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diff --git a/doc/umbrello/uml_basics.docbook b/doc/umbrello/uml_basics.docbook new file mode 100644 index 00000000..e9ad0d0d --- /dev/null +++ b/doc/umbrello/uml_basics.docbook @@ -0,0 +1,616 @@ +<chapter id="uml-basics"> +<title>&UML; Basics</title> +<sect1 id="about-uml"> +<title>About &UML;</title> +<para> +This chapter will give you a quick overview of the basics of &UML;. Keep in mind +that this is not a comprehensive tutorial on &UML; but rather a brief introduction to &UML; which can be read as a &UML; tutorial. +If you would like to learn more about the +Unified Modelling Language, or in general about software analysis and design, refer to one of the +many books available on the topic. There are also a lot of tutorials on the Internet which you +can take as a starting point. +</para> + +<para> +The Unified Modelling Language (&UML;) is a diagramming language or notation to specify, visualize and document +models of Object Orientated software systems. &UML; is not a development method, that means it does not tell you +what to do first and what to do next or how to design your system, but it helps you to visualize +your design and communicate with others. &UML; is controlled by the Object Management Group (<acronym>OMG</acronym>) and is the +industry standard for graphically describing software. +</para> +<para> +&UML; is designed for Object Orientated software design and has limited use for other programming paradigms. +</para> +<para> +&UML; is composed of many model elements that represent the different parts of a software system. +The &UML; elements are used to create diagrams, which represent a certain part, or a point of view of +the system. +The following types of diagrams are supported by &umbrello;: +</para> + +<itemizedlist> + +<listitem><para><emphasis><link linkend="use-case-diagram">Use Case +Diagrams</link></emphasis> show actors (people or other users of the +system), use cases (the scenarios when they use the system), and their +relationships</para> </listitem> + +<listitem><para><emphasis><link linkend="class-diagram">Class +Diagrams</link></emphasis> show classes and the relationships between +them</para> </listitem> + +<listitem><para><emphasis><link linkend="sequence-diagram">Sequence +Diagrams</link></emphasis> show objects and a sequence of method calls +they make to other objects.</para> </listitem> + +<listitem><para><emphasis><link +linkend="collaboration-diagram">Collaboration +Diagrams</link></emphasis> show objects and their relationship, + putting emphasis on the objects that participate in the message exchange</para> +</listitem> + +<listitem><para><emphasis><link linkend="state-diagram">State +Diagrams</link></emphasis> show states, state changes and events in an +object or a part of the system</para> </listitem> + +<listitem><para><emphasis><link linkend="activity-diagram">Activity +Diagrams</link></emphasis> show activities and the changes from one +activity to another with the events occurring in some part of the +system</para></listitem> + +<listitem><para><emphasis><link linkend="component-diagram">Component +Diagrams</link></emphasis> show the high level programming components +(such as KParts or Java Beans).</para></listitem> + +<listitem><para><emphasis><link +linkend="deployment-diagram">Deployment Diagrams</link></emphasis> show +the instances of the components and their +relationships.</para></listitem> + +</itemizedlist> + +</sect1> <!-- about-uml --> + +<sect1 id="uml-elements"> +<title>&UML; Elements</title> +<sect2 id="use-case-diagram"> +<title>Use Case Diagram</title> +<para>Use Case Diagrams describe the relationships and dependencies between a group of <emphasis>Use Cases</emphasis> +and the Actors participating in the process.</para> +<para>It is important to notice that Use Case Diagrams are not suited to represent the design, +and cannot describe the internals of a system. Use Case Diagrams are meant to facilitate the communication +with the future users of the system, and with the customer, and are specially helpful to determine the required +features the system is to have. Use Case Diagrams tell, <emphasis>what</emphasis> the system +should do but do not — and cannot — specify <emphasis>how</emphasis> this is to be achieved.</para> +<para> +<screenshot> +<screeninfo>An example Use Case diagram.