CHAPTER 1 Introduction To Object Oriented System.ppt

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INTRODUCTION TOObject Oriented SystemsBHUSHAN JADHAV1

CHAPTER 1 Introduction to ObjectOriented SystemsØPreview of Object-orientation.ØConcept of distributed object systems,ØReasons to distribute for centralized objects.ØClient-server system architecture,ØMulti tier system architectures.ØFile Server,ØDatabase Server,ØGroup Server,ØObject Server,ØWeb ServerBHUSHAN JADHAV2

PROCEDURAL PROGRAMMINGProcedural programming is by far the most common form ofprogramming. A program is a series of instructions which operate onvariables. It is also known as imperative programming Examples of procedural programming languages includeFORTRAN, ALGOL, Pascal, C, MODULA2, Ada, BASIC. Despitetheir differences they all share the common characteristics ofprocedural programmingAdvantages of procedural programming include its relative simplicity, and ease ofimplementation of compilers and interpreters.Disadvantages of procedural programming include the difficulties of reasoningabout programs and to some degree difficulty of parallelization. Proceduralprogramming tends to be relatively low level compared to some otherparadigms, and as a result can be very much less productive.BHUSHAN JADHAV3

OBJECT ORIENTED PROGRAMMINGObject oriented programming is characterized by the defining of classesof objects, and their properties. Inheritance of properties is one way ofreducing the amount of programming, and provision of class libraries inthe programming environment can also reduce the effort required.The most widely used object oriented language is C which providesobject extensions to C, but this is rapidly being overtaken by Java.Features Of Object-Oriented ProgrammingData Abstraction and EncapsulationOperations on the data are considered to be part of the data typeWe can understand and use a data type without knowing all of itsimplementation details Neither how the data is represented nor how theoperations are implementedWe just need to know the interface (or method headers) – how to“communicate” with the object Compare to functional abstractionwith methodsBHUSHAN JADHAV4

OBJECT ORIENTED PROGRAMMINGInheritanceProperties of a data type can be passed down to a sub-type – we can buildnew types from old ones We can build class hierarchies with many levelsof inheritancePolymorphismOperations used with a variable are based on the class of the object beingaccessed, not the class of the variableParent type and sub-type objects can be accessed in a consistent wayOOP’s worldClass{Objects} Procedural Language worldstructure{structure variables}BHUSHAN JADHAV5

Distributed System andMiddleware ConceptsBHUSHAN JADHAV6

DISTRIBUTED SYSTEMA distributed system is a collection of independent computers that appears toits users as a single coherent systemImportant characteristics of distributed systems- Differences between the various computers and the ways in which they communicateare hidden from users- Users and applications can interact with a distributed system in a consistent and uniformway, regardless of where and when interaction takes placeGoals of Distributed System4 important goals that should be met to make building a distributed system worththe effort they are1) Easily connect Users to resources, hide the fact that resources are distributedacross a network, open, scalableBHUSHAN JADHAV7

2) TransparencyA distributed system that is able to present itself to users and applications as if itwere only a single computer system is said to be transparent. Which hideswhether a Implementation i.e. software resource is in main memory or diskForms of Transparency in a Distributed SystemTransparencyDescriptionAccessHide differences in data representation and how aresource is accessedLocationHide where a resource is locatedMigrationHide that a resource may move to another locationRelocationHide that a resource may be moved to another locationwhile in useReplicationHide that a resource may be shared by severalcompetitive usersConcurrencyHide that a resource may be shared by severalcompetitive usersFailureHide the failure and recovery of a resourcePersistenceHide whether a (software) resource is in memory or ondiskBHUSHAN JADHAV8

3) OpennessAn open distributed system is a system that offers services according to standard rules.4) ScalabilityScalability of a system can be measured along at Least three differentdimensions-First, a system can be scalable with respect to its size, we can easily addmore users and resources to the system.-Second, a geographically scalable system users and resources may lie farapart.-Third, a system can be administratively scalable; it can still be easy tomanage even if it spans many independent administrative organizations.BHUSHAN JADHAV9

Hardware Concepts General Classification:– Multiprocessor – a single address space amongthe processors– Multicomputer – each machine has its ownprivate memory. OS can be developed for either type ofenvironment. Bus Based or Switch Based ArchitectureOf memory and processor.BHUSHAN JADHAV10

Hardware ConceptsBasic organizations and memories in distributedcomputer systems1.6BHUSHAN JADHAV11

