Glossary

  • Assemble

    To join together two or more parts or subassemblies to form a complete machine, structure, or other article.

    Sources: Maynard’s Industrial Engineering Handbook, Fifth Edition, Kjell B. Zandin (ed.), McGraw-Hill 2001, p G.2
  • Assemble to order (ATO)

    Product put together from parts that are already designed and made so as to meet the specifics of a customer order.

    Sources: “Operations Management: Focusing on Quality and Competitiveness”, 2nd edition, Roberta S. Russell and Bernard W. Taylor III, 1995, pp 43-44, “Operations and Supply Chain Management: The Core”, Third Edition, F. Robert Jacobs and Richard B. Chase, p 276
  • Assembly Line

    The arrangement of machine, equipment, material, and workers that permits work in process to progress sequentially from operation to operation until the product (or product component) has been assembled.

    Sources: Maynard’s Industrial Engineering Handbook, Fifth Edition, Kjell B. Zandin (ed.), McGraw-Hill 2001, p G.2
  • Assembly Process

    An assembly process occurs when two or more completed entities are required before the assembly process can begin. Assembly processes are always preceded by one or more stocks.

  • Automation

    A substitution of machine labor for human labor, either manual or intellectual.

    Sources: Maynard’s Industrial Engineering Handbook, Fifth Edition, Kjell B. Zandin (ed.), McGraw-Hill 2001, p G.2
  • Autonomation

    The transfer of human intelligence to automated machinery so that the machine can detect the production of a defect and immediately stop while asking for help. In Japanese: jidoka.

    Sources: Maynard’s Industrial Engineering Handbook, Fifth Edition, Kjell B. Zandin (ed.), McGraw-Hill 2001, p G.2


  • Balance

    As applied to operations management, it is the condition in which the process times for each operation are approximately equal and the work flows steadily or at a desired rate from one operation to the next.
    Many in industry focus on establishing balanced lines as an objective in and of itself. A balanced line is not an objective for production or projects. The objective for a project is usually on-time delivery at minimal cost with no safety incidents. There are very many instances where having unbalanced resources in a project is the most effective way to achieve on-time delivery at least cost.

  • Balanced Line


    A series of sequential operations with approximately equal process times, arranged so the work flows at a desired steady rate from one operation to the next.

    Sources: Maynard’s Industrial Engineering Handbook, Fifth Edition, Kjell B. Zandin (ed.), McGraw-Hill 2001, p G.2

, Project Production Institute
  • Batch


    The collection of entities on which the same operation is performed. There are two types of batches: process batches and transfer batches. A process batch refers to the amount of entities worked on between setups. A transfer batch is the amount of entities transferred from one operation to the next. Batches are also called lots. In project management, an Integrated Work Package can be modeled as a batch.

  • Batch Flow


    Production system whereby processing stations are laid out by functional grouping so that each unit being produced is likely to have to follow a jumbled flow from one to the next, according to the processing steps it requires.

    Sources: Schmenner, R. W. (1993), Production/operations management: from the inside out. Macmillan College
  • Batch Time Formula


    BT = wait-to-batch time + wait-in-batch time.

    Wait-to-batch time is the time jobs spend waiting to form a batch for either (simultaneous) processing or moving
.

    Wait-in-batch time is the average time a part spends in a (process) batch waiting its turn on a machine.

    Sources: “Factory Physics”, Third Edition, Wallace J. Hopp and Mark L. Spearman, Waveland Pr. Inc., P327


  • Bill of Material

    A bill of material, see also Product Tree Structure, is a formally structured list for an object (semi­-finished or finished product which lists all the component parts of the object with the name, reference number, quantity, and unit of measure of each component. It is a product data structure, which captures the end products, its assemblies, their quantities and relationships.

    Sources: Production & Operations Management: Manufacturing and Services, R. B. Chase, N. J. Aquilano and F. R. Jacobs, Eight Edition, pp 101-102, pp 626-628


  • Bottleneck


    The bottleneck of a routing in a production system is the station in the routing with the highest utilization. In traditional production, constraint is commonly used as another word for bottleneck. This is different than the definition of constraint as used in scheduling for Project Production Control.

    Sources: “Supply Chain Science”, First Edition, Wallace J. Hopp, 2008, MCGraw-Hill, p 11, "Factory Physics", W. J. Hopp and M. L. Spearman, Third Edition, 2011, Waveland Press, p 231
  • Bottleneck Rate

    The Bottleneck Rate of a routing is the rate (parts per unit time or tasks per unit time) of the station having the highest long-term utilization. By “long-term”, it is meant that transitory deviations which are small with respect to the timeframe under consideration, are averaged out in the calculation of the rate.  For example, when considering bottleneck rate over the course of a year, deviations small with respect to a year, such as outages due to machine failures, operator breaks or quality problems are included in the rate calculation. However, a month-long maintenance shutdown is removed from the time available when determining the time period for calculating the rate.

    Sources: "Factory Physics", W. J. Hopp and M. L. Spearman, Third Edition, 2011, Waveland Press, p 231
  • Buffer

    A means or device used as a cushion against the shock of fluctuations in business or financial activity. Due to variability, the demand flow and the process flow never perfectly synchronize and some sort of buffer is required when matching process output to demand. The only buffers available are:

    • Inventory—transformation occurs before demand
    • Time—transformation occurs after demand
    • Capacity—above the average demand. Extra capacity mitigates the need for inventory and time buffers.
    Sources: Project Production Institute, Merriam-Webster on-line
  • Capacity

    The capacity of a process is the maximum output (throughput at the end of the process) as determined by the resource that has the highest long-term utilization.

  • Capacity (System)


    The maximum average rate at which the items/units/products flow through or are processed by the system
.

    Sources: “Supply Chain Science”, First Edition, Wallace J. Hopp, 2008, Waveland Press, p 18


  • Commodity

    A raw material, product or service that is indistinguishable from ones manufactured or provided by competing companies and that therefore sells primarily on the basis of price rather than quality or style.

    Sources: American Heritage Dictionary


  • Component

    Generic term for a basic unit used in the manufacture of a product. Components may be put together in subassemblies or the assembly of a product.

    The hierarchy for the terminology is as follows: parts are elements or units in a component.  Components are elements or units in either subassemblies or assemblies.  Assemblies form a product or system.

    Sources: Production & Operations Management: Manufacturing and Services, R. B. Chase, N. J. Aquilano and F. R. Jacobs, Eight Edition, pp 101-102, pp 626-628


  • Concatenate

    From the Latin, concatenare, to link or chain together. Concatenate means to link, end-to-end. For production systems, elements of a single line or routing are concatenated in a sequence of processes.

