Intelligent Software Architecture for the Service Layer of Wireless Billboard Channels

Zhanlin Ji, Ivan Ganchev, Máirtín O'Droma

Telecommunications Research Centre, University of Limerick, Limerick, Ireland {Zhanlin.Ji;Ivan.Ganchev;Mairtin.O'Droma}@ul.ie

Abstract - This paper 1 proposes an intelligent software architecture for the service layer of wireless billboard channels (WBCs), which facilitates the IP datacasting (IPDC) of services' advertisements in a ubiquitous consumer wireless world (UCWW). The new WBC service layer’s architecture consists of three tiers: a service discovery and maintenance tier acting as a client-server distributed system for data collection and organization; an intelligent application tier holding all business logic and common application programming interfaces (APIs); and a multi-agent system tier maintaining the advertisement, discovery and association (ADA) agents' lifecycle. A message channel, a blackboard and a gateway agent are shared by all three tiers thus enabling ADA processing in a highly efficient way.

Keyword - UCWW, CBM, WBC, ADA, MAS.

I. INTRODUCTION

Wireless billboard channels (WBCs) are novel infrastructural components of the future ubiquitous consumer wireless world (UCWW) originally proposed in [1]. Taking into consideration the potentially large number of wireless services already available - and this is set to grow exponentially-, efficient and easy-to-implement mechanisms for wireless services' advertisement, discovery and association (ADA), adapted to the terminal capabilities, user preferences and user location, need to be developed.

Bearing in mind the various potential broadcast WBC carrier technologies a three layer WBC system architecture has been proposed [2], consisting of a service layer, a link layer and a physical layer. Thus the service layer – realized in the WBC service provider (WBC-SP) node and in the user node (handheld mobile terminal) – may be broadcast carrier technology independent. In the WCB-SP the main functions of this layer focus on accepting wireless services' advertisements and organizing in an efficient way for streamed broadcasts in order to reduce the user access and tuning time. In the user terminal this layer’s main goals are to facilitate discovery all services of interest to its user through these WBC advertisements and association with the ‘best’ according to the full individual users ABC&S paradigm realization [2]. The architectural design of this service layer is the focus of this paper.

II. SOFTWARE ARCHITECTURE FOR THE WBC SERVICE LAYER 1This publication has been supported by the Irish Research Council for Science, Engineering and Technology (IRCSET) and the Telecommunications Research Centre, University of Limerick, Ireland.

To achieve an extensible, flexible, intelligent structure, a three tier WBC service layer's architecture was conceived. This is shown in Fig. 1 and briefly described in the following:

HTML / WML / Applet MIDP / CDC

WBC Web / MU MVC

Service Discovery and Maintenance Tier

WEB Application Context

O/R Mapping DAOMail

Remote / Local Service Builder

Local/Remote POJO APIs

Portlet API (JSR-168)

Business Logic APIs

Common APIs

Shared Ontology

APIs

Rule Engine APIs

WBC AOP

Application Tier

WBC Algorithms

IoC Container

MAS Container Tier

Shared Blackboard

Yellow Page Services

Main WBC Container

Message C

hannel Gateway Agent

DB

WEB Service

IPDC APIs

...

Collecting AgentCollecting

Agent...

Clustering AgentClustering

Agent...

Scheduling AgentScheduling

Agent...

Indexing AgentIndexing

AgentCollecting Agent

Clustering Agent

Scheduling Agent

Indexing Agent

Other Agents

Fig. 1. The WBC Service Layer’s Architecture.

A. Service Discovery and Maintenance Tier This tier provides a scalable, Internet-based enterprise

application in the WBC-SP node and a portable-device-based application in the user mobile node. Thus actors to be catered for are advertisers – mainly the service providers (xSPs), who submit descriptions of their (wireless) services to the WBC content database–; WBC-SP, who maintains and databases manages and runs the business model, etc; and mobile users (MUs), who discover and associate with best wireless services based on their profiles

It consists of three sub-tiers: 1) Presentation Sub-tier: To access the WBC system, the

actors (service providers, WBC-SP, users) use local mode (HTML /WML /Applet or MIDP /CDC) or remote mode to process the requests/responds and define a personalized interface with personal business rules and a history via the WBC-SP web portal or a J2ME application.

