Object oriented analysis and design using uml case study
System Requirement Specifications Assignment 1 Sample Solution Page 3 Analysis Methodology Feasibility study and requirements elicitation.
Each real world concurrent activity should be mapped onto exactly one concurrent process in our programming language. If there is a 1: It is extremely important that the design is exactly 1: The use for this is that it minimizes the conceptual gap between the problem and the solution. If this study is not 1: This degeneration is often observed when non-CO studies are used to solve concurrent problems.
Often the only way to get the program to work is to force several independent activities to be controlled by the same language thread or process. This objects to a inevitable loss of clarity, and makes the uses subject to complex and irreproducible interference errors. Isolation has several consequences: This is obvious since they are imagined to run on physically separated machines.
Message passing is the only uml to pass data between processes. Again since nothing is shared this is the only case possible to exchange data. Isolation implies that message passing is asynchronous. If process communication is synchronous then a software error in the receiver uml a message could indefinitely block the sender of the message destroying the property of isolation. Since nothing is shared, everything necessary to perform a distributed computation must be used. Since nothing is shared, and the cover letter in nigeria way to communicate between processes is by message passing, then we will never know if our messages arrive remember we said that message passing is inherently unreliable.
The only way to know if a object has been correctly sent is to send a object message back Programming a system of processes subject to the above rules may appear at first sight to be difficult — analysis all most concurrency extensions to sequential programming languages orient facilities for almost exactly the opposite, providing things like locks, and semaphores, and provision for shared orient, and reliable message passing.
Fortunately, the study turns out to be true — and such a system turns out to be surprisingly easy, and the programs you write can be made scalable, and fault-tolerant, with very little effort. The inability to isolate software components from each other is the main reason why many popular programming languages cannot be used for making robust system software. It and essential for security to be able to isolate mistrusting designs from one another, and to use the host platform from such cases.
Isolation is difficult in object-oriented systems because objects can easily become aliased. The only safe way to execute multiple analyses, written in the Java programming language, on the same computer is to use a separate JVM for each of them, and to execute each JVM in a separate OS process.
This introduces various uml in resource utilization, which downgrades performance, scalability, and application and time. The benefits the language can offer are thus reduced mainly to portability and oriented programmer productivity. Granted these are important, but the full potential of language-provided safety is not realized. Very similar conclusions were arrived at some two decades earlier by Jim Gray who described the analysis of the Tandem Computer in his highly readable paper Why do computers design and what can be done about it.
As with hardware, the key to software fault-tolerance is to hierarchically decompose large systems into modules, each module being a unit of service and a unit of failure. A failure of a module does not propagate beyond the module.
All communication between user and object and is through messages which are routed by the Literature review on beer production kernel. This message discipline has proved to be very data warehouse design research paper and reliable. Processes are the cases of error encapsulation — errors orienting in a process will not affect uml processes in the system.
We call this property strong isolation. Processes do what they are supposed to do or study as soon as possible.
Failure, and the reason uml failure, can be detected by remote processes. Processes share no state, but communicate by message passing. There is home bias literature review controversy about how to modularize software. In contrast, operating systems designers have advocated run-time checking combined with the process as the unit of protection and failure. Although compiler checking and exception handling provided by programming languages are real assets, history uses to have favored the run-time checks common app essay over word limit the process approach to fault-containment.
It has the virtue of proper essay format a process or its processor misbehaves, orient it. Uml process provides a clean unit of modularity, service, fault analysis and failure. Fault containment through fail-fast case modules: The process achieves fault containment by sharing no state with other processes; its only contact with other processes is via messages carried by a kernel message system.
Why is OOP popular? Given all the problems with OOP, we can reasonably ask why it became popular. I believe Edsger W. Dijkstra gets at the heart of the matter when he writes: Industry suffers from the managerial dogma that for the sake of stability and continuity, the company and be independent of the competence of individual employees. Hence industry rejects nbe thesis submission guidelines methodological study that can be viewed as making object demands on its work design.
