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Symbols and Lines in SDL Diagrams


Symbols in Both SDL Structure and Behavior Diagrams

Symbol Name Explanation

Class

Defines a newtype. Contains three sections: Name, attributes and operators.

Symbols in SDL Structure Diagrams

Symbol Name Explanation

Text

Declares SDL entities such as signals and data types.

Comment

Contains comments in the diagram. Is attached to other symbols.

Text extension

Is attached to other symbols. Used if the text in another symbol is too large for the symbol. Put the last part of the text or the complete text in the text extension symbol.

Block reference

References a block diagram in a system, system type, sub-structure, block or block type diagram. Also used for instantiation of a block type.

Process reference

References a process diagram in a block or block type diagram. Is also used for instantiation of a process type

Block substructure
reference

References a substructure diagram from a block or block type diagram.1

Service reference

References a service diagram in a process or process type diagram, from a service interaction page. Also used for instantiation of a service type.

Procedure reference

References a procedure diagram from any other diagram.

System type reference

References a system type diagram from a package diagram.

Block type reference

References a block type diagram from a package, system, system type, block or block type diagram.

Process type
reference

References a process type diagram from a package, system, system type, block or block type diagram.

Service type reference

References a service type diagram from a package, system, system type, block, block type, process or process type diagram.

Operator reference

References an operator diagram from any other diagram.

Gate

Defines a gate in a block type, process type or service type diagram. Is attached to the diagram frame.

1

Not often used, because "block A in block C" is a commonly used shorthand for the more syntactically correct "block A in substructure B in block C".

Symbols in SDL Behavior Diagrams 1(2)

Symbol Name Explanation

State

Defines a state or terminates a transition in an already defined state. Is followed by an input, save continuous signal or priority output signal.

Input

Receives a signal. Always preceded by a state symbol. Together, they define the start of a transition. Is followed by the behavior of the transition.

Save

Saves signals from being discarded when being received in the current state (that does not handle the signal). Always preceded by a state symbol. Is not followed by any symbols.

Output

Sends a signal from a transition

In/out connector

Out connector: A jump/join/goto symbol that finishes the definition of a transition on one page, if there is not enough space. Is always associated via a name with an in connector that continues the definition.

In connector: The label symbol that is followed by the rest of the transition.

Procedure call

Calls a procedure that does not return a value from a transition. (A value returning procedure is called from a task symbol.)

Create request

Creates an instance of a process in a transition

Enabling condition/ continuous signal

Enabling condition: Is preceded by an input symbol. Contains a boolean expression that decides if the transition below it should be taken or not.

Continuous signal: Is preceded by a state symbol. Is followed by the behavior of a transition. Contains a boolean expression that is continuously evaluated while in the state. The following transition is taken when the expression evaluates to true.

Priority input

Specifies that this signal reception has higher priority than normal signal reception in the same state. Primarily intended to give signals between services in the same process higher priority than other signals. Not often used.

Procedure start

The start symbol in a procedure diagram. Is followed by the behavior of the start transition.

Procedure return

The symbol in a procedure diagram that finishes the execution of the procedure and returns to the procedure caller.

Procedure
reference

References a procedure diagram from any other diagram.

Gate

Defines a gate in a block type, process type or service type diagram. Is attached to the diagram frame.

Symbols in SDL Behavior Diagrams 2(2)

Symbol Name Explanation

Text

Declares the SDL entities such as variables, timers and types.

Comment

Contains comments in the diagram. Is attached to other symbols.

Text extension

Is attached to other symbols. Used if the text in a symbol is too large for the symbol. Put the last part of the text or the complete text in the text extension symbol.

Decision

Specifies alternative paths in the behavior part of a transition. Contains an expression. Each path is labeled with an answer that should match the expression for the path to be taken.

Task

Is used for writing textual code in the behavior part of a transition. Contains for example variable assignments, for-loops and calls of value returning procedures.

Macro call

Calls a macro diagram in the behavior part of a transition. Macros are a depreciated feature of SDL, consider using procedures or diagram inheritance instead.

Transition option

Specifies alternative paths in the behavior part of a transition. Similar to a decision symbol, but the expression must be built up of constants and (external) synonyms that can be evaluated once before execution of the system starts. Not often used.

Start

Starts the execution of the current diagram instance in a process, process type, service or service type diagram. Is followed by the definition of the behavior of the start transition.

Stop

Stops the execution of the current diagram instance in a process, process type, service or service type diagram.

Macro inlet

The start symbol in a macro diagram. Macros are a depreciated feature of SDL, consider using procedures or diagram inheritance instead.

Macro outlet

The end symbol in a macro diagram. Macros are a depreciated feature of SDL, consider using procedures or diagram inheritance instead.

Operator reference

References an operator diagram from any other diagram.

Lines in Both SDL Structure and Behavior Diagrams

Line Name Explanation

Comment line

Associates a comment symbol with another symbol. To create it, select the comment symbol and drag the line handle to another symbol.

Text extension line

Associates a text extension symbol with another symbol. To create it, select the text extension symbol and drag the line handle to another symbol.

Gate line

Defines a gate in a block type, process type or service type diagram. To create it, select it from the symbol menu and attach it to the diagram frame.

Aggregation line

Defines that the class connected to the simple line end is contained in the class connected to the diamond line end. To create it, select the container class symbol and drag the aggregation line handle (a diamond). To create a line breakpoint, click in the diagram background. To attach the aggregation line to its final destination, click the border of the contained class symbol.

Association line

Defines an association between two class symbols, can be unidirected or bidirected. To create it, select one class symbol and drag the association line handle (a rectangle). To create a line breakpoint, click in the diagram background. To attach the association line to its final destination, click the border of the associated class symbol.

Lines in SDL Structure Diagrams Only

Line Name Explanation

Channel

Defines a part of a communication path for signals, either between two blocks or between one block and the environment (i.e. the diagram frame). To create it, select a block symbol and drag the line handle. To make line breakpoints, click in the diagram background. To attach the line to its final destination (either another block or the diagram frame), click the symbol border. After creation, the channel can be reversed or made bidirectional. The arrow is movable and an arrow at the end of the channel indicates that the channel does not delay signals being sent.

Signal route

Similar to a channel. The differences are that a signal route connects to processes and services instead of blocks, and that a signal route arrow cannot be moved around.

Create line

Defines that the process where the create line starts, can create instances of the process where the create line ends. The create line is optional. To create it, select the process symbol and drag the create line handle. To make line breakpoints, click in the diagram background. To attach the create line to its final destination, click the symbol border.

Line in SDL Behavior Diagrams Only

Line Name Explanation

Flow line

Defines the order that symbols are executed in. Starts at the bottom of a symbol and ends at the top of another symbol. To create it, select a symbol that can be followed by other symbols and drag the flow line handle. To make line breakpoints, click in the diagram background. To attach the flow line to its final destination, click the symbol border. Note that two symbols can only be connected with a flow line if the SDL syntax rules allow it.


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