</screeninfo> + <mediaobject> + <imageobject> + <imagedata fileref="use-case-diagram.png" format="PNG"/> + </imageobject> + <textobject> + <phrase>&umbrello; showing a Use Case Diagram</phrase> + </textobject> + <caption> + <para>&umbrello; showing a Use Case Diagram + </para> + </caption> + </mediaobject> +</screenshot> +</para> +<sect3 id="use-case"> +<title>Use Case</title> +<para>A <emphasis>Use Case</emphasis> describes — from the point of view of the actors — a group of activities +in a system that produces a concrete, tangible result.</para> +<para> +Use Cases are descriptions of the typical interactions between the users of a system and the system itself. +They represent the external interface of the system and specify a form of requirements of what the +system has to do (remember, only what, not how). +</para> +<para>When working with Use Cases, it is important to remember some simple rules: + <itemizedlist> + <listitem><para>Each Use Case is related to at least one actor</para></listitem> + <listitem><para>Each Use Case has an initiator (&ie; an actor)</para></listitem> + <listitem><para>Each Use Case leads to a relevant result (a result with <quote>business value</quote>)</para> + </listitem> + </itemizedlist> +</para> +<para> +Use Cases can also have relationships with other Use Cases. The three most typical types of relationships +between Use Cases are:</para> +<itemizedlist> +<listitem><para><emphasis><<include>></emphasis> which specifies that a Use Case takes place <emphasis>inside</emphasis> +another Use Case</para></listitem> +<listitem><para><emphasis><<extends>></emphasis> which specifies that in certain situations, or at some point (called an +extension point) a Use Case will be extended by another.</para></listitem> +<listitem><para><emphasis>Generalization</emphasis> specifies that a Use Case inherits the characteristics +of the <quote>Super</quote>-Use Case, and can override some of them or add new ones in a similar way as the +inheritance between classes. +</para> +</listitem> +</itemizedlist> +</sect3> +<sect3 id="actor"> +<title>Actor</title> +<para> +An actor is an external entity (outside of the system) that interacts with the system by participating +(and often initiating) a Use Case. Actors can be in real life people (for example users of the system), +other computer systems or external events. +</para> +<para> +Actors do not represent the <emphasis>physical</emphasis> people or systems, but their <emphasis>role</emphasis>. +This means that when a person interacts with the system in different ways (assuming different roles) he will be +represented by several actors. For example a person that gives customer support by the telephone and takes +orders from the customer into the system would be represented by an actor <quote>Support Staff</quote> and +an actor <quote>Sales Representative</quote> +</para> +</sect3> +<sect3 id="use-case-description"> +<title>Use Case Description</title> +<para> <!-- FIXME this are not defined by UML. --> +Use Case Descriptions are textual narratives of the Use Case. They usually take the form of a note or +a document that is somehow linked to the Use Case, and explains the processes or activities that take +place in the Use Case. +</para> +</sect3> +</sect2> <!-- use-case-diagram --> + +<sect2 id="class-diagram"> +<title>Class Diagram</title> +<para> +Class Diagrams show the different classes that make up a system and how they relate to each other. Class Diagrams +are said to be <quote>static</quote> diagrams because they show the classes, along with their methods and +attributes as well as the static relationships between them: which classes <quote>know</quote> about which classes +or which classes <quote>are part</quote> of another class, but do not show the method calls +between them. +</para> +<para> +<screenshot> +<screeninfo>An example of a Class Diagram</screeninfo> + <mediaobject> + <imageobject> + <imagedata fileref="class-diagram.png" format="PNG"/> + </imageobject> + <textobject> + <phrase>&umbrello; showing a Class Diagram</phrase> + </textobject> + <caption> + <para>&umbrello; showing a Class Diagram + </para> + </caption> + </mediaobject> +</screenshot> +</para> +<sect3 id="class"> +<title>Class</title> +<para> +A Class defines the attributes and the methods of a set of objects. All objects of this class (instances +of this class) share the same behavior, and have the same set of attributes (each object has its own set). +The