 in hiding model elements (dimension, subdimension, or attribute), adding new model elements, and renaming model elements. The instan- tiation operation allows one to construct concrete profiles and contexts from the customized models (see Figure 10.3). Notice that instantiation operates on custom- ized models only. Besides customization and instantiation, the model management platform pro- vides other functionalities also, such as import/export of profiles/contexts and matching between profiles or contexts (showing particularly the difference between Attribute SubDimension Dimension Personalization Artefact #Attribute #SubDimension #Dimension #ProfileModel ValueType < Defined On AttributeValue Preference Defined #Value #Preference Value PrefValueExpr < Defined On Figure 10.3 Profile and context instantiation. Personalization Paradigm in Service Delivery Platforms Attribute Subdimension Dimension Personalization Artifact #Attribute #Subdimension #Dimension #Profile model Value type Attribute value Preference #Value #Preference Value Pref valueExpr Figure 10.4 Profile and context generic model. two profiles/contexts). Contextualization operation that links profile elements to contexts (see Section 10.3.1) can also be seen as one of the fundamental operations of this platform. The profile and context models described above have been implemented and stored in a model management platform which provides developers and users with the necessary functionalities for profiles and contexts management. The global model underlying this platform is given in Figure 10.4. In this figure, a personalization artifact (PA) is either a GPM (respectively a generic context model (GCM)) or a customized profile model (CPM) (respectively a customized context model (CCM)). Any of these models is defined in a generic way by a set of dimensions, subdimensions, attributes, and preferences. Notice that GPM and GCM are abstract entities that have no instances, while CPM and CCM have, respectively, concrete profiles and concrete contexts as inst