Kang, M. H., O. Costich, and J. N. Froscher, "Using Object Modeling 
  Techniques To Design MLS Data Models," in Security for Object-Oriented 
  Systems, B. Thuraisingham, R. Sandhu, and T.C. Ting, eds., Springer-Verlag, 
  London (ISBN 3540198776), 1994.

<blockquote>
The expressiveness of the data model has a significant impact on the
functionality of the resulting database system. The more general the
data model, the less need be lost when the conceptual model is mapped
onto a particular data model.  In this paper, we explain how MLS data
models can lead to a loss of database functionality or the inability to
model some real world phenomena if data models are not kept general and
independent of other considerations.  We also present our positions
with respect to developing MLS data models for MLS database systems
using the object modeling technique (OMT).
</blockquote>