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The ODMG Standard 2.0 Focusing On The ODMG Object Model


The ODMG Standard 2.0 Focusing On The ODMG Object Model Group Members: Christopher Parrott, Christopher Sinclair, David Tucker & Andrew Wan Presentation Presenters ... – PowerPoint PPT presentation

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Title: The ODMG Standard 2.0 Focusing On The ODMG Object Model

The ODMG Standard 2.0Focusing On The ODMG Object
  • Group Members Christopher Parrott, Christopher
    Sinclair, David Tucker Andrew Wan

Presentation Presenters Christopher Parrott
Christopher Sinclair
  • ODMG (Object Data Management Group) formed in
  • Independent organisation to standardise Object
    Oriented Database Management Systems.
  • Corporate members includes Sun, Poet Computer
  • ODMG covers following key areas
  • Object Model (OM)
  • Object Definition Language (ODL)
  • Object Query Language (OQL)
  • C, Java Smalltalk Bindings.

The Object Model
  • About ODMG Object Model
  • Database Types
  • Specifications Implementations
  • Object type definition consists of two
    components, they are Interface one or more

Type Specification
  • Object Identifiers
  • Object Lifetime
  • Collections
  • Collection Objects
  • Set Objects
  • Bag Objects
  • List Objects
  • Array Objects
  • Dictionary Objects

  • Literal Values.
  • ODMG model supports several literal types
  • Atomic
  • Collection
  • Structured
  • Object Hierarchy

Modelling State
  • Introduction
  • Provides description of data structure relates
    interfaces to a set of object types in a type
  • Object Type Interfaces
  • Describes how data can be stored relations to
    other types of data.

Type diagram of object type definition
Modelling State
  • Attributes Relationships
  • One To One
  • One To Many
  • Many To Many
  • Names

Examples Of Relationships
Representation of how object names can be used
to represent entities with shared components
Modelling State
  • Metadata
  • Descriptive information about persistent objects
    that defines the schema.
  • Used by ODBMS to define structure .
  • Metadata is stored in an ODL Schema Repository.
  • Considered important for object oriented database
  • Example of a operation that returns the class of
    an object.
  • Above operation will store description of
    employee class.
  • EmployeeMetaData is used to print the employees
    name as the getName function is part of the
    employee class.

EmployeeMetaData William-gtgetClass( )
EmployeeName EmployeeMetaData -gtgetName( )
Modelling Behaviour
  • Introduction
  • Objects behaviour is defined by its set of
  • Operation has its specific type defined.
  • Operations
  • Described as a piece of code fragment.
  • Manipulates the properties and data of object.
  • Exceptions

Concurrency Transaction Control
  • ODMG view on locking Concurrency Control
  • Locking Control
  • Types of locks
  • Read Locks
  • Write Locks
  • Upgrade Locks
  • Prevention against form of deadlock when two
    processes both obtain read locks on object then
    attempt to obtain a write lock on the same
  • Deadlock avoided initially by obtaining upgrade
    lock instead of read locks for all objects user
    intends to modify.
  • Avoids potential conflicts when write lock is
    later obtained.

Concurrency Transaction Control
  • Lock Duration
  • Concurrency Control
  • Transactions
  • All programs that implements persistent objects
    must be organised into transactions.
  • Once transaction commits, ODBMS guarantees
    changes made by transaction are never lost.
  • ODMG data supports traditional ACID (Atomicity,
    Consistency, Integrity Durability).
  • Transactions are started with begin command,
    similar to new command when creating objects.
  • Transactions can be initiated started

Concurrency Transaction Control
  • Event Management
  • Managing Logical Databases
  • ODBMS can manage one or more logical databases.
    All of these logical databases are instances of
    type database.
  • Instances of type database created using
    DatabaseFactory interface.
  • Query identifies part of data explicitly by
    naming or by specifying conditions.
  • Database type also supports operations designed
    to aid the administration of the whole system.
    Such operations include
  • Delete
  • Move
  • Copy
  • Backup
  • Restore all of which to keep database in Good

Object Specification Languages
  • About Object Specification Languages
  • Used in representation of ODMG compliant object
    database management systems.
  • Composed of independent languages used in the
    definition of schemas.
  • Objectives of these independent languages are
  • Provide portability of databases across ODMG
    compliant implementations.
  • Interoperability of OODMS from different
    multiple vendors.
  • One of main OSL languages is ODL (Object
    Definition Language), there is also OIF (Object
    Interchange Format).

Object Query Language
  • About Object Query Languages
  • Developed by ODMG for use with ODMG databases.
  • Language Provides mechanism by which user can
    request a subset of data from a database, such
    requests referred to as ad hoc.
  • Object Query Language (OQL) is part of the SQL
    family of languages.
  • Contains query syntax from SQL such as
  • Select From Where

  • The idea of Bindings
  • Binding creates association between run-time
    system of programming language the persistent
    store of database system.
  • Usually takes the form of library functions which
    access the DBMS functionality.
  • ODMG standard implements bindings based on one
    fundamental principle
  • The programmer should perceive the binding as a
    single language for expressing both database
    programming operations, not two separate
    languages with arbitrary boundaries between
    them. ODMG 2.0, 1997

Literature Review
  • Alagic, Suad
  • 1996/1997
  • The ODMG Object Model Does it Make Sense?
  • OOPSLA (ACM Conference on Object-Oriented
    Programming, Systems, Languages, and
    Applications) USA
  • Chaudhri, Akmal B.
  • 1997
  • Experiences Using Object Data Management In the
    Real World
  • OOPSLA 1997 Workshop

The New ODMG 3.0 Standard
  • What's new in the ODMG 3.0 Standard
  • Object Model

  • The ODMG standard Its Real World Application.
  • Conclusions Criticisms of the ODMG Object
  • ODMG model requires careful examination before it
    is accepted.
  • Not yet industry standard.
  • Type checking system in ODMG model is not
  • Dynamic type checking used, but will always be in
    situations where it fails.
  • Means that run-time checks will have to be used.
  • Reduces Efficiency Reliability of overall
  • Parametric types not supported in current issue
    of the object model.
  • Except in C Bindings

  • Lack of self type.
  • Complaints towards ODMG model relate to the fact
    that it is not a formal, mathematical model.
  • ODGM model does have problems, but the model
    itself is still work in progress.
  • Most likely to be adjusted to solve some of the
    major weaknesses in current version.

The ODMG Standard 2.0Focusing On The ODMG Object
End Of Presentation
  • Group Members Christopher Parrott, Christopher
    Sinclair, David Tucker Andrew Wan

Presentation Presented By Christopher Parrott
Christopher Sinclair
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