1/17 DIANE Project Birgitta König-Ries, Michael Klein Information Services to Support E-Learning in Ad-hoc Networks Universität Karlsruhe Institute for Program Structures und Data Organization Universität Karlsruhe GERMANY The First International Workshop on Wireless Information Systems April 2002 – Ciudad Real, Spain

2/17 Our Scenario Anna More on SQL? Official SQL Slides Summary on 2PC Exercise Sheet on UML Exercise Sheet on SQL Solution to SQL Sheet 

3/17 Problems with mobile Ad-hoc Networks Highly dynamic topology due to node movement node fluctuation appearing obstacles No dedicated server, no physical infrastructure

4/17 Little work on higher levels: How to find suitable services effectively? How to use the services found efficiently? Much work on the technical level: How to access the medium? , CSMA, MACA, FSCS-CSMA, TDMA, etc. How to route a package vom A to B? AODV, LAR, DSR, ZRP, STAR, etc. How to assign addresses to devices? IP, Mobile IP How to reliably send a piece of information? TCP Tahoe, TCP Reno, TCP SACK, etc. Work on Ad-hoc Networks Data Link MAC IP Network Transport Application

5/17 Resulting Tasks Service description automatically searchable not only syntactical Exercise Sheet on SQL  Service discovery services move and change no physical infrastructure Service integration combine different services SQL  += Motivation reward intermediate nodes

6/17 One member of the ring acts as service access point (SAP), which offers all services of its ring. Exercise Sheet on SQL Official Slides on SQL Examples on GROUP_BY SQL Service Discovery (1) Our Approach: Service Rings Group devices offering similar services to rings "Similar" can be derived from ontology Exercise Sheet on SQL Examples on GROUP_BY Official Slides on SQL

7/17 relational Model Service Discovery (2) Group SAPs to larger rings, as though they were single devices SQL relational Algebra Normalization We call the highest level ring world ring. It covers all services (directly or indirectly). Every device is (at least an indirect) member of it.

8/17 How to use these rings? Finding a service: SQL Normalization relational Model relational Algebra Exercise on SQL? ? Paper on Projection ? Does not match. Is not included. ? ? Is included! ? Exercise Sheet on SQL ! !

9/17 Advantages of Service Rings Routes are known no flooding necessary strictly decentralised descending only in suitable subrings routing way unique, no exploring (as in graphs) Answer messages always possible even when connections are unidirectional Message loss discoverable each message returns after having visited all ring members Two dedicated neighbors structural integrity can be maintained locally Defined service management position service changes are submitted to the local SAP only, not broadcasted through the whole net No central device each node is basically equal, work is distributed equally no overall important nodes (in contrast to stars or trees)

10/17 Service Description Service Availability Costs... Document... DocumentConsuming Service Encryption Compression... DocumentProducing Service Packaging Compression... PrintingService PagesPerMinute Color... LearningServiceTransformationService LossOfInformation... processes 1..* delivers Separate technical service description from document description

11/17 Semantical issues What is semantically similar? What is semantically disjoint? What is more general? Issues of content What content is in it? Is it included in a series of information? Technical issues How big is is? Who has created it? What format is it in? Document Description (1) Document Author Format Size... Information Title Description... contains 0..*1 is described by 0..*1..* is part of Keyword ontological relationship

12/17 Document Description (2) Document Author Format Size... Information Title Description... contains 0..*1 is described by 0..*1..* is part of Keyword ontological relationship Concrete Document or Document Template LearningDocument Target User Difficulty... contains 0..*1 LearningInformation is prerequisite for

13/17 Service Description Example (1) Exercise Sheet on SQL LearningDocument Author: M. Klein Format: ps Size: 85 kB Target User: University Student Difficulty: advanced LearningInformation Title: Exercise Sheet #3 of SQL course Description: Questions on the SQL commands INSERT, UPDATE and DELETE isPartOf: Exercise Sheets of SQL course DocumentProducingService Availability: always Cost: free Packaging: none Compression: none, zip, gz Keyword Database relational Model SQL INSERTUPDATEDELETE OQL similarTo

14/17 Service Description Examples (2)  consumedDocument Author: Format: ps Size: < 10 MB DocumentConsumingService Packaging: none Encryption: none Compression: none, gz producedDocument Author: Format: pdf Size: DocumentProducingService Packaging: none Encryption: none Compression: none, gz Service Availability: always Cost: free

15/17 Current Research on Service Rings Locally formed, hierarchical rings Ideas: At the beginning, group rings according to their spatial proximity Split rings that are too big into thematically coherent subrings Rings are "logical", their connections are established by an existing Routing Protocol (like DSR)

16/17 Summary Data Link MAC IP Network Transport Application Service Description: by separating different issues for services Service Discovery: by the use of semantical service rings

17/17 Thank you! More information on our project web page: Are there any questions? Thank you for your attention!