Describe distributed database management systems (DDBMSs), only 3-4 sentences. Based on the attached pdf.

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Describe distributed database management systems (DDBMSs), only 3-4 sentences.  Based on the attached pdf.

Describe distributed database management systems (DDBMSs), only 3-4 sentences. Based on the attached pdf.
Chapter 9 Database Management Approaches Starks/Pratt/Last, Concepts of DB Management, 9th Edition. © 2019 Cengage. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part. Objectives • After completing this chapter, you will be able to: • Describe distributed database management systems (DDBMSs) • Discuss client/server systems • Examine the ways databases are accessed on the web • Identify XML and related document specification standards • Define data warehouses and explain their structure and access • Explain the general concepts of object-oriented DBMSs Starks/Pratt/Last, Concepts of DB Management, 9th Edition. © 2019 Cengage. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part. Introduction • Centralized approach to processing data • Users access a central computer through personal computers (PCs) and workstations • Dominated organizations from the late 1960s through the mid- 1980s • Networks connected these computers • Organizations often off-load, or shift, data communications functions from central computers to smaller computers to improve processing speed • Often use client/server systems to off-load database access functions from central computers to other computers Starks/Pratt/Last, Concepts of DB Management, 9th Edition. © 2019 Cengage. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part. Distributed Databases (1 of 3) • Computers at various sites • Connected with communications network or network • Distributed database • Single logical database physically divided among networked computers • Distributed database management system (DDBMS) • Supports and manipulates distributed databases Starks/Pratt/Last, Concepts of DB Management, 9th Edition. © 2019 Cengage. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part. Distributed Databases (2 of 3) Starks/Pratt/Last, Concepts of DB Management, 9th Edition. © 2019 Cengage. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part. Distributed Databases (3 of 3) • Computers in a network communicate through messages • One computer sends a message to another • Access delay required for every message; fixed amount of time • Communication time = access delay + (data volume / transmission rate) Starks/Pratt/Last, Concepts of DB Management, 9th Edition. © 2019 Cengage. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part. Characteristics of Distributed Systems • Homogeneous DDBMS • Same local DBMS at each site • Heterogeneous DDBMS • At least two sites at which local DBMSs are different • Shared characteristics of DDBMSs • Location transparency • Replication transparency • Fragmentation transparency Starks/Pratt/Last, Concepts of DB Management, 9th Edition. © 2019 Cengage. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part. Location Transparency • Characteristics • Remote site: site other than one where user is • Local site: site where user is • Location transparency: users do not need to be aware of location of data in a distributed database Starks/Pratt/Last, Concepts of DB Management, 9th Edition. © 2019 Cengage. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part. Replication Transparency • Data replication creates update problems that can lead to data inconsistencies • Replication transparency: users unaware of steps taken by DDBMS to update various copies of data Starks/Pratt/Last, Concepts of DB Management, 9th Edition. © 2019 Cengage. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part. Fragmentation Transparency (1 of 3) • Data fragmentation: DDBMS can divide and manage a logical object among various locations under its control • Data placed at the location where it is most often accessed • Fragmentation transparency: users unaware of fragmentation Starks/Pratt/Last, Concepts of DB Management, 9th Edition. © 2019 Cengage. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part. Fragmentation Transparency (2 of 3) Starks/Pratt/Last, Concepts of DB Management, 9th Edition. © 2019 Cengage. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part. Fragmentation Transparency (3 of 3) Starks/Pratt/Last, Concepts of DB Management, 9th Edition. © 2019 Cengage. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part. Advantages of Distributed Databases • When compared with a single centralized database, distributed databases offer the following advantages: • Local control of data • Increased database capability • System availability • Improved performance Starks/Pratt/Last, Concepts of DB Management, 9th Edition. © 2019 Cengage. