SE352b: Roadmap. SE352b Software Engineering Design Tools. W5: Database Technology. Database Technology

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1 SE352b Software Engineering Design Tools W5: Technology Fri, Feb 17, 2006 SE352b, ECE,UWO, Hamada Ghenniwa 1 SE352b: Roadmap CASE Tools: Introduction System Programming Tools Programming Paradigms Technology Middleware and Connectivity Tools Web Development Tools Software Tools: Special Topics Fri, Feb 17, 2006 SE352b, ECE,UWO, Hamada Ghenniwa 2

2 Data is the asset! Application-Driven approach vs. Data-Driven Driven approach Fri, Feb 17, 2006 SE352b, ECE,UWO, Hamada Ghenniwa 3 Software Tools System Source Procedure A Programming Source Language Procedure B Tools Systems Programming Tools Source Procedure C Fri, Feb 17, 2006 SE352b, ECE,UWO, Hamada Ghenniwa 4

3 Outlines Basic Definitions Example of a Main Characteristics of Technology Additional Benefits of Technology When Not to Use a DBMS Data Models Schemas vs. Instances Three-Schema Architecture Data Independence DBMS Languages DBMS Component Modules Classification of DBMSs Five-Schema Architecture System Utilities Fri, Feb 17, 2006 SE352b, ECE,UWO, Hamada Ghenniwa 5 Basic Definitions System (DBS) consists of S/W called database management system (DBMS) one or more databases (DB) managed by DBMS Sometimes, the applications are also included Fri, Feb 17, 2006 SE352b, ECE,UWO, Hamada Ghenniwa 6

4 System Users / Programmers Management System (DBMS) A software system to facilitate the creation and maintenance of a database A collection of related data Data Known facts that can be recorded and have an implicit meaning DBMS Application Program/Queries Application Program/Queries Software Software to to Process Process Queries/Programs Queries/Programs Software Software to to Access Access Stored Stored Data Data Fri, Feb 17, 2006 SE352b, ECE,UWO, Hamada Ghenniwa 7 Benefits of DBS Complex data structure Data reusability Representing complex relationships among data Sharing of data among multiple users Controlling redundancy Flexibility Data security in data storage, and in development and maintenance efforts to change data structures with minimum impact Restricting unauthorized access to data Fri, Feb 17, 2006 SE352b, ECE,UWO, Hamada Ghenniwa 8

5 Benefits DBS (Cont.) Data-services provision Providing multiple interfaces to different classes of users Providing backup and recovery services Enforcing integrity constraints on the database Availability of up-to-date information Reduced application development time Economies of scale Potential for enforcing standards Fri, Feb 17, 2006 SE352b, ECE,UWO, Hamada Ghenniwa 9 When not to use a DBMS Main inhibitors (costs) of using a DBMS High initial investment Overhead possibly need for additional hardware for providing generality, security, recovery, integrity, and concurrency control DBMS may be unnecessary database and applications are simple, well defined, and not expected to change real-time requirements that may not be met because of DBMS overhead data access by multiple users/programs is not required Fri, Feb 17, 2006 SE352b, ECE,UWO, Hamada Ghenniwa 10

6 When not to use a DBMS(Cont.) (Cont.) No DBMS may suffice system is not able to handle the complexity of data because of modeling limitations Users need special operations not supported by the DBMS Fri, Feb 17, 2006 SE352b, ECE,UWO, Hamada Ghenniwa 11 Data Models Data Model A set of concepts to describe the structure of a database certain constraints that the database should obey Data Model Operations Operations for specifying database retrievals and updates System Management System by referring to the concepts of the data model Application Application Application Fri, Feb 17, 2006 SE352b, ECE,UWO, Hamada Ghenniwa 12

7 Categories of Data Models Conceptual/Logical (high-level, semantic) data models Provide concepts that are close to the way users perceive data Also called entity-based or object-based data models Physical (low-level, internal) data models Provide concepts that describe details of how data is stored in the computer Implementation (record-oriented) data models Provide concepts that fall between the above two, balancing user views with some computer storage details Fri, Feb 17, 2006 SE352b, ECE,UWO, Hamada Ghenniwa 13 Example: Conceptual CLIENT Own ACCOUNT Hold FUNDS Participate Hold INDIVIDUAL ORGANIZATION TRANSACTION SECURITY REGULAR INDIVIDUAL FINANCIAL ADVISOR PURCHASE REDEMPTION IDEF1X Fri, Feb 17, 2006 SE352b, ECE,UWO, Hamada Ghenniwa 14

