Evolution of Database Since 1960
Evolution of Database Since 1960 document sample
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DATABASE EVOLUTION & ENVIRONMENT Chandra S. Amaravadi IN PREVIOUS DISCUSSION Database concept Database importance Development cycle Example application IN THIS DISCUSSION Evolution The database approach Definitions and terminology Database architecture DBMS architecture DBMS EVOLUTION EVOLUTION OF DBMS Introduction of business computers (1950‟s & 1960‟s) Use in TP applications (file processing) Problems of data management and data quality Academic formulations of DBMS concepts Standardization of DBMS concepts (by CODASYL 1971) EVOLUTION OF DBMS.. (FYI) Codd‟s paper (1970) System R (early „70‟s) Ingres formed in 1971 Oracle formed in 1977 ORACLE system Britton Lee formed from Ingres team in 1979 “Database machine”, DB2 in 1983 Sybase, OODBMS 1986 THE FILE PROCESSING ERA A period of time following the introduction of computers into business, during which application programs managed their own files. All changes to the data and structure of the files such as the addition of a field or changing the account balances of customers were carried out by utilities within the application program. THE FILE PROCESSING ERA During the DP era Informal handling of data In files (flat files) rather than database Caused many problems THE FILE PROCESSING ERA.. PROBLEMS OF DATA REDUNDANCY CUSTOMER ACCTS. LOANS Acct# Acct# Name Name Address Address Acct. info. loan info. THE FILE PROCESSING ERA.. PROBLEMS OF PROGRAM DATA DEPENDENCE 01 Customer-file 05 Acct# Pic 9(4). 05 Name Pic X(15). APPLICATION ........... PROGRAM Read customer file... 4785 Jim Smith 568697997.. FILE 5676 Jane Fedo 686887997.. (“FLAT FILE”) 5678 Maryann 890874432.. 3215 Jeff Zeeb 980056887.. THE FILE PROCESSING ERA.. PROBLEMS OF REPORTING CROSS REFERENCE REPORT CUSTOMER ACCTS. LOANS ACCT. DATA LOAN DATA EVOLUTION OF DBMS.. PROBLEMS CAUSED BY FILE PROCESSING Uncontrolled redundancy Program data dependence Program maintenance Poor data quality Inability to get reports Application backlog EVOLUTION OF DBMS.. PROBLEMS CAUSED BY FILE PROCESSING Uncontrolled redundancy – Same data is duplicated in multiple files Program data dependence – Application programs dependent on structure of the data Program maintenance – The effort spent in changing programs to accommodate changes in file structures. Poor data quality – Redundancy can often lead to inconsistent updates of the data, leading in turn to problems of data quality. Inability to get reports – Since each file was tied to a particular program, it was hard to get reports involving multiple files Application backlog – Managers‟ requests for report led application programmers to write new applications to fulfill the request. They were typically behind in fulfilling the requests, hence the backlog. EVOLUTION OF DBMS.. Application + Applications Applications Data management File handling DBMS routines Files Files Files EVOLUTION OF DBMS.. ACADEMIC FORMULATIONS OF DBMS CONCEPTS (FYI) 1959 1965 1968 1971 McGee Dobbs Fry CODASYL File defn. File gen. Data defn. Creation Creation Storage struc. Maintenance Maintenance Maintenance File mainten. Retrieval Retrieval Interrogation Report gen. Presentation Presentation Prog. lang. Record gen. Data admin. THE DBMS/DB APPROACH THE DATA BASE APPROACH Entity classes File 1 cust. File 2 emp. Enterprise Data model Data base THE DBMS APPROACH Integrated conceptualization of the data Organized design of database Centralized management of data System controlled access Checks on data quality Ad-hoc query capability Ad-hoc reporting DEFINITIONS AND TERMINOLOGY DEFINITIONS Database - A shared collection of logically related data designed to meet the needs of multiple users in an organization. DBMS - Software used to create, maintain and provide controlled access to the database TERMINOLOGY schema/structure/definition attribute/field name Customer Record/tuple Cust# Name Address Bal. 100 Gordon 10 Oak st. $40 200 Prasad 20 Birch. $50 300 ............ ............... ...... File/table/relation attribute/field value GETTING INFORMATION FROM A DATABASE GETTING INFORMATION FROM A DATABASE Reports Queries Views [forms that display] GETTING INFORMATION FROM A DATABASE CROSS REFERENCE REPORT CUSTOMER ACCTS. LOANS ACCT. DATA LOAN DATA GETTING INFORMATION FROM A DATABASE ACCT ACCT# NAME DT. OPENED BALANCE How can 8895 Smith 4/16/05 $35,000 we get 8896 Farley 4/22/04 $300 Acct & 8897 Gomez 1/10/00 $2,000 Loan info. in LOAN one rpt? LID AMOUNT INT. RATE BALANCE 9978 $6,000 6.0% $2,440 9979 $5,000 7.1% $5,000 9992 $1,000 8.5% $ 400 GETTING INFORMATION FROM MULTIPLE TABLES Two rules for SQL 1. In the Select part, precede each attribute name by name of table e.g. Acct.name, Loan.LID 2. In the Where part, equate values of common key from both tables e.g. Acct.Acct# = Loan.Acct# Write a query to list Name, balance, loan amt and balance for all customers. DATABASE & DBMS ARCHITECTURE THREE-SCHEMA ARCHITECTURE An architecture for databases Introduced by ANSI/SPARC* A prescription for how data should be stored (in a macro sense) Provides benefits of logical and physical independence Lacking in file processing approach *Standards Planning and Requirements Committee THE THREE FORMS OF DATA Cust# Bal. 100 $40 External 200 $50 Cust# Name Address Bal. Conceptual/ 100 Gordon 10 Oak st. $40 200 Prasad 20 Birch. $50 Base table 300 ............ ............... ...... Internal/ Hardware level THREE-SCHEMA ARCHITECTURE.. External View2 View1 Conceptual/ Base Base Base Logical Table Table Table Physical/ Internal THREE-SCHEMA ARCHITECTURE.. Basic concept is that of a view A view is the way data is presented It is a subset of the data The data resides in base tables A base table contains information about an Eclass Applns. access data via views Views are created in SQL or by forms/reports THE THREE FORMS OF DATA.. External/ --- The view of data as seen by a user/ application program (views). Conceptual/ --- The view as seen by a database designer (base table) Internal --- The view of data as it is stored internally These three levels provide logical and physical data independence, the ability to change the structure of the data and the ability to change the internal storage structure, independently of the application program. THE THREE TYPES OF MODELS Create view External Views Drop view Conceptual Schemas Create table Alter table File Create index Internal Organizations drop index Models Facilities Major Components of DBMS D B M S Kernel Prog. Data Screen/ Data Appln. SQL Language Diction- Report Defn. Gen. Interface ary Gen. D B M S Kernel Export/Import DBMS COMPONENTS.. Data definition – the facility through which schema is defined. (how new tables are created). SQL interface – the facility through which SQL commands are typed in. Programming language interface – the facility which processes SQL commands embedded in application program. Also known as the host language interface. Data dictionary – the facility that records details about the schema, reports, data entry forms etc. Screen & reports- the facility through which data entry screens and reports are created. Appln. Generation- the facility through which applications are created. Export/Import -- the facility through which files can be imported/exported in different DBMS formats. DBMS Kernel -- the actual programs which interact with the O/S and carry out data I/O. ODBC -- Open Database Connectivity – middleware to take SQL commands & return data. THE DIFFERENT CLASSES OF USERS IN A DBMS Administrators System developers End Users DBMS An integrated database environment Data Application End Users Administration Developers Data Database Enterprise Dictionary Client Applications Dir. SQL Server Database Server DISCUSSION What organization standardized DBMS concepts? Who was the chief architect of relational systems? What data-related functions were performed in the file processing approach? What are some of the basic features of a DBMS? What is the smallest unit of data in a database? Define the terms: schema, view, database, three-schema architecture. How is redundancy minimized in the database approach? What are advantages of the 3-schema architecture?