Maintenance Ontology
The purpose of this IOF Maintenance Reference ontology is to support semantic interoperatibility through the use modular ontologies in the maintenance domain. This Ontology contains terms and concepts identified as common in a number of application ontologies for maintenance management, maintenance procedures, asset failure and failure modes and effects analysis. The ontology is aligned with the IOF Core Ontology which is aligned with Basic Formal Ontology and importas terms for other domain independent ontologies.
Caitlin Woods, University of Western Australia
Markus Stumptner, University of South Australia
Matt Selway, University of South Australia
Melinda Hodkiewicz, University of Western Australia
IOF Maintenance Working Group
Industrial Ontology Foundry
Industrial Ontology Foundry (IOF) Maintenance Reference Ontology
Copyright (c) 2022, 2023, 2024, 2025 Open Applications Group
degraded state
having a small crack, having a partial blockage, having an oscillating reading
state of reduced ability to perform as required but with acceptable reduced performance
we do not have the terms to deal with the concepts in the 2nd half of the NL definition about 'grade of realization'
if x is a 'degraded state' then x is a 'maintenance state'
disposition to exhibit undesirable behavior
LA1: DispositionToUndesirableBehavior(x) → UndesirableDisposition(x)
LA2: ∀p(DispositionToExibitUndesirableBehavior(d) ∧ Process(p) ∧ realizes(p, d) → ¬ FailureProcess(p))
disposition of an item that would not be expected under normal operating conditions
the item may or may not exhibit this behavior hence this is difficult to define clearly
LA1: if x is a 'disposition to undesirable behavior' then x is a 'undesirable disposition'
LA2: if x is a 'disposition to undesirable behavior' and x 'realizes' some 'process' p then p is not a 'failure process'
disposition to fail
disposition to explode, disposition to fracture, disposition to sieze
DispositionToFail(x) → UndesireableDisposition(x) ∧ ∃y(FailureProcess(y) ∧ hasRealization(x,y))
disposition of an item to undergo a failure process
As a disposition will come into its existance prior to its realization in a failure process necessary and sufficient conditions can not be created at this point due to a lack of patterns to express process types regardless of the time of their existence
if x is a 'disposition to fail' then x is a 'undesireable disposition' that 'has realization' some 'failure process'
failed state
is broken in two, is burst, is failing to turn on
FailedState(o1) ↔ MaintenanceState(o1) ∧ ∃i(MaintainableMaterialItem(i) ∧ hasParticipantAtAllTimes(o1, i) ∧ ∃e(FailureEvent(e) ∧ initiates(e, o1)) ∧ ∃o2((DegradedState(o2) ∨ OperatingState(o2) ∧ hasParticipantAtAllTimes(o2,i)) ∧ precedes(o2, o1)) ∧ ¬∃o3((DegradedState(o3) ∨ OperatingState(o3)) ∧ hasParticipantAtAllTimes(o3,i) ∧ precedes(o2, o3) ∧ precedes(o3, o1)))
state of an item being unable to perform a required function due to a failure event
"failed state': every instance of 'failed state' is defined as exactly an instance of 'maintenance state' o1 that 'has participant at all times' some 'maintainable material item' i and that is 'initiated by' some 'failure event' and is 'preceded by' some ('degraded state' or 'operating state') o2 that 'has participant at all times' i and there is no ('degraded state' or 'operating state' ) o3 such that o3 'has participant at all times' i and o2 'precedes' o3 and o3 'precedes' o1"
failure effect
leaking pipe, erratic operation, equipment does not run
FailureEffect(x) → Process(x) ∧ ∃f((FailureEvent(f) ∨ FailureProcess(f)) ∧ precededBy(x, f))
process that is the consequence of failure, within or beyond the boundary of the failed item
it is not possible to determine that a process is a failure effect from the ontology alone and requires external analysis to identify such an occurrence.
if x is a 'failure effect' then x is a 'process' that is 'preceded by' some 'failure event' or 'failure process'
Failure effect does not make any commitments to what types of BFO:process can or cannot be considered effects of (functional) failure. Therefore, failure effect can classify any BFO:process (part or whole), indicating that the process is considered the result of a failure for the purposes of maintenance.