8 Example: Logical Fri, Feb 17, 2006 SE352b, ECE,UWO, Hamada Ghenniwa 15 Example: Physical Model Fri, Feb 17, 2006 SE352b, ECE,UWO, Hamada Ghenniwa 16

9 Example: Implementation CREATE TABLE CLIENT ( Client_Number VARCHAR2(20) NOT NULL, Client_Type VARCHAR2(20) NULL, Language_Code CHAR(18) NULL, Create_Date DATE NULL, Status_Code_ VARCHAR2(20) NULL, _Address_ VARCHAR2(20) NULL, Web_Site_Address_ VARCHAR2(20) NULL ); CREATE TABLE CLIENT_ROLE ( Client_Role_Type VARCHAR2(20) NOT NULL, Client_Number VARCHAR2(20) NOT NULL ); CREATE TABLE ACCOUNT ( Account_Number VARCHAR2(20) NOT NULL, Investment_Type VARCHAR2(20) NOT NULL, Administration_Type CHAR(18) NULL, Create_Date DATE NULL, No_Statements_Indicator VARCHAR2(20) NULL ); CREATE TABLE REGISTERED_INVESTMENT_ACCOUNT ( Account_Number VARCHAR2(20) NOT NULL, Registered_Plan_Type CHAR(18) NULL, Spousal_Account_Indicator CHAR(18) NULL ); Fri, Feb 17, 2006 SE352b, ECE,UWO, Hamada Ghenniwa 17 Modeling: Main Characteristics Data Abstraction A data model is used to hide storage details and present the users with a conceptual view of the database Self-contained A DBMS catalog stores the description of the database The description is called meta-data This allows the DBMS to work with different databases Users/Programmers Application Program/Queries Application Program/Queries Software Software to to Process Process Queries/Programs Queries/Programs Software Software to to Access Access Stored Stored Data Data Definition (Meta-Data) Fri, Feb 17, 2006 SE352b, ECE,UWO, Hamada Ghenniwa 18

10 Example of a Subject area: Part of a UNIVERSITY environment subject area entities STUDENT COURSE SECTION DEPARTMENT INSTRUCTOR Fri, Feb 17, 2006 SE352b, ECE,UWO, Hamada Ghenniwa 19 Meta-Data Vs. Data Example Definition (Meta-Data) STUDENT Name Student Number Class Major Smith 17 1 CS Brown 8 2 CS COURSE Course Name Name Course Number Number Credit Hours Hours Department Intro to Computer Science CS CS Data Structure CS CS Discrete Mathematics MATH MATH CS CS SECTION Section Course Semester Year Instructor Identifier Number Number 85 MATH 2410 Fall 98 King 92 CS1310 Fall 98 Anderson 102 CS3320 Spring 99 Knuth 112 MATH 2410 Fall 99 Chang 119 CS1310 Fall 99 Anderson 135 CS3380 Fall 99 Stone Fri, Feb 17, 2006 SE352b, ECE,UWO, Hamada Ghenniwa 20

11 Modeling: Main Characteristics (Cont.) Multiple views of the data Each user may see a different view of the database, which describes only the data of interest to that user Insulation between programs and data Also, called program-data independence Allows changing data storage structures and operations without affecting the DBMS access programs Fri, Feb 17, 2006 SE352b, ECE,UWO, Hamada Ghenniwa 21 Views Example TRANSCRIPT Student Name Smith Brown Course Number CS1310 MATH2410 MATH2410 Student Transcript Grade Semester C Fall B Fall A Fall Year Section Id Data generated on the fly Using subject areas entities CS1310 A Fall CS3320 B Spring Definition (Meta-Data) CS3380 A Fall STUDENT Name Student Number Class Major COURSE Course Name Course Number Credit Department SECTION Section Identifier Course Number Semester Year Instructor Fri, Feb 17, 2006 SE352b, ECE,UWO, Hamada Ghenniwa 22

12 Hierarchical Model implemented in a joint effort by IBM and North American Rockwell, 1965 Resulted in the IMS family of systems (The most popular model) Other system based on this model: System 2k (SAS inc.) Advantages simple to construct and operate on Corresponds to a number of natural hierarchically organized domains e.g., assemblies in manufacturing, personnel organization in companies Language is simple; uses constructs like GET, GET UNIQUE, GET NEXT, GET NEXT WITHIN PARENT etc. Disadvantages Navigational and procedural nature of processing is visualized as a linear arrangement of records Little scope for "query optimization" Fri, Feb 17, 2006 SE352b, ECE,UWO, Hamada Ghenniwa 23 Example: A Hierarchical Model DNAME DNUMBER DEPARTMENT MGRNAME MGRSTARTDATE EMPLOEE PROJECT NAME SSN BDATE ADDRESS PNAME PNUMBER PLOCATION Fri, Feb 17, 2006 SE352b, ECE,UWO, Hamada Ghenniwa 24

