Formal and Informal systems  - MRP System

Most production systems are full of 'pushes' and 'pulls'. The formal system issues orders, ie 'pushes'. The informal system tries to expedite the required parts, usually those which are late or missing, hence 'pulls' requirements. There is a lack of contact between these two systems, poor documentation and acknowledgement of the existence and need of the informal system, usually because the formal system is unable to keep up dynamically with the day-to-day changing of priorities. Informal systems develop where there are problems to overcome, ie shortages, backlogs or replacements needed due to poor quality. In general, informal systems are devised as a means of retrieving a problem situation. 

It is within such an environment that the introduction of more coordinated, computer-based techniques such as MRP were developed. Their purpose is to eliminate the need for ad hoc, informal procedures and ensure that the formal system meets the objectives required. We now look at MRP to see how it attempts to deal with the problems that the simple inventory model does not cater for.