ONTOS formerly VBase

1
ONTOS ( formerly VBase)

• Presentation - class CSCI 397C
• Student Son Doan
• Date November 11, 1999

2
ONTOS (formerly VBase)

• Introduction
• What is ONTOS (formerly VBase)?
• Basic Architecture of ONTOS Applications
• Setup a Working Database Using DBATool
• Accessing Persistent Objects
• Metaschema
• Transaction control
• Object SQL

3
Introduction

• GemStone from Servio Corporation, based on
  SMALLTALK.
• ONTOS from Ontos,Inc., based on C.
• O2 from O2 Technology,based on O2C.
• ObjectStore, based on C.
• Objectivity/DB, based on C.
• Versant, based on C.

4
Approaches for OO DBMSs

• Extend a programming language. Example GemStone
  (extends SMALLTALK)
• Extend a data model such as relational data model
  with object-oriented features. Example Oracle,
  IBM DB2
• Provide extendible object-oriented DBMS
  libraries. Example ONTOS

5
What is ONTOS?

• A commercial product of Ontos of Billerica,
  Massachussettes
• Based on making C into a database programming
  language
• Provides a persistent object store for C
• Activate and deactivate objects
• Handle concurrency
• Incorporate ObjectSQL

6
ONTOS Client-Server Architecture

• Application Process
• Virtual Application
  code
• Memory
• 
  Client
• Local Area Network

7
ONTOS Client-Server Architecture (cont.)

• Local Area Network
• Database Primary Secondary
• Registry Server Server
• File System File
  System
• Distributed
  database

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ONTOS object database

• A distributed database and based on the
  client/server architecture for data interaction.
• The server side manages the data store
• The client side provides the interface to user
  processes and manages the mapping of data to the
  application process virtual memory space.

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Large data-intensive applications

• 3 major components of the integrated object
  system
• The kernel database
• meta-schema
• basic functionality.
• The class libraries and the header files
• The utility programs

10
Setup a Working Database Using DBATool

• cd ltdirgt
• cp /usr/local/ONTOS/ONTOSDB/db/OntosSchema
  myKernel
• DBATool
• gtgt register kernel tutorialKern on lthostgt at
  ltdirgt/myKernel
• gtgt register database tutorialDB with kernel
  tutorialKern
• gtgt quit

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Accessing Persistent Objects

• Naming of Objects
• Activation of Persistent Objects
• Deactivation of Persistent Objects
• Deletion of Objects

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Naming of Objects

• The name of an object can serve as an entry point
  to the database.
• The name of an object is typically set in the
  constructor.
• Name is an inherited attribute from the root
  class Object.

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Naming of Objects (Example)

• class Thing public Object
• private
• int priv_value
• public
• Thing(int aValue, char theName)
• int getValue()
• void setValue()

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Naming of Objects (Example)

• // Constructor
• ThingThing(int aValue, char theName) Object
  ( theName )
• priv_value aValue
• A Thing can then be created as follows
• myThing new Thing(someValue,
  myFavoriteThing)

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Access a persistent object

• ONTOSs class Object provides the function
  OC_lookup() to access a particular object in the
  database
• Example
• Thing myThing (Thing)OC_lookup(myFavorit
  eThing)

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Activation of Persistent Objects

• Activation initiates transferring the objects
  state from the database to main-memory and
  transforming references.
• A single object using OC_lookup().
• All objects contained in an Aggregate using
  OC_getCluster()
• All objects reachable from a particular object
  using OC_getClosure().

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Activation of Persistent Objects

• Object OC_lookup ( char objectName, LockType
  lock readLock, )
• Object OC_getCluster ( char clusterName,
  LockType lock readLock, )
• Object OC_getClosure ( char objectName, LockType
  lock readLock, )

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Deactivation of Persistent Objects

• An object is deactivated with the operation
  void ObjectputObject()
• An entire Aggregation is deactivated with void
  AggregateputCluster()
• Implicitly achieved by deleting with
• void ObjectdeleteObject()
• void ObjectdeleteCluster()

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Metaschema

• Metaschema provides the underlying support that
  allows a form of access called programmatic
  access to database.
• Metaschema classes include
• Type
• PropertyType
• PropertyIterator

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Metaschema (Example)

• Type the ThingType (Type) OC_lookup ( Thing
  )
• Type propertyType (Type) OC_lookup (
  Thingpriv_value )
• PropertyIterator propIter new PropertyIterator
  ( theThingType )
• while ( propIter-gtmoreData() )
• // get result with operator() function

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Compare OntosDB with C

• OntosDB C
• Type class
• Property data member
• Procedure member function
• Supertype base class
• Subtype derived class

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Transaction Control

• In a database with many concurrent users,
  conflict between users must be resolved.
• Atomicity of change
• Transaction data pool
• 3 kinds of transactions
• Basic transactions
• Nesting transactions
• Shared transactions

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Basic Transactions

• 3 graduations for locking objects read lock,
  write lock, or no lock.
• The interface to the transaction mechanism
  consists of 3 functions
• TransactionStart
• TransactionCommit
• TransactionAbort

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Nesting Transactions

• Transaction may be nested (i.e., multiple
  TransactionStart calls without intervening
  commits or aborts are activated).
• Nested transactions make long transactions more
  practical. A single long transaction can be
  divided into a series of many small nested
  transactions.

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Shared Transactions

• Cooperating processes can share a single
  transaction.
• The first process to issue a TransactionStart
  call initiates the transaction. Subsequent
  processes issuing a TransactionStart call with
  the same name simply join it.
• A shared transaction may be thought of as one in
  which the transaction data pool is visible to all
  processes participating.

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ObjectSQL

• The interface of the two incompatible systems C
  and Ontos utilizes QueryIterator class.
• Begin with OC_startQuerySession()
• End with OC_endQuerySession().

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ObjectSQL (Example)

• OC_startQuerySession()
• QueryIterator myQuery
• myIter new QueryIterator((select from Thing
  where getValue() 100))
• while(myIter-gtmoreData())
• // get each Thing and process it somehow
• delete myIter
• OC_endQuerySession()

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ObjectSQL (cont.)

• The resulting collection of objects satisfying
  the SQL query can be obtained by using
  QueryIteratormoreData().
• To get each object of the result collection, use
  QueryIteratorYieldRow()
• Example
• ArgumentList anArgList myIter-gtYieldRow()
• Entity ptr (Entity ) (anArgList)0

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References

• Alfons Kemper. Object-Oriented Database
  Management. Prentice Hall, New Jersey, 1994.
• George Wilkie. Object-Oriented Software
  Engineering. Addison-Wesley, 1993.
• R.G.G. Cattell. Object Data Management.
  Addison-Wesley, 1991.
• James A. Larson. Database Directions. Prentice
  Hall, New Jersey, 1995.
• Setrag Khoshafian, Razmik Abnous. Object
  Orientation. John Wiley Sons, Inc., 1995.
• A.A van Rossum. URL http//is.twi.tudelft.nl/data
  bases/1996/ontos/report/ontos.html