Multiprocessors1.7A bus-based multiprocessor.BHUSHAN JADHAV12

MultiprocessorsA crossbar switchAn omega switching networkBHUSHAN JADHAV13

Software Concepts DOS (Distributed Operating Systems) NOS (Network Operating Systems) MiddlewareSystemDescriptionMain GoalDOSTightly-coupled operating system for multiprocessors and homogeneousmulticomputersHide and managehardwareresourcesNOSLoosely-coupled operating system forheterogeneous multicomputers (LAN andWAN)Offer local servicesto remote clientsMiddlewareAdditional layer a top of NOSimplementing general-purpose servicesProvide distributiontransparencyBHUSHAN JADHAV14

Uniprocessor OperatingSystems Separating applications from operating systemcode through a microkernel– Can extend to multiple computersBHUSHAN JADHAV15

Network Operating System OS uses can be different (Windows or Linux) Typical services: rlogin, rcp– Fairly primitive way to share filesBHUSHAN JADHAV16

Network Operating System Can have one computer provide files transparently for others (NFS)Systems,network operating systems do not assume that the underlyinghardware is homogeneousBHUSHAN JADHAV17

Distributed Operating Systems But no longer have shared memory– Provide message passing– Can try to provide distributed shared memory But tough to get acceptable performanceBHUSHAN JADHAV18

Why Middleware ?Distributed operating system is not intended to handle acollection of independent computers, while network operatingsystem does not provide a view of a single coherent systemSo an additional layer of software that is used in networkoperating systems to more or less hide the heterogeneity ofthe collection of underlying platforms but also to improvedistribution transparencyBHUSHAN JADHAV19

Distributed System asMiddlewareBHUSHAN JADHAV20

CLIENT-SERVER ConceptsBHUSHAN JADHAV21

Client-Server Architecture Basic ConceptsClient-Server:The client is the entity accessing the remote resource and the server providesaccess to the resource. Operationally, the client is the caller and the server isthe callee.In Java terms:The client is the invoker of the method and the server is the objectimplementing the method.The client and the server can be heterogeneous:Different implementation languagesDifferent operating systems³The roles can be transientThe definition is with respect to a particular interactionClient and Server refer both to the code and the system on which the code is runningBHUSHAN JADHAV22

Client Server InteractionsClientServer2y F(x)F(x) {return 5;}11.2.3.4.Send message to call Fwith parameter XReceive message that Fwas called with the givenparameterSend message with theresult of calling FReceive message withthe result of calling F34NetworkBHUSHAN JADHAV23

Tiered architecture Single tiered architecture.(Monolithic applications) Ex:- C,Foxpro,ADA etc. Two tiered architecture. Client – Server systems Ex:- Unix client &Mainframes Server.BHUSHAN JADHAV24

Tiered architecture Three tieredarchitecture.ClientServerDatabase Ex:- Yahoo Mail ServerBHUSHAN JADHAV25

Tiered architecture N-Tiered architecture: Various components that make up the application arelogically separated or distributed across network. Client ßà Server ßà Server ßà Database CitiBank ATM implementationBHUSHAN JADHAV26

N-Tier Architecture Front end (Client): Viewed and manipulated by the users. It can live in a Web browser or a standalone application. Presents customized information to clients requirements. Servlets and JSP is used as Front end development. Middle: Contains business logic Ex: Discounts. It may contain two sub-tiers: Web Tier – It handles communication to client. EJB Tier – It manages business logic and access tocorporate data. Backend (Database): Provides access to various corporate data stores(Databases, E-Mail system, Legacy systems )BHUSHAN JADHAV27

N-Tiered architectureBHUSHAN JADHAV28

TYPES OF SERVERSFILE SERVER- A file server is a device that manages file operations and is shared byeach of the client PCs attached to the LAN- Each file server acts as an additional hard disk for each of the clientPCs- Each PC may be called a FAT CLIENT (most processing occurs on theclient) Entire files are transferred from the server to the client forprocessing.BHUSHAN JADHAV29

Problems with file server architecture1. Huge amount of data transfer on the network, becausewhen client wants to access data whole table(s)transferred to PC – so server is doing very little work,network is transferring large blocks of data and client isbusy with extensive data manipulation2. Each client is authorised to use the DBMS when adatabase application program runs on that PC. Thusthere is one database but many concurrently runningcopies of the DBMS (one on each active PC) – so heavyresource demand on clientsBHUSHAN JADHAV30

