Horizontal recursion in soft OR

Abstract

In operational research (OR), the concept of recursion explains particular relationships between modelled systems. It clarifies how the same system properties are replicated vertically across hierarchically interdependent units, meaning these units should be amenable to the same analytical conventions. OR views recursion as hierarchical and therefore does not consider these properties in a horizontal sense. This paper uses theory from other disciplines to develop criteria that define recursive modelling for soft OR as vertical or horizontal. Empirical data was captured using WASAN to improve efficiency in a police force customer contact department. Four units were modelled using WASAN, and additional analysis using recursion was conducted to understand the horizontal interdependence across these four units. Feedback from participants suggests the horizontal recursion analysis provided valuable insights beyond that of individual models.

Keywords:

• Problem structuring
• recursion
• horizontal recursion
• soft OR
• meta-system modelling

Notes

1. To clarify our definition of a model and modelling we distinguish between a unit, a system, and a model. A unit is a real-world entity that could be modelled if desired, e.g., a switchboard where calls are received from the public and routed into an organisation. A system is a conceptual tool used to think about the unit, i.e., “a particular way of describing the world. It does not tell us what the world is…it may only be described as a system” (Checkland, 1983, p. 671) (here the switchboard system, abbreviated to System^SB). A model is a representation of a system using systems concepts and a coding scheme, e.g., for the switchboard this would be Model^SB. Therefore, System^SB refers to the switchboard conceptually and not the real-world entity. When we model the Switchboard in Model^SB we model System^SB based on the experiences of participants included in the modelling process. We cannot detach the modelling conventions from systems concepts; these are applied to the entity as understood through the experiences of participants.