  • Configure to Order (CTO)


    Assemble to order a product from a set of parts that are most often in stock.

    Sources: “Operations Management: Focusing on Quality and Competitiveness”, 2nd edition, Roberta S. Russell and Bernard W. Taylor III, 1995, pp 43-44
  • Constant Work in Process (CONWIP)

    A control protocol wherein a new job is introduced into the process each time a job departs the process. The objective of CONWIP is maintain a nearly constant level of WIP in the process. This does not mean maintaining a constant level of WIP at each operation in the process.

    Sources: “Factory Physics”, Third Edition, Wallace J. Hopp and Mark L. Spearman, Waveland Press, p363

, “CONWIP: a pull alternative to Kanban”. International Journal of Production Research, 1990, Vol 28, pp 879-894 M. L. Spearman and M. A. Zazanis, “Push and Pull Production Systems: Issues and Comparisons”, Operations Research, Vol 40, No. 3, pp 521-531, May-June 1992
  • Constraint


    In Project Production Control, a constraint is a predecessor task that must be completed in order for work to flow through the process.

  • Consumable resources

    Consumable resources do not become part of the entity. Examples include energy, lubricating oil, cooling water, etc.

  • Continual / Continuous Improvement


    A continual improvement process, also often called a continuous improvement process (abbreviated as CIP or CI), is an ongoing effort to improve products, services, or processes for instance by repeated iteration of the PDSA cycle.
    
Continuous Improvement, often known as Kaizen, is essentially a small step-by-step incremental improvement strategy. It is based upon a belief that continual improvement can be brought about by a never-ending series of small changes. Even in the face of enormous innovative improvement strategies, there will always be the need and opportunity to supplement such strategies and initiatives with continual small step changes.”

    Sources: Schonberger, R. J., 1982, “Japanese Manufacturing Techniques: Nine Hidden Lessons in Simplicity”, p55, New York: Free Press
  • Control


    To take actions or steps to regulate or limit the behavior of processes in a production system.

  • Control Mechanism


    A means to control the behavior of or within a process or system.

  • Control Mechanism – Human Decision Making


    A decision made by an individual to start or delay a process in an attempt to keep or bring a process within a desired state.

  • Control Mechanism – Physical

    A physical item that controls the behavior of a process to a desired state e.g. limiting the number of trailers controls the number of deliveries that can be made at a given time.

  • Control Mechanism – Software

    A software that signals whether a process should be started or delayed in order to keep or bring a process to a desired state.

  • Control Protocol


    The means in which production is planned and controlled. There exist three primary control protocols: push, pull, where production is released into the system based on the status of the system, and constant work in process (CONWIP), basically a pull signal that goes to the beginning of a process. 
Most often either push wherein the signal to commence production is based on a predetermined objective, pull wherein the signal to commence production is based on the status of the system or a request from a downstream customer or CONWIP where the signal is based on pull and sent to the beginning of the process (rather than the preceding step as in the case of pull).

  • Controls (Project)

    Forecasting, updating, and reporting of the status of the project in accordance with a baseline plan.

  • Critical Path Method (CPM)

    A mathematical algorithm for computing the shortest duration of a set of project activities given a set of precedence-successor relationships between the activities. The sequence of activities that comprises the shortest duration is called the “critical path”.

    Sources: “Non-Computer Approach to the Critical Path Method for the Construction Industry”, Prof. John Fondahl, Stanford University Paper for US Navy, Kelley, James; Walker, Morgan. Critical-Path Planning and Scheduling. 1959 Proceedings of the Eastern Joint Computer Conference
  • Critical Work-In-Process Level


    The WIP required for a line with no variability to achieve maximum throughput with minimum cycle time.

    Sources: “Factory Physics”, Third Edition, Wallace J. Hopp and Mark L. Spearman, Waveland Press, p231-235
  • Customer


    The direct or indirect consumer or beneficiary of the output of an operation, process or production system.

  • Cycle Time (CT)


    Cycle time is measured as the average time from when a job is released into a station or line to when it exits. 
Cycle Time (CT) is related to Throughput (TH) and Work in Process (WIP) by Little's Law.

    Sources: “Factory Physics”, Third Edition, Wallace J. Hopp and Mark L. Spearman, Waveland Press, p 230


  • Demand

    Demand represents the desire of an external customer and/or downstream process for an entity or a set of entities with particular attributes. Demand is always satisfied by a process. Entities demanded can be physical, information, services, etc. Demand is typically characterized by a rate of consumption. Examples are gallons of gas sold per day, pipe spools installed per week or tasks completed per day.

  • Demand for Services

    Service demand is unique because the demand characteristics are not known until the demand is created. For example, a drawing for a new product cannot be produced until the product is defined. In this sense, the demand for services is always backordered. There can be no stock inventory to satisfy service demand. There is no stock of, for instance, maintenance calls on a crane to repair the lift motor. The maintenance call is not provided until the crane lift motor breaks.

  • Deming Cycle

    Another name of the PDCA cycle (see PDSA) in honor of W. Edwards Deming (1900-1993) and based on the work of Walter A. Shewhart (1891-1967)
.
    First introduced by W. A. Shewhart in “Statistical method from the viewpoint of Quality Control” in 1939, originally introduced as a linear sequence of 3 steps and subsequently evolved into the 4-step cycle by Shewhart.
    Shewhart was one of Deming’s mentors, and introduced him to the cycle. Deming built on Shewhart’s concept emphasizing the interactions between the four steps and popularizing the cycle in the area of Total Quality Management.

    Sources: W. A. Shewhart 1980, “Economic Control of Quality of Manufactured Products/ 50th Anniversary Commemorative Issue. American Society for Quality
    See Also: Shewhart Cycle
  • Earned Value Management System

    An integrated management system that integrates the work scope, schedule, and cost parameters of a program in a manner that provides objective performance measurement data. It measures progress objectively with earned value metrics; accumulates direct costs; allows for analysis of deviations from plans; facilitates forecasting the achievement of milestones and contract events; provides supporting data for forecasting of estimated costs; and fosters discipline in incorporating changes to the baseline in a timely manner.

    Sources: Department of Defense Earned Value Management System Interpretation Guide, Feb 15, 2015, US Department of Defense, page 80 (Definitions)


  • Engineered to Order (ETO)


    Product or item for which design and engineering are performed in response to a specific request (order) from a customer and which is subsequently fabricated and assembled to that specification.