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part. Disadvantages of Distributed Databases • Distributed databases have the following disadvantages: • Update of replicated data • More complex query processing • More complex treatment of concurrent update • Local deadlock: occurs at a single site in a distributed database • Global deadlock: involves more than one site • More complex recovery measures • Two-phase commit: one site acts as coordinator • More difficult management of data dictionary • More complex database design • More complicated security and backup requirements Starks/Pratt/Last, Concepts of DB Management, 9th Edition. © 2019 Cengage. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part. Rules for Distributed Databases • C.J. Date formulated 12 rules that distributed databases should follow • Local autonomy • No reliance on a central site • Continuous operation • Location transparency • Fragmentation transparency • Replication transparency • Distributed query processing • Distributed transaction management • Hardware independence • Operating system independence • Network independence • DBMS independence Starks/Pratt/Last, Concepts of DB Management, 9th Edition. © 2019 Cengage. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part. Client/Server Systems (1 of 5) • File server architecture • File server: stores user files on the network • Client/server architecture • Server: computer providing data to clients • Back-end processor or back-end machine • Clients: computers connected to a network and used by users to access data • Front-end processor or front-end machine Starks/Pratt/Last, Concepts of DB Management, 9th Edition. © 2019 Cengage. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part. Client/Server Systems (2 of 5) Starks/Pratt/Last, Concepts of DB Management, 9th Edition. © 2019 Cengage. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part. Client/Server Systems (3 of 5) Starks/Pratt/Last, Concepts of DB Management, 9th Edition. © 2019 Cengage. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part. Client/Server Systems (4 of 5) • Two-tier architecture • Server performs database functions • Clients perform presentation functions • Fat client • Thin client • Three-tier architecture • Clients perform presentation functions • Database server performs database functions • Application servers perform business functions and interface between clients and database server Starks/Pratt/Last, Concepts of DB Management, 9th Edition. © 2019 Cengage. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part. Client/Server Systems (5 of 5) Starks/Pratt/Last, Concepts of DB Management, 9th Edition. © 2019 Cengage. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part. Advantages of Client/Server Systems • Compared to file server systems, a client/server system has the following advantages: • Lower network traffic • Improved processing distribution • Thinner clients • Greater processing transparency • Increased network, hardware, and software transparency • Improved security • Decreased costs • Increased scalability Starks/Pratt/Last, Concepts of DB Management, 9th Edition. © 2019 Cengage. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part. Web Access to Databases (1 of 4) • Important concepts • Internet: worldwide collection of millions of interconnected computers and computer networks that share resources • World Wide Web (or the web): vast collection of digital documents available on the Internet • Webpage: digital document on the web • Web server: stores webpages • Web client: computer requesting a webpage • Each webpage has a Uniform Resource Locator (URL) • Hypertext Transfer Protocol (HTTP): data communication method • Web browser: computer program that retrieves a webpage • Transmission Control Protocol/Internet Protocol (TCP/IP): standard protocol for communication on the Internet • Webpages usually created using Hypertext Markup Language (HTML) Starks/Pratt/Last, Concepts of DB Management, 9th Edition. © 2019 Cengage. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part. Web Access to Databases (2 of 4) Starks/Pratt/Last, Concepts of DB Management, 9th Edition. © 2019 Cengage. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part. Web Access to Databases (3 of 4) • Static vs. dynamic webpages • Static: same content for all web clients • Dynamic: content changes in response to inputs and choices from web clients • Server-side extensions or server-side scripts • Instructions to tell the web server how to process the page • Client-side extensions or client-side scripts • Other instructions for the web browser to process • Three-tier Web-based architecture • Web clients • Web server • Database server Starks/Pratt/Last, Concepts of DB Management, 9th Edition. © 2019 Cengage. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part. Web Access to Databases (4 of 4) Starks/Pratt/Last, Concepts of DB Management, 9th Edition. © 2019 Cengage. