Object-Process Methodology (OPM) is a systems modeling paradigm that integrates two aspects inherent in any system: its structure and its behavior. Structure is represented via objects and structural relations among them, such as aggregation-participation (whole-part relation) and generalization-specialization ("is-a" relation). Behavior is represented by processes and how they transform objects: How they create or consume objects, or how they change the states of an object. Indeed, OPM is fundamentally simple; it builds on a minimal set of concepts: stateful objects—things that exist or might exist physically or informatically at some state, and processes—things that happen to objects and transform them by creating or consuming the objects or by changing their states.<ref name="Model-Based"/>{{rp|2}}
OPM offers a way to model systems of almost any ___domain, be it artificial or natural. OPM has an [[ontological commitment]] to a universal minimal ontology according to which objects exist, while processes transform them.<ref name="Model-Based"/>{{rp|x}}<ref>See also: {{cite journal |last1=Herre |first1=Heinrich |last2=Heller |first2=Barbara |last3=Burek |first3=Patryk |last4=Hoehndorf |first4=Robert |last5=Loebe |first5=Frank |last6=Michalek |first6=Hannes |date=July 2006 |title=General formal ontology (GFO): a foundational ontology integrating objects and processes: part I: basic principles |journal=Onto-Med Report |volume=8 |page=3 |url=http://www.onto-med.de/publications/2006/herre-h-2006-a.pdf |quote=Current languages in use for conceptual modeling like the [[Unified Modeling Language]] (UML), [[entity–relationship model]]ing in the database field, or the Object-Process Methodology can be examined according to their ontological commitments.}}</ref> Transformation includes object creation and consumption, as well as change of the state of an object. Hence, stateful objects and processes that transform them are the only two concepts in OPM's universal minimal ontology. Two other cornerstones of OPM are its bi-modal graphical-textual representation and its built-in refinement-abstraction [[complexity management]] mechanisms of in-zooming and unfolding of a single type of diagram—Object-Process Diagram (OPD).