    Sources: “Operations Management: Focusing on Quality and Competitiveness”, 2nd edition, Roberta S. Russell and Bernard W. Taylor III, 1995, pp 43-44


  • Extra capacity mitigates stock and time buffers

    Having installed capacity above average demand allows the Stock Inventory and Backorder Time buffers to remain small.

    If the process had infinite capacity, there would never be either Stock or Backorders as the process could satisfy demand instantly.

    See Also: Stock, Process, Demand
  • Fabricate to Order (FTO)

    Product or item put together from parts that are already designed, but remain to be made, so as to meet the specifics of a customer request (order).

    Sources: “Operations Management: Focusing on Quality and Competitiveness”, 2nd edition, Roberta S. Russell and Bernard W. Taylor III, 1995, pp 43-44, “Operations and Supply Chain Management: The Core”, Third Edition, F. Robert Jacobs and Richard B. Chase, p 276

  • Fabrication

    Process of making an item through transforming materials through operations such as cutting, drilling, fastening, welding etc.

    Sources: P2SL glossary, p20
  • Factory Physics®

    The framework applying the science of operations to manufacturing management, after the book by Drs. Wallace J. Hopp and Mark L. Spearman.  Factory Physics® is a registered trademark.

    Sources: Factory Physics, Third Edition, W. J. Hopp and M. L. Spearman, Waveland Press, 2011
  • Float (also called Slack) 
Free

    Float is the amount of time that a schedule activity can be delayed without delaying the early start date of any immediately following schedule activities.
 Total Float is the total amount of time that a schedule activity may be delayed from its early start date without delaying the project finish date or violating a schedule constraint. Calculated using the critical path method technique and determining the difference between the early finish dates and late finish dates.

    Sources: Guide to the Project Management Body of Knowledge, 4th Edition, Project Management Institute, pp 450-451


  • Flow

    A Flow is described by a rate. The measure of a flow is some unit per period of time (e.g., barrels per day).

    A flow can be a set of operations called a process that accomplishes the transformation. A flow can also be a set of individuals creating the demand for the transformed entities. The rate of flow for a process is called its throughput.

    Sources: “Factory Physics”, Third Edition, Wallace J. Hopp and Mark L. Spearman, Waveland Press, p 203
  • Forecast


    An estimate or prediction of conditions and events in the project’s future based on information and knowledge available at the time of the forecast. The information is based on the project’s past performance and expected future performance and includes information that could impact the project in the future, such as estimate at completion and estimate to complete.

    Sources: Guide to the Project Management Book of Knowledge, Fourth Edition, Project Management Institute, p 435


  • Inventory

    Inventory is the accumulation of entities that occurs anywhere within and/or between processes (flows).

    Inventory between two or more flows is called stock while inventory within a flow is called work in process or WIP.

  • Inventory/Order Interface

    The point in a flow where entities switch from make-to-stock to make-to-order.

    Sources: “Supply Chain Science”, Wallace J. Hopp, 2008, Waveland Pr Inc., page 34


  • Job Shop


    Production system that accommodates making one-of-a-kind products whereby processing stations (machines) are laid out by functional grouping, such that each unit being produced is likely to have to follow a jumbled flow from one to the next, according to the processing steps it requires.

    Sources: “Factory Physics”, Third Edition, Wallace J. Hopp and Mark L. Spearman, pp. 9-10


  • Just in Time (JIT)


    Just-in-time means that, in a flow process, the right parts needed in assembly reach the assembly line at the time they are needed and only in the amount needed.

    Sources: Toyota Production System: Beyond Large-Scale Production, Ohno, Taiichi, 1988, Productivity Press, New York, p. 4
  • Kingman’s Equation (VUT equation)

    In queuing theory, a discipline within the mathematical theory of probability, Kingman's formula is an approximation for the mean waiting time in a queue in a system with a single server where arrival times have a general (meaning arbitrary) distribution and service times have a (different) general distribution. It is generally represented as CT = VUT, where CT is Cycle Time, V is a factor representing variability, U is a factor representing utilization, and T represents the mean effective process time.

    Sources: Factory Physics, Third Edition, Wallace J. Hopp and Mark L. Spearman, Page 288
  • Kit


    An assemblage of information, consumables, materials / parts and special tools required to execute a specific operation or element of work.

  • Kitting


    The process of assembling a kit (see Kit above).

  • Last Planner System™


    The collaborative commitment-based planning system that integrates should-can-will-did planning developed by Ballard et al.

    Last Planner is a trademark of the Lean Construction Institute.

    www.leanconstruction.org

    Sources: G. Ballard (1994). The Last Planner, Northern California Construction Institute, Monterey California., G. Ballard (2000) The Last Planner System of Production Control, Ph. D. Dissertation, Univ. of Birmingham UK
  • Last Planner™


    The person making commitments on behalf of and assignments to direct workers.

    Sources: G. Ballard (1994). The Last Planner, Northern California Construction Institute, Monterey California., G. Ballard (2000) The Last Planner System of Production Control, Ph. D. Dissertation, Univ. of Birmingham UK




  • Last Possible Moment (LPM)

    The last point in time when an operation or task can be completed without negatively impacting schedule objectives.

  • Last Responsible Moment (LRM)


    The moment beyond which a decision to select one of several alternatives cannot be taken either because the cost of selecting the alternative exceeds the benefit, or because the alternative is no longer available for selection.

    Sources: “Wicked Problems, Righteous Solutions – Back to the Future on Large Complex Projects”, Proceedings of the Proceedings 8th Annual Meeting of the International Group for Lean Construction, Aug 17-19, 2000, Brighton UK
  • Law of Variability

    Increasing variability always degrades the performance of a production system
.

    Sources: FP Factory Physics, W. J. Hopp and M. L. Spearman, p 309


  • Law of Variability Buffering

    Increased variability always requires increased buffering when trying to synchronize demand and transformation.

  • Lead Time

    The lead time of a given routing or line is the time allotted for production of a part on that routing or line. 
Unlike cycle time, which is generally random depending on utilization, variability and WIP levels, lead time is a constant and a management policy decision. Service Level, a measure of customer delivery performance, is the probability that cycle time is less than or equal to lead time.

    Sources: “Factory Physics”, Third Edition, Wallace J. Hopp and Mark L. Spearman, Waveland Press, 2011, p 230


  • Line of Balance


    The "Line of Balance" (LOB) is a graphic device that enables a manager to see at a single glance which of many activities comprising a complex operation are "in balance" - i.e., whether those which should have been completed at the time of the review actually are completed and whether any activities scheduled for future completion are lagging behind schedule. History: LOB was devised by the members of a group headed by George E. Fouch. During 1941, the Goodyear Tire & Rubber Company monitored production with LOB. It was successfully applied to the production planning and scheduling of the huge Navy mobilization program of World War ll. LOB proved to be a valuable tool for expediting production visibility during the Korean hostilities. During this period, defense suppliers used LOB http://www.valuation-opinions.com/ev/lob.lasso.

