Is an XML document a FRBR manifestation or a FRBR expression? - Both, because FRBR entities are not types, but roles

At Extreme 2003 a "late breaking" presentation by members of the UIUC/GSLIS Electronic Publishing Research group argued that XML Documents could not be assigned to either of the two plausible FRBR entity classes, manifestation or expression, since XML Documents appear to both have and lack some characteristics of each class. A "double aspect" theory was proposed where a single XML Document can function as either a manifestation or an expression depending on the circumstances. We now use the Guarino/Welty ontology evaluation techniques [guarinowelty00:lncs] to generalize and confirm our results, demonstrating that FRBR expression and manifestation entity types are not true types, but rather roles.