13 Network Model the first one to be implemented by Honeywell in (IDS System) Support by CODASYL DBTG report of 1971, Standardization Later implemented in a large variety of systems such as IDMS (Cullinet - now CA), DMS 1100 (Unisys), IMAGE (HP) Advantages: able to model complex relationships and represents semantics of add/delete on the relationships using record types and relationship types navigational language uses constructs like FIND, FIND member, FIND owner, FIND NEXT within set, GET etc. supports optimizing navigation through the database Fri, Feb 17, 2006 SE352b, ECE,UWO, Hamada Ghenniwa 25 Network Model(Cont.) (Cont.) Disadvantages Navigational and procedural nature of processing contains a complex array of pointers that thread through a set of records Little scope for automated "query optimization" Fri, Feb 17, 2006 SE352b, ECE,UWO, Hamada Ghenniwa 26

14 Example: A Network Model STUDENT COURSE Course Offerings Has a Is a Student Grades SECTION PREREQUISITE Section Grades GRADE-REPORT Fri, Feb 17, 2006 SE352b, ECE,UWO, Hamada Ghenniwa 27 Relational Model proposed in 1970 by E.F. Codd (IBM), first commercial system in Now it is the dominant for commercial products e.g., ORACLE, SYBASE, INFORMIX, Advantages: Mathematically Sound able to model complex relationships Can handle most situations for modeling supports "query optimization" Disadvantages Lack of support for complex data Fri, Feb 17, 2006 SE352b, ECE,UWO, Hamada Ghenniwa 28

15 Data Models(Cont.) (Cont.) several models have been proposed for implementing in a database system One set comprises models of persistent OO Programming Languages such as C++ (e.g., in OBJECTSTORE or VERSANT), Smalltalk (e.g., in GEMSTONE). Additionally, systems like O2 (Ardent Software), ORION (MCC - then ITASCA), IRIS (H.P.- used in Open OODB) Object-Relational Model Most Recent Trend Exemplified in ILLUSTRA and UNiSQL systems Fri, Feb 17, 2006 SE352b, ECE,UWO, Hamada Ghenniwa 29 Schemas vs. Instances Schema: the description of a database, includes descriptions of the database structure and the constraints that should hold on the database The database schema dose not change frequently Instance the actual data stored in a database (at a particular moment in time) Also called database state (or occurrence) The database state changes every time the database is updated Fri, Feb 17, 2006 SE352b, ECE,UWO, Hamada Ghenniwa 30

16 Three-Schema Architecture ANSI-SPARC-Proposed to support DBMS characteristics of Program-data independence Support of multiple views of the data Defines DBMS schemas at three levels External schema to describe the various user views usually uses the same data model as the conceptual level Conceptual schema to describe the structure and constraints for the whole database uses a conceptual data model Internal schema to describe data storage structures and access paths Typically uses a physical data model Fri, Feb 17, 2006 SE352b, ECE,UWO, Hamada Ghenniwa 31 Three-Schema Architecture(Cont.) (Cont.) End User End User External Level External External Schema Schema VIEW VIEW External External Schema Schema VIEW VIEW Conceptual Level Conceptual Schema Conceptual Schema Internal Level Internal Schema Internal Schema DATABASE Fri, Feb 17, 2006 SE352b, ECE,UWO, Hamada Ghenniwa 32

17 Three-Schema Architecture(Cont.) (Cont.) End User End User Mappings among schema levels External Level Programs refer to an external schema, then are mapped by the DBMS to the internal schema for execution Conceptual Level External External Schema Schema VIEW VIEW External/Conceptual Mapping Conceptual Schema Conceptual Schema Conceptual/Internal Mapping External External Schema Schema VIEW VIEW Internal Level Internal Schema Internal Schema DATABASE Fri, Feb 17, 2006 SE352b, ECE,UWO, Hamada Ghenniwa 33 Data Independence When a schema at a lower level is changed Changes will only be needed on the mappings between this schema and higher-level schema The higher-level schemas themselves are unchanged application programs need not be changed they only refer to the external schemas Fri, Feb 17, 2006 SE352b, ECE,UWO, Hamada Ghenniwa 34

