  In this paper we form a general conservation law that unifies a class of
physics field theories. For this we first introduce the notion of a general
field as a formal sum differential forms on a Minkowski manifold. Thereafter,
we employ the action principle to define the conservation law for such general
fields. By construction, particular field notions of physics, such as electric
field strength, stress, strain etc. become instances of the general field.
Hence, the differential equations that constitute physics field theories become
also instances of the general conservation law. Accordingly, the general field
and the general conservation law together correspond to a large class of
physics field models. The approach creates solid foundations for multi-physics
analysis and is critical in developing software systems for scientific
computing; the unifying structure shared by the class of field models makes it
possible to implement software systems which are not restricted to finite lists
of admissible problems.
