In this paper, the authors select OQL(object query language) of the object database standard: ODMG-93 suggested by ODMG(object database management group) as global query language in object-oriented multidatabase SCOPE/CIMS and present a formal foundation for implementing OQL, including an object calculus and an object algebra suitable for modeling OQL, normalization rules and normalization steps of the object calculus; mapping rules and translation methods between the calculus and the algebra.