Unit 11 Database systems and new applications A small unit of data is the data field ( or data item ) that consists of a group of related characters treated as a single entity . A collection of related data items treated as a single unit is called record . Records are grouped to form files . A file is a number of related records that are treated as a unit, A database is a collection of logically related data elements that may be structured in various ways to meet the many processing and retrieval needs of people and organizations. Database systems are designed to manage large bodies of information . The management of data involves both the definition of structures for the storage of information and the provision of mechanisms for the manipulation of information . A database management system (DBMS) consists of a collection of interrelated data and a set of programs to access these data . The collection of data , is usually referred to as database. The various data models for databases that have been proposed fall into three different groups: objectbased logical models , record-based logical models , and physical models. The three most widely accepted record-based data models are the relational , network and hierarchical models . The relational model uses a collection of tables to represent both data and the relationship amony these data. Each table has multiple columns and each column has a unique name. Data in the network model are represented by the collections of record and relationships among data are represented by links , which can be viewed as pointers. The records in the database are organized as the collections of arbitrary graphs. The hierarchical model is similar to the network model in the sense that data and relationships among data are represented by records and links, respectively. It differs from the network in that records are organized as the collections of trees rather than arbitrary graphs. Database system architectures can be classified into centralized systems, client-server systems, parallel systems and distributed systems, Relational databases have been in use for over two decades . Several new applications ', which have become increasingly important in recent years are: decision support systems , spatial databases , multimedia databases, mobile databases , information retrieval and distributed information retrieval. From overall system structure point of view, a database system is partitioned into modules that deal with each of the responsibilities of the overall system. some of the functions of the database system may be provided by the operating system of computer . In most cases the operating system of computer provides only the most basic services , and the database system must be built on that base. Thus, the design of a database system must include the consideration of the interface between the database system and the operating system. The functional components of a database system can be broadly divided into query processor components and storage manager components . The query processor components include DML compiler , embedded DML precompiler, DDL interpreter and query evalution engine. The storage manager components provide the interface between the low level data stored in the database and the application programs and queries submitted to the system. The storage manager components include authorization and integrity manager ', transaction: manager , file manager and buffer manager. In addition , several data structures such as data files, data dictionary , indices and statistical data are required as part of the physical system implementation. Acronyms: DBMS: Database Management System DML: Data Manipulation Language DDL: Data Definition Language Exercises 1- Understanding the passage Decide whether the following sentences are true or false (T/F) by referring to the information inthe text. T F 1. A small unit of data consisting of a group of related characters is called data field. 2. Database systems are designed to manage large bodies of information. 3. A.collection of related data items treated a single unit is called file. 4. A collection of logically related data elements that may be structured in various ways to meet the many processing and retrieval needs of people and organizations is called database. 5.The management of data involves only the definition of structures for the storage of information. 6. The various data models for databases that have been proposed fall into two different groups. 7. A database management'system consists of a collection of interrelated data and a set of programs to access these data . 8. Relational databases have been in use for over two decades. 9. Spatial databases and multimedia databases are examples of new applications 10. A hierarchical model uses a collection of tables to represent both data and relationslip among these data . 11. The relational model is similar to the network model in the sense that data and relationships among data are represented by records and links respectively. 12. Data in the network model are represented by pointers as well as tables. 13. Client - server systems and centralized systems are types of database system architectures. 14. A database system is partitioned into modules that deal with each of the responsibilites of the overall system . 15. In most cases , the operating system of computer provides a lot of services for the database system . D 16. The query processor components provide the low level data stored in the database and the application programs and queries submitted to the system. 17. The storage manager components include DML compiler, embedded DML compiler, DDL interpreter and query evaluation engine. 18. Data files , data dictionary , indices and statistical data are also required as part of the physical system implementation. 19. In the hierarchical model records are organized as the collections of trees. 20.1n the network model records are organized as the collections of arbitrary graphs. 2- Understanding words A.Fill in the blanks with the following words. retrieval provision interrelated hierarchical interface evaluation integrity functional based entity 1. The management of data involves the .................. of mechanisms for the manipulation of information. 2. Record ................ logical model is one of the models for databases. 3.Data item is a collection of related characters treated as a single ............... 4. A database is built to meet the many processing and ...................... needs of people and organizations. 5. The ............... model is similar to the network model in the sense that data and relationships among data are repersented by records and links. 6. The collection of .............. data in a DBMS is usually referred to as database. 7. The ............ components of a database system can be broadly divided into query processor components and storage manager components. 8. The storage manager components provide the ............... between the low level data stored in the database and the application programs and queries submitted to the system. 9. Authorization and ....... manager is a componet which belongs to the storage manager components. 