For third-party annotations in the digital edition to be interoperable, we argue they should not be anchored in web pages but in the edition’s abstract information structure. We propose an ontology for the editorial domain based on FRBROO. The ontology distinguishes between the editable domain (works that can be edited) and the edited domain (the result of editing), as well as between the different FRBR levels. The edition’s website, with the help of RDFa (RDF triples expressed by means of HTML attributes in the hierarchical HTML structure) can identify fragments of works and expressions and describe their relations. Annotation tools and other clients can use that information to identify the targets of annotation and perform other types of intelligent processing. We discuss what this facility might mean for annotation in the context of digital editions. We also note that the same functionality is desirable in the context of other types of cultural heritage material, such as newspapers and audio-visual archives.