    Sources: Line of Balance Technology: A graphic method of industrial programming, US Department of Navy, April 1962
  • Linking Processes to Demand

    Because of variability, processes and demand are usually not synchronized meaning that either

    • The process completes before demand thereby creating stock
    • The process completes after demand thereby creating backorders
    See Also: Process, Stock
  • Little’s Law

    Little's Law defines the relationship between system throughput (TH), cycle time (CT), and work-in-process (WIP). CT = WIP/TH. Cycle time is a dependent variable. WIP is a leading indicator of CT.

    Sources: Factory Physics, Third Edition, Wallace J. Hopp and Mark L. Spearman, Waveland Press, p 239, Queues, Inventories and Maintenance: The Analysis of Operational Systems with Variable Demand and Supply, P. M. Morse, Dover, 2004, p 22, A Proof for the Queuing Formula: L = lW, J. D. C. Little, Operations Research, Volume 9, Issue 3, pp 383-387, Little’s Law as viewed on its 50th Anniversary, J. D. C. Little, Operations Research, Volume 59, Issue 3, pp 536-549
  • Made to Stock (MTS)

    A product that is made based on a forecast of customer demand and then stored in inventory (finished goods) until a customer specifically orders it.

    Sources: “Operations Management: Focusing on Quality and Competitiveness”, 2nd edition, Roberta S. Russell and Bernard W. Taylor III, 1995, pp 43-44, “Operations and Supply Chain Management: The Core”, Third Edition, F. Robert Jacobs and Richard B. Chase, McGraw Hill Irwin, p 276, “Factory Physics”, Third Edition, Wallace J. Hopp and Mark L. Spearman, Waveland Pr. Inc., P230
  • Make to Order (MTO)

    A product or item that has been designed but is made (physically realized) only at the time when a customer orders it.

    Sources: “Factory Physics”, Third Edition, Wallace J. Hopp and Mark L. Spearman, Waveland Press, p 230, “Operations and Supply Chain Management: The Core”, Third Edition, F. Robert Jacobs and Richard B. Chase, McGraw Hill Irwin, p 276


  • Matching Problem

    The challenge encountered in avoiding incorrect assembly when combining unique products with other unique products in an assembly operation.

    Sources: “Factory Physics”, Third Edition, Wallace J. Hopp and Mark L. Spearman, Waveland Press, p328


  • Merge Bias


    Refers to the likelihood of a successor starting given the probabilities of a set of parallel predecessor activities completing. All the path probabilities of the predecessors must be combined to describe the likelihood of the successor starting – typically smaller than one might intuitively believe.

    Sources: Integrated Cost and Schedule Control in Project Management, Urusla Kuehn, pp. 172-173


  • Milestone

    A significant point in time or event on the master plan or schedule of a project that defines the end or beginning of a phase or a contractually required event.
 Typically, milestones represent completion of a certain portion of project scope as measured by the achievement of predefined criteria.

    Sources: P2SL Glossary p 38

. “Guide to the Project Management Body of Knowledge”, 4th Edition, Project Management Institute, p 136
  • Milk-Run System


    Refers to automotive industry practice of picking up small quantities of supplies from vendors throughout the day (“milk run”) to ensure that the inventory stayed below a present level. Frequent restocking to limits the maximum WIP in the system.

    Sources: International Business, A. Aswathappa, p55

, “Milk Run Logistics: Literature Review and Directions”, G. S. Brar and G. Saini, Proceedings of the World Congress on Engineering, 2011, Vol I, WCE 2011, July 6-8, 2011, London UK
  • Min / Max Inventory


    An inventory system that is controlled by an (s, S )-replenishment policy is also known as a min-max system. Under the (s, S ) control, a replenishment order is placed to raise the inventory position (= on-hand stock + outstanding orders − backorders) up to S whenever it drops to s or below.

    Sources: T. Wang, Y. Chen, Y. Feng, On the time-window fulfillment rate in a single-item min-max inventory control system, IIE Transactions (2005) 37, 668
  • Modeling – Production System

    A mathematical model of a production system is a description of the system using mathematical concepts ­ equations, graphs, process maps. The model provides an abstraction that reduces the system to its essential characteristics. Using mathematical tools such as linear programming and queuing theory, the mathematical model representation can help explain the behavior of the system. For example, models can explain how different components of the system interact with each other. They can also make predictions about future behavior of the system, such as maximum throughput achievable, where bottlenecks are located, and how much inventory is built up as the system operates.

    Any modeling of any production system should incorporate the relationships of Operations Science. It is common for companies to construct models that poorly reflect reality because of a limited understanding of Operations Science. Math is not the same as science. One can, and people often do, construct precise mathematical models that are wrong because the math does not reflect the underlying Operations Science.

  • Modularization


    Modularization refers to the use of offsite construction (including a segregated area onsite). Modularization includes all work that represents substantial offsite construction and assembly of components and areas of the finished project.

    Sources: Construction Industry Institute SD-25 – Constructability Improvement Using Prefabrication, Preassembly, and Modularization -- Tatum, Vanegas, Williams, https://kb.construction-institute.org/Knowledge-Areas/Modularization


  • Move Time

    The time jobs in a production system spend being moved from one station in the production system to the next station.

    Sources: “Factory Physics”, Third Edition, Wallace J. Hopp and Mark L. Spearman, Waveland Press, p327
  • Non-consumable resources

    Non-consumable resources do not become part of the entity but are required and not consumed.

    Examples include information, plans, designs, CAD drawings, etc.

  • Offsite Assembly


    Assembly of raw materials and fabricated parts performed in a location other than the point of final installation.

  • Operation

    An operation is an act that transforms one or more attributes of an entity or set of entities. Examples include manufacturing, services, transportation, information, projects, etc.

  • Operations and Resources

    An operation will require the use of one or more resources in order to perform the transformation. These resources include raw materials, sub­assemblies, components, labor, machines, information, intelligence, energy, fuel, etc.

    See Also: Operation, Resource
  • Operations Management

    Operations Management is the application of operations science to real-world production, service, and distribution systems. This includes supply chain management as well. Operations management is concerned with the design, control and improvement of any organization’s operations.