File Server ArchitectureFAT CLIENTBHUSHAN JADHAV31

Database server architectures After the file-server approach came two-tiered approaches Client is responsible for managing user interface, I/Oprocessing logic, data processing logic and some businessrules logic (front-end programs) Database server performs all data storage and accessprocessing (back-end functions) – DBMS is only on server Advantages include:Clients do not have to be as powerful,only the database server requires processing poweradequate to handle the database – therefore the servercan be tuned to optimise data processing performance Greatly reduces data traffic on the network, as only thoserecords (rather than tables) that match the requestedcriteria are transmitted to the client Improved data integrity since it is all processed centrallyBHUSHAN JADHAV32

Database server architectures With a database server, the client passesSQL requests as messages to the databaseserver. The results of each SQL commandare returned over the network. The serveruses its own processing power to find therequest data instead of passing all therecords back to the client and then getting itfind its own data. The result is a much moreefficient use of distributed processing power.It is also known as SQL engine.BHUSHAN JADHAV33

Database server architectureClientsDBMS onlyon serverBHUSHAN JADHAV34

TRANSACTION SERVERA Transaction server is a software component that is used in implementingtransactions.A transaction involves multiple steps which must becompletedatomically.For example, when paying someone from your bank, the system must guarantee thatthe money is taken from your account and paid into the other persons account. Itwould simply be unacceptable for just one or the other action to take place; both mustoccur in order for the transaction to have taken place.BHUSHAN JADHAV35

TRANSACTION SERVERWith a transaction server, the client invokes remote procedures that reside on theserver with an SQL database engine. These remote procedures on the serverexecute a group of SQL statements. The network exchange consists of a singlerequest/reply message. The SQL statements either all succeed or fail as a unit.OBJECT SERVERWith an object server, the Client/Server application is written as a set ofcommunicating objects. Client object communicate with server objects using anObject Request Broker (ORB). The client invokes a method on a remote object.The ORB locates an instance of that object server class, invokes the requestedmethod and returns the results to the client object. Server objects must providesupport for concurrency and sharing. The ORB brings it all together.BHUSHAN JADHAV36

GROUPWARE SERVERA SERVER which manages the interaction between a number of users of aGROUPWARE systemWeb ServersClients and servers communicate usingthe Hypertext Transfer Protocol (HTTP)HTTP requestClient and server establish TCPWebconnectionclientClient requests content(browser)Server responds with requestedHTTP responsecontent(content)Client and server close connection(usually)WebserverExamplesApache tomcat ServerSun Java System Web ServerInternet Information ServicesBHUSHAN JADHAVGlassfish ServerJigsaw Server37

APPLICATION SERVERAn Application server is a software framework dedicated to the efficient executionof procedures (scripts, routines, programs, .) for supporting the construction ofapplications. The term was created in the context of web applications. In these, theapplication server acts as a set of components accessible to the softwaredeveloper through an API defined by the platform itself.SOME POPULAR APPLICATION SERVER PROVIDER1) Apache Tomcat (Apache Software Foundation)2) TIBCO Server (TIBCOSoft)3) tc Server (SpringSource)4) WebSphere Application Server (IBM)5) Sybase Enterprise Application Server (Sybase Inc)6) WebLogic Server (Oracle)7) JBoss (Red Hat)8) JRun (Adobe Systems)9) Apache Geronimo (Apache Software Foundation)10)Oracle OC4J (Oracle)11)Sun GlassFish Enterprise Server Sun Microsystems)12)SAP Netweaver AS (ABAP/Java) (SAP)13)Glassfish Application Server(open source)BHUSHAN JADHAV14)WebObjects (Apple Inc.)38

Middleware Models And PresentTechnologies1 )RemoteProcedure Calls (RPCs).2 )CORBA3 )RemoteMethod Invocation (RMI).4 )EnterpriseJava Beans (EJB).5 )ComponentObject Modeling & DistributedComponent Object Modeling (COM AND DCOM with .net )6 )WebServices And SOA (Service OrientedArchitecture)BHUSHAN JADHAV39

ANY QUESTIONBHUSHAN JADHAV40

THANKYOUBHUSHAN JADHAV41

An open distributed system is a system that offers services according to standard rules. 4) Scalability Scalability of a system can be measured along at Least three different dimensions-First, a system can be scalable with respect to its size, we can easily add

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