term <quote>Type</quote> is sometimes used instead of Class, but it is important to mention that these +two are not the same, and Type is a more general term. +</para> +<para> +In &UML;, Classes are represented by rectangles, with the name of the class, and can also show +the attributes and operations of the class in two other <quote>compartments</quote> inside the rectangle. +</para> +<para> +<screenshot> +<screeninfo>A Class in &UML;</screeninfo> + <mediaobject> + <imageobject> + <imagedata fileref="class.png" format="PNG"/> + </imageobject> + <textobject> + <phrase>Visual representation of a Class in &UML;</phrase> + </textobject> + <caption> + <para>Visual representation of a Class in &UML; + </para> + </caption> + </mediaobject> +</screenshot> +</para> +<sect4 id="attribute"> +<title>Attributes</title> +<para> +In &UML;, Attributes are shown with at least their name, and can also show their type, initial value and +other properties. +Attributes can also be displayed with their visibility: +</para> +<itemizedlist> +<listitem><para><literal>+</literal> Stands for <emphasis>public</emphasis> attributes</para></listitem> +<listitem><para><literal>#</literal> Stands for <emphasis>protected</emphasis> attributes</para></listitem> +<listitem><para><literal>-</literal> Stands for <emphasis>private</emphasis> attributes</para></listitem> +</itemizedlist> +</sect4> +<sect4 id="operation"> +<title>Operations</title> +<para> +Operations (methods) are also displayed with at least their name, and can also show their parameters and return +types. +Operations can, just as Attributes, display their visibility: +<itemizedlist> +<listitem><para><literal>+</literal> Stands for <emphasis>public</emphasis> operations</para></listitem> +<listitem><para><literal>#</literal> Stands for <emphasis>protected</emphasis> operations</para></listitem> +<listitem><para><literal>-</literal> Stands for <emphasis>private</emphasis> operations</para></listitem> +</itemizedlist> +</para> +</sect4> + +<sect4 id="templates"> +<title>Templates</title> +<para> +Classes can have templates, a value which is used for an unspecified class or type. The template type is specified +when a class is initiated (&ie; an object is created). Templates exist in modern C++ and will be introduced in Java 1.5 where +they will be called Generics. +</para> +</sect4> +</sect3> + +<sect3 id="class-associations"> +<title>Class Associations</title> +<para>Classes can relate (be associated with) to each other in different ways:</para> +<sect4 id="generalization"> +<title>Generalization</title> +<para>Inheritance is one of the fundamental concepts of Object Orientated programming, in which a class +<quote>gains</quote> all of the attributes and operations of the class it inherits from, and can +override/modify some of them, as well as add more attributes and operations of its own.</para> +<para> +In &UML;, a <emphasis>Generalization</emphasis> association between two classes puts them in a hierarchy +representing the concept of inheritance of a derived class from a base class. In &UML;, Generalizations are +represented by a line connecting the two classes, with an arrow on the side of the base class. +<screenshot> +<screeninfo>Generalization</screeninfo> + <mediaobject> + <imageobject> + <imagedata fileref="generalization.png" format="PNG"/> + </imageobject> + <textobject> + <phrase>Visual representation of a generalization in &UML;</phrase> + </textobject> + <caption> + <para>Visual representation of a generalization in &UML; + </para> + </caption> + </mediaobject> +</screenshot> +</para> +</sect4> + +<sect4 id="uml-associations"> +<title>Associations</title> +<para>An association represents a relationship between classes, and gives the common semantics and structure +for many types of <quote>connections</quote> between objects.