  • Operations Research (OR)

    The application of mathematical (quantitative) techniques to the scientific study and analysis of complex systems and optimization problems of organization and coordination of activities in business operations and decision making.

    Historically the discipline emerged as the confluence of several different threads of scientific application. Charles Babbage conducted research into the cost of transportation and sorting of mail which were applied in the UK’s first postal system. To understand the best choice of railway gauge, he conducted studies into dynamical behavior of railway vehicles on a railway network. Military planners during World War 1 were concerned with the scientific planning and organization of logistics of supplies for troops (convoy theory and Lanchester’s laws). The field expanded with the Second World War conferring several problems for US and UK military planners resulting in the development (among other things) of linear and dynamic programming techniques, and other mathematical tools.
    Since then, the field has found application in many areas in transportation, finance, logistics and government.

    Sources: Introduction to Operations Research, F. S. Hillier and G. J. Lieberman, Eight Edition, McGraw- Hill, p3., Maynard’s Industrial Engineering Handbook, Fifth Edition, Kjell B. Zandin (ed.), McGraw-Hill 2001, p G.2
  • Operations Science

    Is the study of the transformation of resources to create and distribute goods and services.

    Operations Science (OS) focuses on the interaction between demand and production and the variability associated with either or both. OS also describes the set of buffers required to synchronize demand with production.

  • Operations Sciences

    Synonymous with operations research.

  • Operations Strategy

    The design, implementation and control of the portfolio of demand, inventory, time, capacity, variability and cost to achieve a company’s marketing and financial goals.

    Sources: Pound, Spearman and Bell; Factory Physics for Managers, McGraw-Hill, New York, p. 198
  • Part


    Generic term used in manufacturing for a basic item forming part of the whole of a more complex product.
 The hierarchy for the terminology is as follows: parts are elements or units in a component. Components are elements or units in either subassemblies or assemblies. Assemblies form a product or system.

    Sources: Production & Operations Management: Manufacturing and Services, R. B. Chase, N. J. Aquilano and F. R. Jacobs, Eight Edition, pp 101-102, pp 626-628


  • PDSA

    Plan-Do-Study-Act Cycle of Continual Improvement. (Also known as the Deming Cycle.)
The cycle of scientific experimentation used in pursuit of continuous improvement
. First introduced by W. A. Shewhart in “Statistical method from the viewpoint of Quality Control” in 1939, originally introduced as a linear sequence of 3 steps and subsequently evolved into the 4-step cycle by Shewhart.
Shewhart was one of Deming’s mentors, and introduced him to the cycle.  Deming built on Shewhart’s concept emphasizing the interactions between the four steps and popularizing the cycle in the area of Total Quality Management.

    Sources: W. A. Shewhart 1980, “Economic Control of Quality of Manufactured Products/ 50th Anniversary Commemorative Issue. American Society for Quality

  • Percent Plan Complete PPC

    Metric used in Last Planner System to gauge reliability. The number of actual completions divided by the number of planned completions in a given time period, based on a binary assessment on whether a task is 100% complete.

    Sources: P2SL Glossary p44


  • Performance Indicator

    A quantitative or qualitative measurement, or any other criterion, by which the performance, efficiency, achievement, etc. of a person or organization can be assessed, often by comparison with an agreed standard or target.

    Sources: Collins English Dictionary


  • Physical resources

    Physical resources become part of the entity. Examples are raw materials, sub-assemblies, components, individual items, etc.

  • Policy

    A set of ideas, course or principles of action adopted by or proposed for a system or organization. In a production system, policies may be rules related to setting inventory levels, service levels, and other means on imposing constraints on processes and other aspects of a production system.

  • Preassembly


    In manufacturing, preassembly refers to the prior fabrication and assembly of elements of a product in a separate location before assembling the final product on the production line.

    In construction, preassemblies are sections of a facility that are assembled remotely from their final position and transported to the site as a unit.

    Sources: CII SD-25 – Constructability Improvement Using Prefabrication, Preassembly, and Modularization -- Tatum, Vanegas, Williams


  • Process

    A process is a set of one or more operations designed to transform a set of entities into another form to achieve a particular purpose.

    The process begins with the accumulation of all the needed resources and proceeds through a sequence of operations until completion.

    Examples of processes include production lines, construction projects, hospital operating theaters, insurance claims processing, etc. Also called a Value Stream.

  • Process Map


    A graphical flowchart identifying the operations in a process, steps in each operation and work time for each step.

  • Process Time


    The time a job spends at an individual station in a production system from the time the station begins working on it, till the time the station finishes.

    Sources: Factory Physics, Third Edition, W. J. Hopp and M. L. Spearman,Waveland Press, p327


  • Procurement

    Procurement involves the process of sourcing and evaluating suppliers, selecting vendors, establishing payment terms, strategic vetting, selection, the negotiation of contracts and actual purchasing of goods.
  Procurement refers to the process of accessing goods and services necessary for a production system to operate.
 Supply chain refers to the infrastructure (internal or external companies) over which the Procurement process operates.

    Sources: “Purchasing and Supply Chain Management: Analysis, Strategy, Planning and Practice”, A. J. Weele, Fourth Edition, Thomson Publishing
  • Product – Process Matrix

    A graphical method to illustrate the interaction between the characteristics of products being produced by a production system and the processes used to produce those products.

    Sources: “Link Manufacturing Process and Product Lifecycles’, R. H. Hayes and S. C. Wheelwright, Harvard Business Review, January, 1979


  • Product Structure Tree

    In manufacturing the product structure tree provides a hierarchical classification of the items which form a product. With the product structure, the understanding of the components which compose a product as well as their attributes, can be represented. The product structure shows the material, component parts subassemblies and other items in a hierarchical structure that represents the grouping of items on an assembly drawing or the grouping of items that come together at a stage in the manufacturing process.

    In construction, a product structure tree is structured with the following levels:

    • Asset
    • Module
    • Assembly
    • Sub­-Assembly
    • Part
    Sources: Production & Operations Management: Manufacturing and Services, R. B. Chase, N. J. Aquilano and F. R. Jacobs, Eight Edition, pp 101-102, pp 626-628
  • Production


    The act of transforming or changing the shape, composition or combination of materials, parts, subassemblies or information in a production system to increase their value.

    Sources: Maynard’s Industrial Engineering Handbook, Fifth Edition, Kjell B. Zandin (ed.), McGraw-Hill 2001, p G.2


  • Production Control


    Policies, protocols and mechanisms to control transformational processes, the use of resources and variability.

