Dynamic Generation of SMIL-Based Multimedia Interfaces Jos´ e Manuel Oliveira INESC Porto, Faculdade de Economia, Universidade do Porto Eurico Carrapatoso INESC Porto, Faculdade de Engenharia, Universidade do Porto Rua Dr. Roberto Frias, 378, 4200-465 Porto, Portugal Email: {jmo, emc}@inescporto.pt Abstract— The current heterogeneous world of networks and terminals combined with the generalized mobility of users pose telecommunications operators and service providers the challenge of dynamically adapt the services they provide. This paper presents a proposal to solve the problem of the adaptation of multimedia services in mobile contexts. The paper combines context-awareness techniques with user interface modeling and description to dynamically adapt telecommunications services to user resources, in terms of terminal and network conditions. The solution is mainly characterized by the approach used for resolving the exis- ting dependencies among user interface variables, which is based on the constraints theory, and by the mecha- nism for acquiring the user context information, which uses the Parlay/OSA interfaces. The experiments and tests carried out with these techniques demonstrate a general improvement of the adaptation of multimedia services in mobile environments, in comparison to systems that do not dynamically integrate the user context information in the adaptation process. Index Terms— multimedia adaptation, dynamic generation, mobile environments, context gathering, SMIL I. I NTRODUCTION Currently, the evolution of telecommunications is mainly driven by the convergence trend of three traditio- nally separate worlds: Internet, broadcast and mobile. This trend is supported by some standardization efforts, being the IP Multimedia Subsystem (IMS) [1], promoted by the 3 rd Generation Partnership Project (3GPP), the most im- portant one. IMS can be seen as a unified architecture that supports a wide range of multimedia IP-based services to be provided to users across different access networks and device types, with consistent look and feel, and ease of use. The acceptance of new services in this context will only be effective if the user has the possibility to access them anywhere, in any technological circumstances, even in roaming scenarios. This user requirement places mul- timedia service providers under the significant challenge of being able to transform their services in order to adapt them to a great variety of delivery contexts. This need for multimedia service adaptation in mobile environments constituted the main motivation for the research work presented in this paper. The paper defines a generic adaptation methodology targeted to adapt multimedia services provided in the context of a telecommunications operator. The metho- dology is based mainly on two fundamental construc- tions: the Multimedia Presentation Model (MModel) and Media Adapters. The former enables a device independent specification of the user interface, while Media adapters basically enable the materialization of the user interface specification in the most suitable format for a parti- cular user context. The proposed methodology follows the approach of dynamically integrating the user context information, which is by nature very changeable in mobile environments, in order to achieve consistent results in the adaptation process. Following a key point of IMS, which is being an open-systems architecture, we base the approach for the context gathering process on the Parlay middleware, a set of open APIs that enable trusted service providers to directly access network resources, traditionally restricted exclusively to the network operator. The paper is organized as follows. Section II compares our approach for the dynamic adaptation of multimedia services with some related work. Section III presents a generic adaptation methodology suitable to adapt telecom- munications services to different access mechanisms, con- nectivity capabilities and user preferences. Section IV presents the most relevant implementation issues of a Media Adapter targeted to the Synchronized Multimedia Integration Language (SMIL). Section V evaluates the proposed adaptation methodology and draws some con- clusions regarding the qualitative and quantitative aspects of the multimedia adapter, using a case study service. Section VI reports the paper main conclusions. II. RELATED WORK The problem of adapting multimedia services and presentations has received significant attention from the 14 JOURNAL OF MULTIMEDIA, VOL. 3, NO. 4, OCTOBER 2008 © 2008 ACADEMY PUBLISHER