Scheduling Ontology - Informal Concept Definitions

Stephen F. Smith, Ora Lassila, Marcel Becker, CMU

Draft of 10/1/95

1. Basic components of scheduling models and their relationships

2. Demands

2.1 Basic Demand Types

DEMAND - A DEMAND is an input request for goods or services. A DEMAND specifies a QUANTITY of some type of MATERIAL to be processed in some manner. A DEMAND has a DUE-DATE and a READY-DATE, within which processing must take place. DEMANDS may be decomposed into SUB-DEMANDS, subject to any PARTITIONING-CONSTRAINTS (aka SPLITTING-CONSTRAINTS) . A DEMAND may have TEMPORAL-RELATIONS to other DEMANDS, which further constrain when it must be satisfied.

TRANSPORT-DEMAND - A TRANSPORT-DEMAND is a DEMAND to transport some QUANTITY of some MATERIAL from one LOCATION to another. Additional requirements associated with a TRANSPORT-DEMAND include a specification of an ORIGIN and a DESTINATION.

PRODUCTION-DEMAND - A PRODUCTION-DEMAND is a DEMAND for production of some QUANTITY of some MATERIAL .


2.2 Basic Demand Components and Constraints

MATERIAL - Satisfaction of DEMANDS (for purposes of the domains of interest here) involves manipulation of QUANTITIES of MATERIAL in some manner. MATERIAL corresponds generally to the object of the DEMAND (e.g., cargo. parts, patients). The type of MATERIAL designated in a DEMAND can impose constraints on the ACTIVITIES required to satisfy it.

MANUFACTURED-PART - type of MATERIAL referred to by a PRODUCTION-DEMAND. Properties of interest (not elaborated here) relate to constraints on its production.

TRANSPORTABLE-MATERIAL type of MATERIAL, PORTABLE-OBJECT (see Section x.3), and the focus of TRANSPORT-DEMANDS. Properties of interest (elaborated below), relate to transporting constraints. Note that a given material can be both manufactured and transportable.

QUANTITY - The amount of MATERIAL requested by a DEMAND. A quantity of some unit measure indicating either the number of MATERIALS requested or required RESOURCE CAPACITY (depending on DEMAND type).

READY-DATE - The earliest time at which processing of the DEMAND can begin. The READY-TIME-CONSTRAINT states that the start time of all ACTIVITIES required to satisfy the DEMAND >= READY-DATE.

DUE-DATE - The latest time at which processing of the DEMAND can be completed. A DUE-DATE-CONSTRAINT states that the end-time of all ACTIVITIES required to satisfy the DEMAND <= DUE-DATE.

ORIGIN - The initial LOCATION of the MATERIAL to be transported

DESTINATION - The final, required LOCATION of the MATERIAL.

DEMAND-PARTITIONING-CONSTRAINT - It is sometimes necessary (or appropriate) to partition a DEMAND into smaller SUBDEMANDS that can be separately handled. A TRANSPORT-DEMAND might be split into multiple demands to enable transport by multiple RESOURCES; a PRODUCTION-DEMAND may be split into separate LOTS to provide an appropriate production mix in the facility. A PARTITIONING-CONSTRAINT specifies a restriction on resulting SUBDEMANDS.

Examples: ACTIVITIES associated with related transport subdemands may be constrained to all arrive within a given time window; There may be a lower bound on the number of parts of a given type that can be released as a production LOT.

