As we know in OOP that interface provides a set of operations without implementation but
class is the opposite.
in Object oriented design ,we use uml the interface has a set of operations without implementation
and the class also has a set of operations without implementation(i know class has attributes in addition to its operations)?
so, what is the difference in UML?
As we know in OOP that interface provides a set of operations without implementation but class is the opposite.
Not quite true - abstract classes are classes that have one or more methods declared but not defined (in C++ and Java these are abstract methods). You can have a class defined with all its methods abstract - in which case there is close similarity with an interface.
One key idea in UML, though, is that an interface is a set of methods exposed to other classes or components. The purpose is to define a set of operations.
However, moving to programming, a method may be made abstract to aid development (e.g. by ensuring all subclasses have an implementation). This method might be purely internal to the class.
One last observation: the term interface and class in UML are not quite synonymous to interface and class in a language, say Java. For example, Java does not allow multiple class inheritance. Instead Java has the interface which allows a class to implement multiple types (not classes - a subtle difference)
EDIT
Quick note technical words:
Declare: Stating to the system that a variable or operation exists and its type or signature
Define: Same as declaring, but additionally providing a complete implementation of a variable or operation
Interface: A set of declarations of operations
Type: An object's interface(s) and other operations
Class: An object's class defines (not declares) how the object is implemented, including its internal state and the implementation of its operations
Define is to Declare as Class is to Type.
(see What is the difference between Type and Class?)
The purpose of interface is to define a set of operations but we are do the same for class also define a set of operations?
So the purpose of the interface is to declare (not define) a set of public operations that other objects want to use. A class (in UML) is the complete set of operations (public and private). A class (in Java, C++, etc.) additionally defines all non-abstract operations.
So the key is the intent: When other components of the system want to use a set of operations, use interface. When you're using UML to describe an implementation (of a component, algorithm, etc.) use class.
when I go to class that assumed to implement those operations I can't see any implementation for those operations as a diagram describe those operations or anything give a sign for implementation?
UML tool is for modelling and so deliberately avoids providing a place where you enter operation definitions - that is left for later. The idea is that you:
Define the model in UML
Use the UML tool to generate code in the target language
(And some allow you to import your code back into the tool to modify the model with any changes made during implementation. This is called "round-trip" modelling, something which the old TogetherJ product excelled at)
This deliberate gap (you might say deficiency) means that 'define' vs. 'declare' in UML is meaningless. Sorry.
Perhaps you've just seen models created for describing an overview, rather than modelling the system fully, but you can model the behaviour of a class's operations in most UML tools, and some tools also model the behaviour sufficiently that it can be executed .
The behaviour associated with an operation can be modelled using UML state machines, using UML action semantics or in several other ways. Quite often this is left out of the model - it is not always useful to go to that level of detail, so the implementations may just be hinted at in the documentation associated with the operation. But concrete classes in UML definitely have concrete behaviours associated with their operations, so the difference between UML and programming is that UML focuses on behaviour rather than implementation.
According to Wikipedia -
Unified Modeling Language (UML) is a standardized general-purpose
modeling language in the field of object-oriented software
engineering. The Unified Modeling Language includes a set of graphic
notation techniques to create visual models of object-oriented
software-intensive systems.
So, most important thing is UML is general-purpose and graphical. It is not only about classes and interfaces.
UML offers a standard way to visualize a system's architectural blueprints.
Software Construction Needs a Plan. Structure diagrams, Behavior diagrams, Interaction diagrams helps to Visualise In Multiple Dimensions and Levels of Detail which is
Appropriate For Both New and Legacy Systems.
Unified and Universal, Accommodates Parallel Development of Large Systems.
When I think of UML, one term which comes to mind is software quality. One thing that has plagued the software industry in recent year is poor software design. While the software industry has done fairly well for the last decade, the impact of globalization is changing the ways in which software is designed.
Related
When designing software (think UML diagrams for example) and real world objects.
How does one identify a suitable case for an Abstract class?
For example if we had an [Employee] and [Fireman] and [paidFireman] and [unpaidFireman]...I am having trouble seeing whether a Fireman or Employee should be abstract and why?
Abstract classes are one of those more esoteric constructs in UML. Since classes are already an abstraction of real world things, an abstract class is even one level higher. Abstract classes can not be instantiated (since it is assumed they miss something for a real life). Whether you say that Fireman is abstract while the paid/unpaid are not, is a pure point of view and must be argued in the specific domain.
As a rule of thumb: leave abstract classes out of the door until you come to a point where you feel the urgent need for it. Introducing abstractness limits your model (and can help to avoid some malformed results of it). But without those limits the model is still valid as long as the architect sticks to common sense rules.
It mainly depends on your functional requirements.
