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commercial ORDBS (examples):
- ORACLE
- Sybase
- Informix (Illustra)
- IBM
- CinCom (UNISQL, Total)
- Microsoft
- ...
INF4180, Ifi, UiO
commercial OODBS (examples):
- GemStone (Brokat Infosys AG)
- O2 (Ardent -> Informix)
- ObjectivityDB
- ObjectStore (ODI -> eXcelon)
- POET
- Versant
- Jasmine (Computer Associates)
- ...
two ways to integrate object-orientation into DBS
-> both directions are also reflected in standards developments
3
Object-Oriented DBS vs. Object-Relational DBS
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Standardization Efforts
Object-Oriented Database Systems
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2
¥
¥
¥
¥
¥
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4
Prediction:
- both kinds of systems will exist, used for different kinds of applications
¥
¥
¥
substantial investment in
SQL-based relational DBSs
=> evolutionary approach
systems are more robust due
to many years of usage and
experience
application development tools
data security
transaction processing
performance
day-to-day business
requirements,
e.g. online backup
¥
¥
simpler way for programmers to use
DBS (familiar with OOPLs)
ÒseamlessnessÓ, no Òimpedance
mismatchÓ
OO functionality + DBS functionality
=> higher performance for specific
applications
ÒrevolutionaryÓ approach, no legacy
problems
ORDBS
OODBS
Object-Oriented DBS vs Object-Relational DBS
10.09.2003
¥ OMG: Object Model, OMA -> CORBA, POA, PSS
¥ ODMG 3.0 version
Object-Oriented DBS (OODBS) standards
¥ Object-Oriented
¥ Object-Relational
Object Data System Vendors
Overview
Complex Data
Simple Data
INF4180, Ifi, UiO
10.09.2003
INF4180, Ifi, UiO
Examples of other members (vendors and end-users):
Informix Software Inc., Apple Computer, Philips, Olivetti, IBM,
AT&T, Groupe Bull, ICL, Enfin Systems, Canon, Unisys,
Architecture Project Management, British Telecom, Citicorp,
Royal Bank of Canada, John Deere, Microsoft, etc.
Original members:
¥ 3COM
¥ American Airlines
¥ Hewlett-Packard Co. (HP, Palo Alto, CA)
¥ Sun Microsystems Inc. (Mountain View, CA)
International software industry consortium (started 1989)
today: 800+ companies
Object Management Group (OMG)
10.09.2003
How large is the upper-right corner?
¥ ÓMany applications will migrate from the upper-leftÓ
¥ ÓIt is growing and it will engulf upper-left and lower-rightÓ
Object-Oriented DBMS
File System
No Query
Object-Relational DBMS
Relational DBMS
Query
Michael StonebrakerÕs Application Matrix:
¥ Classify your problem into one of the four quadrants
¥ Use a DBMS optimized for the quadrant
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5
Object-Oriented DBS vs. Object-Relational DBS
OMG Focus
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IDL (Interface Definition Language)
OMA (Object Management Architecture)
CORBA (Common Object Request Broker Architecture)
Ð CORBA 1: 1991
Ð CORBA 3: 2000
CORBA Facilities and CORBA Services
10.09.2003
¥
¥
¥
¥
Common Goal: Create a component-based software marketplace
by hastening the introduction of standardized object software.
Establish industry guidelines and detailed object management
specifications to provide a common framework for application
development.
10.09.2003
¥ OMG: Object Model, OMA -> CORBA, POA, PSS
¥ ODMG 3.0 version
Object-Oriented DBS (OODBS) standards
¥ Object-Oriented
¥ Object-Relational
Object Data System Vendors
Overview
8
6
Analysis and Design
Ð UML (Unified Modeling Language)
Ð XMI (XML Metadata Interchange)
Ð MOF (Meta-Object Facility)
Real-Time CORBA
ORB (Object Request Broker)
23 Domain Task Forces
Ð Business Objects, C4I, e-Commerce, Finance, Healthcare,
Life Science, Manufacturing, Telecommunications, etc.
