InformationFlows
The InformationFlows package provides mechanisms for specifying the
exchange of information between entities of a system at a high level of
abstraction. Information flows describe circulation of information in a
system in a general manner. They do not specify the nature of the
information (type, initial value), nor the mechanisms by which this
information is conveyed (message passing, signal, common data store,
parameter of operation, etc.). They also do not specify sequences or
any control conditions. It is intended that, while modeling in detail,
representation and realization links will be able to specify which
model element implements the specified information flow, and how the
information will be conveyed.
The contents of the InfromationFlows package is shown in Figure 413.
The InformationFlows package is one of the packages of the
AuxiliaryConstructs package.
InformationFlow (from InformationFlows)
Description
An Information Flow specifies that one or more information items
circulate from its sources to its targets.
Attributes
None.
Associations
- realization : Relationship [*] : Determines which Relationship
will realize the specified flow
- conveyed : Classifier [1..*] : Specifies the information items
that may circulate on this information flow.
Constraints
[1] The sources and targets of the information flow can only be of
the following kind : Actor, Node, Use Case, Artifact, Class, Component,
Port, Property, Interface, Package, and InstanceSpecification except
when its classifier is a relationship (i.e. it represents a link).
[2] The sources and targets of the information flow must conform with
the sources and targets or conversely the target and sources of the
realization relationships, if any.
[3] An information flow can only convey classifiers that are allowed to
represent an information item. (see constraints on InformationItem)
Semantics
An information flow is an abstraction of the communication of an
information item from its sources to its targets. It is used to
abstract the communication of information between entities of a system.
Sources or targets of an information flow designate sets of objects
that can send or receive the conveyed information item.
When a source or a target is a classifier, it represents all the
potential instances of the classifier; when it is a part, it represents
all instances that can play the role specified by the part; when it is
a package, it represents all potential instances of the directly or
indirectly owned classifiers of the package.
An information flow may directly indicate a concrete classifier, such
as a class, that is conveyed instead of using an information item.
Notation
An information flow is represented as a dependency, with the
keyword <<flow>>.
Changes from UML1.x
InformationFlow does not exist in UML 1.4.
InformationItem (from InformationFlows)
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, which is
cannot be instanciated.
One purpose of Information Items is to be able to define preliminary
models, before having taken detailed modeling decisions on types or
stuctures. 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 betwen entities of a system.
Attributes
No additional attributes.
Associations
- represented : Classifier [*] : Determines the classifiers that
will specify the structure and nature of the information. An
information item represents all its represented classifiers.
Constraints
[4] 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.
[5] An informationItem has no feature, no generalization, and no
associations.
[6] It is not instanciable
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 416).
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.Information items can be
decomposed into more specific information item, 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
these detailed informations belongs to the represented classifiers.
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.
Representation links between a classifier and a representation item are
represented as dashed lines with the keyword
«representation».
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 414)
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 418, two
associations are realizing informations 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 417 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.