In both general systems engineering and in the engineering of computer based systems, there are management processes and technical engineering processes carried out by the systems engineers. This paper treats the steps in the technical engineering work that define the structure of the system. It describes this work when it is done with executable models and with text to explain the models.The work that defines the structure of the system in models is called "creating object models" in the title. Some professionals may prefer to call these models design models or structure models or architecture models. The choice of particular names is difficult because any single concept used by the workers in different engineering disciplines is often named with a different word, and the naming is important to the workers in each field. With the advent and popularity of object-oriented software methodologies, the software engineering world is using concepts of abstraction of things (objects) and the encapsulation of behavior by objects, that have been practiced in mechanical, electrical, and other engineering professions for many years. It is critically important that the systems engineer be able to communicate rigorously with all of the engineering disciplines using the views, representations and notations understood by those disciplines.This paper focuses on several aspects of design and architecture: The semantic constructs required to describe design and architecture in models How architecture and design are generated by the repeated core steps of systems engineering technical work How architecture is related to effectiveness measures and reusable components How design is simplified by architecture and reusable components A behavioral model for the process of creating architectures and designs A view of the extent and impact of automation when architecture and design requirements are rigorously captured in models