Looking at below UML diagram (decorator pattern), what is the name of relationship between Decorator and component? Is it Association?
The two relationships between Component and Decorator constitute another pattern - Composite.
Decorator is a subtype of Component (rel with triangle)
Decorator aggregates (includes) many Components (rel with diamond)
It allows recursive tree structures to be created. Operations called on the aggregate Decorator are delegated to its contained elements. Hence, in your diagram, the behaviour of Decorator.Operation() is to call Component.Operation() on each of its aggregated Components. Since one or more of thpse could themselves be a Decorator, the call to Operation() propagates through the tree structure.
One is an extension the other one aggregation (that's the one with the small nob at Decorator).
Meaning that a Decorator can contain 0 or more Components.
hth
Mario
It's aggregation. Decorator has many Components.
Aggregation. Easiest way to see the difference is with "to be" and "to have".
An object Component "has a decorator". An object Decorator "is a component".
You are describing an aggregation.
The problem is that this diagram should be reversed from your code or you should get a code from your diagram. Just graphical UML designs are not enough for me.
When I use tools with no code mapping to UML then my modeling is sooner or later horrible !!
I create nice diagrams but except for presentation nobody really use them. I have realized that it was a waste of time for everybody in the team.
I have switched to a professional tool then my project was really used by the team and not only a graphical view used once during a story board.
What surprised me is developers have also corrected my diagrams because at implementation stage what was good in UML was impossible in the code :-)
This is why UML as standalone has no value for me if you use the class diagram. I did this mistake using open source graphical tool but will not do it again !!
extends relationship
Related
I have recently been studying UML and drawing simple diagrams with ordinary plain arrows between classes, but I know it'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.
Here's some explanations from the Visual Studio 2015 docs:
UML Class Diagrams: Reference: https://learn.microsoft.com/en-us/previous-versions/visualstudio/visual-studio-2015/modeling/uml-class-diagrams-reference
5: Association: A relationship between the members of two classifiers.
5a: Aggregation: An association representing a shared ownership relationship. The
Aggregation property of the owner role is set to Shared.
5b: Composition: An association representing a whole-part relationship. The Aggregation
property of the owner role is set to Composite.
9: Generalization: The specific classifier inherits part of its definition from the general
classifier. The general classifier is at the arrow end of the connector. Attributes, associations, and
operations are inherited by the specific classifier. Use the Inheritance tool to create a
generalization between two classifiers.
13: Import: A relationship between packages, indicating that one
package includes all the definitions of another.
14: Dependency: The definition or implementation of the dependent classifier might change if
the classifier at the arrowhead end is changed.
15: Realization: The class implements the operations and attributes defined by the interface.
Use the Inheritance tool to create a realization between a class and an interface.
16: Realization: An alternative presentation of the same relationship. The label on the
lollipop symbol identifies the interface.
UML Class Diagrams: Guidelines: http://msdn.microsoft.com/library/dd409416%28VS.140%29.aspx
Properties of an Association
Aggregation: This appears as a diamond shape at one end of the connector. You can use it to
indicate that instances at the aggregating role own or contain instances of the other.
Is Navigable: If true for only one role, an arrow appears in the navigable direction. You can use
this to indicate navigability of links and database relations in the software.
Generalization: Generalization means that the specializing or derived type inherits attributes,
operations, and associations of the general or base type. The general type appears at the arrowhead
end of the relationship.
Realization: Realization means that a class implements the attributes and operations specified by
the interface. The interface is at the arrow end of the connector.
Let me know if you have more questions.
I think these pictures are understandable.
A nice cheat sheet (http://loufranco.com/wp-content/uploads/2012/11/cheatsheet.pdf):
It covers:
Class Diagram
Sequence Diagram
Package Diagram
Object Diagram
Use Case Diagram
And provides a few samples.
My favourite UML "cheat sheet" is UML Distilled, by Martin Fowler. It's the only one of his books that I've read that I do recommend.
