1 / 19

Advanced Database Systems Module 6 Object Oriented and Object Relational

Advanced Database Systems Module 6 Object Oriented and Object Relational. School of Computer Information Engineering S HANDONG F INANCE I NSTITUTE. Objectives. Why ORDB (Object-Relational Database) Compare and Contrast OODB with ORDB What is the Object-Relational Model.

zachary-mccoy
Download Presentation

Advanced Database Systems Module 6 Object Oriented and Object Relational

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Advanced Database SystemsModule 6Object Oriented and Object Relational School of Computer Information Engineering SHANDONG FINANCE INSTITUTE

  2. Objectives • Why ORDB (Object-Relational Database) • Compare and Contrast OODB with ORDB • What is the Object-Relational Model

  3. Flattening and scattering: unnatural? P# P1 P2 P3 P# P1 P2 P3 Qty 600 300 150 Qty 200 100 450 City Status Supplier 20 Melb S1 Syd S2 30 What’s Wrong with Relational View? Business Object Vs. ??

  4. Representing the Real World • Normalisation creates relations • Fragmentation leads to many joins • Inefficient • OO applications support non-first-normal-form values, where an object can contain another object(s)

  5. Limitations of Relational Model • Huge data sets (eg. WWW) • Need for more precise mapping of real world items • New types of database objects • Multimedia like photos, video, and audio • Entire documents • E-mail • Ability to manage complicated network of multiple items, all having complex relationships with one another

  6. What is Wrong? Impedance Mismatch • Mismatch between application and DBMS data structures • Application creates complex data structures • Application wants to access them in specific ways • Procedural Language: “record-at-a-time” while SQL “set-at-a-time” • 30% of programming effort goes to converting database formats into/out of program-internal formats (Atkinson et al., 1983) • need for cursors (temporary memory for query results)

  7. Impedance Mismatch - Who gets the problem? OOPL

  8. “impedance mismatch”, So What? “For years object gurus claimed that you shouldn’t use relational databases to store objects because of the “object/relational impedance mismatch.” Yes, the object paradigm is different from the relational paradigm, but for 99% of you the reality is that your development environment is object oriented and your persistence mechanism is a relational database. Deal with it!” Scott Ambler (2000)

  9. Need to close the Semantic Gap • How do we solve the impedance mismatch problem? • Bring application and database type systems closer. • Integrate programming language and database.

  10. What are the Options? • Object-Oriented DBMS • Add database functionality to object-oriented programming language • Object-Relational DBMS • Add object-oriented functionality to database language (eg. SQL) • OOPL with Relational DBMS • Persistent programming language (PPL) is a programming language extended with constructs to handle persistent data

  11. What do we stand for? • Evolution vs Revolution • Practical Approach vs Ideal Approach • Market Driven vs Research Driven • Exploitative vs Defensive

  12. What is an Object? • Object - An “abstraction” of a real world entity • Contains: • A name • Associated data • Operations & ‘Methods’ • Interface • Operations: a function or transformation that may be applied to or by objects in a class. • Method: The implementation of an operation

  13. Object-Oriented Databases • OODBMS aimed at applications where an object-centric viewpoint is appropriate. • Typical user sessions consist of retrieving a few objects and working on them for long periods • Transactions are likely to be of a very long duration

  14. OODBMS - Advantages • Rich type system • Better at modelling complex objects • Better performance on certain data structures • No impedance mismatch • eg genomics

  15. Complex Object Types • Objects can be aggregates of (sub-)objects. • A particular problem in dealing with these objects is determining the object boundary. • Problematic when some component object is apparently a component of more than one "parent" object at the same time. • eg a software component, such as a file, may be part of several applications. This kind of  situation leads to problems in manipulating the complex objects. • What does it mean to remove, install, copy, or update an application that contains shared components?

  16. Class (Type) Hierarchies • Creation of new types based on existing ones • Eg. Image Compressed image Low resolution image

  17. OODBMS - Disadvanteges • Strong opposition from established players • Lack of theoretical foundation • Retrogressive to the old pointer system • Lack of standard ad hoc query language • Lack of business data design and management tools • Steep learning curve - complexity • Lack of resources • Lack of support for views and security

  18. Object-Relational Approach • Provides an evolutionary migration path for relational DBMS users who need object-oriented features • Makes use of relational DBMS infrastructure • New types required to better represent the application domain • New operators (functions) required to better represent the behaviour of these types • (operators manipulate types)

  19. Object Relational Model (ORM) • Benefit from both relational and OO • RDB: mature, mathematically sound, huge amount of applications • OODB: young, CAD/CAM applications, data abstraction and reusability • Based on standard • SQL3/SQL99 • Allow pre-existing applications • Protect former investment • Easy acceptance

More Related