3. Resources

3.1 Basic Resource Types

RESOURCE - A RESOURCE is an entity with some amount of CAPACITY that is allocatable to ACTIVITIES over time

REUSABLE-RESOURCE - A REUSABLE-RESOURCE provides CAPACITY that is allocatable to an ACTIVITY for its DURATION and subsequently becomes available for re-allocation

NON-DIVISIBLE-RESOURCE - A type of RESOURCE that cannot be split up, and requires that allocation of its CAPACITY to different ACTIVITIES be synchronized over time

UNIT-CAPACITY-RESOURCE - A type of RESOURCE that can be allocated to only one ACTIVITY at a time (i.e., CAPACITY = 1)

Examples: a flight crew, a loading/unloading crane, a milling machine

BATCH-CAPACITY-RESOURCE - A type of RESOURCE that can simultaneously provide CAPACITY to multiple ACTIVITIES, but only if these ACTIVITIES are synchronized to occur over the same time interval

Examples: a ship, a plane

RESOURCE-POOL - A type of RESOURCE that aggregates the CAPACITY of some set of NON-DIVISIBLE-RESOURCEs, and provides CAPACITY that can be independently allocated to different ACTIVITIES

Examples: a plane fleet, airport parking space, hospital beds

CONSUMABLE-RESOURCE - A CONSUMABLE-RESOURCE provides CAPACITY that is used up when it is allocated to an ACTIVITY and must be subsequently replenished

Examples: Fuel, Rations

COMPOSITE-RESOURCE A type of RESOURCE that represents the composition of a set of REUSABLE and/or CONSUMABLE RESOURCES; constituent RESOURCES are individually allocated to ACTIVITIES but unavailability of a COMPOSITE-RESOURCE implies unavailability of all constituents

Examples: A port, with on-ground parking space, ASF, cargo storage, etc.

3.2 Resource Capacity Constraints and Requirements

CAPACITY - The CAPACITY of a RESOURCE constrains the number of ACTIVITIES that it can simultaneously support. CAPACITY is a QUANTITY of some unit measure (e.g., volume, weight, number of activities) that is available for allocation to ACTIVITIES over time. The performance of any given ACTIVITY requires some amount of CAPACITY of one or more resources.

UNIFORM-CAPACITY - UNIFORM-CAPACITY is a single QUANTITY of some unit measure. The CAPACITY-CONSTRAINT of a RESOURCE with UNIFORM-CAPACITY states that, at any point in time, the sum of the CAPACITY-REQUIREMENTS of all supported ACTIVITIES <= the CAPACITY of the RESOURCE

Examples: the "maximum on ground (MOG)" constraint associated with an airfield is represented as a RESOURCE-POOL (the airfield) with UNIFORM-CAPACITY (number of planes allowable on the ground at any point).

HETEROGENEOUS-CAPACITY - HETEROGENEOUS-CAPACITY is a combination of two or more UNIFORM-CAPACITIES, reflecting partitioned sub-CAPACITIES. The CAPACITY-CONSTRAINT of a RESOURCE with HETEROGENEOUS-CAPACITY is the conjunction of the CAPACITY-CONSTRAINTS associated with constituent UNIFORM-CAPACITIES.

Examples: A ship might have separate containerized and roll-on/roll-off storage space.

MULTI-DIMENSIONAL-CAPACITY - MULTI-DIMENSIONAL-CAPACITY is defined in terms of two or more QUANTITIES of different unit measures, each defining a separate CAPACITY-CONSTRAINT that must be satisfied. In the case of MULTI-DIMENSIONAL-CAPACITY, the CAPACITY-CONSTRAINT states that for each different unit measure, the sum of the CAPACITY-REQUIREMENTS of all supported ACTIVITIES <= the CAPACITY of the RESOURCE.

Examples: A plane's capacity might be defined in terms of both weight and volume quantities.

CAPACITY-REQUIREMENT An ACTIVITY has a CAPACITY-REQUIREMENT which indicates the amount of RESOURCE CAPACITY that must be allocated to support (perform) the ACTIVITY. A CAPACITY-REQUIREMENT is a QUANTITY expressed in one or more unit measures.

