Transcript Judul - Binus Repository

Matakuliah
Tahun
Versi
: M0174/OBJECT ORIENTED DATABASE
: 2005
: 1/0
Pertemuan 25
Object Relational Database
Management System
1
Learning Outcomes
Pada akhir pertemuan ini, diharapkan mahasiswa
akan mampu :
• Mahasiswa dapat Menghasilkan
rancangan database objek (C3)
2
Outline Materi
• Limitations of the second generation
databases
• The nested relational data model
• Object relational data models
• SQL3
3
Limitations of the second generation databases
• The main strengths of the Relational Data
model are :
– Simplicity
• All information is visible as values in tables
– Rigour
• The relational data model has been defined with
theoretical rigour and provides a mathematical
basis for researching issue such as database
design, database language, and query
optimisations
– Practicality and generality
4
Limitations of the second generation databases
• In summary, the rules are:
– All information must be represented as values
in tables
– Each data item must be accessible by the
combination of table name, key value, and
column name
– The RDBMS must support null values for
representing missing or inapplicable
information a systematic way
5
Limitations of the second generation databases
– The database description (the schema) must
be represented at the logical level as values
in tables
– At least one relational database language
should be expressible as strings of characters
and have a well defined syntaxs
6
The nested relational data model
• Nested Relational Data Model represent a
data model which developed to close over
lacking of relational data model in order to
defining entities which complex.
• The nested relational data model remove
the constraint that tables are flat.
7
The nested relational data model
• In the nested relational data model, the
values stored in tables can also be tables.
• The nested relational data model can be
viewed as a step towards an object
relational data model.
• NRDM table can be used to represent
hierarchically structured entities. (this was
also possible using the first generation)
But NRDM also provides the strength of
theoretical basis with its algebra
8
The nested relational data model
• Example
Projects
Employee Number
Project_ Number
E1
E2
hours
P1
10
P4
5
P1
20
9
Object relational data models
• There are two general approaches
towards third generation database
technologies with integrate object-oriented
features:
Object Database – this extend object model
Object Relational Database – this extend the
relational data model to include data modeling
features typically associated with object
oriented system.
10
Object relational data models
• In late 1980s, object & object relational database
were seen as rivals, rather than complementary
technologies.
• The respective visions of what the third generation
database technology should be like were
published by groups of leading researchers as
“manifesto” documents – “the object oriented
database manifesto” & “the third generation
database manifesto”.
• The third generation database manifesto sees
them as a means of extending a core relational
data model
11
SQL3
• SQL3 specification extends SQL to
provide object oriented features but
remains upwardly compatible with
previous SQL standards. This feature
include:
Abstract Data Type (ADT)
Generalization & Specialization hierarchies
Assertions & Triggers
• SQL3 provides two way to model entities
as row and as ADT
12
SUMMARY
• Object relational database extend the relational
data model to address its weaknesses.
• In particular, object relational database have
been developed to represent entities with
complex structures & behavior such as exist in
many scientific application, multimedia & GIS
• The main strengths of the Relational Data model
are :
– Simplicity
– Rigour
– Practicality and generality
13