Information and technical applications on the Internet have come to represent great economic values. At the same time it is a well-known fact that the Web and similar digital networks challenge the conventional ways of understanding and managing intellectual property rights. This gives rise to a need for legal advice, but precise answers are rarely found in the law itself. In this context, awareness of the predominating legal principles for protecting DTDs and schemas, stylesheets, markup etc. already during system development may reduce the uncertainty.