Facilitated by the ORB (Object Request Broker)
¥
INF4180, Ifi, UiO
OMA sets the component software environment
Ð how components provide services
Ð how facilities provide services
Ð how CORBA services provide services
¥
10.09.2003
OMA specifies the overall object model that is used in
distributed object computing environments, including
Ð how objects are defined and created,
Ð how client applications invoke objects,
Ð how objects can be shared.
¥
OMA (Object Management Architecture)
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11
OMA (Object Management Architecture and Reference Model)
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¥
Architecture Board
¥
Domain Technology
¥
¥
¥
Platform Technology
OMG Technology
etc.
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ORB:
¥ Name service
¥ Request dispatch
¥ Parameter encoding
¥É
Application objects:
¥ Spreadsheet
¥ CAD tool
¥ Accounting
¥ Editors
¥ É.
Application
Objects
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CORBA Object Services
Object Request Broker (ORB)
Horizontal
Facilities
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12
Object Services:
¥ Naming
¥ Transaction
¥ Persistent State
¥ Security
¥ Query
¥É
Components:
Vertical facilities: ¥ Account Receivable
¥ Healthcare
¥ Account Payable
¥ e-Commerce
¥ Ledger
¥ É.
¥ É.
EJB
CCM
Vertical
Component Component
Facilities
EJB
CCM
Container
Container
OMA Reference Model
Horizontal facilities:
¥ Internationalization
¥ MOF
¥ É.
INF4180, Ifi, UiO
Business Object Initiative
CWM (Common Warehouse Model)
CCM (CORBA Component Model)
Java and Internet integration
MOF (Meta Object Facility)
PSS (Persistent State Service)
Quality of Service Control
Real Time CORBA
UML (Unified Modeling Language)
Workflow Management
XMI (XML Metadata Interchange)
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¥
¥
¥
¥
¥
¥
¥
¥
¥
¥
¥
¥
OMG Current Efforts
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Implementation of OIDs is not specified.
15
Characteristics can vary over time, whereas identity (OID) is constant.
OID provides a means to denote or refer to the object.
Each object has a unique identity (object identifier, OID) that is distinct
from and independent of any of its characteristics.
OMG: Object Identiy & Object Identifiers
10.09.2003
- basic concepts
- object identity and object identifiers
- object types
- value types
- operations
- subtyping and inheritance
- argument passing and results
- interfaces of a type
- implementation
CORBA includes an object model of types, operations, and subtyping.
In the object model, the user can manipulate instances but not types or
operations as first-class objects.
OMG: CORBA Object Model
OMG: Object Types
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Types are arranged into a type hierarchy that forms a lattice
(i.e. a directed acyclic graph).
Every instance of a type satisfies the interface of that type.
The set of operation signatures defined on a type is called the type«s
interface.
Each operation has a signature, which consists of a name, set of
parameters, and set of results.
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Objects are created as instances of their types. Objects cannot change
their types.
Types describe these operations and thus characterize the behavior of
objects.
Operations applicable to an object characterize its behavior.
Objects support only certain operations.
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Attribute: An interface may have attributes. An attribute is logically equivalent to
a pair of accessor functions: one to retrieve the value and one to set the value.
Operation: An operation is an identifiable entity that denotes the
indivisible primitive of service provision that can be requested..
Interface: An interface is a description of a set of possible operations that
a client may request of an object, through that interface.
Type: A type is an identifiable entity with an associated predicate (a
single-argument mathematical function with a boolean result) defined over
entities. An entity that satisfies a type is called a member of the type.
Object: An object is an identifiable, encapsulated entity that provides one
or more services that can be requested by a client.
Client: An object system provides services to clients. A client of a service
is any entity capable of requesting the service..
OMG Object Model - Basic Concepts
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Client
INF4180, Ifi, UiO
A request consists of:
¥ target object
¥ operation
¥ parameters
¥ optional request context
Request
ORB
Object implementation
OMG: Request in OMA
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Each operation has a signature consisting of:
- name
- set of parameters
- the result
- exceptions that may be raised by an invocation
Value Types provide Ópass by valueÓ semantics
OMG: Subtyping and Inheritance
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Operation dispatching: when an operation request is issued, a specific
operation implementation (method) is selected for execution.
