PowerPoint PresentationData Models, Schemas, and InstancesData Models, Schemas, and Instances (cont'd.)Categories of Data ModelsConceptual Data ModelsRepresentational Data ModelsPhysical Data ModelsSchemas, Instances, and Database StateSchemas, Instances, and Database State (cont'd.)Slide 10Slide 11Three-Schema Architecture and Data IndependenceThree-Schema Architecture and Data Independence (cont'd.)Data IndependenceDBMS LanguagesDBMS InterfacesThe Database System EnvironmentThe Database System Environment (cont'd.)Slide 19Centralized and Client/Server Architectures for DBMSsSlide 21Basic Client/Server ArchitecturesBasic Client/Server Architectures (cont'd.)Slide 24Slide 25Two-Tier Client/Server Architectures for DBMSsTwo-Tier Client/Server Architectures (cont'd.)Three-Tier and n-Tier Architectures for Web ApplicationsSlide 29Classification of Database Management SystemsClassification of Database Management Systems (cont'd.)Slide 32SummaryCopyright © 2011 Pearson Education, Inc. Publishing as Pearson Addison-WesleyChapter 2Database System Concepts and ArchitectureCopyright © 2011 Ramez Elmasri and Shamkant NavatheData Models, Schemas, and InstancesData abstraction Suppression of details of data organization and storageHighlighting of the essential features for an improved understanding of dataCopyright © 2011 Ramez Elmasri and Shamkant NavatheData Models, Schemas, and Instances (cont'd.)Data modelCollection of concepts that describe the structure of a databaseProvides means to achieve data abstractionBasic operations •Specify retrievals and updates on the databaseCopyright © 2011 Ramez Elmasri and Shamkant NavatheCategories of Data ModelsHigh-level or conceptual data models Close to the way many users perceive dataLow-level or physical data models Describe the details of how data is stored on computer storage mediaRepresentational data modelsEasily understood by end users Also similar to how data organized in computer storageCopyright © 2011 Ramez Elmasri and Shamkant NavatheConceptual Data ModelsEntity Represents a real-world object or concept AttributeRepresents some property of interest Further describes an entityRelationship among two or more entities Represents an association among the entitiesEntity-Relationship model is a popular high level, conceptual data model.Copyright © 2011 Ramez Elmasri and Shamkant NavatheRepresentational Data ModelsRelational data modelUsed most frequently in traditional commercial DBMSsObject data model New family of higher-level implementation data models Closer to conceptual data modelsCopyright © 2011 Ramez Elmasri and Shamkant NavathePhysical Data ModelsPhysical data models Describe how data is stored as files in the computer Access path •Structure that makes the search for particular database records efficientIndex •Example of an access path •Allows direct access to data using an index term or a keywordCopyright © 2011 Ramez Elmasri and Shamkant NavatheSchemas, Instances, and Database StateDatabase schemaDescription of a databaseSchema diagramA displayed schemaSchema constructEach object in the schemaDatabase state or snapshotData in database at a particular moment in timeCopyright © 2011 Ramez Elmasri and Shamkant NavatheSchemas, Instances, and Database State (cont'd.)Copyright © 2011 Ramez Elmasri and Shamkant NavatheSchemas, Instances, and Database State (cont'd.)Define a new databaseSpecify database schema to the DBMSInitial state Populated or loaded with the initial dataValid stateSatisfies the structure and constraints specified in the schemaCopyright © 2011 Ramez Elmasri and Shamkant NavatheSchemas, Instances, and Database State (cont'd.)Schema evolutionChanges applied to schema as application requirements changeCopyright © 2011 Ramez Elmasri and Shamkant NavatheThree-Schema Architectureand Data IndependenceInternal level Describes physical storage structure of the databaseConceptual levelDescribes structure of the whole database for a community of usersExternal or view level Describes part of the database that a particular user group is interested inCopyright © 2011 Ramez Elmasri and Shamkant NavatheThree-Schema Architectureand Data Independence (cont'd.)Copyright © 2011 Ramez Elmasri and Shamkant NavatheData IndependenceCapacity to change the schema at one level of a database system Without having to change the schema at the next higher levelTypes:LogicalPhysicalCopyright © 2011 Ramez Elmasri and Shamkant NavatheDBMS LanguagesData definition language (DDL)•Defines both schemasStorage definition language (SDL)•Specifies the internal schemaView definition language (VDL)•Specifies user views/mappings to conceptual schemaData manipulation language (DML)•Allows retrieval, insertion, deletion, modificationCopyright © 2011 Ramez Elmasri and Shamkant NavatheDBMS InterfacesMenu-based interfaces for Web clients or browsingForms-based interfacesNatural language interfacesSpeech input and outputInterfaces for parametric usersInterfaces for the DBACopyright © 2011 Ramez Elmasri and Shamkant NavatheThe Database System EnvironmentDBMS component modulesBuffer management Stored data manager DDL compiler Interactive query interface•Query compiler •Query optimizerPrecompilerCopyright © 2011 Ramez Elmasri and Shamkant NavatheThe Database System Environment (cont'd.)DBMS component modulesRuntime database processorSystem catalogConcurrency control systemBackup and recovery systemCopyright © 2011 Ramez Elmasri and Shamkant NavatheCopyright © 2011 Ramez Elmasri and Shamkant NavatheCentralized and Client/Server Architectures for DBMSsCentralized DBMSs ArchitectureAll DBMS functionality, application program execution, and user interface processing carried out on one machineCopyright © 2011 Ramez Elmasri and Shamkant NavatheCopyright © 2011 Ramez Elmasri and Shamkant NavatheBasic Client/Server ArchitecturesServers with specific functionalitiesFile server •Maintains the files of the client machines.Printer server •Connected to various printers; all print requests by the clients are forwarded to this machineWeb servers or e-mail serversCopyright © 2011 Ramez Elmasri and Shamkant NavatheBasic Client/Server Architectures (cont'd.)Client machines Provide user
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