  Certainly, the success of the Unified Modeling Language (UML) as the de facto
standard for modeling software systems does not imply closing the door on
scientific exploration or experimentation with modeling in the field.
Continuing studies in this area can produce theoretical results that strengthen
UML as the leading modeling language. Recently, a new modeling technique has
been proposed called thinging machine (TM) modeling. This paper utilizes TM to
further understand UML, with two objectives: (a) Fine issues in UML are
studied, including theoretical notions such as events, objects, actions,
activities, etc. Specifically, TM can be used to solve problems related to
internal cross-diagram integration. (b) TM applies a different method of
conceptualization, including building a model on one-category ontology in
contrast to the object-oriented paradigm. The long-term objective of this study
is to explore the possibility of TM complementing certain aspects in the UML
methodology to develop and design software systems. Accordingly, we alternate
between UML and TM modeling. A sample UML model is redesigned in TM, and then
UML diagrams are extracted from TM. The results clarify many notions in both
models. Particularly, the TM behavioral specification seems to be applicable in
UML.
