Ada Structure Graph (ASG)

ASGs are used to provide a visual representation of the program units (packages, tasks and subprograms) in an Ada software system.

The structure of Ada software elements is essentially a hierarchy. ASGs allow the software structure to be shown by more than a single hierarchy, by using two forms of decomposition:

• Multiple ASGs, where some ASG symbols can be expanded into ASGs at lower and lower levels, the successive ASG levels showing more detailed view of progressively smaller parts of the system
• Nesting symbols inside each other within ASG diagrams

where both of these forms of decomposition have the common concept that a symbol contains the other symbols, and the containment is shown graphically by one level of diagram, or several.

Both of these forms of decomposition can be used in a model. Both forms of decomposition can be used for the same Ada program elements in the same model. This means that there can be several symbols all referring to the same piece of Ada software structure.

ASGs only appear in the Implementation Domain.

Numbering of ASGs

The identities of ASGs (their diagram numbers) can contain alphanumeric characters. Also, they are not forced to be uppercase.

The decomposition of symbols is indicated by a . between their identities, so if C is part of B which is part of A, then the complete Number attribute of C will be A.B.C and is termed the fully qualified form of its identity. The identity of C is shown in ASGs as either C or A.B.C depending on the situation. The fully qualified identity is the true identity of a symbol and its corresponding description.

As an example of the two forms of decomposition, consider:

In this example:

1. ASG A contains a single package A, so the value of its Number attribute will be A
2. Package A in ASG A contains a package B, so the value of this symbol's Number attribute will be the fully qualified identity A.B
3. Package B inside package A in ASG A can be decomposed into an ASG, so the value of the ASG's Number attribute will be the fully qualified identity A.B
4. Package B inside package A in ASG A contains a package C, so the value of this symbol's Number attribute will be the fully qualified identity A.B.C
5. Package C inside package B inside package A in ASG A can be decomposed into an ASG, so the value of the ASG's Number attribute will be the fully qualified identity A.B.C

but there is also an alternative route to the lowest-level ASG A.B.C:

6. ASG A.B contains a single package A.B and so the value of its Number attribute will be A.B
7. Package A.B in ASG A.B contains a package C, so the value of this symbol's Number attribute will be the fully qualified identity A.B.C
8. Package C inside package A.B in ASG A.B can be decomposed into an ASG, so the value of the ASG's Number attribute will be the fully qualified identity A.B.C

So this means that there will be opportunities for many references to the same entity in an Ada program structure, as in the above example where:

1. Package A appears as:

• An ASG A
• A symbol A in ASG A

2. Package A.B appears as:

• A symbol B inside a symbol A in ASG A
• An ASG A.B
• A symbol A.B in ASG A.B

3. Package A.B.C appears as:

• A symbol C inside a symbol B inside a symbol A in ASG A
• A symbol C inside a symbol A.B in ASG A.B
• An ASG A.B.C
• A symbol A.B.C in ASG A.B.C

These principles extend to the descriptions of diagram symbols, such as the package specification items that are one of the forms of description of the Package symbol (the other being an ASG). Extending the above example to include these package specifications produces:

The comments from the previous example apply here also, together with:

1. Package A in ASG A contains a package B, so the value of this symbol's Number attribute will be the fully qualified identity A.B and the Number attribute of its package specification will also be A.B

2. The package A.B also exists as the symbol A.B in the ASG A.B and so the same package specification A.B can also be accessed from this symbol A.B
3. Package B inside package A in ASG A contains a package C, so the value of this symbol’s Number attribute will be the fully qualified identity A.B.C and the Number attribute of its package specification will also be A.B.C
4. The package A.B.C also exists as the symbol C inside the symbol A.B in the ASG A.B and so the same package specification A.B.C can also be accessed from this symbol C
5. The package A.B.C also exists as the symbol A.B.C in the ASG A.B.C and so the same package specification A.B.C can also be accessed from this symbol A.B.C

The Context ASG will contain the top-level packages in the system, each of which will have their identity in their Number attribute, such as:

Any of the packages in the Context ASG may contain other packages or tasks, where only the final part of their fully qualified identity will be shown in their symbols:

If any of these symbols are expanded into their own ASG, the Number attribute of the new ASG will be set to the fully qualified identity of the originating symbols and the new ASG will have a copy of the originating symbol which will be shown with its fully qualified identity, e.g.:

The above may be summarised as the following rules for the numbering of ASG symbols and diagrams:

1. The fully qualified identity of a symbol is the dot separated concatenation of:

• The fully qualified identity of the symbol containing the symbol and
• The identity of the symbol itself

2. The Number attribute of a symbol is always equal to its fully qualified identity
3. Symbols that are not contained in other symbols always display their fully qualified identity
4. Symbols that are contained in another symbol only show the last part of their fully qualified identity
5. The top-level ASG has a fully qualified identity: C
6. The fully qualified identity of an ASG is the same as the fully qualified identity of its originating symbol
7. The Number attribute of a diagram is always equal to its fully qualified identity
8. ASGs always show their fully qualified identity
9. The fully qualified identity of the specification for an ASG symbol is the same as the fully qualified identity of its originating symbol
10. The Number attribute of a specification is always equal to its fully qualified identity
11. A specification may appear as:

