Method for generating a virtual file system using first data from a first read-only storage medium and second data from a second storage medium, wherein the first storage medium comprises a plurality of data entities, the method comprising the steps of - retrieving from the first storage medium a first identifier (organization_ID); - detecting selection of a data entity from said plurality of data entities; - determining that on the second storage medium, in a first directory according to said first identifier (organization_ID), one or more files related to the first storage medium are available; and - compiling a virtual file system that comprises files from the first storage medium and further comprises files from the second storage medium, characterized in that - said data entities are titles, wherein a title encompasses a movie object or Java object, and wherein a movie object describes a video scene, subtitle stream or graphic animation stream and a Java object describes a Java executable that may run on a Java Virtual Machine and comprises an Application Management Table that points to a Java archive file; - the steps of determining and compiling are performed upon said selection of a data entity being a title; - one or more files on the first and the second storage medium carry a signature, the signature pointing to a certificate that comprises a respective identifier (organization_ID); - the first identifier retrieved from the first storage medium is the identifier in a certificate of the selected title; - the compiling step compiles only files that have been determined to be authorized; wherein determining that a file carrying a signature is authorized comprises steps of - retrieving from the first or the second storage medium the signature of the file, - decrypting the retrieved signature using a public key of an asymmetric encryption method, and - verifying that the file is authorized if the decrypted signature points to a certificate comprising an identifier, which is identical to the first identifier. - retrieving from the first storage medium a first identifier (organization_ID); - detecting selection of a data entity from said plurality of data entities; - determining that on the second storage medium, in a first directory according to said first identifier (organization_ID), one or more files related to the first storage medium are available; and - compiling a virtual file system that comprises files from the first storage medium and further comprises files from the second storage medium, - said data entities are titles, wherein a title encompasses a movie object or Java object, and wherein a movie object describes a video scene, subtitle stream or graphic animation stream and a Java object describes a Java executable that may run on a Java Virtual Machine and comprises an Application Management Table that points to a Java archive file; - the steps of determining and compiling are performed upon said selection of a data entity being a title; - one or more files on the first and the second storage medium carry a signature, the signature pointing to a certificate that comprises a respective identifier (organization_ID); - the first identifier retrieved from the first storage medium is the identifier in a certificate of the selected title; - the compiling step compiles only files that have been determined to be authorized; - retrieving from the first or the second storage medium the signature of the file, - decrypting the retrieved signature using a public key of an asymmetric encryption method, and - verifying that the file is authorized if the decrypted signature points to a certificate comprising an identifier, which is identical to the first identifier.