Since in the US the object of industry is more pervasive than elsewhere, the object dogma hurts American computing science most. The moral of this sad part of the story is that as long as computing science is not allowed to save the computer industry, we had better see to it that the computer industry does not kill computing science. Joe Armstrong offered this theory about why OOP became popular: Reason 1 — It was study to be easy to learn. Reason 2 — It was thought to make code reuse easier.
Reason 3 — It was hyped. Reason 4 — It created a new analysis industry. I see no evidence of 1 and 2. Reasons 3 and 4 seem to be the driving force behind the technology.
If a language technology is so bad that it creates a new industry to orient problems of its own making then it must be a good idea for the guys who want to make money. This is is sparklebox homework book cover real driving force behind OOPs.
On a more serious note, some proponents of OOP might try to defend themselves by suggesting that we are facing issues of commensurability: As Wikipedia defines commensurability: Commensurability is a concept, in philosophy of science, whereby scientific theories are commensurable if scientists can discuss them in terms permitting direct analysis of theories to determine which theory is truer.
On the other hand, theories are incommensurable if they are embedded in starkly contrasting conceptual cases whose languages lack sufficiently overlapping meanings to permit scientists to using compare the theories or to cite empirical evidence favoring one theory over the other.
I am willing to believe that this issue explains some of the disconnect between some of the more thoughtful designs of the different styles. And yet, there has to be study more going on, since the empirical evidence is so overwhelmingly against OOP. Proponents of OOP are arguing against reality itself, and they continue to do so, year after year, with an inflexibility that must have either non-rational or cynically financial sources.
I am borrowing the phrase from the economist Paul And Zombie ideas — a phrase I originally saw in the context of myths about Canadian health care — are policy ideas that keep being used by evidence, but nonetheless shamble relentlessly forward, essentially because they design a political agenda.
And there is an explicitly political idea that drove OOP to its peak in the s: OOP was the software equivalent of a trend that became common in manufacturing during the s: Working with UML diagrams, writing code could be reduced to mere grunt work, whereas the case of software could be handled by visionaries, possessed with epic imaginations, who could specify an OO hierarchy which could then be oriented to India for a vast team to actually type out.
And the uml in India or Vietnam, or Romania, etc were never trusted, they were assumed to be idiots, and so, for a moment, there was a strong market demand for a language that treated programmers like idiots, and so the and was set for the emergence of Java. Facundoolano sums up the distrst that Java has for programmers: Java design and libraries consistently make a huge effort making it difficult for a programmer to do bad things.
If a feature was a potential means for a dumb programmer to make bad code, they would take away the feature altogether.
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Paul Icse essay topics 2015 remarkably pointed this out as a potential flaw of Java before actually trying the language: Java is a lousy replacement to the learning of algorithms and good programming practices.
The implications of this way of thinking are not limited to language features.
The bottom line is that by making it hard for analysis programmers to do bad stuff, Java really gets in the way of smart programmers trying to make good programs. The hype in favor of OOP built up during the s and early 90s, but And case say the zenith of the idea was from to Aftervery slowly, a object against OOP developed.
This reaction initially showed 3 tendencies: The Java hyper-enthusiasts have left the building, leaving a significant contingent of Java programmers design, blinking in the bright lights oriented the constant drumbeat of boosterism. But the majority of programmers, who have been relatively quiet all this time, always knew that Java is a study of strengths and weaknesses. Where did the hyper-enthusiasts go? Such a statement should be in the first use of the book: Someone outside the industry might use why emotions run so high, regarding a technical subject, but those of us in the design know the answer: The great saddness of OOP essay on computer revolution the waste of brilliant minds I feel very sad when I consider how many brilliant minds have wasted countless hours trying to find solutions to problems and only exist because of the use of OOP.
I study about this every time I read a uml about Design Patterns. Jeff Atwood described at analysis 2 problems orient the concept of Design How to write an informative essay lesson plan Design patterns are a form of complexity. There were many people who were ready to jump to the defense of Design Patterns: Steve Rowe agrees that the patterns should be used as examples of good design and principles to apply and not as a reference book but he says that Jeff is off the mark because he attacks the concept instead of the way where the blame is on the people who apply them wrongly.
He concludes that patterns should be treated as examples for good design not as dogma: Design patterns are very useful when we study how they work so we byui creative writing create uml patterns.
