1 Vrijendra Gokhale, Bernard Menezes K. R. School of Information Technology IIT Bombay User Interfaces for Jini Services The Jini Pattern Language Workshop OOPSLA – 2000

2 15 October 2000User Interfaces for Jini Services Pervasive Computing Computing as a technology that hides, like paper Devices around us have increasing computational power Future wireless networks are going to be increasingly dynamic

3 15 October 2000User Interfaces for Jini Services Context Aware Computing Control: ability to control things around me Data manipulation: ability to gather data from gadgets around me and process it Customization: does the environment adapt to my needs?

4 15 October 2000User Interfaces for Jini Services The Jini Technology A federating technology for services Enables impromptu communities Supports service discovery based on attributes Based on the Java Remote Method Invocation (RMI)

5 15 October 2000User Interfaces for Jini Services Key Jini Features Discovery Lookup Leasing Remote Events Transactions Proxy publishing and lookup Soft State and automatic cleanup

6 15 October 2000User Interfaces for Jini Services A Jini Scenario Service discovers a Jini Lookup Multicast request Lookup proxy

7 15 October 2000User Interfaces for Jini Services A Jini Scenario Service publishes a proxy at the lookup Join Protocol

8 15 October 2000User Interfaces for Jini Services A Jini Scenario Client discovers a Jini Lookup Multicast request Lookup proxy

9 15 October 2000User Interfaces for Jini Services A Jini Scenario Client looks up the printer Lookup Printer proxy

10 15 October 2000User Interfaces for Jini Services A Jini Scenario Client uses the print service of the printer print()

11 15 October 2000User Interfaces for Jini Services The Lego Example!

12 15 October 2000User Interfaces for Jini Services A Hypothetical Situation “You enter a room which contains appliances like printers, cameras, music systems, microwave ovens… is it possible to control, compute or manipulate these gadgets without any prior knowledge of their existence?”

13 15 October 2000User Interfaces for Jini Services Issues: A Hypothetical Situation To programmatically talk to a Jini service the client must have the service interface Does the client carry ALL the interfaces it needs to talk to [impractical] How to handle gizmos? Something the Martians left behind! (assuming it participates in a Jini federation)

14 15 October 2000User Interfaces for Jini Services Issues: A Hypothetical Situation Can a common Jini interface allow service specific behaviour? Does the client have a JVM?

15 15 October 2000User Interfaces for Jini Services Solution: User Interfaces All interactive services export UIs. Programmatically such services are known by a well known interface. public interface JUnknown{ public void getBuilder(String id); }

16 15 October 2000User Interfaces for Jini Services Using Patterns to Accommodate Varied Client Display Technologies A Factory encapsulates client side UI capabilities public interface Factory{ public Object getObject(Object which); }

17 15 October 2000User Interfaces for Jini Services Using Patterns to Accommodate Varied UI Construction Logic A Builder encapsulates client UI technology specific UI construction logic public interface Builder { public void buildUI (Factory factory); }

18 15 October 2000User Interfaces for Jini Services the getBuilder(String id) method of JUnknown dynamically loads the appropriate builder for the specified client factory type! this uses underlying RMI class loading mechanisms JUnknown ties it all customized UI construction for different client devices

19 15 October 2000User Interfaces for Jini Services Interactions and code

20 15 October 2000User Interfaces for Jini Services Interactions and code

21 15 October 2000User Interfaces for Jini Services Advantages Dynamically builders can be loaded for various factory types Support for different display technologies Stub is lightweight and does not carry any extra UI classes Dynamically builders can be loaded for various factory types Support for different display technologies Stub is lightweight and does not carry any extra UI classes

22 15 October 2000User Interfaces for Jini Services More Advantages Adding support for new UI tech by simply adding new builders at service end Support for Non JVM clients viz web clients –Using an intermediate tier viz Servlets –Involves an HTMLFactory and HTMLBuilder

23 15 October 2000User Interfaces for Jini Services Future Work Identifying and refining the UI patterns Security in Jini –Who can access services? Authentication –Who can invoke what service? Authorization

24 15 October 2000User Interfaces for Jini Services Thank You!