Alisdar,
        I suggest you look back over past issues of the CNEHA Newsletters
wherein George Miller reviews some of the ups and downs of ceramic
analysis under the title "Thoughts Towards a User's Guide to Ceramic
Assemblages" (part three appeared in July 1992 edition).  As a general
rule I think it is essential to be very explicit in describing how you
arrive at vessel assignment in any report which uses a vessel analysis.  I
have in the past used a modified version of a system proposed by Gordon
Fine which discusses vessels in terms of completeness (ie. whole, complete
from rim to foot/base, represented by rim, represented by foot/base, and
unique body sherds) with notation as to if the sherds mend or are just
attributed.  This type of information is relevant both in terms of
understanding the processes that created the deposit and understanding how
reliable vessel attributions are.   Good luck. - silas