Inheritance allows a type to be defined in terms of another type.
Inheritance is a mechanism for reuse.
20
Relationships between types define the type hierarchy (directed acyclic graph)
Subtyping defines the rules which objects of one type are determined to be
acceptable in contexts expecting another type.
Subtyping (specialization) is a relationship between types based on their
interfaces.
10.09.2003
The set of operation signatures defined on a type is called the type«s interface.
Request and operations are not objects.
Objects + Value Types = Set of Denotable Values
Basic values include Short, Long, LongLong, Ushort, Ulong,
UlongLong, Float, Double, LongDouble, Fixed, Char, Wchar,
String, Wstring, Boolean, Octet, Enum, Any
Operation Invocation = Request: is an event that indicates an operation,
possibly with a list of parameters, to perform on behalf of a requester (client),
possibly causing results to be returned.
Operation (definition of signature) describes an action that can be
applied to parameters.
OMG: Operations
A value type is an entity which shares many of the
characteristics of interfaces and structs. It is a description of
both a set of operations that a client may request and of state
that is accessible to a client. Instances of a value type are
always local concrete implementations in some programming
language.
OMG: Value Types
OMG: Implementation
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Implementations may vary among different instances of a type
and even for the same instance over time.
An individual object, at any given point in time, is an instance of
one class.
The combination of a type specification and one of the
implementations defined for that type is called a class.
23
The object model formally specifies only the semantics of objects,
nothing about implementation.
10.09.2003
If an operation request returns successfully, it was performed
exactly once; if it returns an exception indication, it was
performed at-most-once.
Expressions result in Value Types or OIDs (denotable values).
Operationally, the denotable values are copied into the formal
parameters. The objects the OIDs refer to are not copied.
-> check: is request legal?
Execution semantics consist of arguments and return values to
formal parameters.
OMG: Argument Passing and Results
OMG: CORBA
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- Static and Dynamic Invocation Interfaces (SII, DII)
- Interface Definition Language (IDL)
- C Language Mapping
- Interface Repository (IR)
- ORB Interface and Server Implementation
- Basic and Portable Object Adapter Interfaces
The basis distributed object computing components
defined in CORBA include:
Standard that defines specific ways for objects and clients
within a distributed environment to interact.
10.09.2003
Interface inheritance provides the composition mechanism
for permitting an object to support multiple interfaces.
An interface is a description of a set of possible operations
that a client may request of an object, through that interface.
It provides a syntactic description of how a service provided
by an object supporting this interface, is accessed via the set
of operations of the objectÕs type.
A type exports all the operations that are defined on it.
OMG: Interfaces of a Type
Callee
Skeleton
Request
ORB1
Object implementation
ORB2
INF4180, Ifi, UiO
IIOP (Internet Inter-ORB Protocol) hides differences in
platform and software (programming language, OS, ORB)
27
Object implementation
25
Network
interface
Stub
Caller
OMG: Inter-ORB Interoperability
INF4180, Ifi, UiO
after
Compiler
Basic Object Adapter may only be used in same ORB
POA = Portable Object Adapter is used across ORBs
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Client
10.09.2003
before
Callee
Caller
Interface
description
OMG: CORBA Ð Remote Procedure Calls
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Accesses
Client
Includes
Interface
definitions
INF4180, Ifi, UiO
Client
stubs
Describes
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Object implementation
Includes
Implement.
skeletons
26
Implement.
repository
Implementation
installation
OMG: CORBA - Interfaces
Upcall interface
INF4180, Ifi, UiO
interface/operation
Object
adapter
Normal call interface
Implement.
Skeletons
interface/adaptor
ORB core
ORB
interface
Proprietary interface
Client
stubs
Object
implementation
interface
Interface
repository
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Dynamic
invoke
Client
OMG: CORBA Internal Architecture
OMG: CORBA Object Services
INF4180, Ifi, UiO
INF4180, Ifi, UiO
Naming Service
Trader Service
Event Service
Notification Service
Transaction Service
Concurrency Service
Security Service
Licensing Service
Lifecycle Service
Relationship Service
Persistent State Service
Externalization Service
Property Service
Query Service
Time Service
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¥
¥
¥
¥
¥
¥
¥
¥
¥
¥
¥
¥
¥
¥
¥
10.09.2003
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29
Pseudo-Objects: requests, named-value lists, contexts, interface
definition objects, implementation definition objects
-- integer types
-- floating point types
-- char, boolean, octet
- constructed types (struct, union, enum)
- template types (sequence, string)
- array
IDL Data Types: - basic types:
Object Interfaces (IDL)
Type in general refers to things that may be specified as
arguments or results in the signatures of operations.
