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 1.4, 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 |
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.
Datatypes can also be created with the tool
in the diagram toolbar of a class diagram.
The UML 1.4 standard
allows user defined datatypes to be placed on
class diagrams to define their inheritence structure.
This is also possible in ArgoUML.
It is represented on the diagram by a box with two compartments, of
which the top one is marked with
«datatype»,
and contains the name.
The lower one contains operations.
The details tabs that are active for datatypes are as follows.
ToDoItemStandard tab.
PropertiesSee Section 16.3.2, “ Datatype Property Toolbar ” and Section 16.3.3, “ Property Fields For Datatype ” below.
DocumentationStandard tab. See Section 13.4, “ Documentation Tab ”.
SourceStandard tab. Unused. One would expect a class declaration for the new datatype to support code generation.
Tagged ValuesStandard tab. In the UML metamodel,
Datatypehas the following standard tagged values defined.persistence(from the superclass,Classifier). Valuestransitory, indicating state is destroyed when an instance is destroyed orpersistent, 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). Valuestrue, meaning the class is redundant -it can be formally derived from other elements, orfalsemeaning 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 18.6, “ 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 EnumerationThis creates a new Enumeration (see Section 16.4, “ Enumeration ”) in the same package as the datatype, navigating immediately to the properties tab for that Enumeration.
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 16.6, “ Stereotype ”) within the same package as the datatype, navigating immediately to the properties tab for that stereotype.
DeleteThis deletes the datatype from the model.
NameText 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
(Unnamed Datatype)in the explorer.NamespaceDrop down selector with navigate button. Allows changing the namespace for the datatype. This is the package hierarchy.
ModifiersCheck box, with entries
Abstract,LeafandRoot.Abstractis 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.
Leafindicates that this datatype can have no further sub-types, whileRootindicates it is a top level datatype.Tip You can define the specialization of datatypes in a class diagram by drawing generalizations between them.
VisibilityRadio box, with entries
public,private,protected, andpackage.Records the visibility for the Datatype.
Client DependenciesText area. Lists any elements that depend on this datatype.
![[Caution]](images/caution.png)
Caution It is not clear that dependencies between datatypes makes much sense.
Supplier DependenciesText area. Lists any elements that this datatype depends on.
Caution It is not clear that dependencies between datatypes makes much sense.
GeneralizationsText area. Lists any datatype that generalizes this datatype.
SpecializationsText box. Lists any specialized datatype (i.e. for which this datatype is a generalization.
OperationsText 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 18.8, “ 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
querymodifier must be checked for all operations.