## 1 Introduction: Understanding the Nature of Mashup Services
However, the portal technology is about server-side, presentation-tier aggregation and it cannot be used easily to drive more robust forms of application integration. Mashup services are more loosely defined where content aggregation can take place either on the server or on the client side. The base standards for the mashup content aggregation are the XML interchanged as REST (REpresentational State Transfer) or Web Services. Lightweight protocols for content aggregation such as RSS (Really Simple Syndication) and Atom are commonly used for the purpose of facilitating the aggregation of contents. The major difference between portals and mashups is in the way content or services composition is administered. Portals achieve composition through the use of application server as a mediator between a client browser and services. Mashups, however, perform composition directly from the end user's browser. Although the client-side architecture helps mitigate a performance problem by avoiding the use of the application server, it can introduce its own problems in the design, use and maintenance of mashup applications where often such application users find participating in mash-up process as time-consuming or even a trouble. To address this problem, mashup middlewares provide better support for the users to mash-up or enjoy the result of mash-up. Certainly mashup middlewares have been used for promoting Personalized Learning Environments (PLEs) [3], where it helps the learners in utilizing open and heterogeneous set of learning tools to connect with each other into a learning network and to collaborate with other actors on shared artifacts along different learning activities [4]. The pedagogical motivations behind using mashups within PLEs are obvious as learners have different learning styles, background knowledge, interests and alternative evolution of their learning over time, which makes ineffective offering the same packaged course to each learner. Learning should be a user-centred process focused on learning activities adapted to learner's needs and preferences [5]. Experiments on using mashups for the MUPPLE PLE [6] in writing a collaborative article, for example, showed quite promising success in creating a comprehensive learning environment. There reasons for such success compared to the traditional instructional techniques can be summarized as follows:  
Figure 1: Increasing Levels of Mashup Semantic Awareness. * There is no 'perfect' instructional designer: an environment can only be planned for the average learner, not the individual. Learners need to actively adapt their learning environment to their needs so that they can construct the competences necessary for successful learning. And facilitators can coach them on this way. Learners proactively have to take account of their learning environment [6]. * Learners can develop the judgments and skills or literacy necessary for using new technologies in a rapidly changing society [7]. A response to pedagogic approaches which require that learner's e-learning systems need to be under the control of the learners themselves [8]. * Mashups enables web services to be combined much more tightly so that data from one is used to access information in another. This will enable learners to create larger learning services and applications [9]. PLEs are not an entity, structural object or software program in the sense of a learning management system. Essentially, they are a collection of tools, brought together under the conceptual notion of openness, interoperability, and learner control. As such, they are comprised of two elements - the tools and the conceptual notions that drive how and why we select individual parts. The tools are mainly Web 2.0 tools supporting collaborative and social networking services. The conceptual notions are what users try to achieve with offered services. Hence, PLEs are a concept-entity and they are very personalized and individual.