For quick reference along with clear concise examples, Allen Holub's UML Quick Reference is excellent:
http://www.holub.com/goodies/uml/
(There are quite a few specific examples of arrows and pointers in the first column of a table, with descriptions in the second column.)
The accepted answer being said, It is missing some explanations.
For example, what is the difference between a uni-directional and a bi-directional association? In the provided example, both do exist. ( Both '5's in the arrows)
If looking for a more complete answer and have more time, here is a thorough explanation.
A very easy to understand description is the documentation of yuml, with examples for class diagrams, use cases, and activities.
Aggregations and compositions are a little bit confusing. However, think like compositions are a stronger version of aggregation. What does that mean?
Let's take an example:
(Aggregation)
1. Take a classroom and students:
In this case, we try to analyze the relationship between them. A classroom has a relationship with students. That means classroom comprises of one or many students. Even if we remove the Classroom class, the Students class does not need to destroy, which means we can use Student class independently.
(Composition)
2. Take a look at pages and Book Class.
In this case, pages is a book, which means collections of pages makes the book. If we remove the book class, the whole Page class will be destroyed. That means we cannot use the class of the page independently.
If you are still unclear about this topic, watch out this short wonderful video, which has explained the aggregation more clearly.
https://www.youtube.com/watch?v=d5ecYmyFZW0
If you are more of a MOOC person, one free course that I'd recommend that teaches you all the in and outs of most UML diagrams is this one from Udacity: https://www.udacity.com/course/software-architecture-design--ud821
I would like to know which diagram from those two should be created first when designing large IT system.
In every article I read about UML, the component diagram is mentioned as almost last.
I think that, when designing a larger system is better to divide it to smaller parts/modules on the component diagram and then for every component create a detailed class diagram. Is that correct?
How it look in practice from your experiences?
Do you know of any article/tutorial that shows from beginning to end, the design of system using UML?
There is no mandatory order for UML diagram design - in fact, you will often find yourself creating several simple diagrams of different types, and refining them later. The process is generally iterative but doesn't have a follow a particular order.
That being said, some UML diagrams provide a more abstract view than others, and it may sometimes make sense to start with the most abstract views and work your way down to the most specialised ones. Use case diagrams typically come early, while object diagrams or state diagrams often come later in the design process, once the original, abstract solution has been refined.
You will also want to take a look at consistency between your diagrams: indeed, with several views you will introduce redundant elements, and it is important to make sure that they do not contradict each other. For example, if you have a sequence diagram and a class diagram, any call message in the former should correspond to an operation in the latter. See Alexander Egyed et al's work for automated consistency management and correction in UML models.
Just wondering what's the correct UML Diagram type to show Service Connection? Essentially saying that "Client A needs a function GetFoo that needs to return items whose quantity is bigger than 20" and "Client B needs a function GetFoo that returns all items"?
A Component Diagram looks correct, but already very concrete in terms of types and very vague in terms of single functions. Composite Structure maybe?
Eventually this is used during planning to decide which functions a service actually needs to have (e.g., an inner GetFoo and two outer GetHeavyFoo/GetAllFoo functions)
I think the composite structure diagram will work for you. However, in my opinion you should combine it with sequence or communication diagram or both - whichever works best for you. I also suggest you check all the uml diagrams and compare them and then decide which ones are best suited for you.
Component diagram is a good solution as well as Sequence.
If you are a beginner in UML you can also just create a class diagram and add a constraints on a method. It would do the job and be easy to understand by the developer team.
It used to be OCL in UML 1.X but now with UML2 direct access to the metamodel you can just create any constraints directly in the model without any transformation. I use EclipseUML Omondo and don't want to use OCL because too complex for a very limited return on investment. My workaround is also better because I can write whatever I want and directly put it inside my class diagram without having two different models (e.g. one for UML and one for OCL).
I had some questions regarding the structure and behavior of a model, using UML, and the relationship between the two :
Did you find any limitations for UML regarding the specification or understanding of the relationship between structure and behavior?
