Object Oriented Database By Liem Do And Jesslyn Bui

History of Databases File Systems (1950s) hierarchical/ network (1960s) relational ( s) ODBMS (1990s-today) Store data after process created it has ceased to exist Concurrency, recovery Complex structures, fast access More reliability, less redundancy More flexibility, multiple views Better simulation, more and complex data types, more relationships (e.g.aggregation, specialization) Single language for database AND programming, no 'reconstruction' of objects

OBJECT-ORIENTED DATABASES What is an Object Oriented Database? Comparison with traditional Databases Advantages Disadvantages Code Example Myths about Object Oriented Databases Commercial ODBMS available Real Life uses of ODBMS in Industry

What is Object Oriented Database (OODB)? OODB = Object Orientation + Database Capabilities Provides data and object persistence Representation of complex data models Integrates database capabilities with object programming language capabilites

Transparent persistence

Complex data Complex data is often characterized by: A lack of unique, natural identification. A large number of many-to-many relationships. Access using traversals. Frequent use of type codes such as those found in the relational schema

Database Models Object Relational Object Relational

Object Model Three concepts are critical to understanding object models. They are: Data abstraction Encapsulation Inheritance

Relational Model

Comparison

Mapping

Comparison of object and relational terminology

Relational Database of a Cat

Object-Oriented Database of a Cat

OODB enables complex data types to be stored (e.g. CAD applications)

Object Relational Model  It handles the mapping and has a cache much like an ODBMS.  Data is mapped to the ODBMS and from the ODBMS based on the application needs.  The ODBMS provides high- speed performance for the Internet.

Advantages  Uses object oriented features for data storage.  Provides transparent object persistence  Allows ability to store complex data  High performance  Single data model

Disadvantages Lack of Familiarity Inertia Technology Fear Business Fear

Java Code Example import org.odmg.*; import java.util.Collection; Implementation impl = new com.vendor.odmg.Implementation(); Database db = impl.newDatabase(); Transaction txn = impl.newTransaction(); try { db.open("addressDB", Database.OPEN_READ_WRITE); txn.begin(); // perform query OQLQuery query = new OQLQuery("select x from Person x where x.name = \"Doug Barry\""); Collection result = (Collection) query.execute(); Iterator iter = result.iterator(); // iterate over the results while ( iter.hasNext() ) { Person person = (Person) iter.next(); // do some addition processing on the person (now shown) // now traverse to the address object and update its value person.address.street = " th Avenue South"; } txn.commit(); db.close(); }

Has a steep learning curve Slow Do not support queries Do not scale Myths about OODB

Commercial ODBMS Available  Objectivity  ObjectStore  Goods  Versant

Real Life uses of ODBMS in Industry trade stock use Internet trade use your pager use your voic book a flight use your PCS phone