18 Data Independence Logical Data Independence: The capacity to change the conceptual schema without having to change the external schemas and their application programs Physical Data Independence: The capacity to change the internal schema without having to change the conceptual schema Fri, Feb 17, 2006 SE352b, ECE,UWO, Hamada Ghenniwa 35 DBMS Languages Data Definition Language (DDL) Used by the DBA and database designers to specify the conceptual schema of a database In many DBMSs, the DDL is also used to define internal and external schemas (views) In some DBMSs, separate storage definition language (SDL) to define internal schema view definition language (VDL) to define external schema Fri, Feb 17, 2006 SE352b, ECE,UWO, Hamada Ghenniwa 36

19 DBMS Languages Data Manipulation Language (DML): Used to specify database retrievals and updates Query language stand-alone DML commands applied directly Data sublanguage DML commands can be embedded in a general-purpose programming language (host language), such as COBOL, PL/1 or C. Fri, Feb 17, 2006 SE352b, ECE,UWO, Hamada Ghenniwa 37 System Users / Programmers Application Program/Queries Application Program/Queries DBMS Software Software Software to to Process Process Queries/Programs Queries/Programs Definition (Meta-Data) Software Software to to Access Access Stored Stored Data Data Fri, Feb 17, 2006 SE352b, ECE,UWO, Hamada Ghenniwa 38

20 Typical Components of a DBMS DBA staff DBA staff Casual users APPLICATION PROGRAMS DDL Statements PRIVILEGED COMMANDS INTERACTIVE QUERY Pre-compiler Parametric users Host Language Compiler DDL Compiler Query Compiler DML Statements Compiled (Canned) Transactions Definition (Meta-Data) Stored Data Manger execution Run-time Processor DML Compiler execution Concurrency Control/ Backup/Recovery Subsystems DATABASE Fri, Feb 17, 2006 SE352b, ECE,UWO, Hamada Ghenniwa 39 Classification of DBMSs Based on the data model used: Traditional: Relational, Network, Hierarchical Emerging: Object-oriented, Object-relational Based on the number of users support single-user (typically used with micro-computers) multi-user (most DBMSs). Fri, Feb 17, 2006 SE352b, ECE,UWO, Hamada Ghenniwa 40

21 Classification of DBMSs DBMSs(Cont.) Based on architecture DBMS centralized consists of a single DBMS managing a single DB DB Centralized DBS distributed DDBMS consists of a single DBMS (called distributed DBMS, or DDBMS) that manages several DB that might be located at different computing systems DB DB Distributed DBS Fri, Feb 17, 2006 SE352b, ECE,UWO, Hamada Ghenniwa 41 Classification of DBMSs DBMSs(Cont.) A multi-database system (MDBS) supports operations on multiple DBSs, each consists of separate DBMS or DDBMS DBMS MDBMS DDBMS DB DB Multi-DBS DB Fri, Feb 17, 2006 SE352b, ECE,UWO, Hamada Ghenniwa 42

22 MDBS: 5-Level 5 Schema To support the main characteristics of MDBS, a 5-level schema architecture is required an extended version of the 3-level schema 1. Local schema 2. Component schema the conceptual schema of a component 3. Export schema a subset of the component schema that is available to the FDBS 4. Federated schema an integration of multiple export schemas 5. External schema Fri, Feb 17, 2006 SE352b, ECE,UWO, Hamada Ghenniwa 43 MDBS: 5-Level 5 Schema External External External External External Federated Federated Federated Conceptual Export Export Export MDBMS Component1 Component2 DBMS DDBMS Internal/Local 3-Level Schema Local 5-Level Schema Local DB DB DB DB Centralized DBS DB-Component 1 DB-Component 2 Fri, Feb 17, 2006 SE352b, ECE,UWO, Hamada Ghenniwa 44

23 System Utilities To perform certain functions, such as: Loading data stored in files into a database Backing up the database periodically on tape Reorganizing database file structures. Report generation utilities. Performance monitoring utilities. Others, such as sorting, user monitoring, data compression, etc. Fri, Feb 17, 2006 SE352b, ECE,UWO, Hamada Ghenniwa 45 System Utilities(Cont.) (Cont.) Data dictionary/repository Used to store schema descriptions and other information such as design decisions, application program descriptions, user information, usage standards, etc. Two types of data dictionary Passive Active accessed by users/dba only accessed by DBMS software and users/dba Fri, Feb 17, 2006 SE352b, ECE,UWO, Hamada Ghenniwa 46

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