3.3 Location and Mobility

3.3.1 Basic Concepts.

LOCATION - A point in space (expressed in some coordinate system at some level of granularity)

OBJECT - A physical entity

STATIONARY-OBJECT - (possibly redundant with LOCATION) An object resident at (and thus identified with) a particular LOCATION

MOBILE-OBJECT - An object whose LOCATION can change over time. At any point in time, a MOBILE-OBJECT is either at a particular LOCATION or designated as "in-transit" between a specific LOCATION pair.

SELF-PROPELLED-OBJECT - An object capable of traveling between a given set of LOCATIONS. A SELF-PROPELLED-OBJECT has a TRAVEL-SPEED, which constrains its travel time, and a TRAVEL-RANGE which bounds its maximum travel distance. A SELF-PROPELLED-OBJECT may also have a set of LOCATION-COMPATIBILITY CONSTRAINTS which determine whether a given LOCATION is accessible.

PORTABLE-OBJECT An object that can be moved to different LOCATIONS.

3.3.2 Basic Mobility Attributes and Constraints.

TRAVEL-SPEED - The TRAVEL-SPEED of a SELF-PROPELLED-OBJECT is a ratio expressed in some pair of unit measures indicating distance traveled over some time interval (velocity). Given a pair of locations l1, and l2, the DURATION-CONSTRAINT on movement from one to the other states simply that travel time = Distance(l1,l2) / TRAVEL-SPEED.

TRAVEL-RANGE - The TRAVEL-RANGE of a SELF-PROPELLED-OBJECT is a quantity expressing distance in some unit measure. A RANGE-CONSTRAINT associated with a SELF-PROPELLED-OBJECT states that a non-stop trip between locations l1 and l2 is feasible iff distance(l1,l2) <= TRAVEL-RANGE.

3.4 Resource and Location Compatibility Constraints

COMPATIBILITY-CONSTRAINT - A COMPATIBILITY-CONSTRAINT dictates whether an OBJECT (or type of OBJECT) is compatible with some aspect of the current planning state.

RESOURCE-COMPATIBILITY - A RESOURCE-COMPATIBILITY constraint designates conditions under which usage of the CAPACITY of a given RESOURCE (or type of RESOURCE) is compatible with other characteristics of the ACTIVITY to be supported.

RESOURCE/DEMAND-COMPATIBILITY -A RESOURCE/DEMAND-COMPATIBILITY specifies conditions under which use of a RESOURCE's CAPACITY is consistent with characteristics with the input DEMAND.

RESOURCE/MATERIAL-COMPATIBILITY One type of DEMAND-COMPATIBILITY concerns the type of material designated in a DEMAND. A RESOURCE/MATERIAL-COMPATIBILITY specifies the types of material (or commodity) for which a RESOURCE may be feasibly used.

Examples: tanker ships can only carry POL; C130s can only carry bulk and oversized cargo; a machine tool can support a certain range of products

RESOURCE/PROCESS-COMPATIBILITY A DEMAND may specify constraints on the processing of the designated MATERIAL. A RESOURCE/PROCESS-COMPATIBILITY specifies processing characteristics that must be satisfied for a given RESOURCE's CAPACITY to be used.

Examples: A movement request may designate a particular mode of travel: air or sea.

RESOURCE/GOAL-COMPATIBILITY A DEMAND may specify a goal that can be satisfied by only certain resources. A RESOURCE/GOAL-COMPATIBILITY specifies characteristics of a RESOURCE that are pre-requisite to fulfilling a given DEMAND.

Examples: A patient evacuation request may designate a particular type of medical treatment service.

JOINT-RESOURCE-COMPATIBILITY A JOINT-RESOURCE-COMPATIBILITY defines conditions under which the usage of another resource required to mutually support a given ACTIVITY is compatible with a given RESOURCE.

Examples: A flight-crew must be qualified to fly a given type of aircraft; An operator must possess the requisite skills to operate a given machine tool.

BATCHING-COMPATIBILITY A BATCHING-COMPATIBILITY constrains the circumstances under which BATCH-CAPACITY-RESOURCES can be feasibly shared by multiple ACTIVITIES (or multiple DEMANDS) over a given time interval.

