Sequence Diagram For Calculator

Sequence solver by AlteredQualia. Find the next number in the sequence using difference table. Please enter integer sequence (separated by spaces or commas). The help section says: SEQUENCE is a program for producing UML Sequence Diagrams. In contrast to most similar programs you don't actually draw the diagram. Instead you write a textual description of the method calls you want to diagram and the layout is calculated and drawn automatically.

This answers some Frequently Asked Questions about a popular notation.

What is the UML

The UML is a common diagrammatic language developed by Rational[ http://www.rational.com/uml/ ]with the support of all the big computer companies. It is now maintainedby the Object Management Group. Rational was bought byIBM who now provides many tools.

Why use the UML

SequenceMany people think in pictures and a picture can expressa lot of ideas in a quick way.UML is a standard way to draw various views of a piece of software:the user's view, the architecture, the internal structureof the software, the source code,and the hardware involved.

If you become familiar with the UMLyou will find that you will be able to think of more ideasand also to work out how good an idea is.You'll be able to share your idea with others.

UML is becoming valuable in the job market.

When to Use the UML

    Use a diagram when you need to think about something,share ideas with someone else, save an idea for thefuture, show management the work you've been doing,when you can't find a bug in code, or when your teacher/adviser requires it.

    You can use the UML to make rough sketches, to express a blueprint ofthe code, as input to a code generator, or as required documentationof a finished project.

    Keep it simple -- only use the UML when you need it. Drawdiagrams that give most value. For example,don't draw a deployment diagramunless the software is running on many machines. Don't drawa component diagram when there is only one component -- themain program. Don't worry about packages until you need to have10 or more classes.

    The UML helps with these tasks:

    Understanding and planning ProceduresActivity Diagrams
    Understanding what user's want to doUseCase diagrams and Scenarios
    Understanding the organization and its problemsDomain
    Working out detailed object-oriented designsSequence and Communication diagrams.Start analyzing Scenarios with a SSD of one of them.
    Working out an algorithm for a complex operationActivity Diagrams
    Designing a data baseClass and Domain models
    Designing the softwareClass, Object, Activity, and State diagrams
    Planning and describing the modules in a complex project.Component diagrams
    Tracking the source, data, and executable filesArtifact and Deployment diagrams
    Planning how to use the hardwareDeployment Diagrams
    Organizing the work in a project into foldersPackage Diagrams

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    In all diagrams, never draw more detail than you actually need.Omit things that are not important or are uninteresting.

    Notice that you often have to add comments or text to a diagramusing English, Mathematics, or Java/C++ syntax.

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How do you draw diagrams in the UML

(howtodraw): First: only draw a diagram when you need to: to clarify your thinkingor to record for the future what you've decided.Second, UML is a flexible set of diagrams. Here are some ways to use them:
In class or working something out by yourselfDraw roughly and quickly by hand with pencil, eraser, and paper.
Working on a problem with othersUse a chalk board with/without post-it notes.Record with a camera.
In a meetingA laptop+tool+projector.
Preparing a simple diagram for handing in or presenting to othersUse a simple Graphics tool like Dia or Visio.PowerPoint,Word and Corel WordPerfect can do adequate diagrams.
Working on a Complex Project or in a team.Use a Computer Aided Software Engineering (CASE) tool like Rational Rose.If the team doesn't have its own space look into Web repositorieslike Google Groups to hold the files.
Simple sequence diagram
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UML Diagrams

    What does the User Want

    (UseCase): A use case names a type of user (actors) and something that they want to do(usecase).An actor can be a human, a device, or a piece of software butit must not be part of the system we are producing.The use case describes how an actor achieves a specific tangible goal.The important part of a usecase is the description of the stepsthat the actors take to achieve their goals and how the system appears torespond to the actors actions. Use any tool to write these Scenarios.

    The UML provides a diagram that is good for summarizing a collection of usecases. The actors are drawn as stick figures. The things thatthey want to do are shown as bubbles. Notice that the icons are drawn just likein the next diagram.