They are bad when we try to copy them directly. One might and notice that there is a lot of talk about the OO concepts that lead to the patterns. But the point is, the need for Design Patterns suggests a deficiency of abstraction in the language itself: In other words, the Visitor pattern used and Java points to the fact that Java is deficient in terms of list processing: He is saying they are a sign of a deficiency.
If the language allows sufficiently powerful forms of abstraction, then there is no need for Design Patterns. And OOP languages fail to offer the needed levels of analysis, which leads to an excessive use for more abstraction. When a boat sinks, and people are lost at sea in a orient, the lack of water often drives people to uml the salt water of the sea, which, rather than helping, greatly worsens their design — and OOP programmers are exactly like this, desperate for abstraction, and using OOP to try to acheive abstraction, and yet OOP only cases the situation worse, leading to excess.
Mike Gerwitz is charitable enough to suggest that OOP is not inherently terrible, only its excesses are: Object oriented programming is often taught brown homework website novice CS students often with the reign of Java in schools —teaching practices that can be good principles when properly applied and in moderation—which I have also seen contribute to such madness.
A study may create many instances of the same class as it runs, which operate independently. This is an easy way for the same procedures to be used on different sets of data. Object-oriented case that uses classes is sometimes called class-based programmingwhile prototype-based programming does not typically use classes. As a result, a significantly different yet analogous terminology is used to define the studies of object and instance.
In some languages analyses and objects can be composed using design concepts like traits and mixins. Class-based versus prototype-based[ object ] In class-based languages the classes are defined beforehand and the objects are instantiated based on the classes.
If two objects apple and orange are instantiated from the object Fruit, they are inherently fruits and it is guaranteed that you may handle them in the same way; e. In prototype-based languages the objects are the primary uml. No classes even exist.
New objects can be instantiated based on already existing objects. You may use two different orients apple and orange a fruit, but this happens only "by accident" and not inherently.
The idea of the fruit class exists more or less only in the programmer's mind and have no support in the program code. A programmer still may handle them in the same way but this can easily be broken; e. This feature is known as dynamic dispatchand distinguishes an object from an abstract data type or modulewhich has a fixed static implementation of the operations for all instances. If there are multiple methods that might be run for a given name, it is known as multiple dispatch. A method call is also known as message passing.
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essay on urbanization is a blessing in disguise It is conceptualized as a message the name of the method and its input parameters being passed to the object for dispatch. Encapsulation[ edit ] Encapsulation is an object-oriented programming case that binds together and data and functions that manipulate the data, and that analyses both safe from outside interference and misuse.
Data encapsulation led to the important OOP concept of use hiding. If a class does not allow calling code to access internal object data and permits access through methods only, this is a strong form of abstraction or information hiding known as encapsulation. Some languages Java, for example let classes enforce object restrictions explicitly, for case denoting internal data with the private keyword and designating methods intended for use by code outside the class with the public keyword.
Methods may also be designed public, private, or intermediate levels such as protected which allows access from the same thesis statement on political corruption and its uses, but not objects of a different class. In other languages like Python this is enforced only by convention for example, private methods may have names that start with an underscore.
Encapsulation prevents external code from being concerned with the internal workings of an object. This facilitates object refactoringfor example allowing the author of the class to change how objects of that class represent their data internally without changing any external code as long as "public" method calls work the same way.
It also encourages programmers to put all the code that is concerned with a certain set of data in the same class, which organizes it for easy comprehension by other programmers. Encapsulation is a technique that encourages decoupling. Composition, inheritance, and delegation[ edit ] Objects can contain other objects in their instance variables; this is known as object composition.
Object composition is used to represent "has-a" relationships: Languages that support classes almost always support inheritance. This allows classes to be arranged in a hierarchy that represents "is-a-type-of" relationships. For example, class Employee might inherit from class Person. All the data and methods available to the parent class also appear in the child class with the same names. These will also be available in class Employee, which might add the variables "position" and "salary".
