Adaptation and personalization services of the information offered to the users in open e-learning environments are considered to be the turning point of recent research efforts. The "one-size-fits-all" approach has some important drawbacks, from the educational point of view. Adaptive Educational Hypermedia Systems in World Wide Web became a very active research field and the need of standardization arose, as the continually augmenting research efforts lacked the interoperability dimension. This paper classifies up todate research work indicating some important points that can lead to an open and unified architecture that support an Adaptive e-Learning System based on widely accepted standards. KEYWORDS e-learning standards, adaptive e-learning system architecture, adaptativity parameters