Transcript Object-Oriented Database Management Systems

Murat KARAÖZ
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Scope
 What is an “Object Database”?
 History
 Queries
 When / Where / Why ODMSs
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What is an “Object Database”?
 Integration of database capabilities with object oriented
programming language capabilities.
 Object databases store objects rather than data such as integers,
strings or real numbers.
 The Object-Oriented Database System Manifesto
 It should be a DBMS
 It should be an object-oriented system
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Object databases history
 1985 - The term "object-oriented database system" first appeared
around.
 1991 –The first standard, ODMG 1.0, was released in 1993.
 1995 - The OODBMS Manifesto, Malcolm Atkinson
 2001 - Final ODMG 3.0 standards released. [OQL]
 2004 - Advent of Open Source: db4o released as free, open
source ODBMS. [Native Queries]
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How do we store data?
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How do we store data?
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Object Query Language (OQL)
 Declarative query language
 Not computationally complete
 Syntax based on SQL (select, from, where)
 Additional flexibility (queries with user defined operators and
types)
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Object Query Language (OQL)
Sample query: “what are the names of the black products?”
Select distinct p.name
From products p
Where p.color = “black”
Valid in both SQL and OQL, but results are different.
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Result of the query (SQL)
Original table
Product no
Name
Color
P1
Ford Mustang
Black
P2
Toyota Celica
Green
P3
Mercedes SLK
Black
Result
Name
- The statement queries a relational
database.
Ford Mustang
Mercedes SLK
=> Returns a table with rows.
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Result of the query (OQL)
Original table
Product no
Name
Color
P1
Ford Mustang
Black
P2
Toyota Celica
Green
P3
Mercedes SLK
Black
Result
String
Ford Mustang
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- The statement queries a
object-oriented database
String
Mercedes SLK
Murat KARAÖZ
=> Returns a collection of
objects.
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OQL vs SQL
 Queries look very similar in SQL and OQL, sometimes they
are the same.
 In fact, the results they give are very different.
 Query returns:
OQL
SQL
Object
Tuple
Collection of objects Table
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Querying in db4o
 db4o supports 3 forms of querying:
 Query by Example (QBE)
 Native Queries (NQ)
 Simple Object Database Query API (SODA Query API)
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The Basics – Person Class
 creating and storing
 querying
 updating
 deleting
person objects
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Accessing a Database
ObjectContainer db = Db4o.openFile( "database path");
try {
// access db
}
finally {
db.close();
}
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Creating and Storing Objects
 Create objects as usual and then make them persistent using the
set() method on the database.
Person p1 = new Person("Fred Bloggs", 35);
db.set(p1);
Person p2 = new Person("Mary Jones", 24);
db.set(p2);
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Querying Objects (QBE approach)
// retrieve by age (null default for string)
Person p = new Person (null, 35);
ObjectSet<Person> result = db.get(p);
// retrieve by name (0 default for int)
Person p = new Person ("Mary Jones", 0);
ObjectSet<Person> result = db.get(p);
// retrieve all persons
Person p = new Person (null, 0);
ObjectSet<Person> result = db.get(p);
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Updating Objects
 First retrieve object (or objects), then perform update and then
store.
// update age of person
// assumes single result to query
ObjectSet <Person> res = db.get (new Person ("Mary Jones", 0);
Person p = res.next();
p.setAge (40);
db.set (p);
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Deleting Objects
 As with updating objects, objects must first be retrieved and
then deleted.
// delete Fred Bloggs from database
ObjectSet<Person> res = db.get (new Person("Fred Bloggs", 0);
Person p = res.next();
db.delete(p);
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Object database relationships
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Object database relationships
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Object database relationships
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Benefits of using an ODBMS
 When you use an ODBMS, the way you use your data is the way
you store it.
 If you are working with complex data, an ODBMS can give you
performance that is ten to a thousand times faster than an
RDBMS.
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When should you use an ODBMS?
 Use an ODBMS when you have a business need for high
performance on complex data.
 Embedded DBMS Applications
 Team is Using Agile Techniques
 You're Programming in an OO Language
 Real-Time applications
 Data is Accessed by Navigation Rather Than Query
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Data is Accessed by Navigation
Rather Than Query
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Everyday uses of object databases
 Are you aware that when you;
 use your cell phone,
 book a hotel room or a flight,
 receive health care,
you might very well be interacting with an object database?
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Barriers to using ODBMSs
 Lack of Familiarity: Most programmers understand RDBMSs.
Many do not understand ODBMSs.
 Inertia: It is easier to use what you know.
 Technology Fear: It is scary when you do not know what is
inside ODBMS technology.
 Business Fear: Most of the ODBMS vendors are small
companies. Is this risk worth the technological benefits?
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Performance
Myth: ODBMSs are slow
No, they are not.
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Will ODBMSs replace RDBMSs?
 Before we begin, we should acknowledge reality: RDBMS works
just fine.
 There are plenty of remarkably good applications out there that
have been running on relational databases for years.
 That is highly unlikely. It's difficult, if not impossible, to move
off databases. That would be unrealistic. Where you primarily
see ODBMSs is in new development.
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Summary – Definition
 Object database = OO + DB
 The Object-Oriented Database System Manifesto
 It should be a DBMS
 It should be an object-oriented system
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Summary – Storage
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Summary – Queries
SQL and OQL
Query by Example (QBE)
Native Queries (NQ)
Simple Object Database
Query APIs
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Summary – Relationships
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Summary
 Object databases are a niche field within the broader DBMS
market dominated by relational database management systems
(RDBMS).
 Object databases have been considered since the early 1980s and
1990s but they have made little impact on mainstream
commercial data processing, though there is some usage in
specialized areas.
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References
 http://www.service-architecture.com/index.html
 http://www.odbms.org/
 Object Database Tutorial, Rick Cattell, International Conference
on Object-Oriented Databases Zurich, 2009
 http://en.wikipedia.org/wiki/Object_database
 The OODBMS Manifesto
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Questions?
Thanks for listening.
Murat KARAÖZ
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