Resources and processes

In this lesson you will learn about simulation resources and processes and how they relate to one another.

Resources

Resources represent data about the resources and knowledge of a business at a point in time. They can include concrete things such as equipment and materials, or more abstract things like orders customers have placed that have not yet been delivered. People in a business are represented as resources, too.

Resources can also be purely informational and intended to support the simulation itself, such as describing operating policy, tracking the state of a larger process, or as a place to store aggregated reports. Resources are the simulation "state". You can treat them like global variables in your code, and use them how you wish.

A simulation model permits any number of resources, each with a name and a data type. Resources evolve over time during a simulation, modified by the processes. A simulation begins with a set of initial resources values. The simulation results are derived from the resource values at the end of the simulation. (Since the intermediate values of the resources are not visible after the simulation, the easiest way to observe how key metrics change over time is to produce a report dynamically during the simulation.)

Processes

The only constant is change, and processes describe activities that occur which lead to changes to state of resources (or further, downstream processing). They can represent concrete events like a purchase exchanging money for materials, or the start of a shift. Or they might represent much more abstract processes, facilitating the prediction of future events or production of a report.

Elara simulations are event based and a process executes atomically at an instant time. During execution, the process can perform calculations and read and write to the resources (the simulation state). A process can be scheduled to execute at some future date-time, together with some data (named values with fixed data types).

When a process is scheduled, internally it is added to the simulations event queue. The simulation proceeds by executing the "soonest" events one at a time, until the simulation ends. The simulation can begin with a list of enqueued processes (for instance, to "initialize" the simulation).

Value network

Each process will refer to, use or modify a number of the resources. We can visualize the relationships between processes and resources as a network.

Consider the simple business of an at-home ebay merchant. The processes are to procure inventory and then sell it online. The resources are cash and inventory.

Note how the "network" is complex, closed graph, where changes to the state of resources can be represented as "flow" of value. For example in the process of selling, things flow out of inventory, and money flows into cash. For-profit businesses are ongoing concerns that use today's revenue to pay for tomorrow's costs, so a closed loop is expected.

A value network is a mathematical description of how a business creates value which you will learn how to leverage in later lessons.

Next Steps

In the

next lesson you will learn how to predict future outcomes through simulation with Elara.