OMG: CORBA - Types and Object Interfaces
User Interface Common Facilities
Ð Internationalization
Ð Printing
Information Management Common Facilities
Ð Meta Object Facility
System Management Common Facilities
Ð XCMF (superceded by CCM (CORBA Component Model))
Task Management Common Facilities
Ð Workflow Facility (with Workflow Management Coalition)
10.09.2003
INF4180, Ifi, UiO
Services have now much higher priority than common facilities.
¥
¥
¥
¥
INF4180, Ifi, UiO
OMG: Horizontal (Common) Facilities
10.09.2003
Features of operations that can be specified in IDL:
- invocation semantics
- parameter directions
- exceptions raised
- context
A client initiates a request by calling a stub routine specific to the
object type or by constructing the request dynamically via the DII
(Dynamic Invocation Interface).
A client performs a request by having access to an object
reference for an object and knowing the immediate type of the
object and the desired operation to be performed.
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30
OMG: CORBA - Operations and Requests
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SIGs (Special Interest Groups):
Ð C4I
(Command, Control, Communications, Computers and
Intelligence)
Ð GIS (Geographic Information Systems)
Ð Analytical Data Management
Ð Distributed Simulation
Ð É
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¥
OMG: Vertical (Domain) Facilities Ð 3
INF4180, Ifi, UiO
Business Object Facilities
Ð Task and Session
Ð Document Repository Integration
Finance Facilities
Ð Currency
Ð Party
Ð General Ledger
Electronic Commerce Facilities
Ð Negotiation
Ð Public Key Infrastructure
Manufacturing Facilities
Ð Product Data Management
Ð High-Level Architecture (HLA Simulation)
10.09.2003
¥
¥
¥
¥
OMG: Vertical (Domain) Facilities Ð 1
35
33
34
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INF4180, Ifi, UiO
network-accessible objects
method
Object
method
method
method
method
method
method
method
Object
Object
method
method
method
method
Object
method
method
method
method
Object Request Broker
Object Services:
- interface repository
- lifecycle services
- transaction management
-É
Object
Object
method
Object
method
method
method
method
method
method
method
Object
36
OMG: CORBA Used to Create an OODBS
INF4180, Ifi, UiO
Telecommunications Facilities
Ð A / V Stream Control
Ð Notification
Ð CORBA/TMN (Telecommunication Management Network)
and CORBA/IN (Intelligent Network) Interworking Facilities
Ð Log Facility
Transportation
Ð Air Traffic Control HCI Facility
Healthcare
Ð Person Identifier Service
Ð Lexicon Query Service
Utilities
Ð Utility Management System (in process)
Life Science Research
Ð Biomolecular Sequence Analysis (in process)
Ð Genome Mapping (in process)
10.09.2003
¥
¥
¥
¥
¥
OMG: Vertical (Domain) Facilities Ð 2
INF4180, Ifi, UiO
method
Object
method
method
method
method
method
method
method
Object
Object
method
method
method
method
Object
method
method
method
method
Object
Object
INF4180, Ifi, UiO
¥ An implementation of an Abstract Storagehome, stores
instances of its corresponding Storagetype
Ð Storagehome
¥ The declared type of a container to store instances of an
Abstract Storagetype
Ð Abstract Storagehome
¥ An implementation of an Abstract Storagetype
Ð Storagetype
¥ The declared type of stored data to persistently encode an
object type (struct)
Ð Abstract Storagetype
¥ Provides persistent storage for object data, may be a RDBS,
OODBS, ORDBS or file system
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37
method
Object
method
method
method
method
method
method
method
Object
Database (persistent objects)
ODBMS
PSS: Basic Concepts Ð 1
Basic Concepts
Ð Datastore
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¥
10.09.2003
application
structures
or objects
method
method
method
method
Application
Program
OMG: Application Access to an OODBS
PSS: Sub-Storagetyping
INF4180, Ifi, UiO
internal interface
Datastore domain
type_B
type_A
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store_B
store_A
If type_B is a subtype of type_A, and
if store_B is a storagehome for type_B, and
if store_A is a storagehome for type_A,
then store_B must be a subtype of store_A.