</para> +<para>Associations are the mechanism that allows objects to communicate to each other. It describes the connection +between different classes (the connection between the actual objects is called object connection, or +<emphasis>link</emphasis>. +</para> +<para> +Associations can have a role that specifies the purpose of the association and can be uni- or bidirectional +(indicates if the two objects participating in the relationship can send messages to the other, of if only +one of them knows about the other). Each end of the association also has a multiplicity value, which dictates +how many objects on this side of the association can relate to one object on the other side. +</para> +<para> +In &UML;, associations are represented as lines connecting the classes participating in the relationship, +and can also show the role and the multiplicity of each of the participants. Multiplicity is displayed as a +range [min..max] of non-negative values, with a star (<literal>*</literal>) on the maximum side representing infinite. +<screenshot> +<screeninfo>&UML; Association</screeninfo> + <mediaobject> + <imageobject> + <imagedata fileref="association.png" format="PNG"/> + </imageobject> + <textobject> + <phrase>Visual representation of an Association in &UML;</phrase> + </textobject> + <caption> + <para>Visual representation of an Association in &UML; + </para> + </caption> + </mediaobject> +</screenshot> +</para> +</sect4> + +<sect4 id="aggregation"> +<title>Aggregation</title> +<para>Aggregations are a special type of associations in which the two participating classes don't have +an equal status, but make a <quote>whole-part</quote> relationship. An Aggregation describes how the class +that takes the role of the whole, is composed (has) of other classes, which take the role of the parts. +For Aggregations, the class acting as the whole always has a multiplicity of one. +</para> +<para> +In &UML;, Aggregations are represented by an association that shows a rhomb on the side of the whole. +<screenshot> +<screeninfo>Aggregation</screeninfo> + <mediaobject> + <imageobject> + <imagedata fileref="aggregation.png" format="PNG"/> + </imageobject> + <textobject> + <phrase>Visual representation of an Aggregation relationship in &UML;</phrase> + </textobject> + <caption> + <para>Visual representation of an Aggregation relationship in &UML; + </para> + </caption> + </mediaobject> +</screenshot> +</para> +</sect4> +<sect4 id="composition"> +<title>Composition</title> +<para>Compositions are associations that represent <emphasis>very strong</emphasis> aggregations. This means, +Compositions form whole-part relationships as well, but the relationship is so strong that the parts cannot +exist on its own. They exist only inside the whole, and if the whole is destroyed the parts die too.</para> +<para>In &UML;, Compositions are represented by a solid rhomb on the side of the whole. +</para> +<para><screenshot> +<screeninfo>Composition</screeninfo> + <mediaobject> + <imageobject> + <imagedata fileref="composition.png" format="PNG"/> + </imageobject> + <textobject> + <phrase>Visual representation of a Composition relationship in &UML;</phrase> + </textobject> + </mediaobject> +</screenshot></para> +</sect4> +</sect3> <!--class-associations--> + +<sect3 id="other-class-diagram-items"> +<title>Other Class Diagram Items</title> +<para>Class diagrams can contain several other items besides classes.</para> +<sect4 id="interfaces"> +<title>Interfaces</title> +<para>Interfaces are abstract classes which means instances can not be directly created of them. They can contain operations but no attributes. Classes can inherit from interfaces (through a realisation association) and instances can then be made of these diagrams.</para> +<!-- FIXME screenshot --> +</sect4> +<sect4 id="datatype"> +<title>Datatypes</title> +<para>Datatypes are primitives which are typically built into a programming language. Common examples include integers and booleans. +They can not have relationships to classes but classes can have relationships to them.</para> +<!-- FIXME screenshot --> +</sect4> +<sect4 id="enum"> +<title>Enums</title> +<para>Enums are a simple list of values. A typical example is an enum for days of the week. The options of an enum are called Enum Literals. +Like datatypes they can not have relationships to classes but classes can have relationships to them.</para> +<!-- FIXME screenshot --> +</sect4> +<sect4 id="package"> +<title>Packages</title> +<para>Packages represent a namespace in a programming language. In a diagram +they are used to represent parts of a system which contain more than one class, maybe hundereds of classes.</para> +<!-- FIXME screenshot --> +</sect4> +</sect3> + +</sect2> <!-- class diagram --> + +<sect2 id="sequence-diagram"> +<title>Sequence Diagrams</title> + +<para> Sequence Diagrams show the message exchange (&ie; method call) +between several Objects in a specific time-delimited +situation. Objects are instances of classes. +Sequence Diagrams put special emphasis in the order and the +times in which the messages to the objects are sent.