InformationFlows

*Generalizations

•

Classifier (from Kernel , Dependencies , PowerTypes ) on page 51

*Description

Issue 8508 -fix capitalization and some typos and clarifications

An information item is an abstraction of all kinds of information that can be exchanged between objects. It is a kind of classifier intended for representing information at a very abstract way, one which cannot be instantiated.

One purpose of information items is to be able to define preliminary models, before having made detailed modeling decisions on types or structures. One other purpose of information items and information flows is to abstract complex models by a less precise but more general representation of the information exchanged between entities of a system.

Attributes No additional attributes Associations • represented : Classifier [*] Constraints

Determines the classifiers that will specify the structure and nature of the information. An information item represents all its represented classifiers.

Issue 8506 -add OCL expressions

[1] The sources and targets of an information item (its related information flows) must designate subsets of the sources and targets of the representation information item, if any. The Classifiers that can realize an information item can only be of the following kind: Class, Interface, InformationItem, Signal, Component.

(self.represented.select(p | p->oclIsKindOf(InformationItem))->forAll(p | p.informationFlow.source->forAll( q | self.informationFlow.source->include(q) ) and p.informationFlow.target->forAll( q |self.informationFlow.target->include(q) ) ))

and

(self.represented->forAll(p |p->oclIsKindOf(Class) or oclIsKindOf(Interface) or oclIsKindOf(InformationItem) or oclIsKindOf(Signal) or oclIsKindOf(Component)))

[2] An information item has no feature, no generalization, and no associations.

self.generalization->isEmpty() and self.feature->isEmpty()

[3] It is not instantiable.

isAbstract

Semantics

Information as represented by an information item encompasses all sorts of data, events, facts that are exploited inside the modeled system. For example, the information item wage can represent a Salary Class, or a Bonus Class (see example Figure 17.5 ). An information item does not specify the structure, the type, or the nature of the represented information. It specifies at an abstract level the elements of information that will be exchanged inside a system. More accurate description will be provided by defining the classifiers represented by information item.

Issue 8508 - fix capitalization and typos

Information items can be decomposed into more specific information items using representation links between them. This gives the ability to express that in specific contexts (specific information flows) a specific information is exchanged.

Information items cannot have properties, or associations. Specifying this detailed information belongs to the represented classifier.

Notation

Being a classifier, an information item can be represented as a name inside a rectangle. The keyword «information» or the black triangle icon on top of this rectangle indicates that it is an information item.

<<inform ation>>

wage wage

Figure 17.4 - Information Item represented as a classifier

Representation links between a classifier and a representation item are represented as dashed lines with the keyword «representation».

Figure 17.5 - Examples of «representation» notation

An information item is usually represented attached to an information flow, or to a relationship realizing an information flow. When it is attached to an information flow (see Figure 17.3) its name is displayed close to the information flow line. When it is attached to an information channel, a black triangle on the information channel indicates the direction (source and target) of the realized information flow conveying the information item, and its name is displayed close to that triangle. In the example Figure 17.7, two associations are realizing information flows. The black triangle indicates that an information flow is realized, and the information item name is displayed close to the triangle.

The example Figure 17.6 shows the case of information items represented on connectors. When several information items having the same direction are represented, only one triangle is shown, and the list of information item names, separated by a comma is presented.

The name of the information item can be prefixed by the names of the container elements, such as a container information flow, or a container package or classifier, separated by a colon.