• One symbol in one ASG
• Multiple symbols in one ASG
• One symbol in multiple ASGs
• Multiple symbols in multiple ASGs

12. An ASG may be referenced by:

• One symbol in one ASG
• Multiple symbols in one ASG
• One symbol in multiple ASGs
• Multiple symbols in multiple ASGs

So the Number attribute of an ASG will not be used as the basis for:

1. The Number attributes of any symbols in the ASG
2. The Number attributes of any child ASGs of symbols in that ASG
3. The Number attribute of any specification items associated with any of the symbols in the ASG

You can control whether the full Number attribute values are shown in ASGs in the same way that this is controlled for other notations:

1. The Always show full symbol numbers checkbox in Edit > Preferences > UI Control > Diagrams
2. The Show full symbol number checkbox in the symbol graphics properties shown in the Control sidebar when a diagram is being edited

but the defaults for ASG symbols will be as indicated in this section and its example figures.

Symbols

An example ASG is:

The symbols available in ASGs are:

Symbol	Name	Description	Definition	Expansion
	Comment	Makes a note anywhere in the diagram. Are always surrounded by * characters.	None	None
	Boundary Point	A connection point for the initial transition to enter the initial state.	None	None
	Picture	Allows you to choose the location of a GIF or JPEG image to be displayed as a diagram symbol or to be embedded in an existing diagram symbol.	None	None
	Package	Representation of an Ada package specification or body. There is a class/object symbol in the Software Architecture Diagram (SAD) notation that is similar, but the characteristics of this Package symbol are unique to ASGs.	Package specification	ASG
	Generic Package	Representation of an Ada generic package's specification or body.	Package specification	ASG
	Foreign Package	Representation of an Ada program unit that is not elaborated in this model.	None	None
	Task	Representation of an Ada task specification or body. There is a process/task symbol in the SAD notation that is similar, but the characteristics of this Task symbol are unique to ASGs.	Task specification	ASG
	Task Type	Representation of an Ada task type specification or body.	Task specification	ASG
	Subprogram	Representation of an Ada routine (procedure or function), There is a class/object routine symbol in the SAD notation that is similar, but the characteristics of this Subprogram symbol are unique to ASGs.	Subprogram specification	ASG
	Generic Subprogram	Representation of an Ada generic routine.	Subprogram specification	ASG
	Generic Subprogram Parameter	Representation of a generic formal subprogram to an Ada generic package.	Subprogram specification	none
	Foreign Subprogram	Representation of a routine that is not elaborated in this model.	none	none
	Data Object	Representation of an Ada data object, such as may be declared in a package or task specification or body.	Data object data definition	none
	Data Type	Representation of a generic Ada data object, such as may be instantiation in a package or task specification or body.	Data object data definition	none
	Task Entry	Representation of an entry that can be called in an Ada task. There is a process/task entry symbol in the SAD notation that is similar, but the characteristics of this Entry symbol are unique to ASGs.	none	none
	Guarded Task Entry	Representation of an entry which has a conditional guard.	none	none
	Selective Wait	Representation of a selective wait construct that provides a timeout for a collection of one or more entries in an Ada task.	none	none
	Off Page Connector	A connector that can be used to link ASGs together.	none	ASG STC
	Generic Connector	Similar to the Off Page Connector but used as to connect an instantiation of a generic package or task to the ASG containing the details of the generic.	none	ASG
	With from Spec	The inclusion of another Package or Task by the specification of a package or task, which allows the use of the public declarations of the referencing program unit.	none	none
	With from Body	The inclusion of another Package or Task by the body of a package or task, which allows the use of the public declarations of the referenced program unit in the internal (private) declarations of the referencing program unit.	none	none
	Call	Representation of a call by a part of one program unit to another program unit, such as between subprograms, or to task entries. There is a data link symbol in the SAD notation that is similar, but the characteristics of this Entry symbol will be unique to ASGs.	none	none
	Conditional Call	Representation of a conditional call to a task entry.	none	none
	Timeout Call	Representation of a call to a task entry that has a timeout.	none	none
	Instantiation	Representation of the instantiation of a generic package, task type, data type or generic subprogram into an actual, package task, data object or subprogram.	none	none
	Data Couple	A piece of data that is passed in one direction in a Call, Conditional Call, Timeout Call or Instantiation, either from the caller or to the caller.	Couple data definition	none
	Dialogue Couple	A piece of data that is passed in one direction in a Call, Conditional Call, Timeout Call or Instantiation and is returned in a possibly updated state to the caller.	Couple data definition	none
	Exception	A representation of an error condition that has occurred in a subprogram or task and which is received by a higher-level subprogram or task.	none	none
	Cloud	A representation of a program unit who type has not yet been defined.	none	none

The Off-Page Connector and Generic Connector symbols provide convenient navigation links between ASGs, so that an Off-Page Connector and Generic Connector symbol can be expanded into the ASG whose identity is the same as the connector. Therefore, Off-Page Connector and Generic Connector symbols will always have a fully qualified identity in their Number attributes and will always display this complete fully qualified identity in the symbol shown in the ASG.