Manual authoring of hypermedia from collections of media and metadata is an hardly manageable task for non-professional users. The use of semantic annotation and intelligent authoring systems allows the automatic generation of stereotyped hypermedia presentations with effective communication power by entrusting to the intelligent system the management of constraints, content structuring and design decisions. In this work we present a software platform supporting the development of hypermedia authoring applications. The platform is composed by several web services based on a combination of logic programming and semantic web technologies. Every services share a common underlying semantic layer describing media assets, concepts representations and attributes of the authoring process. Two sample applications illustrate the usage of the platform: the Semantic Image Gallery service which allows to semantically search and virtually organize collections of images and the Hyper Atlas service which realizes the automatic generation of hypermedia presentations navigable according to a hierarchy of concepts.