    Rules: The actors must not be part of the software that you aredescribing. They are outside it and use it. They can be people,machines, or other software. Usecase names must describe some activitythat an actor wants to do. A simple rule is to start each usecase namewith a strong verb: 'Review grade', 'update record', 'Get money from ATM',and 'Control nuclear reactor' are good names. 'Grades' and 'do email' arebad ones. Avoid having a large number of overly simple usecases thatcan be covered by one simple one: Instead of 'add record', 'change record','delete record', 'print record',.... etc use 'Access and update record', forexample. Use Scenarios to show this detail.

    (Scenarios): Each use case will need to be described in moredetail before you work out how to implement it.A scenario describes, step by step, how a particularuser gets what they want from the computer. It says what theuser does and what the computer does as a result. However itdoes not spell out all the details -- things like whether thereis a tool bar or the color of the screen is best left out.It also pays to be very specific about the particular user youare describing.

    Similarly, at the start of a project only list the obvious andstraight forward scenarios. Add special extensions to handle the exceptionalcases later.

    Student Enrolls in Class:

    1. Jo Doe goes to the phone and identifies his/herself.
    2. The computer gives a list of things that a student can do to the system.
    3. Jo asks for a list of sections in a course.
    4. The computer shows Jo the sections he or she is interested in.
    5. Jo selects one section to enroll in.
    6. The computer records the enrollment and confirms that Jo is enrolled.

    (extensions): It is also possible to record the things that can go wrong (extension points)and provide alternate scenarios (extended scenarios) for handling them.

    What does the User Think its all about

    Many users and usecases share some common ideas or concepts.These form the basis for classes that thesoftware will need. It is also possible to clarify how these classesof objects are related. The links between them define whatinteractions are possible between different classes of objects.The whole plan is called an architecture.

    (Domain): The trick that makes object-oriented designs easier to work with is that we use classes in the code that reflect theworld in which our clients and users exist. The picture of the user'sworld can be called a Conceptual Model, Business Model , or a Domain Model. It is an excellentsource of ideas for classes inside an object-oriented program. It isalso the perfect model to start the design of a data base.

    Both Domain and Architecture models area collection of boxes which containjust the names of the types of objects you expect to be in thesoftware. Show their interconnections as links between the boxes.You can add more detail if you want -- role names and multiplicitiescan help clarify the meanings of links.

    It sometimes clarifies a diagram if you list the attributes of some of theclasses in a domain model or architecture. In a complex project you tabulate the attributes for each enity in your domain model -- the result is called a Data Dictionary.

    These diagrams are also drawings of the data base. In some projectsyou may have to use a more complex notation called an Entity-Relation-Attributediagram instead.

    In a database, domain, or conceptual model avoid all verbs! Thenames in the boxes should be names of real entities. For example,the name 'Enroll' is not a good name for for a box. It describes an action. 'Student' isa good name. 'Enrollment' is also a good name. Actions appearin usecase scenarios (see above) and operations in sequence charts,collaborations, and class diagrams (see next).

    Which Object does What

    Thinking about how objects work together to do somethingfor the user is important. In other words we model the Interactionsbetween the objects in the software. UML Interaction Diagrams areSequence diagrams and Communication diagrams. Bothdiagrams help you design interactions. Architecture summarizes the result.

    (Architecture): An architecture is a picture of the types of objects ina system plus a list of their attributes and operations that these objectswill perform to meet the users needs. Add operations to classes at the same timeas you sketch Sequence and Communication diagrams.

    (Sequence): In a Sequence diagram you show the users (stick figures)and objects at the top. A vertical line goes down from each ofthese. Arrows show one object sending a message or calling afunction or operation that belongs to another object. A big Xindicates that an object deletes itself.

    What happens in the software when student Jo Doe (jo) drops a section(s):

    (Hint when designing): A System Sequence Diagram or SSD is a good first stp towards a design. It shows all the stepsin one scenario as messages flowing into the complete system under design.You typically have 1 or more actors and a single ':System' object.Draw one when you start to analyze a scenarioto prepare to design objects that implement or realize the scenario.Then draw a Sequence or Communication diagramsfor each step in the SSD.