Examples: different types of cargo may not be simultaneously transportable by a given ship, even though it is feasible to transport each separately; 2 movements requests can be handled by a single trip only if they designate the same POEs and PODs.

LOCATION-COMPATIBILITY A LOCATION-COMPATIBILITY constraint is associated with a MOBILE-OBJECT (or type of MOBILE-OBJECT), and designates conditions under which it can access (occupy) a given LOCATION.

Examples: An aircraft has runway length requirements for takeoff/landing at a given airport.

3.5 Resource Availability Constraints

UNAVAILABILITY-INTERVAL - An UNAVAILABILITY-INTERVAL is an interval of time during which a RESOURCE is not available for use.

Examples: A port is closed due to fog; A resource is down for repairs or maintenance; a crew rest period.

SETUP-TIME - A REUSABLE-RESOURCE may require preparatory SETUP-TIME to enable its usage in a particular context. A SETUP-TIME-CONSTRAINT states that for any two consecutive allocations a1 and a2 of the same RESOURCE, start-time(a2) - end-time(a1) >= SETUP-TIME.

CONSTANT-SETUP-TIME - For some RESOURCES, the time required for setup does not depend on its previous usage state. A CONSTANT-SETUP-TIME is a scalar quantity , expressed in some unit measure of time, representing the amount of time required to configure a required RESOURCE for usage.

STATE-DEPENDENT-SETUP-TIME - For other RESOURCES, the time required for setup is a function of its previous usage state. .

SEQUENCE-DEPENDENT-SETUP-TIME - A SEQUENCE-DEPENDENT-SETUP-TIME is a function which maps any pair of consecutive allocations <a1,a2> to a minimal separation time.

Examples: machine setup time for a given manufacturing operation may be a function of the last part that was processed; the time delay before a transport vehicle can carry out a given transport operation depends on its current location.

CONTINUOUS-USAGE-LIMIT - A CONTINUOUS-USAGE-LIMIT is an upper bound on the length of time that a RESOURCE may be continuously allocated before requiring an UNAVAILABILITY-INTERVAL.

Examples: a crew "duty day"; the maintenance cycle associated with a machine tool.

CUMULATIVE-USAGE-LIMIT A CUMULATIVE-USAGE-LIMIT is an upper bound on the amount of RESOURCE usage over a given time interval. It is a number in some unit measure of time that indicates the maximum amount of time that the RESOURCE can be used over a designated period of time.

Examples: crew flight hours per week or month.

4. Activities

4.1 Basic Activity Types

ACTIVITY - (aka OPERATION in the current implementation) An ACTIVITY specifies a process that may be executed to satisfy a DEMAND. An ACTIVITY has a START-TIME, an END-TIME and a set of RESOURCE assignments. Various process-related constraints restrict the possible assignments to these "variables", including RESOURCE-REQUIREMENTS, TEMPORAL-RELATIONS with other ACTIVITIES, and DURATION-CONSTRAINTS. An ACTIVITY may have other ENABLING-CONDITIONS and a set of resulting EFFECTS. An instantiated ACTIVITY is associated with a particular DEMAND, which contributes additional constraints on START-TIME, END-TIME and RESOURCE values.

PROCESSING-ACTIVITY An activity that takes place at a particular location and transforms MATERIAL in some manner. Basic ENABLING-CONDITIONS include availability of required resource capacity (appropriately configured or setup) and arrival of MATERIAL at the LOCATION of the resource. The basic EFFECT of a PROCESSING-ACTIVITY is to make the allocated RESOURCE CAPACITY unavailable for the DURATION of the ACTIVITY (and for any necessary setup ACTIVITY). Other ENABLING-CONDITIONS and EFFECTS (if modeled) might relate to the state of the material.

