Datatypes can be thought of as simple classes. They have no attributes, and any operations on them must have no side-effects. A useful analogy is primitive datatypes in a language like Java. The integer “3” stands on its own—it has no inner structure. There are operations (for example addition) on the integers, but when I perform 3 + 4 the result is a new number, “3” and “4” are unchanged by the exercise.
Within UML 1.3, DataType is a sub-class of the Classifier metaclass. It embraces the predefined primitive types ( byte, char, double, float, int, long and short), the predefined enumeration, boolean and user defined enumeration types.
![[Note]](images/note.png) | Note |
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Also void is implemented as a datatype within ArgoUML | |
Within ArgoUML new datatypes may be created using the New datatype button on the property tabs of the model and packages (in which case the new datatype is restricted in scope to the package), as well as the properties tab for datatype.
| Note |
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UML 1.3 allows user defined datatypes to be placed on class diagrams. This is not permitted in ArgoUML. | |
The details tabs that are active for datatypes are as follows.
- ToDoItem
Standard tab.
- Properties
See Section 15.3.2, “Datatype Property Toolbar” and Section 15.3.3, “Property Fields For Datatype” below.
- Documentation
Standard tab. See Section 12.4, “Documentation Tab”.
- Source
Standard tab. Unused. One would expect a class declaration for the new datatype to support code generation.
- Tagged Values
Standard tab. In the UML metamodel, Datatype has the following standard tagged values defined.
persistence (from the superclass, Classifier). Values transitory, indicating state is destroyed when an instance is destroyed or persistent, marking state is preserved when an instance is destroyed.
![[Tip]](images/tip.png)
Tip Since user defined datatypes are enumerations, they have no state to preserve, and the value of this tagged value is irrelevant.
semantics (from the superclass, Classifier). The value is a specification of the semantics of the datatype.
derived (from the superclass, ModelElement). Values true, meaning the class is redundant—it can be formally derived from other elements, or false meaning it cannot.
Tip While formally available, a derived datatype does not have an obvious value, and so datatypes should always be marked with derived=false.
Go upNavigate up through the package structure.
New datatypeThis creates a new datatype (see Section 17.5, “Class”) within the same package as the current datatype.
Tip While it can make sense to create datatypes this way, it can be clearer to create them within the package or model where you want them.
New enumeration literalThis creates a new enumeration literal within the datatype, navigating immediately to the properties tab for that literal.
![[Caution]](images/caution.png)
Caution ArgoUML does not actually have a separate concept of a literal. The navigation will navigate to the property sheet for an attribute of a class (see Section 17.6, “Attribute”). When defining a literal, all that matters is its name. Other parts of the attribute property sheet should be ignored. Also the name of the literal must obey the rules for an Attribute or a critic will fire.
New OperationThis creates a new operation within the datatype, navigating immediately to the properties tab for that operation.
New StereotypeThis creates a new Stereotype (see Section 15.5, “Stereotype”) within the same package as the datatype, navigating immediately to the properties tab for that stereotype.
DeleteThis deletes the datatype from the model.
- Name
Text box. The name of the datatype. The primitive datatypes all have lower case names, but there is no formal convention.
Note The default name supplied for a newly created datatype is the empty string “”. Datatypes with empty string names will appear with the name (anon Datatype) in the explorer.
- Stereotype
Drop down selector. Stereotype is provided by default with the UML standard stereotypes for classifier (metaclass, powertype, process, thread and utility).
Tip The stereotype enumeration should always be used for any created enumeration datatypes.
Caution In ArgoUML version 0.18 the stereotype enumeration must be created before it can be used. However, by creating an Enumeration Literal, the stereotype enumeration is created automatically.
- Navigate Stereotype
icon. If a stereotype has been selected, this will
navigate to the stereotype property panel (see
Section 15.5, “Stereotype”).- Namespace
Drop down selector. Allows changeing the namespace for the datatype. This is the package hierarchy.
- Modifiers
Check box, with entries Abstract, Leaf and Root.
Abstract is used to declare that this datatype cannot be instantiated, but must always be specialized.
Note ArgoUML provides no mechanism for specializing datatypes, so this check box is of little use.
Leaf indicates that this datatype can have no further sub-types, while Root indicates it is a top level datatype.
Tip In the absence of specialization of datatypes within ArgoUML these have little value. In effect all datatypes are both Root and Final
- Visibility
Radio box, with entries public, private, protected, and package.
Records the visibility for the Datatype.
- Client Dependencies
Text area. Lists any elements that depend on this datatype.
Caution It is not clear that dependencies between datatypes makes much sense.
- Supplier Dependencies
Text area. Lists any elements that this datatype depends on.
Caution It is not clear that dependencies between datatypes makes much sense.
- Generalizations
Text area. Lists any datatype that generalizes this datatype.
Caution It is not clear that generalizing datatypes makes much sense.
- Specializations
Text box. Lists any specialized datatype (i.e. for which this datatype is a generalization.
Caution It is not clear that specializing datatypes makes much sense.
- Operations
Text area. Lists all the operations defined on this datatype. Button 1 double click navigates to the selected operation. button 2 click brings up a pop up menu with two entries.
Move Up. Only available where there are two or more operations, and the operation selected is not at the top. It is moved up one.
Move Down. Only available where there are two or more operations listed, and the operation selected is not at the bottom. It is moved down one.
See Section 17.7, “Operation” for details of operations.
Caution ArgoUML treats all operations as equivalent. Any operations created here will use the same mechanism as operations for classes. Remember that operations on datatypes must have no side effects (they are read-only). This means the query modifier must be checked for all operations.
- Literals
Text area. Lists all the enumeration literals defined for this datatype. Button 1 double click navigates to the selected literal, button 2 click brings up a pop up menu with two entries.
Move Up. Only available where there are two or more literals, and the literal selected is not at the top. It is moved up one.
Move Down. Only available where there are two or more literals listed, and the literal selected is not at the bottom. It is moved down one.
Caution ArgoUML does not actually have a separate concept of a literal. The navigations listed above will all navigate to a property sheet equal to an attribute of a class (see Section 17.6, “Attribute”). When defining a literal, all that matters is its name. Other parts of the attribute property sheet should be ignored.