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Data Modeling and Database Design Chapter 1: Database Systems: Architecture and Components.

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Presentation on theme: "Data Modeling and Database Design Chapter 1: Database Systems: Architecture and Components."— Presentation transcript:

1 Data Modeling and Database Design Chapter 1: Database Systems: Architecture and Components

2 Chapter 1 – Database Systems: Architecture and Components2 Terminology Data Information Metadata

3 Information vs Data: Compare and EID Salary E1 10k E2 12k E3 10k E4 15k EID E1 E2 E3 E4 Salary 10k 12k 10k 15k

4 Chapter 1 – Database Systems: Architecture and Components4 Data Management 1.Creation of data 2.Retrieval of data 3.Update or modification of data 4.Deletion of data For that, data must be accessed and, for the ease of access, data must be organized. Quickly, Reliably and Securely.

5 Chapter 1 – Database Systems: Architecture and Components5 Exercise Assume you want to organize your DVD collection. The only tool available is an Excel sheet. What would your columns and rows in Excel look like?

6 Chapter 1 – Database Systems: Architecture and Components6 Exercise (continued) Maybe like this?

7 Chapter 1 – Database Systems: Architecture and Components7 Data Management Only two approaches for accessing data exist: Sequential access Direct access Important: A DBMS facilitates access of data without burdening the user with details of how the data is physically organized. It does this by using a declarative query language.

8 Chapter 1 – Database Systems: Architecture and Components8 History of Data Management File systems Hierarchical DBMS Network DBMS Relational DBMS Object-oriented DBMS

9 Chapter 1 – Database Systems: Architecture and Components9 Limitations of File-Processing Systems Lack of Data Integrity Data integrity (data values are correct, consistent, complete, and current) is often violated in isolated environments. Lack of Standards Organizations find it hard to enforce standards for naming data items as well as for accessing, updating, and protecting data. Lack of Flexibility/Maintainability File-processing systems are not amenable to structural changes in data and are therefore dependent upon a programmer who can either write or modify program code.

10 Chapter 1 – Database Systems: Architecture and Components10 Limitations of File-Processing Systems (continued) The limitations to file-processing systems are due to: Lack of Data Integration Data are separated and isolated in a file-processing environment. Lack of Program-Data Independence The structure of each file is embedded in the application programs.

11 Chapter 1 – Database Systems: Architecture and Components11 Limitations of File-Processing Systems (continued)

12 Chapter 1 – Database Systems: Architecture and Components12 So, What Is Desirable? Integrated data –Not data in isolation to be integrated by the application program/programmer Data Independence –Application program(s) immune to changes in storage structure and access strategy –Independent user views of data

13 Chapter 1 – Database Systems: Architecture and Components13 History of Data Management In the 1970s, the Standards Planning and Requirements Committee (SPARC) of the American National Standards Institute (ANSI) proposed what came to be known as the ANSI/SPARC three-schema architecture: conceptual, internal and external schema.

14 Chapter 1 – Database Systems: Architecture and Components14 Three Perspectives of Metadata in a Database

15 Chapter 1 – Database Systems: Architecture and Components15 Conceptual Schema Core of the architecture Represents the global view of the structure of the entire database for a community of users Captures data specification (metadata) Describes all data items and relationships between data together with integrity constraints Separates data from the program (or views from the physical storage structure) Technology independent

16 Why is the Conceptual Model so Important to You? The world wants “T-shaped People”:

17 Chapter 1 – Database Systems: Architecture and Components17 Internal Schema Describes the physical structure of the stored data (e.g., how the data is actually laid out on storage devices) Describes the mechanism used to implement access strategies (e.g., indexes, hashed addresses, etc.) Technology dependent Concerned with the efficiency of data storage and access mechanisms

18 Chapter 1 – Database Systems: Architecture and Components18 External Schema Represents different user views, each describing portions of the database Technology independent Views are generated exclusively by logical references

19 Chapter 1 – Database Systems: Architecture and Components19 Physical and Logical Data Independence Physical Data Independence Definition: External views unaffected by changes to the internal structure How?: Introduction of conceptual schema between the external views and the internal (physical) schema

20 Physical and Logical Data Independence (continued) Logical Data Independence Definition: External views unaffected by design changes (growth or restructuring) in conceptual schema How?: External views generated exclusively through logical reference to elements in the conceptual schema Consequence: External views unaffected by changes to other external views Chapter 1 – Database Systems: Architecture and Components20

21 Chapter 1 – Database Systems: Architecture and Components21 What is a Database System? A self-describing collection of integrated records Self-describing The structure of the database (metadata) is recorded within the database system – not in the application programs. Integrated The responsibility for 'integrating' data items as needed is assumed by the DBMS instead of the programmer.

22 Chapter 1 – Database Systems: Architecture and Components22 Characteristics of a Database System Database A single, integrated set of files Database Management System (DBMS) A collection of general-purpose software that facilitates the process of defining, constructing, and manipulating a database for various applications DDL vs DML

23 Chapter 1 – Database Systems: Architecture and Components23 An Early View of a Database System

24 Chapter 1 – Database Systems: Architecture and Components24 What is a Database? A database is a self-describing collection of interrelated files. Data consists of recorded facts that have implicit meaning. Viewed through the lens of metadata, the meaning of recorded data becomes explicit. A database is self-describing in that the metadata is recorded within the database – not in applications programs.

25 Chapter 1 – Database Systems: Architecture and Components25 What is a Database Management System (DBMS)? A DBMS is a collection of general-purpose software that facilitates the processes of defining, constructing, and manipulating a database.

26 Chapter 1 – Database Systems: Architecture and Components26 Components of a DBMS The major components of a DBMS include one or more query languages; tools for generating reports; facilities for providing security, integrity, backup and recovery; a data manipulation language for accessing the database; and a data definition language used to define the structure of data.

27 Chapter 1 – Database Systems: Architecture and Components27 Components of a Database System

28 Chapter 1 – Database Systems: Architecture and Components28 An Example of a Database System

29 Chapter 1 – Database Systems: Architecture and Components29 Types of Database Systems Number of users  Single-user Desktop database system  Multi-user Workgroup database system Enterprise database system Scope  Desktop database system  Workgroup database system  Enterprise database system

30 Chapter 1 – Database Systems: Architecture and Components30 Some Commercial DBMS IBM & DB2: www-306.ibm.com/software/data/db2/ www-306.ibm.com/software/data/db2/ Oracle: Microsoft & SQL Server:

31 Chapter 1 – Database Systems: Architecture and Components31 Important Terms Data Integrity (correct, consistent, complete and current) Data Redundancy

32 Chapter 1 – Database Systems: Architecture and Components32 Data Models A model is an expression of “observed or unobservable” reality. Example: chair versus department A database represents some aspect of the real world that is called the Universe of Interest. The initial step in the design process is the requirements specification activity (i.e., business rules).

33 Chapter 1 – Database Systems: Architecture and Components33 Steps in Database Design Conceptual design ---> Conceptual schema capturing user-specified business rules –Tool: e.g., ER modeling, NIAM modeling –Presentation Layer ER Model ER diagram and semantic integrity constraints –Design-Specific ER Model Coarse and fine level of granularity

34 Steps in Database Design (continued) Logical Design ---> Logical schema –Tool: normalization –Architecture: hierarchical, network, or relational Physical Design –Specifying internal storage structure and access strategies Chapter 1 – Database Systems: Architecture and Components34

35 Chapter 1 – Database Systems: Architecture and Components35 Steps in Database Design (continued)


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