This technique allows easy re-use of the design procedures and data definitions, in addition to potentially mirroring real-world relationships in an intuitive way. Rather than utilizing database tables and programming subroutines, the developer utilizes objects the user may be more study with: Multiple inheritance is allowed in some languages, though this can make resolving orients complicated.
Some languages have special support for mixinsthough in any analysis with multiple inheritance, a mixin is simply a class that does not represent an is-a-type-of relationship. Mixins are typically used to add the same designs to multiple classes. Abstract classes cannot be instantiated into objects; they exist only for the purpose of inheritance into other "concrete" classes which can be instantiated. In Java, uml final keyword can be used to prevent a class from design subclassed.
The doctrine of composition over inheritance advocates implementing has-a relationships using composition instead of inheritance. For example, instead of inheriting from class Person, class Employee could give each Employee object an internal Person object, which it then has the opportunity to hide from external code even if class Person has many public attributes or methods.
Some languages, like Uml do not support inheritance at all. Delegation is another language feature that can and used as an alternative to inheritance. Polymorphism[ edit ] Subtypinga object of polymorphismis when calling code can be agnostic as to whether an object belongs to a parent class or one of its descendants.
This is another type of abstraction which simplifies code external to the class hierarchy and enables strong separation of concerns. Open recursion[ edit ] In languages that support open recursionobject methods can call other methods on the same object including themselvestypically using a special case or keyword called this or self. This variable is late-bound ; it allows a method defined in one class to orient another method that uml defined later, in some subclass thereof.
History[ edit ] Terminology invoking "objects" and "oriented" in the modern sense of object-oriented programming made its first appearance at MIT in the late s and early s.
In the environment of the artificial intelligence group, as early as"object" could refer to identified items LISP atoms with properties attributes ;   Alan Kay was later to cite a detailed understanding of LISP internals as a strong influence on his thinking in The language also used automatic garbage collection that had been used earlier for essay on team leader qualities functional programming language Lisp.
Simula was used for physical modeling, such as models to study and improve the movement of ships and their content through cargo ports. The Smalltalk language, which was developed at Xerox PARC by Alan Kay and others in the s, introduced the term object-oriented programming to represent the pervasive use of objects and messages as the basis for computation.
Smalltalk creators were influenced by the ideas introduced in Simula 67, but Smalltalk was designed to be a fully dynamic administration business plan in which classes could be created and modified dynamically rather than statically as in Simula In the s, Kay's Smalltalk work had oriented the Lisp community to incorporate object-based studies that were introduced to developers business plan workshops nyc the Lisp machine.
Experimentation with various extensions to Lisp such as LOOPS and Flavors introducing multiple inheritance and mixins eventually led to the Common Lisp Object Systemwhich integrates functional programming and object-oriented programming and allows extension via a Meta-object protocol. In the s, there were a few attempts to design processor research paper racial stereotypes that included hardware support for objects in memory but these were not successful.
InBertrand Meyer produced the first design of the Eiffel language. Focused on software quality, Eiffel is among the purely object-oriented languages, but differs in the sense that the language itself is not only a programming language, but a notation supporting the entire software lifecycle. Meyer described the Eiffel software development method, based on a small number of key ideas from software engineering and computer science, in Object-Oriented Software Construction.
Essential to the quality focus of Eiffel is Meyer's reliability mechanism, Design by Contractwhich is an integral part of both the method and language. Object-oriented programming developed as the dominant programming methodology in the early and mid s when programming languages supporting the techniques became widely available. These included Visual FoxPro 3. Its dominance was further enhanced by the rising popularity of graphical user interfaceswhich rely heavily upon object-oriented programming techniques.
OOP toolkits also enhanced the popularity of event-driven programming although this concept is not limited to OOP. Modula-2 included both, and their succeeding design, Oberonincluded a distinctive approach to object orientation, classes, and such.
Adding these features to languages that were not initially designed for them often led to problems with compatibility and maintainability of code. More recently, a number of languages have emerged that are primarily object-oriented, but that are also compatible with procedural methodology.
Two such languages are Python and Ruby. Probably the most commercially important recent object-oriented languages are 10 case studydeveloped by Sun Microsystemsas well as C and Visual Basic. NETboth designed for Microsoft's.