Active Components as a Method for Coupling
Data and Services – A Database-Driven
Application Development Process
Beat Signer and Moira C. Norrie
Department of Computer Science
Vrije Universiteit Brussel
1050 Brussels, Belgium
http://vub.academia.edu/BeatSigner
2 December 2005

Motivation
package org.penAndPaper;
import java.io.IOException;
...
public class PaperPoint {
Rectangle slide1
= new Rectangle(10,10,70,50);
// if input within slide1 then
// execute application logic
}
ICOODB, July 3, 2009 Beat Signer - Department of Computer Science - bsigner@vub.ac.be

Problems
 No separation of data objects (e.g design elements) and
application logic
 changes to the design require a recompilation
 limited reusability of application logic
 Authoring of paper interface requires programming
 designer has to be a programmer
 programming rather than authoring approach
 Design elements cannot easily be reused with different
application logic variants
 replication of code
ICOODB, July 3, 2009 Beat Signer - Department of Computer Science - bsigner@vub.ac.be

Active Component Approach
 Database driven application development where the
database contains
 data objects
 active components (application logic)
 Data objects can be associated with active components at
 instance level
 type level
 role level (classification)
 Access to data object might trigger the execution of an
active component
 active component runtime environment
 database-driven application logic on server and/or client side
ICOODB, July 3, 2009 Beat Signer - Department of Computer Science - bsigner@vub.ac.be

Active Component
 Active component contains data about a service
 name
 identifier
 timeout
 parameters
- key/value string pairs
 Active component runtime environment executes the
corresponding application logic
 service binding
 initialisation
ICOODB, July 3, 2009 Beat Signer - Department of Computer Science - bsigner@vub.ac.be

Active Component Runtime Environment
ICOODB, July 3, 2009 Beat Signer - Department of Computer Science - bsigner@vub.ac.be

Active Component Registry
 Binding of identifier to stub and logic components
 Reconfigurable at runtime
ICOODB, July 3, 2009 Beat Signer - Department of Computer Science - bsigner@vub.ac.be

Server-side Functionality
ICOODB, July 3, 2009 Beat Signer - Department of Computer Science - bsigner@vub.ac.be

Client-side Functionality
ICOODB, July 3, 2009 Beat Signer - Department of Computer Science - bsigner@vub.ac.be

Client- and Server-side Funtionality
ICOODB, July 3, 2009 Beat Signer - Department of Computer Science - bsigner@vub.ac.be

Active Component Stub and Logic
ICOODB, July 3, 2009 Beat Signer - Department of Computer Science - bsigner@vub.ac.be

Active Component Example
package org.ximtec.iserver.activecomponent.logic;
public class CommandLine extends EmptyLogic {
}
package org.ximtec.iserver.activecomponent.stub;
import java.io.IOException;
...
public class CommandLineStub extends SingleEventStub {
public static final String PARAM_COMMAND = "command";
public void finish() {
try {
Runtime.getRuntime().exec(getParameter(PARAM_COMMAND));
}
catch (IOException e) {
LOGGER.log(Level.SEVERE, Constant.EMPTY_STRING, e);
}
} // finish
}
ICOODB, July 3, 2009 Beat Signer - Department of Computer Science - bsigner@vub.ac.be

Active Component Stub Example ...
ICOODB, July 3, 2009 Beat Signer - Department of Computer Science - bsigner@vub.ac.be

Client and Server AC Interaction
ICOODB, July 3, 2009 Beat Signer - Department of Computer Science - bsigner@vub.ac.be

Active Components
Button Image
Slider Sound
Slider2D Movie
DateSelector SQLClient
Browser XCMRequest
MapSelector CommandLine
Capture PaperPointControl
CaptureAndIcr PaperPointAnnot
CaptureAndSpeak ...
ICOODB, July 3, 2009 Beat Signer - Department of Computer Science - bsigner@vub.ac.be

Slider / Slider2D Active Component
ICOODB, July 3, 2009 Beat Signer - Department of Computer Science - bsigner@vub.ac.be

Slider2D Active Component
 Slider2D active component properties
 startValueX
 endValueX
 stepsizeX
 invertedX
 startValueY
 endValueY
 stepsizeY
 invertedY
ICOODB, July 3, 2009 Beat Signer - Department of Computer Science - bsigner@vub.ac.be

Authoring
ICOODB, July 3, 2009 Beat Signer - Department of Computer Science - bsigner@vub.ac.be

Active Component Editor
PP_SLIDE_SELECTOR
Show slide 1
command showSlide
slide 1
ICOODB, July 3, 2009 Beat Signer - Department of Computer Science - bsigner@vub.ac.be

Other Use Cases
 Rich internet applications
 active component runtime environment within browser
 "Internet of Things"
 active component runtime environment for augmented
physical objects
 lightweight solution for database updates (e.g. sensor data)
 Implicit service execution at object access time
 service associated at instance, type or role level
 media service components
ICOODB, July 3, 2009 Beat Signer - Department of Computer Science - bsigner@vub.ac.be

Media Service
 No longer deal with "raw" media types
ICOODB, July 3, 2009 Beat Signer - Department of Computer Science - bsigner@vub.ac.be

Ongoing and Future Work
 Integration of concepts into the ODBMS
 role-driven service invocation
 separation of intrinsic (type) and extrinsic object behaviour
 Communication between different active components
 AC runtime environments for alternative programming
languages
ICOODB, July 3, 2009 Beat Signer - Department of Computer Science - bsigner@vub.ac.be

Conclusions
 Database-driven application development
 reusability due to separation of data objects and services (ACs)
 flexible configuration of active component services
 instance, type and role-driven service invocation
 Client- and server-side execution of application logic
 autonomous component-based client-server interaction
 Automatic deployment of services to the client side
 simplifies updates of client-side application logic
 Authoring rather than programming approach
 rapid prototyping (growing set of active components)
ICOODB, July 3, 2009 Beat Signer - Department of Computer Science - bsigner@vub.ac.be

Further Information
 Beat Signer, Fundamental Concepts for Interactive
Paper and Cross-Media Information Spaces,
ISBN 978-3-8370-2713-6, May 2008
ICOODB, July 3, 2009 Beat Signer - Department of Computer Science - bsigner@vub.ac.be