The thesis addresses three main problems in the area of user modeling and adaptation in the context of online communities:<p> 1) Dealing with unique and changing user modeling needs of online communities. <p> 2) Involving users in design of the user modeling process.<p> 3) Interoperability of user models across different communities.<p> A new policy based-approach for user modeling is proposed, that allows explicit declarative representation of the user modeling and adaptation process in terms of policies, which can be viewed and edited by users. This policy-based user model framework is implemented in the MCComtella community framework, developed as part of this thesis work, which allows hosting multiple communities, creating new communities by users, and which supports users in setting explicit user modeling policies defining participation rewards, roles and movement of users across communities.

The thesis addresses three main problems in the area of user modeling and adaptation in the context of online communities:<p> 1) Dealing with unique and changing user modeling needs of online communities. <p> 2) Involving users in design of the user modeling process.<p> 3) Interoperability of user models across different communities.<p> A new policy based-approach for user modeling is proposed, that allows explicit declarative representation of the user modeling and adaptation process in terms of policies, which can be viewed and edited by users. This policy-based user model framework is implemented in the MCComtella community framework, developed as part of this thesis work, which allows hosting multiple communities, creating new communities by users, and which supports users in setting explicit user modeling policies defining participation rewards, roles and movement of users across communities.