  • Production Control Solution


    An integrated configuration of sensor measurements, business processes, rules and performance indicators to enable effective control based on desired objectives.

  • Production Control Solution Design

    Selection, configuration and integration of business processes, rules and performance indicators to effectively control production in accord with objectives.

  • Production Control System


    Software application that automates and enables scalable and sustainable implementation of the production control solution.

  • Production System


    Any of the methods used in industry to create goods and services from various resources.

    Sources: Encyclopedia Britannica


  • Production System Definition

    The purpose, objectives and constraints upon which the production system design is based
.

  • Production System Definition Process

    Setting forth business purpose and objectives for the project, establishing project objectives and identification of constraints upon which the production system design is based.

  • Production System Design

    Engineering of processes, selection of resources and designation of controls to effectively transform inputs into outputs in accord with desired objectives.

  • Production System Design Process

    Production system design is done by mapping, analyzing and modeling processes, resources and controls in accord with objectives.

  • Program Evaluation and Review Technique (PERT)

    Planning technique developed in the late 1950s to determine the duration of projects with highly uncertain activity durations.

    Sources: B. Ralph Stauber, H. M. Douty, Willard Fazar, Richard H. Jordan, William Weinfeld and Allen D. Manvel. Federal Statistical Activities. The American Statistician 13(2): 9-12 Malcolm, D. G., J. H. Roseboom, C. E. Clark, W. Fazar Application of a Technique for Research and Development Program Evaluation OPERATIONS RESEARCH Vol. 7, No. 5, September–October 1959, pp. 646–669


  • Project

    A temporary endeavor undertaken to create a unique product, service, or result.
 A project is temporary in that it has a defined beginning and end in time, and therefore defined scope and resources.
And a project is unique in that it is not a routine operation, but a specific set of operations designed to accomplish a singular goal. So, a project team often includes people who don’t usually work together – sometimes from different organizations and across multiple geographies.
 The development of software for an improved business process, the construction of a building or bridge, the relief effort after a natural disaster, the expansion of sales into a new geographic market — all are projects. And all must be expertly managed to deliver the on-time, on-budget results, learning and integration that organizations need.
 Project management is the application of knowledge, skills, tools, and techniques to project activities to meet the project requirements.

    Sources: Guide to Project Management Body of Knowledge, Fourth Edition, Project Management Institute, p 442., https://www.pmi.org/about/learn-about-pmi/what-is-project-management


  • Project Controls

    The data gathering, management and analytical processes used to predict, understand and constructively influence the time and cost outcomes of a project or program; through the communication of information in formats that assist effective management and decision making.

    Sources: Guide to the Project Management Body of Knowledge, Fourth Edition, pp 60-64, Project Management Institute, “Project controls: how much is enough?”, G. E. Heywood, G.E. Project Management Institute, PM Network, vol. 10, no. 11, Nov 1996


  • Project Delivery Process



    Project Management
. The application of knowledge, skills, tools, and techniques to project activities to meet the project requirements.

    Sources: Guide to the Project Management Body of Knowledge, Fourth Edition, p 443, Project Management Institute., https://www.pmi.org/about/learn-about-pmi/what-is-project-management


  • Project Production Management

    The application of Operations Science theories, principles and methods to better understand, control and improve project delivery.

  • Project Production System

    The collection of production systems comprising the interconnected network of processes and operations that represent all the work activities to execute a project from start to finish.

  • Pull (Control Protocol)


    Pull systems establish an a priori limit on work in process. A pull system, which triggers releases of work based on the amount of work in the system, will not allow WIP to grow without bound. In projects, this is a fundamental control to prevent projects from blowing up on cost and missing schedules. Using Operations Science, the optimal amount of WIP for a project can be determined during design of the Project Production Management system.

    Sources: Hopp and Spearman 1990 and MW Factory Physics, W. J. Hopp and M. L. Spearman, 3rd Edition, Waveland Press, p358
  • Purchasing

    Refers to the transaction of buying goods and services as a result of the procurement decisions. 
Purchasing is a subset of Procurement.

    Sources: “Purchasing and Supply Chain Management: Analysis, Strategy, Planning and Practice”, A. J. Weele, Fourth Edition, Thomson Publishing


  • Push (Control Protocol)

    A Push control protocol releases work to the process based on external information—external means external to the status of the system. Push control release work independent of the amount of WIP in the process. For instance, a project schedule will direct shipment of modules to the worksite independent of whether or not the site is ready for the module. Push control protocol allows WIP to grow without bound which has contributed in very large part to poor performance on cost and delivery for projects.”

    Sources: Factory Physics, Third Edition, W. J. Hopp and M. L. Spearman,Waveland Press, p358
  • Push versus Pull


    Pull systems establish an a priori limit on work in process, push systems do not. There is much confusion on this topic. The key distinguishing characteristic is WIP control. Any kind of production system, such as make-to-order, make-to-stock, engineer-to-order or configure-to-order can use push or pull control. Further, the fundamental objective of WIP control is maintain the optimal WIP in the system to achieve maximum throughput with minimum time and cost. This fundamental objective is a central design question for any Project Production Management system.

    Sources: Factory Physics, Third Edition, W. J. Hopp and M. L. Spearman,Waveland Press, p358
  • Queue


    A set of objects, task, or other things waiting for something, typically an action to be processed in a production system
.

    Sources: Queues, Inventories and Maintenance: The Analysis of Operational Systems with Variable Demand and Supply, P. M. Morse, Dover 2014, p. 14


  • Queue Time

    Queue Time is the time that parts or tasks spend waiting for processing at a station or to be moved to the next station.

    Sources: "Factory Physics", W. J. Hopp and M. L. Spearman, Third Edition, 2011, Waveland Press, p 327
  • Queuing Theory

    Queuing theory is the mathematical study of waiting lines, or queues. In queuing theory, a probabilistic model of arrival times (of tasks, objects for work to be performed) and waiting times (waiting time in the queue before work starts) is constructed so that queue lengths and waiting time can be predicted.

    Sources: “Fundamentals of Queuing Theory”, D. Gross and J. F. Shortle., Queues, Inventories and Maintenance: The Analysis of Operational Systems with Variable Demand and Supply, P. M. Morse, Dover 2014, p. 2


  • Rate

    Rate - a fixed ratio between two things. For production systems, rate is a measure of throughput or output and is stated as units per period of time or tasks per period of time.

    Sources: Merriam-Webster on-line, Project Production Institute
  • Raw Process Time


    The sum of the long-term average process times of each operation in a process. Alternatively, Raw Process Time can be described as the average time it takes a single job to traverse an empty process, i.e. it does not have to wait behind other jobs at any time.

