page_title: Control–feedback–abort loop
section_title: The abort element
hierarchical_section_title: Control–feedback–abort loop / A description of the control–feedback–abort (CFA) loop / The abort element
caption_attribution_description: English: Control-Feedback-Abort Loop with Alternate Path highlighted.
context_page_description: Too often systems fail, sometimes leading to significant loss of life, fortunes and confidence in the provider of a product or service. It was determined that a simple and useful tool was needed to help in the analysis of interactions of groups and systems to determine possible unexpected consequences. The tool didn’t need to provide every possible outcome of the interactions but needed to provide a means for analysts and product/service development stakeholders to evaluate the potential risks associated with implementing new functionality in a system. They needed a brainstorming tool to help ascertain if a concept was viable from a business perspective. The control–feedback–abort loop and the analysis diagram is one such tool that has helped organizations analyze their system workflows and workflow exceptions.
  The concept of the Control–Feedback–Abort loop is based upon another concept called the ‘Control – Feedback Loop'. The Control – Feedback Loop has been around for many years and was the key concept in the development of many electronic designs such as Phase-Lock Loops.
context_section_description: The abort element (see Figure 5) is so named because it responds to conditions that resulted in the primary path being ‘aborted’. The Abort element then takes over the act of control until conditions can be brought back into acceptable parameters.
  The ‘Alternate Path’ (see Figure 6) is used for communication between the Alternate Control (Abort) and the Feedback. The Feedback at this point may be a different set of feedbacks than was defined for the primary path.
  To demonstrate that the Feedback may be another set of feedback elements, we look at the following example.
  Let’s use the act of driving the auto once more for our example (see Figure 7). When a driver is driving the car, the primary path is the Control element (gas pedal) and the Feedback element (speedometer and street signs). Once a stop sign is detected ahead, the driver will take the foot off the gas pedal (primary control) and press the brake pedal (alternate control). Note that the driver is no longer looking at the speedometer or street signs once the auto gets to the stop sign. The driver is looking for other cars that may cross his path. In other words, the driver is looking for a different set of feedback sources. Once he feels it is safe to go, he will go back to the primary control and feedback and the primary path.
caption: Figure 6 – CFA loop – alternate path
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