I am reviewing my knowledge in object-oriented programming. Under the relationship between classes topic, I have encountered some relationships which are a bit ambiguous to me.

I know dependency &quot;uses-a&quot; and inheritance &quot;is-a&quot; but I&#39;m a bit unfamiliar with Aggregation, Composition, Association and Direct Association; also, which of them is &quot;has-a&quot; relationship. Some use Aggregation interchangeably with Association.

What is Direct Association? Also, what is Composition? In UML diagrams, the arrows that represents them are different. I would be really thankful if you could clear these things out for me.

Aggregation vs Composition vs Association vs Direct Association

With Enterprise Architect (Version 9.2), I created some Class and Sequence UML Diagrams. Now I need those Diagrams in a Word document. 

My first approach was to just cut them out with the Windows 7 Snipping Tool and paste them into the document. But for printing purposes the quality was way too poor.

The second approach was to &quot;Save them as Images&quot; as offered in Enterprise Architect. But with this, the quality was even worse.

The third way was to export them into a pdf file. With this the quality was quite decent and I could import those pdfs into Inkscape and then convert them into *.png files to import them to word. The problem is, that Enterprise Architect kinda fails with the fonts. Meaning the picture itself has high-quality, but it tries to convert the font of the classes and then I have some spaces between letters where there should be none.

So long story short - is there a way to export my UML Diagrams from Enterprise Architect to a common picture format like `.png` or `.tiff`, while retaining decent quality?

Enterprise Architect: Export UML Diagrams in high quality

I have recently been studying UML and drawing simple diagrams with ordinary plain arrows between classes, but I know it&#39;s not enough. There are plenty of other arrows: generalization, realisation and etc. which have meaning to the diagram reader. 

Is there a nice resource which could explain each arrow (ordinary, plain, dotted, diamond-filled, diamond)? 

It would be the best if it will have some code examples for them.

Explanation of the UML arrows

I&#39;m creating a sequence diagram, and one of the classes is being observed by another class.  The observed class is calling update in the observer every 5 seconds in a loop.  I need to show this in the sequence diagram.  Is there a way to show it looping indefinitely out of sequence as it were?

Or does it not make sense in the context of a sequence diagram; should I not include it? Or should I include it in a different type of diagram?

How to represent a call being made in a loop in a sequence diagram?

I&#39;m studying UML and I am confused. What&#39;s the difference between activity diagram and sequence diagram? I haven&#39;t got the crucial point yet.

What&#39;s the difference between activity diagram and sequence diagram?

Here I am, with another question about aggregation and association. I wanted to learn some basics of UML, so I started reading &quot;UML distilled&quot; by Martin Fowler. I read both chapters about classes, and there is one thing that I can&#39;t fully grasp I think, and that is aggregation vs association. In the book there is this quote:

&gt; In the pre-UML days, people were usually rather vague on what was aggregation and what was
association. Whether vague or not, they were always inconsistent with everyone else. As a result,
many modelers think that aggregation is important, although for different reasons. So  the UML
included aggregation (Figure 5.3) but with hardly any semantics. As Jim Rumbaugh says, &quot;Think of it
as a modeling placebo&quot; *[Rumbaugh, UML Reference].*

As I understand from this quote and topics that I read on Stack Overflow it doesn&#39;t matter which one of those two relations I use, they mean basically the same, or is there any situation where the usage of aggregation instead of association would be justified and/or I could not change one to the other without changing the &quot;meaning&quot; of a class diagram?

I am asking this, because this book is from 2003 and some things could have changed during those few years.


UML aggregation vs association

On a UML diagram, what is the correct way to represent a template class?

What is the correct way to represent template classes with UML?

I want to use **[Graphviz][1]** + **[Doxygen][2]** to generate a class diagram based on C++ code. This works already as Doxygen comes with a native DOT support; but is it possible, to produce a **UML-like output** with the corresponding access modificators (public, private etc.), return and parameter types of the class methods, similar to the diagram below?

I&#39;m aware of thread https://stackoverflow.com/questions/4755913/how-to-use-doxygen-to-create-uml-class-diagrams-from-c-source, but it doesn&#39;t answer the question, though.