TRANSPORT-ACTIVITY An ACTIVITY that moves MATERIAL from one LOCATION to another. A TRANSPORT-ACTIVITY has an ORIGIN and DESTINATION. ENABLING-CONDITIONS include availability of required resource capacity, and positioning of both the target MATERIAL and RESOURCE at the ORIGIN location. The EFFECTS of a TRANSPORT-ACTIVITY make the required RESOURCE CAPACITY unavailable for the DURATION of the ACTIVITY and position both the MATERIAL and the RESOURCE at the DESTINATION LOCATION at the end of the ACTIVITY.

COMPOSITE-ACTIVITY An aggregate ACTIVITY that decomposes into some temporally related set of more-detailed ACTIVITIES.

5. Temporal (Process) Constraints

TIME-CONSTRAINT

TEMPORAL-RELATION - A TEMPORAL-RELATION imposes a synchronization constraint between the occurrence of two TIME-INTERVALS (e.g., ACTIVITIES). It specifies an ordering with respect to respective START-POINTS and/or FINISH-POINTS of related intervals. A TEMPORAL-RELATION may be quantified by a metric LOWER-BOUND and UPPER-BOUND on the temporal separation between relevant TIME-POINTS. An unquantified TEMPORAL-RELATION is interpreted as having a LOWER-BOUND, UPPER-BOUND values of 0, [[infinity]].

BEFORE - For two INTERVALS i1 and i2, "i1 BEFORE i2 [lb, ub]" implies that START(i2) >= FINISH(i1) + lb and START(i2) <= FINISH(i1) + ub.

SAME-START - For two INTERVALS i1 and i2, "i1 SAME-START i2 [lb, ub]" implies that START(i2) >= START(i1) + lb and START(i2) <= START(i1) + ub.

SAME-END - For two INTERVALS i1 and i2, "i1 SAME-START i2 [lb, ub]" implies that FINISH(i2) >= FINISH(i1) + lb and FINISH(i2) <= FINISH(i1) + ub.

ABSOLUTE-TIME-CONSTRAINT - An ABSOLUTE-TIME-CONSTRAINT anchors a TIME-POINT to a absolute time on a calendar

DUE-DATE-CONSTRAINT

READY-DATE-CONSTRAINT

EARLIEST-COMPLETION-DATE

DURATION-CONSTRAINT A DURATION-CONSTRAINT restricts the temporal separation between the START-POINT and FINISH-POINT of an INTERVAL.

ACTIVITY-DURATION-CONSTRAINT

CUMULATIVE-USAGE-CONSTRAINT

6. Transportation Domain Specializations

6.1 Move Requirements

MOVE-REQUIREMENT - A type of TRANSPORT-DEMAND. A MOVE-REQUIREMENT specializes TRANSPORT-DEMAND for military deployment planning. A MOVE-REQUIREMENT specifies a QUANTITY of a given CARGO-TYPE (MATERIAL) to be transported from a given POE - Port of Embarkation (ORIGIN) to a given POD - Port of Debarkation (DESTINATION) within a time interval delineated by an ALD - Available-to-Load-Date (READY-DATE) and a RDD - Required-Delivery-Date (DUE DATE). An Earliest-Arrival-Date or EAD constraint is also specifiable, which defines an allowable arrival time window. Finally, a travel MODE (i.e., air or sea) may be designated.

CARGO - A type of TRANSPORTABLE-MATERIAL. Quantities are expressed in MTONS, STONS. CARGO subtypes can only be handled by certain types of RESOURCES (see COMPATIBILITY-CONSTRAINTS below).

CONTAINERIZED-CARGO - sea CARGO that is packaged in containers

RORO-CARGO - "Roll on/roll off" type of sea CARGO (e.g., a tank or truck)

OVERSIZE-CARGO - largest volume type of air CARGO

OUTSIZE-CARGO - intermediate sized air CARGO

BULK-CARGO - standard type of air CARGO

POL - A type of TRANSPORTABLE-MATERIAL. Petroleum products. Quantities are expressed in CBARRELS (100 barrel units). POL is transportable only by TANKERS.