I was wondering if you have any practical ideas of how one can optimize the relationship between structure and behavior, using UML.
Do you know any UML tools that help understand better this relationship or represent it much easier?
Thanks
Yes:
A sequence diagram is readable at a high level, showing how a transaction involves a few components; but it's not good (not readable) at the detailed level, showing how a transaction involves dozens of methods (method A calls method B, which gets data from methods D and E, and then invokes method F, etc.).
Looking at a class diagram, you might see a based class with several subclasses; this tells you nearly nothing about the behaviour of the classes (it only tells you that they may have some behaviour in common, or at least a common API, plus some individual behaior that's unique to each subclass).
That's a big question. A quick answer is, "Attach text notes to the objects: diagrams aren't sufficient without descriptive text."
No, I don't really; a UML tool help you create UML diagrams (and generate code from the diagrams), but it's up to you how you use it. There was a neat product described in the book titled Real-Time Object-Oriented Modeling (1994) which was an executable model, i.e. the model itself had behaviour, but I know of no UML tool quite like that. The closest I know of is being able to "round trip" between the model and code (i.e. generate code from the model, and the model from code).
Sounds like a homework problem. Wiki can tell you all about UML.
The limitations of UML are the same as any form of communication. The simpler your language, the fewer things you can communicate and the clearer your communications will become. A shape like a square or circle identifies a structure, a line indicates relationship, an arrow indicates movement, or flow. You could enhance this by defining the meaning of other properties, like direction, boldness, color, number count, different shapes. You could incorporate multimedia layers like audio or video, motion, tooltips- but now we're not talking about UML anymore.
My favorite UML tools are a whiteboard and some dry erase markers.
I think that things have changed, regarding UML's usefulness to melculetz.
In Visual Studio 2010, I can define an association relationship, that will generate composite classes. I can specify the multiplicity and class qualifiers. I can also generate classes from the model.
Presently, I am attempting to visually model the phases of a system, in order to visually define the methods for a state-machine object. That is my attempt to integrate structure and behaviour. Check my blog to see how I get on.
Class Analyser visually expresses the behaviour of class objects. Limitation removed.
I think that the answer is to turn your development methods towards MDA. You will generate more classes, but the payoff is in terms of manageability and re-use (where you template your efforts).
I am still working through my model but, I find VS2010 promises good tools for managing the development process. I have yet to investigate UI modelling, but have heard the rumours. I may have it all wrong but I think that, by working with Lightswitch, I may be able to model the UI also.
UML allows you to specify the signature of a method, and group methods into classes, but it says nothing at all about what code you use as implementation. If that's what you mean by "behavior", I don't think UML addresses it at all at the class level.
It's even worse at the UI level. My impression of UML is that it's woefully inadequate for specifying UIs.
I think the effort required to embed everything into UML is greater than or equal to coding the application, with the added burdens of UML tools being poor IDEs and inability to prove correctness of UML the way you can with unit testing.
UML is way oversold, IMO. I consider it a convenient notation for informal communication between developers, nothing more. It has never been and never will be the object oriented equivalent of engineering drawings.
I'm drawing some UML in which a concrete class inherits from an abstract class which defines a pure virtual method. Is it required to show this method in the concrete class as well? It's implied by inheriting from the abstract class.
Nope, you don't need to. in fact, in general, don't put any more in the UML than you must have to clarify what you're saying, unless you're (god forbid) trying to generate code from it.
The best guide I know of for UML is UML Distilled by Martin Fowler.
The funny thing about UML is that it has a pretty loose and varied definition. Most things that are called UML are actually not much more that block diagrams. There is a lot of ambiguity in any UML implementation.
I would say that if you are doing this for a presentation or architectural diagram, you can take care of a lot of the possible ambiguity with 'words'. If you will be generating code from it using some application, you should check the docs of that particular application.
It's implied and in fact, many CASE tools would show you the inherited method as part of the list of the methods of the subclass when clicking on the class at looking at its properties (and some CASE tools even have the option of showing also the inherited methods in the diagram)