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¥
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external interface
Servants
ORB domain
Interfaces
OMG Persistent State Service
40
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41
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INF4180, Ifi, UiO
43
Note: Any change to a storage object incarnation is reflected in the
persistent state of the corresponding storage object
(after commit, flush, etc.)
storagehome PersonStoreImpl of PersonImpl implements
PersonStore {};
storagetype PersonImpl implements Person {};
#include <People.psdl>
// In file PeopleImpl.psdl
INF4180, Ifi, UiO
¥ A CORBA object (in a process) bound to a Storage Object
Ð Storage Object Incarnation
¥ A persistent state stored for an object. Is not a CORBA object,
cannot be invoked, has a pid, not a CORBA Ref
Ð Storage Object
¥ Kind of catalog, provides transactional semantics
Ð Session
¥ Superset of IDL, used to declare PSS entities
¥ IDL + abstract storagetype, abstract storagehome, storagetype,
storagehome, catalog
Ð PSDL
¥ Provides access to a storagehome
Basic Concepts, cont.
Ð Catalog
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¥
PSS: Basic Concepts Ð 2
Using PSS
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44
CosPersistentState.ConnectorRegistry connectorRegistry
= CosPersistentState.ConnectorRegistryHelper.narrow(
myOrb.resolve_initial_references(ÒPSSÓ) );
CosPersistentState.Connector connector
= connectorRegistry.find_connector(ÒÓ);
// create session
CosPersistentState.Session mySession
= connector.create_basic_session(
org.omg.CosPersistentState.READ_WRITE,ÒÓ,parameters);
// find person home
(personHome is a storage home instance)
PersonHome personHome = (PersonHome)
mySession.find_storage_home(ÒPSDL:PersonHomeImpl:1.0Ó);
// create person Knut
Person p = personHome.create(00010154321, ÒKnutÓ, Ò2200 9000Ó);
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abstract storagetype Person {
readonly state long social_security_number;
state string full_name;
state string phone_number;
};
abstract storagehome PersonHome of Person {
Person create(in long ssn, in string full_name, in string
phone);
};
catalog People {
provides PersonHome person_home;
};
// In file People.psdl
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DBMS
¥
10.09.2003
Clustering Strategies
¥
get
set
INF4180, Ifi, UiO
Access Paths (Indexes)
Schema
Types from Application Object Model
¥
¥
Changes for a DBMS
INF4180, Ifi, UiO
get
set
47
10.09.2003
¥
What Changes?
INF4180, Ifi, UiO
45
¥ Must create an Object-Relational mapping to overcome
the impedance mismatch
Ð In the application only (RDBMS)
Ð In both application and database (OODBMS)
Ð In the database only (ORDBMS?)
¥ When using ÒObjectsÓ in an application,
Where are the objects?
Object-Relational Data Mapping
get
set
Naive Architecture for a Database
10.09.2003
public class JPersonImpl implements JPerson {
private long _ssn;
private String _name;
private String _phoneNumber;
public long socialSecurityNumber() { return _ssn }
// etc.