PAX - A type of TRANSPORTABLE-MATERIAL. People. Quantities are expressed in numbers.

PATIENT - type of PAX transported in medical evacuation operations

ALD - synonym for READY-DATE. "Available-To-Load" Date at POE

RDD - synonym for DUE-DATE. "Required Delivery Date" at POD

EAD - "Earliest-Arrival-Date" at POD. The EAD-CONSTRAINT states that the end-time of all ACTIVITIES required to satisfy the DEMAND >= EAD.

POE - An ORIGIN, A type of PORT. "Port of Embarkation"

POD - A DESTINATION, A type of PORT. "Port of Debarkation"

MODE - "air" or "sea", placing a constraint on the type of transport vehicle that can be used, or "unspecified"

SUBDEMAND-ARRIVAL-WINDOW A bound, expressed as some unit of time, on the allowable separation between satisfaction of partitioned MOVE-REQUIREMENTS.

MARRY-UP-CONSTRAINT A type of SAME-END, A type of DEMAND-PARTITIONING-CONSTRAINT. The MARRY-UP-CONSTRAINT states that for any two SUBDEMANDS of a given MOVE-REQUIREMENT, their respective CARGOs must arrive at the POD within SUBDEMAND-ARRIVAL-WINDOW. In other words, for ACTIVITIES a1 and a2 which satisfy any two SUBDEMANDS d1 and d2 of DEMAND d, | end-time(a1) - end-time(a2) | <= subdemand-arrival-window(d).

6.2 Transportation Resources

TRANSPORT-VEHICLE - A type of BATCH-CAPACITY-RESOURCE, a type of MOBILE-OBJECT. A TRANSPORT-VEHICLE provides CAPACITY for moving MATERIAL from one LOCATION to another. A TRANSPORT-VEHICLE has a LOAD-TIME and an UNLOAD-TIME, each a quantity of some unit measure of time which specifies (respectively) the time required to load and unload MATERIAL for transport. A TRANSPORT-VEHICLE also has a set of COMPATIBLE-CARGO-TYPES that it is capable of transporting.

AIRCRAFT - A TRANSPORT-VEHICLE that moves material between AIRPORTS. Has a MINIMUM-RUNWAY-LENGTH required for landing/takeoff.

C5, C9, C130, ...

SHIP - A TRANSPORT-VEHICLE that moves material between SEAPORTS. Has a MINIMUM-CHANNEL-DEPTH and MINIMUM-CHANNEL-WIDTH required for access.

TRUCK

...

TRANSPORT-FLEET - A type of RESOURCE-POOL, A type of MOBILE-OBJECT

AIRCRAFT-FLEET

SHIP-FLEET

TRUCK-FLEET

...

PORT - A STATIONARY-OBJECT, a type of COMPOSITE-RESOURCE (can be defined more simply as a RESOURCE-POOL if only concerned with modeling one type of port capacity constraint)

AIRPORT - e.g., a COMPOSITE-RESOURCE providing AIRFIELD-SPACE, and an AIR-STAGING-FACILITY; or synonym for AIRFIELD-SPACE (see below). Has a RUNWAY-LENGTH and a RUNWAY-WEIGHT (indicating the maximum AIRCRAFT weight that can be supported).

SEAPORT - Has a CHANNEL-DEPTH and CHANNEL-WIDTH that constrains entry/exit

AIR-SEA-PORT - COMPOSITE-RESOURCE composed of an AIRPORT and a SEAPORT

DEPOT

PARKING-SPACE - A STATIONARY-OBJECT, RESOURCE-POOL with UNIFORM-CAPACITY

AIRFIELD-SPACE - number of aircraft allowable on ground

DOCKING-SPACE - number of ship berthing slots available

MEDICAL-FACILITY - STATIONARY-OBJECT, RESOURCE-POOL with UNIFORM-CAPACITY (reflecting available patient beds)

A MEDICAL-FACILITY has a set of PROVIDED-SERVICES.

