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INTRODUCTION TO UML in Java Embed 2d Data Matrix barcode in Java INTRODUCTION TO UML




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INTRODUCTION TO UML generate, create none none on none projects qr dispatched the none for none operation. The global stereotype indicates that the object is in an enclosing scope. The local stereotype indicates that the object is in the local scope.

The parameter stereotype indicates that the object is in scope because it is a parameter. Most attributes of an association are applicable to a link as well, with the exception of the multiplicity indicator, which cannot be applied to links. When an object passes a message to another object, it is delegating an action to the receiving object.

A sequence of messages always has a beginning and continues for the duration of the process or thread that owns it. Each process or thread contains a unique ow of control that contains messages ordered sequentially by time. These sequences are most commonly modeled as nested ows of control with solid, lled arrowheads.

Alternatively, they can be represented by at ows of control, which are modeled as solid lines with stick arrowheads. The name of the controlling process or thread can be placed at the root of the sequence, and, if speci ed, should take the form threadOrProcessName:methodCall You may also specify its return values. More speci city can be given to a sequence with timing marks and constraints, guarded conditions, branching, and iteration.

There are several stereotypes that can be applied to links to illustrate the creation and destruction of objects. The new stereotype speci es that the instance is created at that point in the interaction; the destroyed stereotype signi es that the object is destroyed before the termination of that interaction. The transient stereotype indicates that the object is created during the interaction and destroyed before the interaction completes.

Changes to the state of an object during the course of an interaction are illustrated by multiple copies of an object, each showing different states. In a sequence diagram, these two objects would be placed on the same lifeline to show that they are different states of the same object, whereas on a collaboration diagram they would be connected and marked with the become stereotype. Sequence and collaboration diagrams vary greatly in their manner of displaying messages, and, as such, each is better suited for displaying certain kinds of information.

Sequence diagrams, for example, are easily able to illustrate separate paths extending from a branch, where each has separate messages extending from it, as well as message returns and both synchronous and asynchronous messages. Collaboration diagrams, by contrast, are not terribly well suited for displaying detailed information about messages and are better able to illustrate simple messages in the context of the overall relationship of objects in a diagram, because a complex arrangement of messages or various message types easily clutters up a collaboration diagram..

4.4.2 Sequence Diagrams Sequence diagr none none ams typically contain objects, links, and messages. Like all diagrams, they can also contain notes and constraints. The two features that distinguish sequence diagrams from their semantic equivalents, collaboration diagrams, are lifelines and focus of control.

You can think of a sequence diagram as a table that. 4.4 The Behavioral View shows objects none for none on its X axis and messages progressing through time along its Y axis. Although there is no particular meaning to the order of objects in a sequence diagram from left to right, by convention the object that initiates the action speci ed in the diagram will be listed at the left of the diagram and increasingly subordinate objects will be listed to the right. The order of messages does have a special signi cance, which is their temporal ordering.

Messages occurring rst should be placed at the top of a sequence diagram; subsequent actions should follow, in sequential order. A sequence diagram represents the detail of how a behavior gets completed by showing classes exchanging messages sequentially over time. It displays messages in order of occurrence, which build on one another to accomplish a desired behavior.

Sequence diagrams portray a behavior, which can consist of either a single message exchange or a set of them. Sequence diagrams illustrate the states of an object and its communications over time. Sequence diagrams can take either a generic form or an instance form.

The generic form describes a message exchange sequence within a set of classes. The instance form of the sequence diagram describes a single message exchange that follows the generic form. The generic form includes neither loops nor branches.

Sequence diagrams are especially good at specifying scenarios where the sequence of events or the timing of a message exchange is critical, or where concurrency needs to be modeled, or for a synchronous message exchange. Sequence diagrams illustrate the passage of time in the vertical dimension of the diagram. Typically time begins at the top of the page and proceeds toward the bottom.

This can, however, be reversed. Although the passage of time illustrated in a sequence diagram may be quanti ed in the diagram, the sequence of events is more important than the amount of time that passes during the illustrated sequence. The horizontal plane of a sequence diagram shows the class roles that participate in the speci ed sequence.

The ordering of these roles is insigni cant. Because many other diagrams do not show time, it can be dif cult to tell how a system operates in time. Sequence diagrams clarify this as well as concurrent processes.

A simple sequence diagram shows only a single scenario (or one instance) and shows simple messages, each moving the ow of control from one object to another. A simple diagram does not show concurrency. There are some simple things that you can do while building a sequence diagram that will make it more useful and effective.

First, giving the diagram a clear name helps communicate its purpose to others. Next, you only need to include the elements that are essential to the understanding of the interaction that the diagram models. Adding too much information can obscure the interaction rather than clarifying it.

However, you should use caution and avoid making the diagram so minimalist that it misinforms the diagram viewer. Finally, use branching sparingly as it can make a sequence diagram that is dif cult to follow. Complex branching sequences are better illustrated in activity diagrams.

The elements of sequence diagrams are listed in Table 4.6. In Figure 4.

8 we see a high-level interaction among a mobile user, a traf c service, and a map service. The diagram is laid out vertically with the actions presented progressing in order from top to bottom. The diagram is divided by.

INTRODUCTION TO UML T ABLE 4.6. The Elements of Sequence Diagrams Element Lifeline Description A lifeline is a dashed line arranged vertically down a sequence diagram that represents an objects existence through the passage of time.

Lifelines represent the life of an object during an interaction. If the object that the lifeline represents exists when the interaction starts, the lifeline must begin at the top of the diagram. If the lifeline s object exists at the end of the interaction, then the lifeline must end at the bottom of the diagram.

Otherwise, the lifeline must start at the point in the diagram where the object is created. The message that creates it should have an arrowhead pointing to it. If the lifeline s object is destroyed during the interaction, the lifeline must be terminated with an X at the point that the object is destroyed.

Because most objects exist for the entirety of an interaction, most lifelines extend from the top of the diagram to the bottom, with all of an interaction s objects aligned at the top. However, when an object is created during the interaction, the object s lifeline will start at the message that creates it. This message will be marked with the create stereotype to show that the object is being created at that point.

Similarly, if an object is destroyed during an interaction, its lifeline will stop at the point that it is destroyed, and the message that causes the object s destruction will be marked with the <<destroy>> stereotype. The end of the lifeline on a destroyed object will be marked with a large X to identify the object s destruction. Activations represent a focus of control and are represented as a thin rectangular box shown over the lifeline during a method call.

An activation must have an initiation time, which should be aligned with the top of the rectangle that represents it. The completion time of an activation should be aligned with the bottom of the rectangle. Activations may have a label that states their operation and have the ability to call or pass control to other objects.

They may be recursive (i.e., they may be self-invoking) and may be used in conjunction with a variety of different objects, including concurrent or nonconcurrent objects and multiple active objects.

They extend along the lifeline for the period of time that an object is performing an action, whether it performs the action directly or via a subordinate procedure. Additionally, the completion of an action may be marked explicitly with a return.Recursion, which is either a self-call or a callback.

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