    This is not the same as Value-Added Time though the two are similar. Raw Process Time accounts for real-world effects such as outages, setups and batching which Value-Added Time does not.

    Sources: Factory Physics, Third Edition, W. J. Hopp and M. L. Spearman, Waveland Press, p.232
  • Reliability


    The characteristic of an item expressed by the probability that it will perform a required function under stated conditions for a stated period of time.

    Sources: An Elementary Guide to Reliability, G. W. A Dummer, M. H. Tooley, R. C. Winton, 5th Edition, Butterworth-Hintion


  • Resource

    An operation will require the use of one or more resources in order to perform the transformation. These resources include raw materials, sub-assemblies, components, labor, machines, information, intelligence, energy, fuel, etc.

  • Resource Types
    1. Consumable resources do not become part of the entity. Examples include energy, lubricating oil, cooling water, etc.
    2. Non-consumable resources do not become part of the entity but are required and not consumed. Examples include information, plans, designs, CAD drawings, etc.
    3. Physical resources become part of the entity.  Examples are raw materials, sub-assemblies, components, individual items, etc.
    4. Capacity resources are required to transform the entity but do not become part of the entity such as machines, labor, transportation.
  • Routing

    In a production system, work to transform inputs into finished outputs may take place in different parallel paths simultaneously, as different aspects of a finished work product or service are worked on simultaneously.  An individual path is referred to as a routing.
 The sequence of processes, operations, transportations and machines, equipment, tools, workstations  and miscellaneous information that a particular part, batch or work-in-process item follow in a production system.

    Sources: Supply Chain Science, Wallace. J. Hopp, 2008, Waveland Press, p10, Maynard’s Industrial Engineering Handbook, Fifth Edition, Kjell B. Zandin (ed.), McGraw-Hill 2001, p G.18


  • Rule

    An accepted principle or instruction that states the way things are or should be done and tells you what you are allowed or are not allowed to do (Cambridge Dictionary).

  • Service Level


    A performance metric measuring the extent to which demand (orders) are satisfied by a station in a production system or by the system as a whole.
 For flows, service level is measured as the fraction of jobs for which cycle time is less than or equal to lead time. For demand satisfied from stock inventory, service level is measured as the fill rate, or fraction of demands that are filled from stock.

    Sources: Factory Physics, W. J. Hopp and M. L. Spearman, Third Edition, Waveland Press, pp 73-74 and p. 230
  • Service Processes and Stock

    Because service processes cannot be done before the service is requested, there will never be a stock inventory of “completed services.” The time between the initiation of demand and its satisfaction is the backorder time.

    Consequently, all service processes are effectively backordered even when they are delivered within an agreed to lead time.

  • Set Up Time

    A Set Up process corresponds to the time required to go from the end of the last good part from one batch to when the first good part of the following batch is produced. With this definition, the trials needed to obtain the first good work product are considered part of the setup process and therefore, must be studied, analyzed and improved.

    Sources: Shigeo Shingo, A Revolution in Manufacturing: The SMED System. Portland: Productivity Press Inc, 1985
  • Shewhart Cycle

    Another name of the PDCA (see PDSA) in honor of W. Edwards Deming (1900-1993) and based on the work of Walter A. Shewhart (1891-1967)
First introduced by W. A. Shewhart in “Statistical method from the viewpoint of Quality Control” in 1939, originally introduced as a linear sequence of 3 steps and subsequently evolved into the 4-step cycle by Shewhart.
 Shewhart was one of Deming’s mentors, and introduced him to the cycle. Deming built on Shewhart’s concept emphasizing the interactions between the four steps and popularizing the cycle in the area of Total Quality Management.

    Sources: W. A. Shewhart 1980, “Economic Control of Quality of Manufactured Products/ 50th Anniversary Commemorative Issue. American Society for Quality
  • Six Sigma (Continuous Improvement)


    A family of methods for creating radically better products and processes originally branded and developed by Motorola – the primary focus being the measurement and reduction of defects in product and service quality.

    Sources: Factory Physics, W. J. Hopp and M. L. Spearman, Third Edition, Waveland Press, pp 171-172


  • SMED
 Single Minute Exchange of Die (SMED)

    Refers to the methodology developed by Shigeo Shingo in the 1950s to reduce Set Up Time in manufacturing processes. Shingo’s basic insight was that a Set Up process could be decomposed into:
 External Set Up tasks – those tasks that could be performed while the previous batch was still being worked on
 Internal Set Up tasks – those tasks that could be performed only after the previous batch had been completed and before the current batch could start.
 He identified ways in which to reduce overall Set Up time by converting where Internal Set Up tasks into External Set Up tasks where possible, through a 4-step analysis:

    • An examination of the current Set Up
    • Separating Internal and External Set Up
    • Converting Internal Set Up to External Set Up
    • Streamlining all aspects of the adjusted process
    Sources: Shigeo Shingo, A Revolution in Manufacturing: The SMED System. Portland: Productivity Press Inc, 1985
  • Spectrum of Manufacturing Processes


    Manufacturing processes are categorized along a spectrum from Project at one end (unique or one-off event) to Continuous Flow at the other end. Job Shop, Batch Flow, and Line Flow are processes that fall along the spectrum.

    Sources: “Link Manufacturing Process and Product Lifecycles’, R. H. Hayes and S. C. Wheelwright, Harvard Business Review, January, 1979
  • Spectrum of Product Characteristics


    Product types are categorized along a spectrum according to their lifecycle characteristics ranging from great variety in startup form to standardized commodity at the other extreme. In between, a product might have the form of a number of basic models with a variety of options through to a few models with basic options.

    Sources: “Link Manufacturing Process and Product Lifecycles’, R. H. Hayes and S. C. Wheelwright, Harvard Business Review, January, 1979
  • Station


    In a production system, an individual step where inputs have some work task(s) performed upon them and the resulting outputs flow through another part of the production s is referred to as a station.

    Sources: “Supply Chain Science”, First Edition, Wallace J. Hopp, 2008, Waveland Press, p 3
  • Station Cycle Time Formula


    The Station Cycle time formula states that the average cycle time at a station in a production system includes actual Processing Time (PT), as well as Move Time (MT), Setup Time (ST), Queuing Time (QT), Batch Time (BT) (CT=PT + MT + QT + ST + BT) Cycle time for an end-to-end process is CT = PT + MT + SDT + BT + QT where SDT represents the shift differential time.

