Current end user devices are not able to display all kind of multimedia data. However, this does not conform to the vision of universal multimedia access (UMA). Server side resource adaptation can solve some of the problems caused by heterogeneity because the multimedia resources are transformed sufficiently such that they fit the consumer's preferences and usage environment before they are sent to client. MPEG-21 is the ISO/IEC standard that defines a normative open framework for multimedia delivery and consumption concerning all parties in the delivery and consumption chain. However, the implementation of an intelligent adaptation engine (AE) capable of determining the required transformations is intentionally left to the tool vendors. An AE, based on the MPEG-21 digital item adaptation (DIA) framework, has an adaptation decision-taking engine (ADTE). In this paper, we present research efforts on ADTEs and consider how intelligent ADTEs can be designed and developed.