;
N := num(‘X’);
I := “+”(I,1);
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36. Boolean "NOT" : Boolean -> Boolean
"AND" : Boolean, Boolean -> Boolean
"OR" : Boolean, Boolean -> Boolean
"XOR" : Boolean, Boolean -> Boolean
"=>" : Boolean, Boolean -> Boolean
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37. Character "<" : Character, Character -> Boolean;
Num : Character -> Integer;
Chr : Integer -> Character;
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38. Charstring MkString : Character -> Charstring;
Length : Charstring -> Integer;
First : Charstring -> Character;
Last : Charstring -> Character;
"//" : Charstring, Charstring -> Charstring;
SubString : Charstring, Integer, Integer
-> Charstring;
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39. Duration "+" : Duration, Duration -> Duration;
"*" : Duration, Real -> Duration;
"*" : Real, Duration -> Duration;
"/" : Duration, Real -> Duration;
">" : Duration, Duration -> Boolean;
"<" : Duration, Duration -> Boolean;
">=" : Duration, Duration -> Boolean;
"<=" : Duration, Duration -> Boolean;
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40. Time "+" : Time, Duration -> Time; "+" : Duration, Time -> Time;
"<" : Time, Time -> Boolean;
"<=" : Time, Time -> Boolean;
">" : Time, Time -> Boolean;
">=" : Time, Time -> Boolean;
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41. Integer, Natural "-" : Integer -> Integer;
"+" : Integer, Integer -> Integer;
"-" : Integer, Integer -> Integer;
"*" : Integer, Integer -> Integer;
"/" : Integer, Integer -> Integer;
"mod" : Integer, Integer -> Integer;
"rem" : Integer, Integer -> Integer;
"<" : Integer, Integer -> Boolean;
">" : Integer, Integer -> Boolean;
"<=" : Integer, Integer -> Boolean;
">=" : Integer, Integer -> Boolean;
Float : Integer -> Real;
Fix : Real -> Integer;
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42. PId The type PId is used as a reference to process instances.
PId has only one literal, Null.
All other values are obtained from the SDL predefined variables Self, Sender, Parent, and Offspring.
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43. Real "-" : Real -> Real; "+" : Real, Real -> Real;
"<" : Real, Real -> Boolean;
">" : Real, Real -> Boolean;
"<=" : Real, Real -> Boolean;
">=" : Real, Real -> Boolean;
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44. New Type Definition (example of abstract data type)
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45. Syntype Definition syntype example2 = integer endsyntype;
constant 0:10;
endsyntype;
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46. Enumeration
An enumeration sort is a sort containing only the values enumerated in the sort.
newtype KeyPosition
literals Off, Stand_by, Service_mode
endnewtype;
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47. Struct newtype Person struct endnewtype; Name Charstring;
Address Charstring;
PhoneNumber Charstring;
endnewtype;
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48. Array
The predefined generator Array takes two generator parameters, an index sort and a component sort.
There are no restrictions in SDL on the index and component sort.
newtype A1 Array(Character, Integer)
endnewtype;
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49. Array (III)
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50. String
The String generator takes two generator parameters, the component sort and the name of an empty string value.
A value of a String type is a sequence of component sort values.
There is no restriction on the length of the sequence.
newtype S1 String(Integer, Empty)
endnewtype;
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51. String (II) MkString : Itemsort -> String
Length : String -> Integer
First : String -> Itemsort
Last : String -> Itemsort
"//" : String, String -> String
SubString : String, Integer, Integer
-> String
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52. Powerset
The Powerset generator takes one generator parameter, the item sort, and implements a powerset over that sort.
A Powerset value can be seen as: for each possible value of the item sort it indicates whether that value is member of the Powerset or not.
syntype SmallInteger = Integer
constants 0:31
endsyntype;
newtype P1 Powerset(SmallInteger)
endnewtype;
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53. Powerset (II) "IN" : Itemsort, Powerset -> Boolean
Incl : Itemsort, Powerset -> Powerset
Del : Itemsort, Powerset -> Powerset
Length : Powerset -> Integer
Take : Powerset -> Itemsort
Take : Powerset, Integer -> Itemsort
"<" : Powerset, Powerset -> Boolean
">" : Powerset, Powerset -> Boolean
"<=" : Powerset, Powerset -> Boolean
">=" : Powerset, Powerset -> Boolean
"AND" : Powerset, Powerset -> Powerset
"OR" : Powerset, Powerset -> Powerset
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54. Imported and Exported Value
The exported declaration and the imported specification must both be equal to the remote variable specification.
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55. Shared Variables
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56. Shared Variables (II)
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