Database Systems: Three-Schema Architecture
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Database Systems: Three-Schema Architecture

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Questions and Answers

What is the primary difference between an active and a passive data dictionary?

  • Passive data dictionaries are updated in real time.
  • Active data dictionaries are used only by users.
  • Passive data dictionaries contain more detailed schema information.
  • Active data dictionaries are accessible by DBMS software. (correct)

    • Which of the following is NOT an example of a specialized server in a client-server architecture?

  • Print server
  • Operating system server (correct)
  • DBMS server
  • Web server

    • In a centralized DBMS architecture, where is the processing primarily done?

  • At a centralized site (correct)
  • At user terminals
  • At a remote server
  • At any client machine

    • What does the internal schema describe in the three-schema architecture?

    <p>Physical storage structures and access paths</p> Signup and view all the answers

    Which schema level is responsible for defining the structure and constraints for the database?

    <p>Conceptual schema</p> Signup and view all the answers

    What role do clients play in a client-server architecture?

    <p>Clients provide interfaces to access server resources.</p> Signup and view all the answers

    What is the purpose of mappings among schema levels in the three-schema architecture?

    <p>To transform requests and data between levels</p> Signup and view all the answers

    Which tool is categorized under CASE (computer-aided software engineering)?

    <p>PowerBuilder</p> Signup and view all the answers

    What is a characteristic of a 2-tier client-server architecture?

    <p>Clients and servers have specialized functions.</p> Signup and view all the answers

    What does logical data independence allow for in a database system?

    <p>Changing the conceptual schema without affecting the external schemas</p> Signup and view all the answers

    What happens when a schema at a lower level is modified in a DBMS that supports data independence?

    <p>Only mappings to higher-level schemas need adjustment</p> Signup and view all the answers

    Which component is described as a repository for schema descriptions and other important information?

    <p>Data dictionary</p> Signup and view all the answers

    How can clients connect to specialized servers in a client-server architecture?

    <p>Via any form of a network.</p> Signup and view all the answers

    Which type of data independence allows changing the internal schema without needing to alter the conceptual schema?

    <p>Physical data independence</p> Signup and view all the answers

    In which schema level would you typically find the various user views of the database?

    <p>External schema</p> Signup and view all the answers

    What is an example change that might affect the internal schema without impacting the conceptual schema?

    <p>Reorganizing file structures</p> Signup and view all the answers

    Which programming interface allows embedding DML in Java applications?

    <p>SQLJ</p> Signup and view all the answers

    What defines a forms-based user-friendly interface?

    <p>It is designed for naïve users who enter data through forms.</p> Signup and view all the answers

    Which utility is NOT typically part of database system utilities?

    <p>User authentication modules</p> Signup and view all the answers

    What is the purpose of ODBC in database programming?

    <p>To provide a universal data connection for various programming languages.</p> Signup and view all the answers

    Which of the following is an example of a natural language interface?

    <p>Speech recognition system for queries</p> Signup and view all the answers

    Which of the following best describes the embedded approach for database programming?

    <p>Directly embedding SQL code into a programming language.</p> Signup and view all the answers

    What is a common characteristic of mobile interfaces in DBMS?

    <p>They allow users to perform transactions using apps.</p> Signup and view all the answers

    Which approach is utilized by Oracle for its database programming language?

    <p>PL/SQL</p> Signup and view all the answers

    What is a notable advantage of the Network Model in database management?

    <p>It can model complex relationships and handle add/delete semantics.</p> Signup and view all the answers

    Which of the following is a disadvantage of the Hierarchical Model?

    <p>It offers minimal scope for query optimization.</p> Signup and view all the answers

    In which year was the Relational Model proposed by E.F. Codd?

    <p>1970</p> Signup and view all the answers

    Which of the following options describes the language used in the Hierarchical Model?

    <p>It uses constructs like GET, GET NEXT, and GET UNIQUE.</p> Signup and view all the answers

    What characterizes the navigational nature of both the Network and Hierarchical Models?

    <p>They require users to follow specific paths through records.</p> Signup and view all the answers

    What is a common characteristic of the Database Management Systems (DBMS) mentioned?

    <p>They can handle varying complexities in data relationships.</p> Signup and view all the answers

    Which database model resulted from a joint effort by IBM and North American Rockwell?

    <p>Hierarchical Model</p> Signup and view all the answers

    What is a primary disadvantage of the Network Model?

    <p>It utilizes a network of pointers that complicate data navigation.</p> Signup and view all the answers

    Which of the following is a characteristic of object-oriented data models?

