Glossary

An input-process-output representation of design tasks or construction processes. The model depicts the specification of directives (entering the process rectangle from above), prerequisites (including materials and information to be transformed into the desired output, entering the process rectangle from the left), and resources (entering the process rectangle from below). It also shows an inspection process resulting either in redo or release to the customer process. The model is used as a guide to exploding scheduled tasks into a level of detail at which their readiness for execution can be assessed and advanced.

ADM

assignment

A directive or order given to a worker or workers directly producing or contributing to the production of design or construction.

Example: Scott, you and Julie are to make the changes in wall locations detailed in memo #123 by the end of the week. Anne, you find out what the building authorities will require for a structural permit.

backlog

buffer

A mechanism for deadening the force of a concussion; e.g., a capacity buffer is created by scheduling less than all the time available. If production falls behind schedule, there is capacity available for catching up. (Lean production/construction generally prefers capacity buffers to inventory buffers.)

capacity

The amount of work a production unit, whether individual or group, can accomplish in a given amount of time.

Example: Jim the engineer can perform 10 piping stress analyses per day on average, but the analyses to be done this week are particularly difficult. He will only be able to do 7. Jim’s average capacity is 10, but his capacity for the specific work to be done this week is 7.

commitment planning

The bottom level in the planning system hierarchy, below lookahead planning, that results in commitments to deliver on which others in the production system can rely because they follow the rule that only sound assignments are to be accepted or made.

Example: On my work plan for next week, I have included providing Cheryl the soils data she needs to evaluate alternative substructure systems for the building. All known constraints have been removed from my task, I understand what’s required and how the information will be used, and I have reserved needed labor and equipment.

conditions of satisfaction (COS)

Directives, often criteria, imposed by the entity initiating a process (usually the owner) that specify how success of the outcome will be gauged.

constraint

Something that stands in the way of a task being executable or sound. Typical constraints on design tasks are inputs from others, clarity of criteria for what is to be produced or provided, approvals or releases, and labor or equipment resources. Typical constraints on construction tasks are the completion of design or prerequisite work; availability of materials, information, and directives. Screening tasks for readiness is assessing the status of their constraints. Removing constraints is making a task ready to be assigned.

control

Example: Exploding master schedule activities into greater detail, screening the resultant tasks against constraints, and acting to remove those constraints are all control actions intended to cause events to conform to plan, or to identify as early as practical the need for replanning. Learning is initiated through analysis of reasons for failing to cause events to conform to plan.

COS

criteria (plural of criterion)

Criteria are a subset of directives, specifically those used to evaluate process outputs.

customer

Example: John needs the results of our acoustical tests in order to select the best location for his mechanical equipment. John is our customer because he will use what we produce.

cycle time

The time it takes a product to go from beginning to end of a production process; i.e., the time it is work-in-process .

definition

Quality criterion for assignments that questions whether or not assignments are specific enough so that the right type and amount of information and materials can be collected, work can be coordinated with other disciplines or trades, and it is possible to tell at the end of the week if the assignment has been completed.

design

A type of goal-directed, reductive (not deductive) reasoning. There are always many possible designs, especially if one is willing to relax constraints. Product design reasons from function to form. Process design reasons from ends to means.

design criteria

Example 1: The structural engineer needs both geometric and load inputs from the architect, mechanical engineer, and electrical engineer. Loads need only be accurate within 20%.

Example 2: The cladding design must be consistent with the architectural standards of the local historical society. In addition, it must be within the 2 million dollar budget and installable within a 6 week window concluding no later than April 6, 2000.

directive

exploding

Expressing a task in greater detail, typically by producing a flow diagram of the process of which the output is the task being exploded, then determining the sub-tasks needed to make the task ready for assignment and execution when scheduled. Sub-tasks are categorized in terms of the activity definition model , resulting in actions to clarify or specify directives, requests for prerequisites from suppliers, and reservation of needed resources .

first-run study

Trial execution of a process in order to determine the best means, methods, sequencing, etc. to perform it. First-run studies are done a few weeks ahead of the scheduled execution of the process, while there is time to acquire different or additional prerequisites and resources .

flow

front end planning

The top level in the planning system hierarchy, above lookahead planning, dedicated to articulating high-level activities and their duration and sequencing for an entire project and resulting in a master schedule. Also see lookahead planning and commitment planning.

input

inventory

Stock on hand; often divided between raw materials inventory, work-in-process, and finished goods inventory.

last planner™

The person or group that makes assignments to direct workers. ‘Squad boss’ and ‘discipline lead’ are common names for last planners in design processes. ‘Superintendent’ (if a job is small) or ‘foreman’ are common names for last planners in construction processes.

learning

The process of gaining new knowledge or insights whose implementation may improve product and process development.

load

The amount of output expected from a production unit or individual worker within a given time. Within a weekly work plan, what is to be accomplished by a design squad or individual designer, engineer, draftsperson, construction craftworker, crew, etc. A quality assignment ‘loads’ a resource within its capacity.