}
// Java
public interface JPerson {
public long socialSecurityNumber();
public String fullName();
public void fullName(String newName);
public String phoneNumber()
public void phoneNumber(String newNumber);
}
Transparent Persistence
48
46
Overview
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50
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¥ OMG: Object Model, OMA -> CORBA, POA, PSS
¥ ODMG 3.0 version
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52
¥ Most important application domains: GIS (Geographic IS),
CAD (Computer Aided Design) and Genome DBS
¥ Incorporate most object-oriented concepts, but lack good
support of several DBS concepts
Object-Oriented DBS (OODBS) standards
¥ Developed from object-oriented programming languages (PL)
Object-Oriented Databases (1. Generation)
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¥ Intermediate stadium: persistent object-oriented PL
(persistence means that data survive program run-time)
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49
¥ There are many links to info on both OODBMSs and ORDBMSs
at http://www.cetus-links.org/oo_db_systems_2.html
¥ http://www.rational.com/products/rose/whitepapers.jsp
¥ http://www.sun.com/software/javablend/index.html
¥ There are links to several whitepapers on the ODMG site
http://www.odmg.org/library/whitepapers.htm#Database
¥ Crossing Chasms (from PLoP 95)
http://members.aol.com/kgb1001001/Chasms.htm
¥ Connecting Business Objects to Relational Databases
(from PLoP 98) http://www.joeyoder.com//papers/patterns/
¥ Relational Database Access Layers (from PLoP 96)
(PLoP = The Pattern Languages of Programs Conference)
http://www.sdm.de/en/tec/pub/art/art/arcus/relz_abstract.htm
Object-Relational Mapping References
¥ Object-Oriented
¥ Object-Relational
Object Data System Vendors
10.09.2003
>
<
Encapsulated Database Architecture
53
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55
- Language Bindings (OML - Object Manipulation Language)
- Object Query Language (OQL)
- Object Definition Language (ODL)
- Object Model
- (Architecture)
Main components:
Designed for ODS
The Object Data Standard (Version 3.0)
INF4180, Ifi, UiO
- ObjectDesign
- Objectivity
- Ontos
- O2 Technology (Ardent)
- POET Software
- Servio (Gemstone)
(- SunSoft)
- Versant
10.09.2003
other members:
- American Management Systems
- Anderson Consulting
- EDS
- Fujitsu
- Hewlett-Packard
- Intellitic
- MITRE
- Persistence Software
- Sybase
- UniData
- Texas Instruments
voting members:
started in 1991
ODMG (Object Database Management Group)
- CERN
- Micro Data Base Systems
- NEC
- Versant
other members:
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56
- DBMS: shared service for transaction and lock management
- DBs can be shared among applications on a network
- applications access DBs, types must conform to declarations
- schema declarations
- source program
- declarations for application schema (data + operations)
- common architecture for ODS products
ODMG: Architecture
10.09.2003
Object Data: OO and OR
Plus 8 academic reviewers
(Alagic, Dittrich, King, Liskov, Maier, Moss, Soloman, Zdonik)
- eXcelon (was ObjectDesign)
- Objectivity
- POET Software
- Sun Microsystems
voting members:
Release 3.0 in 2000
ODMG (Object Data Management Group) Today
- syntax for object model based on IDL (CORBA) +
referential integrity and collections
- common data model to be supported by OODBS
-- objects with OIDs
-- object behavior, state of objects, named objects
-- operation signatures
-- properties (attributes or relationships)
-- attribute / relationship signatures
-- collection types
-- inheritance
-- ...
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INF4180, Ifi, UiO
-> OQL as embedded language
-> complex OQL queries
-> simple OQL queries
- based on SQL syntax whereever possible
- declarative query language for querying DB objects
ODMG: Object Query Language (OQL)
10.09.2003
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- subset of the object model provides interoperability across PLs
ODL is intended to define object types that can be implemented
in a variety of PLs:
- based in OMG specifications, ODMG object model is
superset of OMG object model)
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INF4180, Ifi, UiO
- 3 components of PL binding: ODL, OQL, OML
60
- PL-specific binding respects the syntax and semantics of the
base PL -> small set of extensions to the base PL
- one single unified type system across PL and DBS
- based on extending a PL syntax and semantics in order to
provide DBS capabilities rather than embedding statements in
SQL or another language
-> goal: seamlessness
ODMG: Object Manipulation Language (OML)
- Language Bindings (C++, Smalltalk, Java) -
10.09.2003
- used to define application schema; schema can subsequently
be translated into declarations of desired PL
ODMG: Object Definition Language (ODL)
ODMG: Object Model
10.09.2003
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}
INF4180, Ifi, UiO
0
boolean dirty
...