    <p>Use of persistent programming languages</p> Signup and view all the answers

    What is a primary feature of object-relational models?

    <p>Incorporation of object database concepts</p> Signup and view all the answers

    Which SQL standard follows SQL-92?

    <p>SQL-99</p> Signup and view all the answers

    Which DBMS is known for being an example of an object database?

    <p>OBJECTSTORE</p> Signup and view all the answers

    What is the primary trend involving relational DBMSs in recent years?

    <p>Extension to process non-relational data types</p> Signup and view all the answers

    What does the term 'Three-Schema Architecture' refer to?

    <p>A framework for data independence</p> Signup and view all the answers

    Which of these databases is primarily open-source?

    <p>PostgreSQL</p> Signup and view all the answers

    What does the Object Database Standard include?

    <p>ODMG-93, ODMG-version 2.0, ODMG-version 3.0</p> Signup and view all the answers

    Study Notes

    Three-Schema Architecture

    • Comprised of three levels: internal schema (physical storage), conceptual schema (entire database structure), and external schema (user-specific views).
    • Internal schema utilizes physical data models; conceptual schema uses conceptual or implementation data models; external schemas generally mirror conceptual models.
    • Mappings are required between schema levels to transform user requests into data executions and to format internal data for user views.

    Data Independence

    • Logical Data Independence: Ability to modify the conceptual schema without altering external schemas or application programs.
    • Physical Data Independence: Ability to change the internal schema without affecting the conceptual schema.
    • Changes at lower schema levels require only adjustments in mappings, not changes to higher-level schemas, allowing application programs to remain unchanged.

    DBMS Programming Language Interfaces

    • Embedded Approach: Integrates DML within programming languages (e.g., embedded SQL, SQLJ).
    • Procedure Call Approach: Utilizes APIs like JDBC for Java and ODBC for various programming languages.
    • Database Programming Language: PL/SQL, a derivative language for Oracle, incorporates SQL data types fully.
    • Scripting Languages: PHP and Python are utilized for writing client-side and server-side database programs.

    User-Friendly DBMS Interfaces

    • Menu-based: Widely used for web browsing and navigating databases.
    • Forms-based: Designed for novice users, resembling traditional form filling.
    • Natural Language: Enables queries in written language, simplifying user interaction.
    • Combines various interface types, enhancing usability in web database interactions.

    Other DBMS Interfaces

    • Speech Input/Output: Allows voice commands and responses.
    • Web Browsers: Utilize keyword searches to interact with databases.
    • Parametric Interfaces: Used in specific applications (e.g., banking systems) leveraging function keys.

    Database System Utilities

    • Essential functions include data loading tools, backup systems, reorganization utilities, and performance monitoring.
    • Other functions encompass reporting, sorting, user monitoring, and data compression.

    Data Dictionary / Repository

    • Stores schema descriptions, design considerations, and application details.
    • Divided into active (accessible by DBMS software) and passive (accessible only by users/DBAs).

    Application Development Environments and CASE Tools

    • Programs to facilitate application development include PowerBuilder, JBuilder, and Oracle's JDeveloper 10G.

    Centralized and Client-Server DBMS Architectures

    • Centralized DBMS: Integrates all software, hardware, and user interface processing into a single system.
    • Clients connect remotely, but all processing occurs at a centralized site.

    Client-Server Architectures

    • Features specialized servers fulfilling distinct functions (e.g., DBMS server, web server).
    • Clients access these services via networks, which can be LAN or wireless.

    Network Model

    • Advantages: Efficiently models complex relationships and navigates databases.
    • Disadvantages: Procedural processing and a complex pointer structure limit automated query optimization.

    History of Data Models

    • Hierarchical Model: Originated in the 1960s with IBM's IMS system, favored for simple construction but limited in query optimization.
    • Relational Model: Introduced by E.F. Codd in 1970, dominating databases today with widespread commercial and open-source implementations.
    • Object-oriented Data Models: Developed to integrate with persistent programming languages like C++ and Smalltalk, standardized in ODMG.
    • Object-Relational Models: Emerged from blending relational and object-oriented paradigms to handle diverse data types.

    Chapter Summary

    • Key topics include data models, schemas, three-schema architecture, data independence, DBMS languages, utilities, tools, architectures, and the evolution of data models.

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    Description

    Explore the Three-Schema Architecture in Database Management Systems (DBMS) through this quiz. Understand how internal, conceptual, and external schemas define the structure and constraints of a database. Test your knowledge on physical storage structures and access paths.

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