lookahead planning

The middle level in the planning system hierarchy, below front end planning and above commitment planning, dedicated to controlling the flow of work through the production system.

lookahead schedule

The output of lookahead planning, resulting from exploding master schedule activities by means of the activity definition model, screening the resultant tasks before allowing entry into the lookahead window or advancement within the window, and execution of actions needed to make tasks ready for assignment when scheduled. Lookahead schedules may be presented in list form or bar charts.

lookahead window

How far ahead of scheduled start activities in the master schedule are subjected to explosion, screening, or make ready . Typically lookahead windows extend from 3 to 12 weeks into the future.

make ready

master schedule

output

percent plan complete

plan reliability

The extent to which a plan is an accurate forecast of future events, measured by PPC.

Example: If your weekly work plans have a 60% PPC, they accurately predict completion/release of 60% of the weekly assignments.

planning

Defining criteria for success and producing strategies and directives for achieving success.

PPC

Percent plan complete; i.e., the number of planned completions divided into the number of actual completions, usually referring to activities on a weekly work plan.

prerequisite work

Work done by others on materials or information that serves as an input or substrate for your work.

Example: You need to know the surface area of glass, provided by the architect, in order to size cooling equipment.

production unit

A group of direct production workers that do or share responsibility for similar work, drawing on the same skills and techniques.

Example: a team of electrical designers and engineers responsible for a specific area or functions of a building.

productivity:

pulling

Initiating the delivery of input based on the readiness of the process into which they will enter for transformation into outputs.

Example: Request delivery of prerequisite information at or before the time you will be ready to process that information. Note: what’s different here is that the readiness of the process is known rather than wished. Either the process is ready prior to requesting delivery or plan reliability is sufficiently high that work plans can be used to predict readiness.

push vs. pull

A push system schedules the release of work based on demand, while a pull system authorizes the release of work based on system status (from Hopp and Spearman 1996 p. 317)

pushing

Releasing materials, information, or directives possibly according to a plan but irrespectively of whether or not the downstream process is ready to process them.

quality assignment

quality criteria

reasons

...for failing to complete weekly assignments; e.g., lack of prerequisites, insufficient time, unclear directives. Reasons can also be sought for failing to advance scheduled tasks from master schedule to lookahead schedule or from one week to the next within the lookahead schedule.

resource

Labor or instrument of labor, including tools, equipment, and space. Resources have production capacities as well as costs. Consequently, materials and information are not resources, but rather what resources act on or process.

screening

Determining the status of tasks in the lookahead window relative to their constraints, and choosing to advance or retard tasks based on their constraint status and the probability of removing constraints.

sequence

Quality criterion for selecting assignments among those that are sound in priority order and in constructability order.

shielding

Not releasing work to production units because it does not meet quality criteria; the work is not a quality assignment . It is akin to ‘stopping the assembly line.’ The purpose of shielding is the make production units less subject to uncertainty and variation, thereby providing them with greater opportunity to be reliable.

should-can-will-did

To be effective, production management systems must tell us what we should do and what we can do, so that we can decide what we will do, then compare with what we did to improve our planning.

size

Quality criterion whereby the amount of work included in an assignment is made to match the capacity of the production unit that will do the work.

Example: Ruben and James should be able to collect that data and analyze it by Thursday. But, I forgot, it’s Ruben and Tim. Tim’s not as experienced as James, so I’d better give them an extra day.

sound(ness)

Example: We never intentionally make assignments that are not sound. We always check if we have or can get necessary information from others, if the directives are clear, etc.

Making assignments to a production unit or resource within a production unit that absorbs less than 100% of its capacity. Underloading is necessary to accommodate variation in processing time or production rate, in order to assure plan reliability. Underloading is also done to release time for workers to take part in training or learning, conducting first-run studies, implementing process improvements, or for equipment to be maintained.

utilization

Example 1: Because of time lost waiting for materials, our labor utilization last week was only 40%.

Example 2: We deliberately reduced next week’s planned labor utilization rate so crew members could attend a training course.

weekly work plan

A list of assignments to be completed within the specified week; typically produced as near as possible to the beginning of the week.

window of reliability

Example: If you can accurately forecast only 1 day in advance when work will be completed, then your window of reliability is 1 day.

workable backlog

Assignments that have met all quality criteria , except that some must yet satisfy the sequence criterion by prior execution of prerequisite work already scheduled. Other backlog assignments may be performed within a range of time without interfering with other tasks.

Example: Those spare parts lists don’t have to be completed for 3 months, but it won’t harm anything if they are produced earlier, so use them as fallback or fill-in work when needed.

work flow

The movement of information and materials through a network of production units, each of which processes them before releasing to those downstream.

work flow control

Causing information or materials to move through a network of production units in a desired sequence and at a desired rate.

work-in-process (WIP)

work structuring

Process of breaking work into pieces, where pieces will likely be different from one production unit to the next, so as to promote flow and throughput.