If it makes sense in your application just to have simple employees (without designating them as firemen, policemen, or craftsmen), then the class may not be abstract, as the application will have to make instances just of the Employee class.
If that doesn't make sense, i.e. the occupation of each of your employees needs to be known at creation time, abstract classes come into consideration. But still they aren't necessary in every case. The easiest way to make sure the occupation is known is to model it as a mandatory attribute. Introducing a subclass only makes sense if there is specialized behavior for each of those subclasses. If, e.g., the salary of the firemen is calculated as 50$ * count of the fires he exstinguished, but the salary of the policemen is 1000$ + 50 * rank, then you model an abstract operation getSalary() in the Employee class, which will be concretely specified and implemented in each of the subclasses.
As the concept of interface also got mentioned in one of the answers, an interface describes the obligation to implement certain operations in all classes realizing that interface. That's much the same as an abstract operation in an abstract class. But the abstract class can contain much more than an interface: attributes and non-abstract operations.
So the rule of thumb is: For concepts of your domain for which interface and behavior can be fully described, use non-abstract classes. For concepts for which only interfaces and no behavior can be described, use interfaces. For concepts for which interfaces and part of the behavior can be described, use abstract classes.
There are many uses for an abstract class. An abstract class is one that cannot have any direct instances.
In software design, it is one way to describe an interface. Some of the declared operations can be implemented in the superclass. Any remaining implementations must be specified in sub-classes. Regardless of where the implementations exist, an abstract class means there can be no direct instances, only instances of some non-abstract subclass.
In a domain analysis, an abstract class is a way of modeling an abstraction. For example, think of the abstraction Role. It is useful to say that a Person plays a number of Roles. However, there is no instance of a Role that makes sense, without it also being a more specific kind of Role, such as Employee, Fireman, or Teacher. For this situation, you not only want Role to be abstract, you also want a covering axiom. For more on that, please read https://stackoverflow.com/a/35950236/2596664.
I am a student and we have a Object-Oriented Project that we have to do to pass Object-Oriented course. My problem is to design the project. Teacher wants two different class diagram.Teacher said "One is high level, other one is normal class diagram." I know that high-level class diagram have detailed information such as attributes and methods. Additionally, I think high-level diagram covers normal diagram. What is normal class diagram? What is the difference between high-level and normal class diagram? I think that if we draw a high-level diagram normal diagram is redundant. Why Did teacher want normal diagram? I am confused.
There are typically 5 "levels" of design that one should think of, so that is where the "high-level" comes from. They are usually like this:
Software System - This is where you think of the software in terms of entire packages, or in terms of its subsystems.
Subsystems - This is the part where you ID all of the major subsystems, such as database, user interface, reporting engine, etc. This is the part where you define how each subsystem uses one another, and how they work together.
The first two are probably what your teacher meant by "High Level Design".
Classes - This further partitions the subsystems by classes. For instance, if you had a database system, you might have a class that manages the persistent connections, the metadata, etc. The way each class works with classes in other subsystems are also defined. This is probably what your teacher means by "class design".
Below that, you further divide each class into routines and internal routines, but I assume your teacher does not want you to get that detailed. However, for completion's sake, I will define them:
Routines - Design at this level includes dividing each class into routines. It is the "how" to the "what" answered in level 3.
Internal Routine - Design of the individual routines.
I have a program I made in C++ that does not use classes, just simply functions and main().
I want to know what kind of diagrams I can draw for it. Here are a couple of things I have in mind.
Activity diagram
Sequence diagram
class diagram - obviously can't draw this because I didn't use classes
system architecture
state diagrams
use case diagrams
Out of these what can I draw?
I'm guessing from the diagrams that you are aligned to a * Unified Process approach.
IMHO:
Use Case - definitely - eliciting business and system level requirements is implementation agnostic
System Architecture - definitely - layers, processes, network, db and modules / packages.
Activity Diagrams - definitely - use this to describe process flows for key processes
State Diagrams - applicable, although usually associated with the state and lifespan of a single object instance, but it is still conceptually useful if you are maintaining state through other means
Sequence Diagram - applicable, although you will probably need to provide an arbitrary class name to attach your functions (if you are using namespaces, then possibly aggregate to these these instead?)
However, you might hit issues if you want to generate and round-trip code from your diagrams e.g. from a CASE tool such as Rational Rose - most will assume an OO implementation language (noting that the three Amigos are strongly associated with OO!)
I guess this begs the question as to why you would need to develop a procedural app using an OO language and document it with OO techniques?
HTH
As a generalization: You can use all types except the class diagrams. If you could draw a class diagram, you should ask yourself, why you did not use classes in this case.
For all other diagrams, you can use parts of your app as "actors" or "components". It seems like you have not researched yet what these diagrams are used for and what you express with them. If you do that you should be able to determine which diagram makes sense for you.