MEDICAL-TREATMENT-FACILITY - (aka HOSPITAL)

AIR-STAGING-FACILITY - temporary medical facility co-located at an airport

FLIGHT-CREW - UNIT-CAPACITY-RESOURCE, PORTABLE-OBJECT

SUPPLY-POINT - STATIONARY-OBJECT, COMPOSITE-RESOURCE composed of a number of different commodity inventories

INVENTORY - A CONSUMABLE-RESOURCE with UNIFORM-CAPACITY

6.3 Compatibility Constraints

ASSET/PORT-COMPATIBILITY - A type of LOCATION-COMPATIBILITY

SEAPORT-ACCESSIBILITY - A given SHIP r1 and SEAPORT p1 are compatible if CHANNEL-DEPTH(p1) >= MINIMUM-CHANNEL-DEPTH(r1) and CHANNEL-WIDTH(p1) >= MINIMUM-CHANNEL-WIDTH(r1).

AIRPORT-ACCESSIBILITY - A given AIRCRAFT r1 and AIRPORT p1 are compatible if RUNWAY-LENGTH(p1) >= MINIMUM-RUNWAY-LENGTH(r1) and RUNWAY-WEIGHT(p1) >= CARGO-WEIGHT(r1).

ASSET-CARGO-COMPATIBILITY - A type of MATERIAL-COMPATIBILITY. A type of CARGO c is transportable by a given TRANSPORT-VEHICLE r if c is an element of COMPATIBLE-CARGO-TYPES(r).

MODE-COMPATIBILITY - A type of PROCESS-COMPATIBILITY. A given TRANSPORT-VEHICLE r can transport a given CARGO only if the travel MODE specified in the DEMAND includes MODE(r).

MEDICAL-SERVICE-COMPATIBILITY - A type of GOAL-COMPATIBILITY. A MEDICAL-FACILITY r is a viable destination of a PATIENT-EVACUATION-DEMAND d if MEDICAL-SERVICE(d) is an element of PROVIDED-MEDICAL-SERVICES(r).

SAME-ORIGIN/SAME-DESTINATION - A type of BATCHING-COMPATIBILITY. The CARGOs of two MOVE-REQUIREMENTS d1 and d2 can be transported together only if POE(d1) = POE(d2) and POD(d1) = POD(d2). [could be relaxed to allow multiple stops.]

CARGO-COMPATIBILITY - The CARGOs of two MOVE-REQUIREMENTS d1 and d2 can be transported together only if the types of CARGOs are compatible. (need to make this more precise)

6.4 Transportation Activities

TRANSPORT-LOAD - type of PROCESSING-ACTIVITY. Represents CARGO load and unload activities at PORTS.

MISSION-LEG - type of COMPOSITE-ACTIVITY. A non-stop trip between two LOCATIONS. Decomposes into contiguous sequence of LOAD, TRANSPORT, AND UNLOAD ACTIVITIES. Requires TRANSPORT-VEHICLE for entire DURATION, and PORT CAPACITY (e.g., PARKING SPACE) for LOAD and UNLOAD subintervals.

MISSION - type of COMPOSITE-ACTIVITY. An aggregate activity representing sequence of MISSION-LEGS

FLIGHT-PLAN - Aggregation of MISSION-LEGS to be executed contiguously by a particular TRANSPORT-VEHICLE/FLIGHT-CREW

TRAVEL-ITINERARY - Aggregation of MISSION-LEGS that a particular CARGO (e.g., patient) is allocated to.

6.5 Units, Quantities

QUANTITY

CARGO-QUANTITY

VOLUME-QUANTITY

SHORT-TON

CBARREL

WEIGHT-QUANTITY

METRIC-TON

TIME

CDAY

HOUR

MINUTE

7. Open Issues