  To provide a foundation for conceptual modeling, ontologies have been
introduced to specify the entities, the existences of which are acknowledged in
the model. Ontologies are essential components as mechanisms to model a portion
of reality in software engineering. In this context, a model refers to a
description of objects and processes that populate a system. Developing such a
description constrains and directs the design, development, and use of the
corresponding system, thus avoiding such difficulties as conflicts and lack of
a common understanding. In this cross-area research between modeling and
ontology, there has been a growing interest in the development and use of
domain ontologies (e.g., Resource Description Framework, Ontology Web
Language). This paper contributes to the establishment of a broad ontological
foundation for conceptual modeling in a specific domain through proposing a
workable ontology (abbreviated as TM). A TM is a one-category ontology called a
thimac (things/machines) that is used to elaborate the design and analysis of
ontological presumptions. The focus of the study is on such notions as change,
event, and time. Several current ontological difficulties are reviewed and
remodeled in the TM. TM modeling is also contrasted with time representation in
SysML. The results demonstrate that a TM is a useful tool for addressing these
ontological problems.
