Document generation is based on a stepwise pipeline concept in order to achieve code reuse and higher performance through caching mechanisms. In the beginning, a complex document according to the proposed model is dynamically assembled from a component repository according to a user's request. It contains information about subcomponents to be included and metadata describing adaptation rules. All possible presentation forms of the component concerning content, layout, and structure are encapsulated. Depending on the current user model - which comprises both the user's semantic preferences and her client's technical capabilities - it is subdued to a series of transformations. Each step considers a certain aspect of adaptation by performing conversions to the document (selection and configuration of components). Finally, a Web document in a specific output format (HTML, WML etc.) is generated. The document generator was realized on the basis of the pipeline-based publishing framework Cocoon.
One very important aspect of pipeline design is the proper arrangement of transformation blocks in order to support caching by reusing partially adapted documents. By caching the output of particular transformers a significant performance improvement can be achieved.