  With the transformation of computing from personal computers to the Internet,
document formats have also seen some changes over the years. Future document
formats are likely going to adapt to the emerging needs of ubiquitous
computing, where information processing is embedded in everyday activities and
objects. While most existing document formats have originally been a digital
emulation of paper documents, over the years they have been enriched with
additional digital features. These features were mainly incorporated to take
advantage of the new functionality offered by the devices on which the
documents are accessed. With the advent of ubiquitous computing, document
formats seem to be facing the next evolutionary step. They will have to adapt
to novel mobile devices, innovative interaction modalities, the distribution
over multiple devices as well as heterogeneous input sources. This adaptation
to the age of ubiquitous computing asks for several new document features. We
outline a roadmap towards future fluid document representations for ubiquitous
information environments. Based on the resource-selector-link (RSL) hypermedia
metamodel - a general hypermedia metamodel supporting distribution, user rights
management and content adaptation - we developed a metamodel for fluid document
formats and the corresponding online text editor for fluid documents.