oid
myDB
0
db_Object_Id
DatabaseName
Type*
aRef<Type>
Database
Memory
Typical Proxy Implementation
INF4180, Ifi, UiO
An object which is an instance of a class that
inherits from d_Object is said to be
Òpersistence capableÓ.
class d_Object {
public:
mark_modified();
//mark Object as modified
void* operator new(size_t size);
void* operator new(size_t size, const d_ Ref_Any &cluster,
const char *typename);
void* operator new(size_t size, d_Database *database,
const char *typename);
virtual void d_activate();
virtual void d_deactivate();
}
ODMG C++ Binding
63
61
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INF4180, Ifi, UiO
T* operator->() {
//dereference the Ref
if (cachePtr != 0)
return cachePtr;
else {
// validate myDB exists, permissions, etc, then
...
DatabasePage* temp = new DatabasePage;
// read database page containing object oid
// from database myDB into temp
...
// locate object oid in temp
...
cachePtr = ... // Ptr to local object copy
}
}
Typical Ref-> Implementation
INF4180, Ifi, UiO
d_Ref is an example of the Proxy Design Pattern
template <class T> class d_Ref {
public:
d_Ref();
d_Ref(T *fromPtr);
//constructor
d_Ref(const d_Ref<T>&); //constructor
...
T* operator->();
//dereference the Ref
operator T*();
//applies to non-const
T& operator T*() const;
void delete_object();
//delete object - all copies
...
}
ODMG C++ Binding (cont.)
64
62
Database
Sets or Navigation? Both ways!
INF4180, Ifi, UiO
}
65
INF4180, Ifi, UiO
Ð The result of a navigational query is the desired object in
the database, from which one can use a PL for further
computation
OQL also supports navigational queries that use paths based
on pointers and relationships to navigate in the database to
locate the desired data (like the network data model)
67
Ð The result to such queries is a collection object containing a
collection of objects, an object, a collection of literals, or a
literal (or undefined)
OQL supports declarative queries that return a set of objects
(like SQL does for relational databases)
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¥
¥
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0
boolean dirty
...
oid
myDB
db_Object_Id
DatabaseName
Type*
aRef<Type>
Memory
Typical Ref-> Result
INF4180, Ifi, UiO
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INF4180, Ifi, UiO
¥ Names of attributes, relationships, operations and
other variable names are written in lower case (smŒ
bokstaver)
¥ Names of classes (of mutable objects) are written
beginning with a capital letter (stor forbokstav)
¥ OQL reserved words are written in bold font
Conventions (like Eaglestone & Ridley)
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68
66
¥ OQL can also be used from PLs like C++, Smalltalk, and
Java
¥ OQL can be used as a stand-alone query language to
write ad hoc queries
¥ OQL is a declarative (not procedural) language allowing
to define what you want to know, instead of how you get
to the result
¥ OQL is the query language of the ODMG standard
Object Query Language (OQL)
:String ÒConsultantÓ
Title
Engineer
Consultant
Salesman
Secretary
Recursing on OQL expr
INF4180, Ifi, UiO
:String ÒSecretaryÓ
69
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INF4180, Ifi, UiO
71
query
In the OQL grammar, there is a
selectExpr | expr
production rule from the undercastExpr
lined non-terminal to the next line
orExpr | ( type ) castExpr
orelseExpr { or orelseExpr }
andExpr { orelse andExpr }
quantifierExpr { and quantifierExpr }
andthenExpr | for all inClause : andthenExpr | É
equalityExpr { andthen equalityExpr }
relationalExpr { ( = | != ) relationalExpr } | É
additiveExpr { ( < | <= | > | >= ) additiveExpr } É
multiplicativeExpr { + multiplicativeExpr } | É
inExpr { * inExpr }
unaryExpr { in unaryExpr }
+ unaryExpr | É | postfixExpr
primaryExpr { ( . | -> ) identifier [ argList ] } | É
( query )
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:String ÒEngineerÓ
Result in SQL:
:String ÒSalesmanÓ
:Set<String>
Result in OQL:
select distinct E.title
from Employees E
where department = 4
Example: set query
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INF4180, Ifi, UiO
INF4180, Ifi, UiO
conversionExpr
| collectionExpr
| aggregateExpr
| undefinedExpr
| objectConstruction
| structConstruction
| collectionConstruction
| identifier [ argList ]
| queryParam
| literal
| ( query )
OQL Grammar primaryExpr
primaryExpr ::=
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<query> ::= <selectExpr> | <expr>
<expr> <op> <expr>
¥
or
The type of sub-expressions are subject to restrictions
depending on the type checking rules for the operator used
<op> <expr>
72
70
With unary and binary operators <op>, expressions can be built
recursively from sub-expressions:
An expression returns an object or a literal
A query is a query expression with no bound variables
¥
¥
¥
¥
OQL: a Typed Expression Language
literal with value 17 of type integer
INF4180, Ifi, UiO
::=
first ( query )
| last ( query )
| unique ( query )
| exists ( query )
distinct(bag(1,2,1,2,3)) = a set of 1,2,3
bag(1,2,1,3) minus bag(2) = a bag of 1,1,3
bag(1,2) union bag(1,2,3)) = a bag of 1,2,1,2,3
Operators work with multiplicity on bags.
