The need to deal with vague information in Semantic Web languages is rising in importance and, thus, calls for a standard way to represent such information. We may address this issue by either extending current Semantic Web languages to cope with vagueness, or by providing a procedure to represent such information within current standard languages and tools. In this work, we follow the latter approach, by identifying the syntactic differences that a fuzzy ontology language has to cope with, and by proposing a concrete methodology to represent fuzzy ontologies using OWL 2 annotation properties. We also report on the prototypical implementations. Comment: v3: 32 pages, LaTeX; the new version includes a restriction in the syntax of weighted sum concepts, and changes the order of the paragraph "Notation". v2: 32 pages, LaTeX; the new version extends the previous one with fuzzy modified datatypes, which means changes in the syntax (Section 3.1), semantics (Section 3.2), and their representation using OWL 2 (Section 4.4)