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part. XML (1 of 4) • HTML: a text-based markup language • Describes content and appearance of Web pages • Does not describe structure and meaning of data • Extensible Markup Language (XML): a metalanguage or a language used to define another language • Tags can define meaning and structure of data • XML document should begin with an XML declaration Starks/Pratt/Last, Concepts of DB Management, 9th Edition. © 2019 Cengage. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part. XML (2 of 4) • Extensible Hypertext Markup Language (XHTML) • Markup language based on XML • Stricter version of HTML • Defining structure, characteristics, and relationships of data • Document Type Definition (DTD) • XML schema • Presentation of data • Extensible Stylesheet Language (XSL) Starks/Pratt/Last, Concepts of DB Management, 9th Edition. © 2019 Cengage. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part. XML (3 of 4) Starks/Pratt/Last, Concepts of DB Management, 9th Edition. © 2019 Cengage. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part. XML (4 of 4) Starks/Pratt/Last, Concepts of DB Management, 9th Edition. © 2019 Cengage. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part. Data Warehouses (1 of 2) • Online transaction processing (OLTP) systems • Users use transactions when interacting with an RDBMS • Data warehouse • Subject-oriented, integrated, time-variant, nonvolatile collection of data in support of management’s decision-making process Starks/Pratt/Last, Concepts of DB Management, 9th Edition. © 2019 Cengage. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part. Data Warehouses (2 of 2) Starks/Pratt/Last, Concepts of DB Management, 9th Edition. © 2019 Cengage. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part. Data Warehouse Structure and Access (1 of 3) • Star schema: conceptual shape • Fact table • Dimension table • Online analytical processing (OLAP) software • Access to a data warehouse • Data cube • Shape for visualizing a data warehouse as a multidimensional database • Data mining • Uncovering new knowledge, patterns, trends, and rules from data in a data warehouse Starks/Pratt/Last, Concepts of DB Management, 9th Edition. © 2019 Cengage. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part. Data Warehouse Structure and Access (2 of 3) Starks/Pratt/Last, Concepts of DB Management, 9th Edition. © 2019 Cengage. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part. Data Warehouse Structure and Access (3 of 3) Starks/Pratt/Last, Concepts of DB Management, 9th Edition. © 2019 Cengage. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part. Rules for OLAP Systems • E. F. Codd and colleagues formulated 12 rules • Multidimensional conceptual view • Transparency • Accessibility • Consistent reporting performance • Client/server architecture • Generic dimensionality • Dynamic sparse matrix handling • Multiuser support • Unrestricted, cross-dimensional operations • Intuitive data manipulation • Flexible reporting • Unlimited dimensions and aggregation levels Starks/Pratt/Last, Concepts of DB Management, 9th Edition. © 2019 Cengage. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part. Object-Oriented Systems • Complex objects: graphics, drawings, photographs, video, sound, voice mail, spreadsheets, etc. • RDBMSs store complex objects using special data types • Binary large objects (BLOBs) • Object-oriented DBMSs used with applications whose focus is on complex objects Starks/Pratt/Last, Concepts of DB Management, 9th Edition. © 2019 Cengage. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part. What Is an Object-Oriented DBMS? • Object-oriented database management system (OODBMS): database management system in which data and associated actions are encapsulated into objects • Object: set of related attributes along with associated actions Starks/Pratt/Last, Concepts of DB Management, 9th Edition. © 2019 Cengage. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part. Objects and Classes • Each entity is represented as an object • Rather than a relation • Attributes are listed vertically below object names • Followed by name of domain • Objects can contain other objects • An object can contain a portion of another object Starks/Pratt/Last, Concepts of DB Management, 9th Edition. © 2019 Cengage. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part. Methods and Messages (1 of 2) • Methods: actions defined for a class • Defined during data definition process • Executed when user sends a message to the object Starks/Pratt/Last, Concepts of DB Management, 9th Edition. © 2019 Cengage. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part. Methods and Messages (2 of 2) Starks/Pratt/Last, Concepts of DB Management, 9th Edition. © 2019 Cengage. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part. Inheritance • For any class, you can define a subclass • Every occurrence of subclass is considered an occurrence of the class • Subclass inherits structure and methods of the class • You can define additional attributes and methods for the subclass Starks/Pratt/Last, Concepts of DB Management, 9th Edition. © 2019 Cengage. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part. Unified Modeling Language (UML) (1 of 3) • Used to model all aspects of software development for object-oriented systems • Includes a way to represent database designs • Class diagram: most relevant diagram type for database design • Rectangles represent classes • Associations: lines joining classes represent relationships • Visibility symbol: indicates whether other classes can view or update value in attribute • Multiplicity: number of objects that can be related to an individual object • Superclass: second class of first class • Generalization: relationship between a superclass and a subclass Starks/Pratt/Last, Concepts of DB Management, 9th Edition. © 2019 Cengage. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part. Unified Modeling Language (UML) (2 of 3) Starks/Pratt/Last, Concepts of DB Management, 9th Edition. © 2019 Cengage. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part. Unified Modeling Language (UML) (3 of 3) Starks/Pratt/Last, Concepts of DB Management, 9th Edition. © 2019 Cengage. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part. Rules for OODBMSs • Benchmarks to measure object-oriented systems • Complex objects • Object identity • Encapsulation • Information hiding • Types of classes • Inheritance • Late binding • Computational completeness • Extensibility • Persistence and performance • Concurrent update support • Recovery support • Query facility Starks/Pratt/Last, Concepts of DB Management, 9th Edition. © 2019 Cengage. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part. Summary (1 of 5) • Distributed database: single logical database physically divided among computers at several sites on a network • Computers in a network communicate through messages • A homogenous DDBMS is one that has the same local DBMS at each site, whereas a heterogeneous does not • Location, replication, and fragmentation transparency are important characteristics of DDBMSs • DDBMSs permit local control of data, increased database capacity, improved system availability, and added efficiency • The two-phase commit usually uses a coordinator to manage concurrent update Starks/Pratt/Last, Concepts of DB Management, 9th Edition. © 2019 Cengage. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part. Summary (2 of 5) • C.J. Date presented 12 rules that serve as a benchmark against which you can measure DDBMSs • A file server stores the files required by users and sends entire files to the users • Two-tier client/server architecture: DBMS runs on file server and server sends only the requested data to the clients • Three-tier client/server architecture: clients perform presentation functions, database servers perform database functions, and application servers perform business functions Starks/Pratt/Last, Concepts of DB Management, 9th Edition. © 2019 Cengage. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part. Summary (3 of 5) • There are many advantages of client/server systems • Web servers interact with web clients using HTTP and TCP/IP to display HTML Web pages • Dynamic webpages are used in e-commerce • XML was developed because of need for data exchange between organizations and inability of HTML to specify structure and meaning of data • XHTML: markup language based on XML; stricter version of HTML Starks/Pratt/Last, Concepts of DB Management, 9th Edition. © 2019 Cengage. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part. Summary (4 of 5) • Data warehouse: subject-oriented, integrated, time- variant, nonvolatile collection of data in support of management’s decision-making process • A typical data warehouse data structure is a star schema consisting of a central fact table surrounded by dimension tables • Users perceive data in a data warehouse as a multidimensional database in data cube shape • Data mining: uncovering new knowledge, patterns, trends, and rules from data stored in a data warehouse Starks/Pratt/Last, Concepts of DB Management, 9th Edition. © 2019 Cengage. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part. Summary (5 of 5) • Object-oriented DBMSs deal with data as objects • UML is an approach to model all aspects of software development for object-oriented systems • Properties that serve as a benchmark against which you can measure object-oriented systems are complex objects, object identity, encapsulation, information hiding, types or classes, inheritance, late binding, computational completeness, extensibility, persistence, performance, concurrent update support, recovery support, and query facility Starks/Pratt/Last, Concepts of DB Management, 9th Edition. © 2019 Cengage. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part.

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