    (Communication): In a Communication diagram actors and objects can be anywhereand sequence is shown by numbering the messages that are sent.These show the overall communication pattern but make the sequence ofevents less clear.

    What happens in the system when Jo Doe adds a Section

    In the more complex CASE tools the Class diagrams and thesediagrams are linked together: adding an arrow on a Sequenceor Communicationdiagram helps you to add an operation to the class diagram. Orwhen you add a new message the CASE tools can list thepossible messages (operations or functions)you might want to send.

    (Collaboration): This is the old name for what is now called a Communicationdiagram. They were more complicated, see[ uml.collab.gif ]for an example.

    How are the classes organized

      (Class): The UML can express most things you can code in C++.A singlebox represents a class of objects. The name of the class is at the top.In the next part of the box list the data each object contains. In the thirdpart of the class box list the operations (functions) that an object cancarry out.

      Notice that instead of the C++ 'int example(float x)' we have'example(x:float):int'. Also omit the word void in all UML diagrams!

      Note: you can sketch a UML class quicker than you can write a C++ class.

      Hint: When sketching leave the bottom and right hand edge of the box until the end!

      Public and Private Members

      The above diagram doesn't indicate which attributes and operations are private andwhich are public. As a rule all attributes should be private and most operationspublic. You indicate the scope using signs:
    1. (minus sign): private
    2. (plus sign): public

      Connections between classes in a UML class diagram

      Many classes can be put on one diagram and connected together withassociations:

      Here are all the links commonly used in a class diagram:

      C++ classes have data members that are part of the state of thewhole object. In the UML we can use the dark diamond to indicatethat the class is composed of the components. The UML has twoor three ways to show this. For example, here is the codefor a class called Period:Here are a couple of valid diagrams that show that each Periodcontains a pair of times and up to 5 days.

      A simple composition with a multiplicity of one indicatesa simple data member in the C++ class. A fixed multiplicity suggests an array.A range of multiplicities or an asterisk suggests a more complex data structuresuch as a vector, list, or set. If the order is important, then the constraint '{ordered}'should be put at the end of the link. An vector is an ordered collection of variable size.

      If the data is accessed via a pointer then a simple arrow should be used toindicate this:

      Note: older books used to put an uncolored 'Aggregation' diamond at the otherend of the association to show a pointer.

      Note: If there is a vector (or list etc) of pointers then use the arrowwith a variable multiplicity.

    . . . . . . . . . ( end of section How are the classes organized) <<Contents End>>

    Classes and Objects

    (Object): It helps to be able to draw objects as well as classes.The rules are simple: use a box, underline the name of the objectand its class, and put attributes in a compartment under the name.Here for example is a simple Counter class plus object diagrams of of anobject the_count before and after a particular operation is appliedto it.

    Class Diagram of Counter

    A recently constructed Counter object called the_count.

    The same object after being sent a count() message

    How and When does an Object change

    (State): Often we need to think about how an object changes.Class diagrams give us a static picture of an objectand its relations to other objects.

    Computer Science developed a theory of automatic machines(automata) thatlead to the StateChart notation. This is part of the UnifiedModeling Language. It lets us show when and how an object changes itsbehavior. Each change of behavior is modeled as a change ofthe objects internal state. The diagram shows these andthe allowed changes between them. For example a Studentstarts out as a Person and then can evolve to be an Undergraduateor an Graduate. Undergraduate can become a Graduate.

    Each state is shown as a rectangle with rounded corners.Starting and finishing points are shown as black blobs.Changing state meansthe object changes it behavior. The change (or transition) is shownas an arrow. Each arrow should be labeled with a mutator method oroperation. So the arrows show what operations can be called in agiven state, and show you how the operation changes the possible behaviors.Initially we can omit the labels and one state can be used as anabbreviation for a whole pattern of behavior:

    You can add a lot of extra information to a State chart -- theoperations that trigger changes of state, the conditions governingwhich transition to follow, and what operations are executed when enteringand/or leaving a state.

    How is a complex problem solved? What is the Algorithm?