INF4180, Ifi, UiO
INF4180, Ifi, UiO
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75
Set Operators
INF4180, Ifi, UiO
Set operators: union, intersect, and except (minus or
difference)
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Type of e1+e2: if type(e1) = list(t1) and type(e2) = list(t2)
and t1 is compatible with t2,
then type(e1+e2) = list(lub(t1,t2))
(lub = least upper bound)
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listtoset ( query )
| element ( query )
| distinct ( query )
| flatten ( query )
array ( [ valueList ] )
| set ( [ valueList ] )
| bag ( [ valueList ] )
| list ( [ valueList ] )
| list ( listRange )
element({person1}) = Person: person1
::=
::=
Example:
Class City {array(museum) museums }
oslo.museums[2]
norskMuseums = oslo.museums+bergen.museums
collectionConstruction
OQL Collections
flatten(list(set(1,2,3),set(3,4,5,6),set(7)) = a set of 1,2,3,4,5,6,7
flatten(list(list(1,2),list(1,2,3)) = a list of 1,2,1,2,3
flatten(set(list(1,2),list(1,2,3)) = a set of 1,2,3
conversionExpr
73
(element)
(element)
(boolean)
(boolean)
First(select students from course where course.name=ÒINF4180Ó)
collectionExpr
Conversion Operators for Collections
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select c.name
bag of String (names of cities) where the city
from c in Cities
has more than 5 museums in the database
where c.name in (
select m.name
from m in Museums
group by m->city
having count > 5)
Cities
set of City objects in the database
assuming City.extent is named Cities and there are no duplicates
set of Person objects with name=ÒEarlÓ
or the unique Person object with name = ÒEarlÓ
assuming type(Pindex) is dictionary<Person, String>
Pindex.lookup(ÒEarlÓ)
17
Example OQL Queries
76
74
INF4180, Ifi, UiO
scope of y
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INF4180, Ifi, UiO
The LEAST_FIXED_POINT operator can easily be
implemented by a method written in this language
However, OQL is computationally supplemented by
an OO programming language through one of the
ODMG programming language bindings (DML)
The LEAST_FIXED_POINT operator (as defined in
OMGÕs object algebra) cannot be expressed in OQL
OQL is not Computationally Complete!
10.09.2003
select f ( y [, partition] )
from x in X
where p(x)
scope of x
group by y: g(x)
having h(y, partition)
order by o(y, partition)
selectExpr ::=
select [ distinct ]
projectionAttributes
fromClause [ whereClause ] [ groupClause ]
[orderClause ]
OQL selectExpr
79
77
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from w in t.description ) ) )
INF4180, Ifi, UiO
Type of result = struct(Museum, set(Tour))
from m in Museum
where m in ( select distinct w.what
from t in Tour
and s.capacity > 20 )
where s.theme = t.theme
from s in Tour
Tours: flatten ( select ( select s
select struct( M: m,
have the same theme as some tour that already visits the museum.
For each museum, find all tours with a capacity of more than 20 that
Complex Example
78