
The OAR model is an Instructional Design model created for a specific context: distance education courses delivered through a LMS (Learning Management System) in higher education.
This is an excerpt from a chapter which my colleagues and I have in publication:
"The OAR model is a visual tool which represents the components of SME-F (Subject-Matter Expert facilitated) online courses in higher education, and their relationship to each other. The OAR model was developed to meet four criteria: a) maintain a strict focus on our particular learning system context, b) create a simple graphic-based aid which facilitates communication among design stakeholders, c) remain inclusive by avoiding the use of jargon, and d) represent the basic order of operations in our ID (Instructional Design) process. The OAR model has proven effective in meeting these criteria by organizing the components of SME-F online courses in higher education into three domains: Resources, Objectives and Activities.

The OAR model defines resources as the physical, electronic and intellectual assets with which a course can be created. These resources are determined by an analysis of the learners, SME/F (Subject Matter Expert/facilitator), ID (Instructional Designer), learning and performing environments, available instructional technology, and other relevant contextual factors associated with a course. IDs and SME/Fs use the results of this analysis to identify real-world problems and tasks to inform the design of objectives.
The objectives domain contains the learning and performance goals that are designed to guide the course. Objectives determine which resources will be delivered to influence learner behavior under specified conditions to meet defined criteria. Opportunities for learners to accomplish the objectives are created through activities that are as closely aligned with real-world problems and tasks as the available resources will allow.
Activities are the actual events that learners engage in to acquire and develop new knowledge and skills. At a minimum, these events involve an agent (most often the learner, but at times the facilitator) following an objective to engage with a resource. Activities are primarily delivered by a LMS and are facilitated and assessed by the SME/F."
Reference:
Joeckel III, G.L.; Jeon, T.; Gardner, J. (2009). Instructional Challenges in Higher Education Online Courses Delivered Through A Learning Management System By Subject Matter Experts. In H. Song (Ed.),
Distance Learning Technology, Current Instruction, and the Future of Education: Applications of Today, Practices of Tomorrow, Idea Group Publishing, New York. Chapter accepted for publication.