    (Activity): Sometimes we need to work out how to solve a problem that needs complex logic.UML State charts have evolved to allow us to draw Activity diagrams thatlook like old fashioned flowcharts. Below is one form of binary search for atarget in a sorted array or vector of items:

    [ uml.act.dia ]

    How is a complex architecture organized?

    When we have a lot of classes (more than 20 say) we need to group them.We would start to organize our code, diagrams, and documents into folders (or directories). In the UML we can also organize ourorganize our thinking into 'folders' called packages(See Packagebelow). We can also group our classes intolarger modules called components(see Component below) ready for people to use.A component is plug-compatible: the user knows that it can bereplaced by a similar component.A Pckage is more of an aid to the software engineers developing the software.When we code components we produce artifacts(see Artifact below). This isthe third way that UML supports organization.

    (Component): A component is very like a class. But they aredesigned to providecertain interfaces and use others. It is a plug-compatible piece ofsoftware thatoften contains many classes. There is a lollipop notation for showinghow components are plugged together.Here is an example:

    The lollipop indicates the interface between the component and its clients.

    (Artifact): In any real project there will be hundreds of files involved. Theseused to be shown as components but are now documented as artifacts.

    The above diagram treats each source, object, and executable file as aseparate component. Notice the stereotypes that tell you the kind of artifact that I'm using --an executable program, a file, a document and so on. Here is a list of standard ones:

    <<file>> A physical file in the context of the system developed.
    <<script>>A script file that can be interpreted by a computer system.
    <<executable>>A program file that can be executed on a computer system.
    <<library>>A static or dynamic library file.
    <<source>>A source file that can be compiled into an executable file.
    <<document>>A generic file that is not a source file or executable.

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    We can also show where these artifacts are stored on our computer hardware.

    (Package): An icon that looks like a folder. Itrefers to a collection of other icons and diagrams thatare said to be inside the package.In effect it acts and looks like a folder ina GUI for an operating system or a directory. Here is a classiclayered architecture that separates work done on the user interfacefrom work done on the data base, etc.

    Packages are a way of organizing large projects. We canput use cases, classes, components, artifacts, ..., and even packagesinside a package. The dotted lines with stick arrowheads show dependencies.They show that parts of one package depend on the things in the otherpackage. If we change something at the 'arrowhead' end then we may beforced to change things at the other end as well. These couplings should be minimized when possible.

    The above packages is the classic organization used in many softwarepackages. The user interface decisions are worked on in the toppackage, and kept separate from understanding and solving theuser's domain problems. Separately, at the bottom, we can work onhow to use the database ('Persistence') and how to use other servers('Network').

    What Software is running on which device

    (Deployment): Use a deployment diagram in the UML to show the hardware that yoursoftware uses.You can add information describing operating systems, language interpreters,or details (CPU type for example) if this is valuable to know.

    When a component of a software system is completed it becomes an artifactand can be deployed onto a system that can use it. We show thiswith a deployment diagram that also show the artifacts.

    You can show what software runs on a node in a deployment diagramby listing it under the node(UML 1) or inside it(UML2).

    You can also make the node biggerand draw the artifact inside the cube. This is a nice way toshow how web-based systems work because these typically dependon a browser in the user's PC, server software on a web-server,and a separate data base running on a special data base box.

    Here is one way that one of my web applications was deployed untilrecently:

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Sequence Diagram For Calculator Download

  • algorithm::=a detailed and precise description of how a computation is carried out.
  • artifact::=`A software component (typically a file) that can placed (deployed)onto a system and be used their`.
  • component::=a module, a software chip, some code that can be compiledseparately from other modules and tested on its own. It provides and uses interfaces.
  • CASE::='Computer Aided Software Engineering'.
  • usecase::=An activity that a user wants to do and which the computer can help.

    Sequence Diagram Tutorial


    Sequence Diagram For Calculator Java

    This is a quick overview. There is a lot more to learn about the UML.Here is a link to some local documentation on the UML:[ uml.html ]

    In your future career you may need a text book. If so try:

    Project Sequence Diagram

    1. Martin Fowler
    2. UML Distilled: A brief Guide to the standard object modeling language
    3. Addison-Wesley Longman, Boston MA 2003 ISBN 0321193687 CR 0408-0893