A Component-based Architecture for Mobile Information Access Anupam Joshi CSEE Department, UMBC joshi@cs.umbc.edu http://www.cs.umbc.edu/~joshi/

Overview The Problem - The information required by a mobile user may not be readily available on the network. It is possible to compute required information dynamically using available resources on the network. Thesis provides an architecture to compute information ‘on the fly’, taking into account various limitations of mobile scenario. Implement this architecture to build a financial services system.

Problems w/ Mobile Computers Network layer Low/variable Bandwidth Network disconnection Application layer Limited capability ( Display, Compute power etc)

Existing Efforts in Mobile Information Access Focuses on delivering available information to mobile computers Principally proxy based transcoding or caching What if information needs to be computed ‘on the fly’? Server side ( e.g. : CGI scripts ) Location of resources is ‘known’ Almost all computation at server Client side ( e.g. : Java script, java ) Assumes some capability at client. Size of data transfer may be large. Statically defined location of execution

Need for distribution of computation depending on Needed Features Need for distribution of computation depending on capabilities of client, mobility of components, data size, cost, security. Service location mechanisms Disconnection Management. Componentization of software, Raw data availability

Proposed Architecture Delivery layer - Handles the limitations of mobile client and wireless network. (e.g.: Use Transcoding) Broker Layer - Determine services required, locate services, distribute computations effectively, shield the mobile client from limitations of service location platform. Dynamic service location layer - Mechanisms for locating services.

Dynamic service location Implementation based on ‘XReggie’ platform XReggie overcomes some limitations of Jini platform XML match at lookup service instead of normal Java interfaces. Constraints and similarity match. Services express their constraints as XML attributes. Example constraints for software services. Mobility RAM-required Size JVM version Cost Data-Format

Dynamic service location Examples of constraints for data services Size Local-processing Cost Format

Broker Determines individual services required Locates the services Use XML attributes to locate appropriate service Distributes computations Many ways of distributing computation. Move data, move code, move data and code. Take into account constraints of services and mobile client Constraints of services known from XML attributes with which services register Constraints of mobile client also known from XML attributes.

Broker The objective of the broker is to optimize “cost” subject to various constraints such as Processing power of mobile client Size of data and software Cost of services Network bandwidth and disconnection possibility Decision depends on which parameters are considered Brokers registers a “GUI” interface with Xreggie May be voice in the future.

Execution Platform as a Service Mobile client may not be powerful enough to compute. Execution Platform Generic ‘computational power’ service Executes Jini services in succession For each service to be executed Service ID Method name Argument List Registers as a Jini service

Delivery Handles limitations of mobile client and wireless network Implemented using Ronin framework Key feature used is - ‘Delegation’ Advantages Transport object appropriate for a mobile client could be chosen Transport object appropriate for a network could be chosen Shields rest of application from mobility aspects Implemented a Disconnection handling deputy

Mobile client To execute a software component on mobile client Following arguments are supplied Service ID Method name argument list Mobile host need not have any prior information about service. Broker acts as middleware between mobile client and Jini. Results are either sent back to broker for further computation or displayed.

Application Financial services system Quote service Real time quote from yahoo Average of stock price over any period Historic stock data from yahoo Component for ‘mean’ Option pricing Options pricing component based on Black-Scholes model Profit-loss on options Options pricing component Component to compute profit-loss

Infrastructure overview

Averaging of stock price Components involved Historic stock data provider Software component to compute mean Execution platform Options for distribution Send software component to data site and return the results to mobile user Send data and software component to execution platform and return the results to mobile user Send data and software component to mobile user for execution at client

Experiments

Options for distribution Options pricing Components involved Software component to compute the option price Execution platform Options for distribution Send software component to mobile host for execution Send software component to execution platform and return the results to the user

Experiments

Conclusions Presented an architecture to compute information required by a mobile user ‘on the fly’ using available resources. The architecture takes into consideration, the resources available at mobile client and other factors such as cost while distributing computation. The architecture also supports handling of limitations of mobile client and wireless network. Presented an implementation of this architecture using extensions to Jini and Ronin frameworks. Developed a financial information system using the implementation.

Future work Importance of standards - XML, software components, data formats Improvement of broker Consider more parameters in distributing computation knowledge recommender agents such as PYTHIA could be used to effectively distribute computation Non Java mobile client