![enter image description here][3]


  [1]: http://www.graphviz.org/
  [2]: http://www.doxygen.nl/
  [3]: http://i.stack.imgur.com/NuPoo.png

Graphviz + Doxygen to generate UML class diagrams

I’m looking for a collaborative UML-compliant tool. I work in the context of two geographically spread out teams and we need to work together on the designed models. 

Is there a web-based UML modeling tool with model sharing?

Is there a Google Doc-style UML tool?

What is the difference between aggregation, composition and dependency?

I was wondering, how can one represent &quot;`if`&quot; statement on a sequence diagram?


	if (somethingShouldBeDone) {
           // Do it
	} else {
           // Do something else
	}

Can it be represented at all? The thing is ... in my code, fair amount of conditions are checked to determine a variety of actions. If i am going to show the actions, I&#39;d like to explicitly state that actions are caused by particular events.

If possible create an image representation of a solution.

How to show &quot;if&quot; condition on a sequence diagram?

Is there a good tool that can help to reverse engineer Java classes to UML that will show an overview of how my classes are related to each other? It doesn&#39;t need to decompile from JAR file because I have the sources. I know there are quite a few out there but most of those can only generate individual class. I hope there is a tool that can generate class diagram that shows an overview of how all my current classes and packages work together, so that I can analyse my current architecture design. Of course, analysing is one thing. The other is for documentation purposes. 

I know of a few so far. But they cannot do an overview class diagram. Here&#39;s a list of Java UML tool that I have tried and is capable of doing reverse engineer but cannot do an overview class diagram of my whole project:

- StarUML (Really good &lt;s&gt;Opensource&lt;/s&gt; UML tool but cannot generate not overview class diagram)
- ArgoUML (It is slow and sluggish and it keeps crashing)
- UModel (This is a commerical software. I used before some time ago but found it difficult to use)
- MS Visio (It doesn&#39;t support Java UML reverse engineer. Only for VB)

Are there any other recommendations to add to this list? And hopefully, can generate an overview Java class diagram. I am using Eclipse, by the way.

Generate UML Class Diagram from Java Project

I am modeling a class diagram. An attribute of a class is an enumeration. How do I model this? Normally you do something like this:

    - name : string
But how does one do this with an enum?

UML class diagram enum

*Note: Questions are at the end of the post.*

I have read the other stackoverflow threads regarding **Abstract Factory vs Factory Method**. I understand the intent of each pattern. However, I am not clear on the definition.

&gt; Factory Method defines an interface
&gt; for creating an object, but lets
&gt; subclasses decide which of those to
&gt; instantiate. A factory method lets
&gt; classes defer instantiation to
&gt; subclasses.
&gt; 
&gt; By contrast, an Abstract Factory
&gt; provides an interface for creating
&gt; families of related or dependent
&gt; objects without specifying their
&gt; concrete classes.

-[John Feminella][1]


The **Abstract Factory** looks very similar to the **Factory Method**. I have drawn a few UML classes to illustrate my point. 

Note: 

- The diagram are from *www.yuml.com* so they are not perfectly oriented. But its a free service :).
- The diagrams may not be perfect. I am still learning the **GoF** design patterns.

**Factory Method:**

![Factory Method][2]

**Abstract Factory (only 1 member):**

![Abstract Factory (only 1 member)][3]

**Abstract Factory (more members):**

![alt text][4]

**Questions:**

1. If the **Abstract Factory** has only one creator and one product, is it still the **Abstract Factory** pattern? *(an interface for creating familes)*
2. Can the **Factory Method** concrete creator be created from an Interface or does it have to be from a class? *(classes defer instantiations to subclasses)*
3. If the Abstract Factory can have only one creator and one product, is the only difference between the **Abstract Factory** and the **Factory Method** that the creator for the former is an Interface and the creator for the latter is a Class?

  [1]: https://stackoverflow.com/a/1001803/45112
  [2]: http://i.stack.imgur.com/69jJo.jpg
  [3]: http://i.stack.imgur.com/BQOzX.jpg7866ef51
  [4]: http://i.stack.imgur.com/yMP7a.jpg

Design Patterns: Abstract Factory vs Factory Method

How do I get IntelliJ 10.5 (on the Mac) to generate a class diagram showing all of the classes in my project?  I&#39;m sure I&#39;m overlooking something obvious, but I can only get the &quot;Show Diagram&quot; feature to show one class at a time.  (I also figured out how to add additional classes, but again, only one at a time.)


