Transcript Folie 1 - hs-weingarten.de

Modern Database Techniques
Part 1: Object Oriented Databases
3. Different Kinds of OODB
Overview
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OO language + persistence
Pure OODB
DB with object and relational access
Object-Relational Databases
Object oriented interface to relational databases
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OO language + persistence
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Use a class library with an abstract class or
interface for persistent objects.
In your application create persistent classes as
subclasses of that abstract class.
Search for objects by object navigation. Write code
for search yourself.
No additional software like a database browser
provided.
Often only one OO language supported. No access
to data by other languages.
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OO language + persistence
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Dependent on the special product more or less
support for transactions or concurrent access
provided.
Advantage: Not much overhead
Disadvantage: Not much functionality
Examples: GemStone, ozone
Persistance
Interface
Your code
DB
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Pure OODBMS
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Pure OODBMS are similar to "OO language +
persistence"
They enhance this model considerably:
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OODBMS implement a subset of the ODMG-model
Variety of predefined template classes for sets, lists,
arrays, … with appropriate functions
Persistent class offers a query-function
Transactions, concurrency, logging, recovery,
constraints, and triggers are supported.
Tools for DB-schema development
Tools like DB-browser
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Pure OODBMS (cont.)
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Advantage: Complete DB functionality
Disadvantage: Often only one or two OO
languages supported.
Examples: ObjectStore, Versant
Application 1
OODBMS
DB
Application 2
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DB with object and relational access
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Like pure OODBMS and relational databases
Two different interfaces to database:
OO interface and SQL interface
SQL is also used for DB queries on the object side.
Advantages:
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Well known query language
Support of standard interfaces e. g. ODBC and JDBC
Disadvantage: Not ODMG compliant.
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DB with object and relational access
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Examples:
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Caché (InterSystems)
Titanium (Savitar Corp.)
Application 3
Application 1
SQL access
OODBMS
Application 2
DB
OO access
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Object-Relational Databases
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Object oriented technology on top of relational
technology and in the relational context.
Define types instead of classes. Objects are stored
in tables of objects rather than in tables of rows.
Support of major object oriented features:
complex types, inheritance, aggregation, methods
Advantage: Extension of a well known technology
Disadvantages:
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Mixture of both technologies may result in difficult to
understand schemas
Performance problems
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Object-Tables instead of Tuple-Tables
Object-Table Persons
Meier, 1.5.60, ...
Huber, 11.5.69, ...
Miller, 1.12.60, ...
Tuple-Table Persons
Name
Meier
Huber
Miller
Meier
DateOfBirth
1.5.60
11.5.69
1.12.60
7.5.80
...
Meier, 7.5.80, ...
Person_type:
Name,
DateOfBirth,
...
Separation of structure definition
and table definition as set of
objects instead of set of tuples
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Object-Relational Databases
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Examples:
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Oracle 10g
IBM DB2
PostgreSQL
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Object Oriented Interface to Relational
Databases
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Object oriented access to persistent objects
Persistent objects stored as rows in relational
database
Mapping of objects to rows transparent to
application
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Object Oriented Interface to Relational
Databases
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Advantage: Use familiar object oriented
programming techniques for your applications and
relational techniques for databases.
Disadvantages:
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Mapping not fully transparent
Performance problems
Example: Hibernate
Application
p.Save() object rel.
side side
insert into
persons …
relational
DBMS
DB
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