Remember that each diagram should have a purpose. If you do it just for the sake of being there, then don't do it.
Me and several other developers are currently cleaning up our legacy code base, mostly separating visual and data layers. To help developers not involved in this refactoring understand the model, I'd like to introduce a (rather informal) class diagram with comments about scope and desired usage for each class. Since I'm lazy, I'd like to use UMLGraph for that.
However there is a small problem: we've got a perl code base and the refactoring uses Moose roles extensively. Now I don't know UML good enough to find a proper abstaction for roles -- my first guess would be interfaces, but they also contain implementation; multiple inheritance doesn't quite cut it either.
How do I (or how would you) represent roles properly in a class diagram?
I'm no UML expert but in the original paper Traits were represented like this
Traits Diagram http://img.skitch.com/20100422-8iey4atkkama53ni81c3pca562.jpg
I would represent a role as a UML class with the «role» stereotype. The class composing the role would then have an association to the role with the stereotype «does».
Simple Composition http://img820.imageshack.us/img820/5665/simplecomposition.png
If I needed to further adapt the role, with aliases or exclusions, I'd create that as an association class with properly annotated members and with the «adaptation» stereotype. The name of the association class wouldn't matter, because it won't be a real type in the design; so I'd leave it unnamed.
Composition with Conflict Resolution http://img828.imageshack.us/img828/244/conflictcomposition.png
(Please note that I have shown the adaptation "class" connected to the composition and the role it adapts. What I really wanted to do was connect it to the association between MyComposition and MyRole1. It's just that the tool I used didn't support association classes).
We are developing an extension (in C# .NET env.) for a GIS application, which will has predefined types
for modeling the real world objects, start from GenericObject, and goes to more specific types like Pipe and Road with their detailed properties and methods like BottomOfPipe, Diameter and so on.
Surely, there will be an Object Model, Interfaces, Inheritance and lots of other essential parts in the TypeLibrary, and by now we fixed some of them. But as you may know, designing an Object Model is a very ambiguous work, and (I as much as I know), can be done in many different ways and many different results and weaknesses.
Is there any distinct rules in designing O.M.: the Hierarchy, the way of defining Interfaces, abstract and coclasses enums?
Any suggestion, reference or practice?
A couple of good ones:
SOLID
Single responsibility principle
Open/closed principle
Liskoff substitution principle
Interface segregation principle
Dependency inversion principle
More information and more principles here:
http://mmiika.wordpress.com/oo-design-principles/
Check out Domain-Driven Design: Tackling Complexity in the Heart of Software. I think it will answer your questions.
what they said, plus it looks like you are modeling real-world entities, so:
restrict your object model to exactly match the real-world entities.
You can use inheritance and components to reduce the code/model, but only in ways that make sense with the underlying domain.
For example, a Pipe class with a Diameter property would make sense, while a DiameterizedObject class (with a Diameter property) with a GeometryType property of GeometryType.Pipe would not. Both models could be made to work, but the former clearly corresponds to the problem domain, while the latter implements an artificial (non-real-world) perspective.
One additional clue: you know you've got the model right when you find yourself discovering new features in the code that you didn't plan from the start - they just 'naturally' fall out of the model. For example, your model may have Pipe and Junction classes (as connectivity adapters) sufficient to solve the immediate problem of (say) joining different-diameter pipes to each other and calculating flow rates, maximum pressures, and structural integrity. You later realize that since you modeled the structural and connectivity properties of the Pipes and Junctions accurately (within the requirements of the domain) you can also create a JungleGym object from connected pipes and correctly calculate how much structural load it will bear.
This is an extreme example, but it should get the point across: correct object models support extension and often manifest beneficial unexpected properties and features (not bugs!).
The Liskov Substitution Principle, often expressed in terms of "is-a".
Many examples of OOP would be better off making use of "has-a" (in c++ private inheritance or explicit composition) rather than public inheritance ("is-a")
Getting Inheritance right is hard. Doing so with interfaces (pure virtual classes) is often easier than for base/sub classes
Check out the "principles" of Object oriented design. These have guidelines for all the questions you ask.
References:
"Object oriented software construction" by Robert Martin
http://www.objectmentor.com/resources/publishedArticles.html
Checkout the "Design Principles" articles at the above site. They are the best references available.
"BottomOfPipe"? Is that another way of saying the depth of the Pipe below the Road?
Any kind of design is difficult and can be done different ways. There are no guarantees that your design will work when you create it.
The advantage that people who design ball bearings and such have is many more years of experience and data to determine what works and what does not. Software doesn't have as much time or hard data.
Here's some advice:
Inheritance means IS-A. If that doesn't hold, don't use inheritance.
A deep hierarchy is probably a sign of trouble.
From Scott Meyers: Make non-leaf classes interfaces or abstract.
Prefer composition to inheritance.