Use IntelliJ to generate class diagram

Is there a tool that can parse C++ files within a project and generate UML from it?

Generating UML from C++ code?

In college I&#39;ve had numerous design and [UML][1] oriented courses, and I recognize that UML can be used to benefit a software project, especially [use-case][2] mapping, but is it really practical?  I&#39;ve done a few co-op work terms, and it appears that UML is not used heavily in the industry.  Is it worth the time during a project to create UML diagrams?  Also, I find that class diagrams are generally not useful, because it&#39;s just faster to look at the header file for a class.  Specifically which diagrams are the most useful?

**Edit:** My experience is limited to small, under 10 developer projects.

**Edit:** Many good answers, and though not the most verbose, I belive the one selected is the most balanced.


  [1]: http://en.wikipedia.org/wiki/Unified_Modeling_Language
  [2]: http://en.wikipedia.org/wiki/Use_case

Is UML practical?

How do I generate UML diagram based on existing classes in PHP?

PHP UML Generator

I have been searching for some material that describes how to generate simple class diagrams with doxygen, but couldn&#39;t find one. Can anybody help?

I need to create diagrams as shown below from a set of C++ files.
![alt text][1]

If there are better tools to achieve this easier, please let me know.

  [1]: http://i.stack.imgur.com/puHrq.gif

How to use doxygen to create UML class diagrams from C++ source

In a UML class diagram, what is the difference between an association relationship and a dependency relationship?

From what I know, an association is a stronger relationship than a dependency, but I&#39;m not sure how it is stronger.

Any example would be more than welcome :)

Difference between association and dependency?

What is a good Eclipse plugin for generating a class diagram (for a project)?

[This image right here][1] is **exactly** what I&#39;m talking about.

  [1]: http://www.moparisthebest.com/downloads/rs377.jpg

Eclipse plugin for generating a class diagram

I&#39;m now using NetBeans as my IDE-of-choice, and it has a plugin for UML modeling. In the class diagram, there are model elements known as `Boundary Class`, `Control Class`, and `Entity Class`. However, I can&#39;t find a good definition of them, but I did find [this site][1] on UML Class Diagrams.


  [1]: http://www.developer.com/design/article.php/10925_2206791_2

In UML class diagrams, what are Boundary Classes, Control Classes, and Entity Classes?

What is the difference between association, aggregation, and composition? 
Please explain in terms of implementation.

What is the difference between association, aggregation and composition?

I&#39;m trying to choose a tool for creating &lt;acronym title=&quot;Unified Modeling Language&quot;&gt;UML&lt;/acronym&gt; diagrams of all flavours. Usability is a major criteria for me, but I&#39;d still take more power with a steeper learning curve and be happy. Free (as in beer) would be nice, but I&#39;d be willing to pay if the tool&#39;s worth it. What should I be using?

What&#39;s the best UML diagramming tool?

I&#39;ve had a hard time understanding the difference between composition and aggregation in UML. Can someone please offer me a good compare and contrast between them? I&#39;d also love to learn to recognize the difference between them in code and/or to see a short software/code example.

Edit: Part of the reason why I ask is because of a reverse documentation activity that we&#39;re doing at work. We have written the code, but we need to go back and create class diagrams for the code. We&#39;d just like to capture the associations properly.

Aggregation versus Composition

I want to publish some programming documentation I have in a public available repository. This documentation has formatted text, some UML diagrams, and a lot of code examples. I think that GitHub or GitLab are good places to publish this.

To publish the UML diagrams, I would like to have some easy way to keep them updated into the repository and visible as images in the wiki. I don&#39;t want to keep the diagrams in my computer (or on the cloud), edit them, generate an image, and then publish it every time.

Is there a way to put the diagrams in the repository (in PlantUML syntax would be ideal), link them in the markdown text, and make the images auto-update every time the diagram is updated?

How to integrate UML diagrams into GitLab or GitHub

How can I generate UML diagrams (especially sequence diagrams) from existing Java code?

How to generate UML diagrams (especially sequence diagrams) from Java code?

What is the difference between **`include`** and **`extend`** in a [use case diagram][1]?

