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Chapter 8 | Complex Data Types

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Object-based Databases

  1. Advanced Database Applications need Complex Data Types

  2. Applications are often written in object-oriented programming languages（OOPL）

    • Type system does not match relational type system
    • Switching between imperative language and SQL is troublesome

  3. Approaches for integrating object-orientation with databases

    • Build an object-oriented database（OODB） that natively supports object-oriented data and direct access from programming language
    • Build an object-relational database（ORDB）， adding object-oriented features to a relational database
    • Automatically convert data between programming language model and relational model; data conversion specified by object-relational mapping(ORM)

Object-Relational Mapping

  1. Object-relational mapping (ORM) systems allow

    • Specification of mapping between programming language objects and database tuples
    • Automatic creation of database tuples upon creation of objects
    • Automatic update/delete of database tuples when objects are update/deleted
    • Interface to retrieve objects satisfying specified conditions
      • Tuples in database are queried, and object created from the tuples

  2. Details in Section 9.6.2

    • Hibernate ORM for Java
    • Django ORM for Python

Semi-Structured Data

  1. Many applications require storage of complex data, whose schema changes often

  2. The relational model’s requirement of atomic data types may be an overkill

    • E.g., storing set of interests as a set-valued attribute of a user profile may be simpler than normalizing it

  3. Data exchange can benefit greatly from semi-structured data

    • Exchange can be between applications, or between back-end and front-end of an application
    • Web-services are widely used today, with complex data fetched to the front-end and displayed using a mobile app or JavaScript

  4. XML and JSON are widely used semi-structured data models

    • XML: Extensible Markup Language
      • Earlier generation notation, still used extensively
    • JSON: JavaScript Object Notation
      • Widely used today

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