10. DDL interpreter and query ............. are components which belong to the query processor components. B. Consider the meaning of the words in the text, then write synonyms for the following words in the spaces provided. 1. related ................................ 2. involve ................................ 3. manipulation ................................ 4. collection ................................ 5. structure ................................ 6. embedded ................................ 7. submit ................................ 8. authorization ................................ 9. deal with ................................ 10. partition ................................ C.Consider the meaning of the words in the text, then write antonyms for the following words. 1. logically ................................ 2. retrieval ................................ 3. integrity ................................ 4. various ................................ 5. arbitrary ................................ 3- Content review Match the following words and phrases in column A with the phrases and clauses in column B. AB ( 1. transaction manager ( 2. operating system ( 3. object- based logical models ( 4. data dictionary and data files ( 5. database system design ( 6. DDL interpreter (7. database ( 8. DML ( 9. DDL ( 10. files a. records are grouped to form b. a collection of logically related data elements c. is an acronym for data manipulation language d. a query processor component e. a storage manager component f. may provide some of the functions of the database system g. are data models for databases h. are required as part of the physical system implementation i. must include the consideration of interface between the database system and the operating system. j. is an acronym for data definition language. 4- Word forms Choose the appopriate form 'of the words to complete the sentences. 1. consistency , consistent,consistently,consistence The data values stored in the database must satisfy certain types of.............. constraint 2. simultaneous, simultaneously, simultaneousness, simultaneity Many systems allow multiple users to update the data………………. 3. accessible, access, accessibility,accessibly ,Not all the users of the database system need............. to all the data. 4. abstracter, abstractly , abstracted, abstraction The lowest level of ............... describes how the data are actully stored . 5. independennce, independent, independency, independently The ability to modify a schema definition in one level without affecting a schema definition in the next higher level is called data .................... 6. develop, developed, develops, development The importance of formation in most organizations has led to the .................. of a large body of concepts and techniques for the efficient management of data. 7. special, specially, specialized, specialization .................... users are sophisticated users who write specialized database application that do not fit into the traditional data processing framework. 8. interact, interaction, interacts, interacted Naive users are unsophisticated users who ............. with the system by invoking one of the permanent application programs that have been written previously. 9. write , wrote, writing, written Sophisticated users interact with the system without ................ programs . Instead , they form their requests in a database query language. 10. evaluate, evaluation, evaluting, evaluated DML compiler translates DML statements in a query language into low-level instructions that query ............ engine understands. 5- Translation Translate the following text into Persian. A major purpose of a database system is to provide users with an abstract view of data . That is , the system hides certain details of how the data are stored and manipulated. It does so by defining three level of abstraction at which it may be viewed: the physical level, the logical level , and the view level Databases change over time as information is inserted and deleted . The collection of information stored in the database at a particular moment is called an instance of the database. The overall design of the database is called the database schema. There are two levels of data independence in a database called physical data independence and logical data independence. A database schema is specified by a set of definitions that are expressed by a data definition language . DDL statements are compiled into a set of tables that is stored in a special file called data dictionary . The data dictionary thus contains metadata. A data manipulation language is a language that enables users to access or manipulate data. 6- Equivalent words Write the Persian equivalents of the following words in the spaces provided . 1. access…………………………… 2. accept…………………………… 3. among…………………………… 4. architecture…………………………… 5. arbitrary…………………………… 6. authorization…………………………… 7. body…………………………… 8. broadly…………………………… 9. case…………………………… 10. centralized…………………………… 11. classity…………………………… 12. client…………………………… 13. collection…………………………… 14. column…………………………… 15. component…………………………… 16. consideration…………………………… 17. consist…………………………… 18. data…………………………… 19. database…………………………… 20. data item…………………………… 21. data model…………………………… 22. deal with…………………………… 23. decade…………………………… 24. definition…………………………… 25. differ…………………………… 26. distributed…………………………… 27. element…………………………… 28. embedded…………………………… 29. engine…………………………… 30. entity…………………………… 31. evaluation…………………………… 32. field…………………………… 33. file…………………………… 34. function…………………………… 35. functional…………………………… 36. graph…………………………… 37. group…………………………… 38. hierarchical…………………………… 39. information…………………………… 40. implement…………………………… 41. important…………………………… 42. increasingly…………………………… 43. integrity…………………………… 44. interface…………………………… 45. interrelated…………………………… 46. involve…………………………… 47.level…………………………… 48. link…………………………… 49. logical…………………………… 50. logically…………………………… 51. low…………………………… 52. management…………………………… 53. manager…………………………… 54. mechanism…………………………… 55. mobile…………………………… 56. multimedia…………………………… 57. multiple…………………………… 58. network…………………………… 59. object-based…………………………… 60. operating system…………………………… 61. organize…………………………… 62. organization…………………………… 63. parallel…………………………… 64. partition…………………………… 65. physical…………………………… 66. pointer…………………………… 67. precompiler…………………………… 68. propose…………………………… 69. provide…………………………… 70. provision…………………………… 71. query…………………………… 72. record…………………………… 73. record-based…………………………… 74. refer…………………………… 75. related…………………………… 76. relational…………………………… 77. relationship…………………………… 78. represent…………………………… 79. require…………………………… 80. respectively…………………………… 81. retrieval…………………………… 82. sense…………………………… 83.. server…………………………… 84. similar…………………………… 85. single…………………………… 86. statistical…………………………… 87. storge…………………………… 88. structure…………………………… 89. submit…………………………… 90. table…………………………… 91. transaction…………………………… 92. treat…………………………… 93. unique…………………………… 94. unit…………………………… 95. various…………………………… 96. view…………………………… 97. widely……………………………


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