## 4 Outline of the Approach
### Exchange Patterns and Processes  
We identify the following exchange patterns to fulfill the goals described in Section 4.0. In the first exchange pattern, data from social network applications, devices and semantic web technologies like FOAF and microformats are harvested, interpreted and integrated to a ubiquitous user model. From this moment on, the user knowledge can be used to personalize web services or user model enrichment by the mediation of the ubiquitous user model (see Section 6.1).  
In the second exchange pattern, a profile supplier changes its role to profile consumer and reuse information of the ubiquitous user model to enrich its profile. A new application or system can take advantage of the knowledge acquired from the user also. Figure 2 shows these two exchange patterns. The case of Web Services is interesting because the system can reuse ubiquitous user model's data to populate Web Services' input requirements, and some providers' web services functionality permit the enrichment of some applications (see Section 6.2). To achieve the data exchange between these heterogeneous sources, it is necessary to establish communications and relate syntactically and semantically the concepts of the profiles with each other. The number of bridges between every two applications is from order of N\({}^{2}\) if we choose a peer-to-peer communication. At syntactic level, this means speaking the same language and using the same format and protocol when communicating. From the semantic point of view, it entails sharing the same meaning, or finding a way to interpret and translate each concept.  
Figure 2: Exchange patterns between profile suppliers and consumers.  
We propose an approach establishing a central ubiquitous user model, and defining semantic mappings between the profile suppliers and consumers with the central model at concept level. From the exchange patterns in Figure 2, we determined that we need one semantic bridge from each supplier/consumer to the ubiquitous user model. These one-to one mappings at concept (attribute) level allow the interpretation of the information. The collection of user profile data and enrichment of user profiles has to take place according to the nature and conditions of each actor.  
Given the nature of the heterogeneous profile suppliers and consumers, and the flexibility needed to add new actors, and the complexity of ubiquitous environment, an integrated user model is a better option. The number of bridges decreases from order of N2 between every two applications, to order of N between each application and a user model [5]. Nevertheless, it is still a difficult task to communicate and build an understanding between each supplier/consumer and the user model, without mentioning the design and implementation of the user model itself.  
We try to benefit from the distribution of the profiles, but simplify the task of communication with a centralized user model. This implies great flexibility for adding new sources, but on the other hand, some choices on the data structure and means of translation to enable interoperability with the ubiquitous user model.  
The actors (profile suppliers and consumers) will not interact with each other. Every exchange will be performed with the mediation of the ubiquitous user model. The required processes performed by the adaptive system are:  
1. The construction of the ubiquitous user model by harvesting, interpreting and integrating data from the suppliers to the user model.
2. Update and maintenance of the ubiquitous user model.
3. The selection and extraction of personal data from the ubiquitous user model in order to personalize web services.
4. The selection and extraction of data from the ubiquitous user model to enrich new or existing user models.