SDL Data

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Chapter 5

• SDL - Data

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Contents

• Data
• Simple data in SDL
• Dynamic generation of process instances
• SDL symbol summary
• Example

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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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5.2 Simple Data in SDL
Cid (integer) Digit (integer) DCL
no_dig integer DCL cardid integer
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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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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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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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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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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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Decision Symbol

• Used to choose between different alternative
  courses of action upon a question.

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Output Signal with Data

• Full expression can be in signal parameters, not
  only variables.

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Process PanelControl
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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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TIME, Duration, and TIMERS
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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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TIMER Automata
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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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Use of PId Variables
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Use of PId Variables (II)
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Output Symbols
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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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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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Creation of Processes
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PROCESS CUControl
Create Symbol
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Dynamic Process Creation
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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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Daemongame System
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Block Structure of Daemongame
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Process and Dynamic Process Creation
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5.6 SDL Symbol Summary
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SDL Symbol Summary (II)
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SDL Data Part 2

• SDL data types
• Abstract data types
• Shared variables and enabling conditions

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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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Infix and Prefix Operators

• Integer,Integer -gt Integer
• num Character -gt Integer
• I I1
• N num(X)
• I (I,1)

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Boolean

• "NOT" Boolean -gt Boolean
• "AND" Boolean, Boolean -gt Boolean
• "OR" Boolean, Boolean -gt Boolean
• "XOR" Boolean, Boolean -gt Boolean
• "gt" Boolean, Boolean -gt Boolean

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Character

• "lt" Character, Character -gt Boolean
• "lt" Character, Character -gt Boolean
• "gt" Character, Character -gt Boolean
• "gt" Character, Character -gt Boolean
• Num Character -gt Integer
• Chr Integer -gt Character

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Charstring

• MkString Character -gt Charstring
• Length Charstring -gt Integer
• First Charstring -gt Character
• Last Charstring -gt Character
• "//" Charstring, Charstring -gt Charstring
• SubString Charstring, Integer, Integer
• -gt Charstring

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Duration

• "" Duration, Duration -gt Duration
• "-" Duration -gt Duration
• "-" Duration, Duration -gt Duration
• "" Duration, Real -gt Duration
• "" Real, Duration -gt Duration
• "/" Duration, Real -gt Duration
• "gt" Duration, Duration -gt Boolean
• "lt" Duration, Duration -gt Boolean
• "gt" Duration, Duration -gt Boolean
• "lt" Duration, Duration -gt Boolean

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Time

• "" Time, Duration -gt Time
• "" Duration, Time -gt Time
• "-" Time, Duration -gt Time
• "-" Time, Time -gt Duration
• "lt" Time, Time -gt Boolean
• "lt" Time, Time -gt Boolean
• "gt" Time, Time -gt Boolean
• "gt" Time, Time -gt Boolean

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Integer, Natural

• "-" Integer -gt Integer
• "" Integer, Integer -gt Integer
• "-" Integer, Integer -gt Integer
• "" Integer, Integer -gt Integer
• "/" Integer, Integer -gt Integer
• "mod" Integer, Integer -gt Integer
• "rem" Integer, Integer -gt Integer
• "lt" Integer, Integer -gt Boolean
• "gt" Integer, Integer -gt Boolean
• "lt" Integer, Integer -gt Boolean
• "gt" Integer, Integer -gt Boolean
• Float Integer -gt Real
• Fix Real -gt Integer

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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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Real

• "-" Real -gt Real
• "" Real, Real -gt Real
• "-" Real, Real -gt Real
• "" Real, Real -gt Real
• "/" Real, Real -gt Real
• "lt" Real, Real -gt Boolean
• "gt" Real, Real -gt Boolean
• "lt" Real, Real -gt Boolean
• "gt" Real, Real -gt Boolean

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New Type Definition (example of abstract data
type)
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Syntype Definition

• syntype example2 integer
• constant 010
• endsyntype

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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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Struct

• newtype Person struct
• Name Charstring
• Address Charstring
• PhoneNumber Charstring
• endnewtype

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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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Array (II)

• GENERATOR Array
• (TYPE Index,TYPE Itemsort)
• OPERATORS
• Make! Itemsort?Array
• Modify! Array,Index,Itemsort?Array
• Extract! Array,Index?Itemsort
• AXIOMS
• ...
• ENDGENERATOR Array

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Array (III)
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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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String (II)

• MkString Itemsort -gt String
• Length String -gt Integer
• First String -gt Itemsort
• Last String -gt Itemsort
• "//" String, String -gt String
• SubString String, Integer, Integer
• -gt String

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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 031
• endsyntype
• newtype P1 Powerset(SmallInteger)
• endnewtype

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Powerset (II)

• "IN" Itemsort, Powerset -gt Boolean
• Incl Itemsort, Powerset -gt Powerset
• Del Itemsort, Powerset -gt Powerset
• Length Powerset -gt Integer
• Take Powerset -gt Itemsort
• Take Powerset, Integer -gt Itemsort
• "lt" Powerset, Powerset -gt Boolean
• "gt" Powerset, Powerset -gt Boolean
• "lt" Powerset, Powerset -gt Boolean
• "gt" Powerset, Powerset -gt Boolean
• "AND" Powerset, Powerset -gt Powerset
• "OR" Powerset, Powerset -gt Powerset

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Imported and Exported Value

• The exported declaration and the imported
  specification must both be equal to the remote
  variable specification.

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Shared Variables
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Shared Variables (II)