Canali C, Colajanni M, Malandrino D et al. A novel intermediary framework for dynamic edge service composition. JOUR- NAL OF COMPUTER SCIENCE AND TECHNOLOGY 27(2): 281{297 Mar. 2012. DOI 10.1007/s11390-012-1223-2 A Novel Intermediary Framework for Dynamic Edge Service Composition Claudia Canali1, Member, IEEE, Michele Colajanni1, Member, IEEE, Del¯na Malandrino2, Vittorio Scarano2, Member, ACM, and Ra®aele Spinelli2 1Department of Information Engineering, University of Modena and Reggio Emilia, Modena, I-4125, Italy 2Department of Computer Science, University of Salerno, Fisciano (SA), I-84084, Italy E-mail: fclaudia.canali, [email protected]; fdelmal, vitsca, [email protected] Received February 25, 2011; revised December 7, 2011. Abstract Multimedia content, user mobility and heterogeneous client devices require novel systems that are able to support ubiquitous access to the Web resources. In this scenario, solutions that combine flexibility, e±ciency and scalability in o®ering edge services for ubiquitous access are needed. We propose an original intermediary framework, namely Scalable Intermediary Software Infrastructure (SISI), which is able to dynamically compose edge services on the basis of user prefer- ences and device characteristics. The SISI framework exploits a per-user pro¯ling mechanism, where each user can initially set his/her personal preferences through a simple Web interface, and the system is then able to compose at run-time the necessary components. The basic framework can be enriched through new edge services that can be easily implemented through a programming model based on APIs and internal functions. Our experiments demonstrate that flexibility and edge service composition do not a®ect the system performance. We show that this framework is able to chain multiple edge services and to guarantee stable performance. Keywords ubiquitous Web, edge service, intermediary framework, service flow, performance 1 Introduction content: we de¯ne service flow the sequence of applica- tions that are able to transform the original content In the ubiquitous computing epoch, one of the main into the modi¯ed version delivered to the end user. challenges of Web-based system is to guarantee any- Most edge services are based on user preferences that time/anywhere access to any data and information are explicitly declared by the user or inferred by the through any client device and access network. The ad- system. This means that the provider's system must vent of novel Web applications has led to a new way of support a per-user pro¯ling and the possibility of per- interaction, has multiplied the heterogeneity of o®ered sonal customization. The framework proposed in this contents and has promoted interactive forms of infor- paper supports edge services that are able to manage mation sharing among users. At the same time, wireless per-user pro¯les. technologies have allowed these interactive Web appli- Edge services may include a wide range of Web con- cations to be accessed through a large variety of mobile tent transformations, such as content adaptation, con- devices, such as tablet computers (e.g., iPad), smart tent ¯ltering and privacy protection, and many oth- phones (e.g., iPhone, NexusOne), car-based systems. ers are appearing and will appear in the future. For These devices are characterized by heterogeneous ca- this reason, flexibility and scalability are mandatory re- pabilities in terms of hardware and software properties, quirements of the provider's system. Content adapta- thus opening several challenges to the content providers tion services involve the transformation of textual and for the delivery and presentation of Web resources. In multimedia contents (e.g., text compression, HTML this scenario, edge services are needed to tailor Web structure manipulations, image removal and/or quality contents according to the user preferences and needs reduction, text-to-speech translation, video-on-demand and to the capabilities of mobile client devices. adaptation, video streams transcoding) to match user A modern content generation and delivery function preferences, client device capabilities, and available net- is now composed by more edge services that should work connections[1-6]. Content ¯ltering services al- be applied to obtain the ¯nal required version of the low to control which Web sites users can access, thus Regular Paper ©2012 Springer Science + Business Media, LLC & Science Press, China 282 J. Comput. Sci. & Technol., Mar. 2012, Vol.27, No.2 making contents accessible only to authorized users and edge services, as we will describe in Subsection 2.2. avoiding children to see inappropriate documents (e.g., However, none of them support an e±cient and flexi- access control, URL blocking, banners and pop-up ¯l- ble dynamic composition of edge services based on user tering). Privacy protection services address the issue preferences and device capabilities. to protect users from privacy leakage and identity theft The proposed Scalable Intermediary Software Infras- during Web navigation (e.g., HTTP request/response tructure (SISI) is a flexible intermediary infrastructure header analysis, disabling of dangerous third party for ubiquitous Web access that integrates advanced script executions, blocking of identifying URLs, Web edge services dynamically composed to match user bugs and other well-known harmful activities[7]). preferences and device capabilities. Unlike other in- Edge services can be provided client-side[8], by termediary frameworks providing general services, SISI the content server[9] or by an intermediary frame- associates each user to one or more pro¯les contain- work[6;10-11] after the content generation. In this paper, ing personal preferences and device capabilities. In this we consider the last scenario, where, a network interme- way, each user can have his/her requests served accord- diary component, interposed between the client device ing to personal settings, independently of the choices and the content provider, analyzes and transforms the of other users. The possibility of managing multiple requested content on-the-fly before delivering the re- pro¯les for each user allows the system to change edge sult to the end user. A typical service flow includes the services and related parameters on the basis of current following steps: the intermediary framework intercepts user condition and/or device. the client request, it fetches the contents from the ori- The flexibility is another important feature of SISI. gin server, it applies the edge services that modify the The proposed framework simpli¯es the integration and original contents to match the user pro¯le and/or ex- con¯guration of other services and facilitates program- pectations, and it delivers the modi¯ed content to the mers to create new edge services. Several experiments client. demonstrate that the dynamic composition of multiple A solution based on an intermediary framework edge services in SISI is not detrimental for performance shifts the computational load away from content as in other intermediary frameworks. provider servers, thus simplifying their design. The The paper is organized as follows. Section 2 dis- intermediary-based approach represents the preferable cusses the main requirements of intermediary frame- approach to develop Web applications that require works for edge services and presents some existing so- transparency, real time processing, easy usage, sharing lutions. Section 3 describes the SISI architecture and of access from several Web users, high scalability and its main components. Section 4 outlines the SISI pro- performance[10;12]. grammability and flexibility by showing how program- Speci¯cally, we designed a \close to clients" interme- mers can easily implement new edge services and in- diary framework because this solution presents several tegrate them into SISI. Section 5 describes some SISI advantages. First, an intermediary framework located edge services that are not o®ered by other intermediary close to the clients may adapt contents coming from systems. Section 6 presents a qualitative comparison multiple sources. Second, the impact on network traf- between SISI and existing frameworks for ubiquitous ¯c of services that considerably increase the size of the Web access. Section 7, Section 8 and Section 9 intro- delivered content, such as the Text2Speech service de- duce the testbed and analyze the performance and the scribed in Section 5, is limited because contents have scalability of SISI, respectively. Section 10 concludes to travel only the last mile to the client. Third, perfor- the paper with some ¯nal remarks. mance may be improved by exploiting caching policies of original and adapted content. It is worth to note 2 Motivation and Background that several caching strategies already exist[13-15] that Providing advanced edge services for the ubiquitous can be easily integrated into our intermediary frame- Web poses several challenges to the underlying systems. work. In this section, we ¯rst discuss the main requirements On the other hand, an important issue when provid- that an intermediary framework for edge services has ing third party managed services is the privacy of users, to satisfy, then we present some existing frameworks since there is a potential for privacy violation. However, o®ering edge services for the ubiquitous Web. an intermediary system is often viewed as a trusted en- [16] tity if users con¯gure their browsers to go through it . 2.1 Requirements of Intermediary Frameworks