2) Business Sub-tier: Facades and delegates are the key design patterns at this sub-tier (Fig.2). By hiding complex business APIs and exposing a simpler interface, the business services are decoupled from distributed clients and agents. Moreover, the maintenance cost can be reduced due to the fact

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that the business rules are redefined by modifying the business delegates XML files.

HTMLHTMLRemot

eClient

Business Sub-tier

WBC AOP Interceptors

WBC IoC Container

WBC MVC Actions

WBC Business Delegate

MUMU

Security Filter / Portal Pages

RemoteClient

Fig. 2. The Business Sub-tier.

3) Persistence Sub-tier: The three main components located at this sub-tier are: a mail component concerned with xSPs, WBC-SP, and MUs mail notifications; an O/R mapping component used for conversion between Java objects and a relational database; and a DAO component used to abstract and encapsulate all accesses with different data source.

B. Intelligent Application Tier This contains an expert system for maintaining the business

logic and the WBC algorithms. For uniform expert knowledge-base in the WBC system, an ontology technique is used to describe concepts and their relationships. The design pattern of ontologies follows the singleton design pattern to enable the sharing of the same ontology object among the three tiers. Each ontology scheme is built up with vocabulary, concept, predicate, and action.

To achieve a loose-coupling system and enable WBC data organizing algorithms to run in an intelligent way, a rule-based expert system runs at the intelligent application tier for facilitating the data broadcasting in the WBC-SP node and data receiving in the user mobile node (Fig. 3).

ConflictResolutionStrategy

Concept, Predicate and Action schemes

Data Source Ontology

Extended Dictionary

& Ontology

Task Ontology

Pattern Matcher

Working Memory

WBC Rule List

Data Provider, e.g. xSP, MU.WBC-SP

Agenda Select Rule

to Fire

Exit

Rule Found No Rule

Found

Agent Call

Agents

Execution Engine

Fire Rule

Fig. 3. The WBC Rule-based Expert System.

C. Multi-Agent System (MAS) Tier This is an agent run-time environment tier for facilitating the

collection, clustering, scheduling, indexing, broadcasting of (wireless) services advertisements, and their discovery, and association in users handhelds. To build a heterogeneous distributed system on the WBC-SP side and to improve the

mobility of the user terminal, a goal-oriented, flexible, reactive, and communicative MAS runs here to deal with wireless services' ADA processing. Each running instance of MAS is called a container with a set of agents. The collecting, clustering, scheduling, indexing and broadcasting agents are logic-based agents. The user profile agent is a belief-desire-intention agent, whose actions depend on the user history records, plans, beliefs/desires, and intentions. A gateway agent acts as the bridge between the distributed enterprise platform and multi-agent middleware. Its sequence diagram is shown in Fig. 4.

Fig. 4. The Sequence Diagram of the Gateway Agent.

III. IMPLEMENTATION

Developing the WBC service layer's application according to this architectural model has been possible to do successfully, quickly and efficiently using low complexity, low cost, open-source, academic-licensed APIs including : JADE – a MAS implemented in Java and developed by TILIB with the FIPA specifications. OSS – Nokalva OSS ASN.1 Tools for Java API. Protégé – for ontology building and editing. Drools (JBOSS with LGPL, & JESS (Sandia National Laboratories) rule-engine based expert systems; DB4O – a high performance, embeddable OO database.

IV. CONCLUSION

The core of a new heterogeneous-software-based WBC service layer architecture has been set out. Results to date from a testbed implementation demonstrate that this proposed WBC ADA processing architectural design performs both well and efficiently, which in part is due to the heterogeneous aspect of the software APIs used.

REFERENCES [1] O'Droma M. and I. Ganchev. "Towards a Ubiquitous Consumer Wireless

World". IEEE Wireless Communications, Vol. 14, Issue 1, Pp. 52-63. ISSN: 1536-1284. DOI: 10.1109/MWC.2007.314551. February 2007.

[2] Ji Zh., I. Ganchev, M. O’Droma. 2007. “On WBC Service Layer for UCWW”. Proc. of the 9th International Conference on Mobile and Wireless Communications Networks (IFIP MWCN’07), Pp. 106-110, 19-21 September, Cork, Ireland.

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