The FRBR WEMI classes are aspects of a whole; a "full" catalogue record will usually consist of a Work, an Expression, a Manifestation, and an Item. A significant utility of FRBR is that it gives cataloguers a better context for their activity, as the WEMI classes and individual properties are assigned to the four identified user tasks (find, identify, select, acquire/obtain). A corollary is that FRBR makes it easier to present the metadata in more useful ways to the user; typically, the user can drill-down from Work (essentially equivalent to the brief author/title display often seen in library interfaces) to Expression (content-related stuff like editions, translations) to Manifestation (carrier-related stuff) to Item (is it on the shelf?) There is also the potential for more effective metadata management through reduction of duplication (one Work record can be linked to multiple Expression records, etc.) and increased sharing of the cataloguing effort (only create a Manifestation if no-one else has done so, and then link it to an existing Expression)

But I see WEMI as an intermediate stage twixt the record and the statement. The WEMI classes essentially group bibliographic metadata properties at a lower granularity than the traditional full record, and perhaps the greatest utility of FRBR will be to break the hegemony of the catalogue record in the cult(ure) of cataloguing. See my presentation at http://gordondunsire.com/pubs/pres/EvolCatRec.ppt (also listed on the wiki).

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