Interoperating with Services in a Mobile Environment Andreas Dahl, Pål Rolfsen Grønsund, Per Thomas Kraabøl, Presentation

ReMMoC: A Reflective Middleware to Support Mobile Client Interoperability Paul Grace, Gordon Blair Distributed Multimedia Research Group, Computing Department, Lancaster University, UK Sam Samuel Global Wireless Systems Research, Bell Laboratories, Lucent Technologies, UK

1.The challenges for mobile computing middleware 2.Middleware heterogeneity 3.The ReMMoC approach 4.Reflection, components & component frameworks 5.Evaluation 6.Future work & concluding remarks Outline

The Challenges of Mobile Computing The characteristics of the mobile environment present a number of challenges for middleware developers. For example: 1.Disconnection 2.Low & variable Bandwidth 3.Address Migration 4.Low Power 5.Small Storage Capacity Middleware seeks to overcome these to better support distributed mobile applications.

Mobile Computing Middleware Different styles of mobile middleware have emerged to solve these challenges. Asynchronous paradigms: –Publish-Subscribe (REBECA, STEAM) –Tuple Spaces (LIME, L 2 IMBO) Context-based adaptation: –CHARISMA, OpenORB, Odyssey Enhancements to established middleware: –RAPP, Alice, Dolmen (CORBA) & Wireless RMI (Java RMI) middleware heterogeneity. This explosion of middleware solutions creates middleware heterogeneity. No interoperability between different middleware styles.

A Mobile Computing Scenario

The ReMMoC Approach A Reflective Middleware to support mobile client interoperability. –Find mobile services irrespective of the service discovery protocol –Interoperate with services implemented by different middleware types Design of ReMMoC built upon three concepts: 1.Components (OpenCOM) 2.Reflection 3.Component Frameworks (CFs)

The ReMMoC Architecture Binding CF Binding type implementations Service Discovery CF Service Discovery protocols Top-level ReMMoC CF ReMMoC abstract programming Model Binding mapping implementations Discovery mapping implementations Concrete Middleware Abstract to Concrete Abstract Middleware

Component Frameworks in ReMMoC CF Service Interfaces (Can be exposed interfaces of internal components) IMetaInterface ILifeCycle IConnections OpenCOM component framework CF receptacles (Can be exposed) ICFMetaArchitecture Lock Interceptor Validation Plug-in Graph of internal components

The Service Discovery Framework Discover Services advertised by different protocols. Dynamically reconfigures itself based upon current environment conditions. –Cycles through tests for known types of service discovery. –Single-personality – discovery performed over a single protocol type. –Multi-personality – discovery executed simultaneously over a number of types. Current Implementations – UPnP and SLP lookup.

The Binding Component Framework Dynamic replacement of binding types (implemented as OpenCOM components) based upon information the from service discovery CF. Configurations we’ve implemented - IIOP client, IIOP Server, SOAP client, subscriber, publisher

Evaluation - Mobile Applications Goal to develop a mobile application using ReMMoC that operates in different locations exhibiting middleware heterogeneity. Three Applications implemented: –Jukebox, Chat Service, Sport News. –Different locations (e.g. Office & Home Environment). –Heterogeneous discovery protocols (UPnP & SLP). –Heterogeneous binding protocols (P/S, SOAP, IIOP). The same application code (containing only abstract operations) operates continuously across different locations.

Evaluation – Memory Capacity Mobile devices are resource light and reflection is expensive; why not reconfigure at the server side? Reflective Non- Reflective FunctionARM (Bytes)x86 (Bytes)ARM (Bytes)x86 (Bytes) Platform Core OpenCOM n/a Binding CF n/a Service Discovery CF n/a Binding Configurations IIOP Client SOAP client Subscribe Service Discovery Configurations SLP Lookup UPnP Lookup

Future Work Dynamic component downloading architecture based upon context information. Extension to include other binding paradigms: –Tuple spaces, data-sharing, multimedia streaming etc. Integration with resource management architecture. Evaluation using more complex applications: –Ambient intelligent environments, ubiquitous computing. Investigate Web Service description formats that include non- functional aspects (e.g. Web Services Endpoint Languages) and more complex interaction patterns (e.g. Web Services Flow Language).

Concluding Remarks Mobile environments contain heterogeneous middleware ReMMoC developed to support application developers in face of this type of heterogeneity –Reconfiguration of binding and service discovery Evaluated and demonstrated across a set of mobile applications: –Jukebox –Chat service –Sport News Service

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