    Sources: Factory Physics, Third Edition, Wallace J. Hopp and Mark L. Spearman, Waveland Press, p 327
  • Statistical Process Control (SPC)


    The (continuous) monitoring of processes with respect to mean and variability of performance to determine when problems occur or when the process has gone out of control.

    Sources: Factory Physics, W. J. Hopp and M. L. Spearman, Third Edition, Waveland Pr. Inc., p 404


  • Stock

    Stock represents a set of completed transformations or entities. As such the entities in stock are immediately ready to satisfy demand immediately.

    Since Demand is a flow and the transformation Process is a flow, there will always be a stock between demand and transformation.

    However, since the demand for services is always backordered, such a stock will always be empty but will nonetheless function as a stock.

  • Subassembly

    Two or more parts joined together to form a unit that is only part of a complete machine, structure, or other article being manufactured in a production system.

    Sources: Maynard’s Industrial Engineering Handbook, Fifth Edition, Kjell B. Zandin (ed.), McGraw-Hill 2001, p G.20


  • Supply Chain

    A supply chain is a goal-oriented network of processes and stock points used to deliver goods and services to customers.

    Sources: “Supply Chain Science”, First Edition, Wallace J. Hopp, 2008, Waveland Press, p 1
  • Supply Chain Management

    See Operations Management.

  • Supply Flow


    All processes necessary to engineer, fabricate, assemble, transport, install and commission a specific system.

  • System

    The word system is derived from the ancient Greek sustema and thence the Latin systema. Thus, it has two distinct sets of meanings, from which numerous specializations exist:

    1. A set of interconnected things or parts working together to form a complex whole e.g. a manufacturing assembly line consists of a series of manufacturing stations working together in an interconnected network
    2. A set of principles or procedures according to which something is done; an organized scheme or method e.g. the metric system, a set of rules in measurement or classification

    For the purposes of this glossary, we adopt definition (1) for use in phrases like “Production System” or “Project Production System” – a set of interconnected processes working together to form a complex whole.

    Sources: PPI, F. Harary and M. F. Batell “What is a System”, Social Networks, Vol. 3, 1981, pp. 29 – 40.
  • Takt Time

    The interval of time between outputs.

    Allowable time for production divided by required number of units that need to be produced (e.g. 200 days / 1,000 spools = .2 days per spool).

    Sources: Factory Physics, W. J. Hopp and M. L. Spearman, Third Edition, Waveland Press, p495, P2SL Glossary p 59
  • Task


    Within the context of a production step, the smallest basic step or unit of activity that takes place within the system in the production of goods and services.

  • Task Interdependence


    Work tasks can be generally classified as Pooled (completely independent), Sequential (one follows after another), or Reciprocal (mutually interdependent).

  • Throughput (TH)


    Measured as the average output of a production process (machine, station, line, plant) per unit time. Throughput is related to Cycle Time (CT) and Work in Process (WIP) by Little's Law.

    Sources: Factory Physics, W. J. Hopp and M. L. Spearman, Third Edition, Waveland Press, p229


  • Utilization

    Utilization is a measure of the fraction of time that a station in a production system is not idle. 
Utilization = rate at which the station accepts inputs divided by the capacity of the station.

    Sources: Supply Chain Science, Wallace J. Hopp, 2008, McGraw-Hill, p 14
  • Value Chain



    A value chain is a set of activities that an organization carries out to create value for its customers. The idea of the value chain is based on the process view of organizations, the idea of seeing a manufacturing (or service) organization as a system, made up of subsystems each with inputs, transformation processes and outputs. Inputs, transformation processes, and outputs involve the acquisition and consumption of resources - money, labor, materials, equipment, buildings, land, administration and management.

    Sources: Porter, Michael E., "Competitive Advantage". 1985, Ch. 1, pp 11-15. The Free Press. New York, Rowe, Mason, Dickel, Mann, Mockler; "Strategic Management: a methodological approach". 4th Edition, 1994. Addison-Wesley. Reading Mass
  • Value Stream


    See definition of Process.

  • Value Stream Mapping

    A value stream map is the graphical representation of all the actions (both value added, and non-value added) currently required to bring a product through the main flows essential to every product: (1) the production flow from raw material into the arms of the customer, and (2) the design flow from concept to launch.

    Sources: Learning to See: Value Stream Mapping to Add Value and Eliminate MUDA Spiral-bound – June 1, 1999 by Mike Rother (Author), John Shook (Author), Jim Womack (Foreword), Dan Jones (Foreword) ISBN-13: 978-0966784305 ISBN-10: 0966784308


  • Value-Added Activity

    Any step in the production process that improves the product for the customer. Also, any activity that the customer cars about, that changes the product and that is done right the first time. The value-added concept and value stream mapping approach is very subjective and thereby often causes confusion concerning the underlying science of a process. The value-added concepts were first promoted in the 1990s and became highly popular when Rother and Shook published “Learning to See” in 1998. For further discussion, see “The Value-Added Fantasy” in Factory Physics for Managers.

    Sources: Pound, Bell and Spearman, Factory Physics for Managers, 2014 McGraw-Hill, New York, pp. 172-176
  • Variability

    Variability is the term used to describe any dissimilarity between specific instances of a particular operation or process, particular entity output from an operation, or a particular Demand. The dissimilarity may manifest itself in terms of attributes of the entities/ operations or in the timing of those entities/ operations.

  • Variability – Types
    • Entity variation includes differences in any attribute such as size, color, hardness, density, quantity, quality, etc.
    • Process variation includes differences in the output of the process itself such quality of service, application of the process, etc.
    • Time variation deals with time to obtain or produce entities and/or services.
  • Variability – Beneficial


    A change in operating parameters that improves overall project performance. For example, the unexpected arrival time of raw materials earlier than expected, can in the right circumstances, lead to an earlier than planned completion time for the project. Other examples of beneficial variability are the introduction of new technology or processes that improve overall project performance e.g., new technology or process design. that allows one to plan for less inventory (and thus less cost) than originally envisaged.

  • Variability – Detrimental


    A change in operating parameters that worsens overall project performance. For example, rework due to quality issues increases costs and extends completion time. Other examples of detrimental variability are bad weather than causes work to be delayed or rescheduled, also potentially adding costs and extending completion times.

  • VUT Equation

    See Kingman's Equation.

  • Work in Process (WIP)


    Work in process or WIP is the set of entities that are partially transformed within any given process. WIP does not include stock inventory which is composed of completed entities.

    WIP typically accumulates while waiting for available capacity in front of an operation. Stock accumulates between two or more processes (e.g., finished inventory between a process and its demand).