According to the predominant computing environments, the history of Computing can be classified into the initial period of mainframes, the current one of personal computers, and the future one of Ubiquitous Computing whose goal is to provide the user with easy access to and processing of information at any time and from anywhere.
Mobile communication has contributed to drive the leap of Computing into this new era, since it has given users unprecedented choice and freedom, enabling them to search for new and rewarding ways to conduct their personal and professional affairs.
Globalized mobility requires new architectures and protocols that allow mobile networks to connect easily to several types of services and content providers spread over the Internet. The futuristic view of the mobile Internet presupposes users with different profiles using different access networks and mobile devices, requiring personalized services that meet their needs, availability and locations. In this context, it is necessary to describe information about people, places, devices and other objects that are considered relevant for the interaction between users and services, including the users and services themselves. The fields of Ubiquitous Computing include content adaptation, which involves converting an original content into a large number of formats compatible with the user preferences, the access device capabilities, the access network characteristics, and the delivery context. Due to the infinity of possible adaptations, the greater the quantity of available adaptation services, the higher the chances of meeting the user’s needs. The content adaptation can occurs at several points along the data path, including the origin server, the user device, and the edge device. An essential requirement for carrying out this process is the establishment of an adaptation policy, which defines what adaptation is to be done on a given content, when, and who should do it. To be effective, this policy must take into account information on users, devices, access network, content, and service agreement.
Content adaptation involves modifying the representation of Internet content in order to come up with versions that meet diverse user requirements and the distinct characteristics of devices and access networks.
Content adaptation services require from an adaptation server special processing functions, such as video and voice trans-coding, intelligent text processing and filtering, and many others. Performing the adaptation services at the origin server has the advantage that the content author has a full control on what and how to present the content to the user. On the other hand, since these functions are quite different from the basic functions needed for building Web servers, the authoring process becomes more complex and time consuming. Another major drawback is the cost and the performance scalability issue of the origin server. Performing the adaptation services at the end user device limits the adaptation to the available functionality and capability of the device. It is therefore recommended to locate these functions in a separate computer that could be shared by many different applications.
One fundamental aspect in content adaptation is the definition of an adaptation policy, i.e., what adaptation services are to be offered, which local or remote adaptors will execute these adaptations, and when the latter should be requested. Information that is necessary regarding the adaptation environment includes: characteristics and capacities of the access device; personal user information and preferences; conditions of the communication network; characteristics of the requested content; and the terms of the service agreement between the service provider and the end user.
One major challenge in Ubiquitous Computing is the description of the delivery context, which is as a set of attributes that characterizes aspects related to the delivery of Web content. For content adaptation the delivery context must contain even more information that can be described in a set of profiles.An example showing the Execution sequence of a content adaptation
Applications involving multimedia usually require a certain level of QoS and, if this quality cannot be guaranteed over the Internet, these applications should be able to adapt to the available quality.
