Using Stored Behaviour in ObjectOriented Databases

1
Using Stored Behaviour in Object-Oriented
Databases

• Dalen Kambur
• Interoperable Systems Group
• Dublin City University

2
Overview

• Introduction
• Problem and Motivation
• Background
• Server architecture
• Future work

3
Introduction

• IOMPAR (Internet Object Management Privacy
  ARchitecture) project of
• Dublin City University
• Iona
• Versant
• Orbism
• Enterprise Ireland Research Grant
• To provide a framework for querying, modification
  and secure transport of complex objects including
  multimedia content.

4
Problem and Motivation
INSERT INTO Pyramid SELECT OID FROM Movies
m WHERE m.appears( Pyramid )
Selecting movies from all databases in which a
pyramide appears.
Movie
appears
DB1
DB2
DBn
DBx

5
Topics covered

• Introduction
• Problem and Motivation
• Background
• Server architecture
• Future work

6
Behaviour in object models

• Two ways to model behaviour
• Passive
• Methods
• Active
• Rules, usually based on Event-Condition-Action
  model
• Using Passive or Active behaviour
• Designers choice, but often restricted with
  particular technology
• Some programming languages (C, Java) do not
  facilitate active behaviour

7
Example of forms of behaviour
Invoice
Entry
Total
Amount

• Passive
• Invoice i
• ianEntry.changeAmount(100)
• // Recalculation is initiated as
• // part of the method
• // implementation

• Active
• In Entry class definition
• ON Entry insert, update, delete UPDATE Invoice
• SET Total SUM( Amout )...
• anEntry.quantity 100
• // This initiates
• // recalculation

8
ODMG database

• ODMG is the standard for object-oriented
  databases
• Does not facilitate behaviour storage
• some vendors (e.g. Versant) provide vendor
  specific interface for active behaviour, but no
  vendor allows stored behaviour
• Problems
• protecting object model consistency? (as all
  object properties are public, and no active
  behaviour)
• performing complex pattern searches, such as
  multimedia? (as pattern matching has to be done
  locally)
• implementing behaviour of object-oriented
  views?(services are part of client applications,
  i.e. behaviour is not shared)

9
Object-oriented view

• is a means of redesigning an object model to
  accommodate specific purpose, i.e.

Object-oriented view with 2 virtual classes
Base class

• Redesigning includes
• restructuring of the object state
• redefinition of behaviour

10
Topics covered

• Introduction
• Problem and Motivation
• Background
• Server architecture
• Future work

11
System model
Database server
Application 1
Core DBMS
Application 2
. . .
Behaviour
Application n
Database requests
12
Characteristics of the Architecture

• Provides behaviour sharing for persistent objects
• Maintains existing ODMG interface
• Database vendor independence (all database
  dependencies integrated in Event processor)
• Requires an extended metaclass repository for
  behaviour storage

13
Server Architecture
Extended
Services
Clients
Query Processor
Request Broker
Behaviour Processor
Event Processor
Extended Services Layer (ESL)
Existing
Clients
Database
14
Request Broker

• Interface of the ESL for client applications
• Connect
• Disconnect
• Relays request to one of three processors
• Database access (Event Processor)(containing
  object and attribute identification and
  parameters or database operation specific
  parameters)
• Behaviour invocation (Behaviour
  Processor)(containing object and method
  identification and parameters)
• Query execution (Query Processor)(containing
  query text)

15
Server Architecture
Extended
Services
Clients
Query Processor
Request Broker
Behaviour Processor
Event Processor
Extended Services Layer (ESL)
Existing
Clients
Database
16
Event Processor

• Commonly known as Database Accessor
• Database dependent
• Provides an uniform database interface to other
  processors and the Request Broker
• Find an object by unique identification
• Execute a query
• Create and delete objects
• Transaction control (commit, rollback) operations
  
• Query repository interface for the ESL (metadata)
• Performs optional event detection

17
Server Architecture
Extended
Services
Clients
Query Processor
Request Broker
Behaviour Processor
Event Processor
Extended Services Layer (ESL)
Existing
Clients
Database
18
Behaviour Processor

• Provides an interface for service invocation
• A request may have object identification and
  method parameters
• Loads the service into memory
• Executes the service
• Makes results available

19
Server Architecture
20
Query Processor

• Provides an interface for query execution
• The request is a textual representation of the
  query
• Creates two query segmets segment for Event
  Processor and segment for Behaviour Procesor
• Retrieves two separate result sets
• Constructs one overall query set

21
Service request

• SELECT SelfOID FROM Person p
• WHERE p.hasChild()
• AND NOT p.employed

22
Other target areas

• e-Business
• Health-care, e.g. X-rays
• Data mining applications
• Any other kind of applications that require
  shared services

23
Ongoing research

• Extending ODLv to facilitate behaviour definition
  in views
• Planned experiments
• Performance impact when compared to ODMG database
• Pattern search within video database (in
  cooperation with other research groups)