</para> + +<para> +In Sequence Diagrams objects are represented through vertical dashed lines, with the name of the Object +on the top. The time axis is also vertical, increasing downwards, so that messages are sent from one Object +to another in the form of arrows with the operation and parameters name. +</para> + +<!-- FIXME update screenshot to show synchronous messages --> +<screenshot> +<screeninfo>Sequence Diagram</screeninfo> + <mediaobject> + <imageobject> + <imagedata fileref="sequence-diagram.png" format="PNG"/> + </imageobject> + <textobject> + <phrase>&umbrello; showing a Sequence Diagram</phrase> + </textobject> + <caption> + <para>&umbrello; showing a Sequence Diagram + </para> + </caption> + </mediaobject> +</screenshot> + +<para>Messages can be either synchronous, the normal type of message call where control is passed to the called object until that +method has finished running, or asynchronous where control is passed back directly to the calling object. Synchronous messages have +a vertical box on the side of the called object to show the flow of program control.</para> +</sect2> <!-- sequence diagrams --> + +<sect2 id="collaboration-diagram"> +<title>Collaboration Diagrams</title> + +<para>Collaboration Diagrams show the interactions occurring between the objects participating in a specific +situation. This is more or less the same information shown by Sequence Diagrams but there the emphasis is +put on how the interactions occur in time while the Collaboration Diagrams +put the relationships between the objects and their topology in the foreground.</para> + +<para>In Collaboration Diagrams messages sent from one object to another are represented by arrows, showing +the message name, parameters, and the sequence of the message. Collaboration Diagrams are specially well suited +to showing a specific program flow or situation and are one of the best diagram types to quickly demonstrate +or explain one process in the program logic. +</para> + +<screenshot> +<screeninfo>Collaboration</screeninfo> + <mediaobject> + <imageobject> + <imagedata fileref="collaboration-diagram.png" format="PNG"/> + </imageobject> + <textobject> + <phrase>&umbrello; showing a Collaboration Diagram</phrase> + </textobject> + <caption> + <para>&umbrello; showing a Collaboration Diagram + </para> + </caption> + </mediaobject> +</screenshot> + +</sect2> <!-- collaboration diagrams --> + +<sect2 id="state-diagram"> +<title>State Diagram</title> +<para>State Diagrams show the different states of an Object during its life and the stimuli that +cause the Object to change its state. +</para> +<para>State Diagrams view Objects as <emphasis>state machines</emphasis> or finite automates that can +be in one of a set of finite states and that can change its state via one of a finite set of stimuli. For example +an Object of type <emphasis>NetServer</emphasis> can be in one of following states during its life: +</para> +<itemizedlist> +<listitem><para>Ready</para></listitem> +<listitem><para>Listening</para></listitem> +<listitem><para>Working</para></listitem> +<listitem><para>Stopped</para></listitem> +</itemizedlist> +<para>and the events that can cause the Object to change states are</para> +<itemizedlist> +<listitem><para>Object is created</para></listitem> +<listitem><para>Object receives message listen</para></listitem> +<listitem><para>A Client requests a connection over the network</para></listitem> +<listitem><para>A Client terminates a request</para></listitem> +<listitem><para>The request is executed and terminated</para></listitem> +<listitem><para>Object receives message stop</para></listitem> +<listitem><para>etc</para></listitem> +</itemizedlist> +<para> +<screenshot> +<screeninfo>State Diagram</screeninfo> + <mediaobject> + <imageobject> + <imagedata fileref="state-diagram.png" format="PNG"/> + </imageobject> + <textobject> + <phrase>&umbrello; showing a State Diagram</phrase> + </textobject> + <caption> + <para>&umbrello; showing a State Diagram + </para> + </caption> + </mediaobject> +</screenshot> +</para> +<sect3 id="state"> +<title>State</title> +<para>States are the building block of State Diagrams. A State belongs to exactly one class and represents +a summary of the values the attributes of a class can take. A &UML; State describes the internal state of an +object of one particular class +</para> +<para>Note that not every change in one of the attributes of an object should be represented by a State +but only those changes that can significantly affect the workings of the object</para> +<para> +There are two special types of States: Start and End. They are special in that there is no event that +can cause an Object to return to its Start state, in the same way as there is no event that can possible take +an Object out of its End state once it has reached it. +</para> +</sect3> + +</sect2> <!