  [1]: http://en.wikipedia.org/wiki/Use_case_diagram


What&#39;s is the difference between include and extend in use case diagram?

I was reading Algorithms in a Nutshell (O&#39;Reilly) and came across this symbol in a class diagram.  My guess is that it means the member is protected, but I wanted to see if anyone knows for sure what it means.

What does the &#39;#&#39; symbol mean in a UML class diagram?

Consider the below two diagrams. The top one contains a plain arrow at the right end, and the bottom one contains an arrow with a diamond at the left end and a plain arrow at the right end. The [great book GoF][3] has usages of  both of these two kinds of diagrams. 

I want to understand what does the **diamond** signify in the second case, and which one of these two gives a stronger association between `Customer` and `Order`. 

Is the `Customer` class responsible for the lifecycle of `Order` class in either of the two cases?

![enter image description here][1]
![enter image description here][2]


  [1]: http://i.stack.imgur.com/sta7R.png
  [2]: http://i.stack.imgur.com/e4SrZ.png
  [3]:http://www.amazon.com/Design-Patterns-Object-Oriented-Professional-Computing/dp/0201634988

What does a diamond sign signify in UML class diagrams?

What is the difference between these 2 relationships?

![enter image description here][1]

Edit: Also if you could provide a simple code example illustrating the difference, that would be really helpful!


  [1]: http://i.stack.imgur.com/sLFw1.png

UML relationships - dashed line vs solid line

What&#39;s a good workflow (usage procedure) for creating a UML Sequence diagram in Dia?

UML Sequence Diagram in Dia?

How can you clearly illustrate multiple threads of execution in a sequence diagram or similar diagram?  

I haven&#39;t been able to find any clear examples.  All diagrams I see are used to illustrate a single thread.

---

**Update**: The accepted answer was the best example I saw but it does leave a fair bit to be desired.  I ended up illustrating the threads in separate sequence diagrams.  I&#39;m not sure if the sequence diagram necessarily works for multiple threads.

How to illustrate multiple threads in sequence diagram?

I want to know in detail about the difference between alt and opt fragment in sequence diagram, they seem similar, I can&#39;t distinguish them. Anyone knows about this thing?

Difference between alt and opt fragment in sequence diagram?

I am looking for a UML design tool (just for design, no need for code generation). 

Key features

1. Free
2. For Linux
3. Easy to use
4. Lightweight

Are there any good + free + Lightweight+ Linux UML Design tools?

I have installed Visio 2013 Standard and I&#39;m trying to create an UML diagram.

I choose the &quot;UML class&quot; template but when it opens, the Shapes panel is empty. As recomended, I go to &quot;More Shapes&quot; menu, but cannot find anything related to UML.

Have anyone had this problem and got a solution?

Thanks

UML diagram shapes missing on Visio 2013

A colleague is looking to generate UML class diagrams from heaps of Python source code. 
He&#39;s primarily interested in the inheritance relationships, and mildly interested in compositional relationships, and doesn&#39;t care much about class attributes that are just Python primitives.

The source code is pretty straightforward and not tremendously evil--it doesn&#39;t do any fancy metaclass magic, for example.  (It&#39;s mostly from the days of Python 1.5.2, with some sprinklings of &quot;modern&quot; 2.3ish stuff.)  

What&#39;s the best existing solution to recommend?

What&#39;s the best way to generate a UML diagram from Python source code?

More specifically, how do you model a functional program, or one developed using the Functional Style (without classes) using a diagram, and not textual representation.

Can UML be used to model a Functional program?

I have a `SportsCentre` class which contains an array of `Employee` objects.

Which is the right way to show that an attribute&#39;s data type is an array of objects?

I have found two different versions online:

- the first one uses the `ArrayList&lt;&gt;` keyword:

  |                SportsCentre                 |
  | --------------------------------------------|
  | `- listOfRegistered : ArrayList&lt;Employee&gt;`  |
  | `getRegisteredList() : ArrayList&lt;Employee&gt;` |

- the second one uses square brackets `[]`:

  |                SportsCentre                 |
  | --------------------------------------------|
  | `- listOfRegistered : Employee[0..*]`  |
  | `getRegisteredList() : Employee[0..*]` |


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