-- state diagrams --> + +<sect2 id="activity-diagram"> +<title>Activity Diagram</title> +<para>Activity Diagrams describe the sequence of activities in a system with the +help of Activities. Activity Diagrams are a special form of State Diagrams, that only (or mostly) contains +Activities. +</para> +<para> +<screenshot> +<screeninfo>An example Activity Diagram.</screeninfo> + <mediaobject> + <imageobject> + <imagedata fileref="activity-diagram.png" format="PNG"/> + </imageobject> + <textobject> + <phrase>&umbrello; showing an Activity Diagram</phrase> + </textobject> + <caption> + <para>&umbrello; showing an Activity Diagram + </para> + </caption> + </mediaobject> +</screenshot> +</para> +<para>Activity Diagrams are similar to procedural Flux Diagrams, with the difference that all Activities +are clearly attached to Objects.</para> + +<para>Activity Diagrams are always associated to a +<emphasis>Class</emphasis>, an <emphasis>Operation</emphasis> or a +<emphasis>Use Case</emphasis>.</para> + +<para>Activity Diagrams support sequential as well as parallel Activities. Parallel execution is represented +via Fork/Wait icons, and for the Activities running +in parallel, it is not important the order in which they are carried out (they can be executed at the same +time or one after the other)</para> +<sect3 id="activity"> +<title>Activity</title> +<para>An Activity is a single step in a process. One Activity is one state +in the system with internal activity and, at least, one outgoing transition. Activities can also have +more than one outgoing transition if they have different conditions. +</para> +<para>Activities can form hierarchies, this means that an Activity can be composed of several <quote>detail</quote> +Activities, in which case the incoming and outgoing transitions should match the incoming and outgoing transitions +of the detail diagram. +</para> + +</sect3> +</sect2> <!-- activity diagram --> + +<sect2 id="helper-elements"> +<title>Helper Elements</title> +<para>There are a few elements in &UML; that have no real semantic value for the model, but help to clarify +parts of the diagram. These elements are </para> +<itemizedlist> +<listitem><para>Text lines</para></listitem> +<listitem><para>Text Notes and anchors</para></listitem> +<listitem><para>Boxes</para></listitem> +</itemizedlist> +<para> +Text lines are useful to add short text information to a diagram. It is free-standing text and has no +meaning to the Model itself. +</para> + +<para> +Notes are useful to add more detailed information about an +object or a specific situation. They have the great advantage that +notes can be anchored to &UML; Elements to show that the note +<quote>belongs</quote> to a specific object or situation. +</para> + +<para>Boxes are free-standing rectangles which can be used to group items together to make diagrams more readable. They +have no logical meaning in the model.</para> + +<!-- FIXME, screenshot --> +</sect2> <!-- helper elements --> + +<sect2 id="component-diagram"> +<title>Component Diagrams</title> +<para>Component Diagrams show the software components (either component technologies such as KParts, CORBA components or Java Beans or +just sections of the system which are clearly distinguishable) and the artifacts they +are made out of such as source code files, programming libraries or relational database tables.</para> + +<para>Components can have interfaces (&ie; abstract classes with operations) that allow associations between components.</para> +</sect2> + +<sect2 id="deployment-diagram"> +<title>Deployment Diagrams</title> + +<para>Deployment diagrams show the runtime component instances and their +associations. They include Nodes which are physical resources, +typically a single computer. They also show interfaces and objects (class instances).</para> + +</sect2> + +</sect1> +</chapter> |