failure event
explosion, seizure, loss of power, loss of control
the event can be the loss of the primary function or a combination of functions
FailureEvent(e) ↔ Event(e) ∧ ∃o(FailedState(o) ∧ initiates(e, o)) ∧ ∃i,f,p1(MaintainableMaterialItem(i) ∧ hasParticipantAtAllTimes(e, i) ∧ PrimaryFunction(f) ∧ hasFunction(i, f) ∧ FunctioningProcess(p1) ∧ realizes(p1, f) ∧ precedes(p1, e) ∧ ¬∃p2(FunctioningProcess(p2) ∧ realizes(p2,f) ∧ precedes(p1, p2) ∧ precedes(p2, e)))
event that causes an item to lose its ability to perform a required function
every instance of 'failure event' is defined as exactly an instance of 'event' e that 'initiates' some 'failed state' and that 'has participant at all times' some 'maintainable material item' that 'has function' some 'primary function ' f that 'has realization' some 'functioning process' p1 that 'precedes' e and there is no 'functioning process' p2 such that p2 'realizes' f and p1 'precedes' p2 and p2 'precedes' e
failure mode code
ISO14224 for example list of failure modes
The natural language definition is adapted from EN:13306
FailureModeCode(x) → InformationContentEntity(x) ∧ ∃y(UndesirableDisposition(y) ∧ describes(x,y))
information content entity that describes an undesireable disposition
at this stage we do not have sufficient constructs to create necessary and sufficent conditions for this class.
if x is a 'failure mode code' then x is an 'information content entity' and there is some 'undesirable disposition' that 'is described by' x
failure process
short circuiting process, deformation process, corrosion process
FailureProcess(x) ↔ Process(x) ∧ ∃y(DispositionToFail(y) ∧ realizes(x,y))
process that changes some quality of an item causing the item to become degraded or failed
every instance of 'failure process' is defined as exactly an instance of 'process' that 'realizes' some 'disposition to fail'
functioning process
ISO81346 for examples of functioning processes associated with functions
sensing process, controlling process, transforming process
FunctioningProcess(x) ↔ Process(x) ∧ ∃y(Function(y) ∧ realizes(x,y))
process in which an item performs its function
every instance of 'functioning process' is defined as exactly an instance of 'process' that 'realizes' some 'function'
maintenance activity
replace activity, repair activity, inspect activity
Maintenance Activity(x) → MaintenanceProcess(x)
maintenance process that is a single task to retain or restore the function of a maintainable material item
if x is a 'maintenance activity' then x is a 'maintenance process'
maintenance process
process of replacing a pump, process of calibrating a sensor
LA1: PlannedProcess(p) ∧ (∃x(MaintenanceStrategy(x) ∧ prescribes(x, p)) → MaintenanceProcess(p)
LA2: MaintenanceProcess(p) → ∃x(MaintenanceStrategy(x) ∧ prescribes(x, p))
LA3: MaintenanceProcess(p) → ∃x(MaintainableMaterialItem(x) ∧ hasParticipantAtAllTimes(p, x) ∧ hasInput(p, x))
process to do with retaining or restoring the function of a maintainable material item under a maintenance strategy
Additional analysis to be performed, particularly w.r.t. the associated maintenance strategy.
LA1: if p is 'planned process' that is prescribed by some 'maintenance strategy' then x is a 'maintenance process'
LA2: if p is 'maintenance process' then there is some 'maintenance strategy' that 'prescribes' p
LA3: if p is 'maintenance process' then there is some 'maintainable material item' x such that p 'has input' x and p 'has participant at all times' x
maintenance state
is broken in two, is running at desired speed
MaintenanceState(x) ↔ Operating State(x) ∨ DegradedState(x) ∨ FailedState(x)
stasis that holds during a temporal interval when the realizable functions and capabilities of the participating item, or the grade of realization of those functions and capabilities, remain unchanged
every instance of 'maintenance state' is defined as exactly an instance of 'operating state' or exactly an instance of 'degraded state' or exactly an instance of 'failed state'.
maintenance strategy
specification of a corrective strategy for maintaining a pump (or pumps) of a plant
PlanSpecification(x) ∧ (∃p(MaintenanceProcess(p) ∧ prescribes(x, p)) → MaintenanceStrategy(x)
maintenance (method/ approach/ actions) to enable (the/an) asset to achieve (management's/ desired) objectives
Additional analysis to be performed on this concept. Involves agents, organisations, and business objectives.
if x is a 'plan specification' that 'prescribes' some 'maintenance process' then x is a 'maintenance strategy'
maintenance work order record
a record in a (computerised) maintenance management system that contains fields for due and actual date of the maintenance, a description of the maintenance task, actual and budget costs and other fields
the record has a number of commonly used fields including dates, task description, task codes, costs
this definition remains provisional because it assumes that a work order must involve a 'maintenance process'. In the current definition, a work order cannot be made up of purely 'supporting maintenance activity' tasks.
MaintenanceWorkOrderRecord(x) ↔ InformationContentEntity(x) ∧ ∃y(MaintenanceProcess(y) ∧ describes(x, y) ∧ isInputOf(x, y))
information content entity that describes a maintenance process
every instance of 'maintenance work order' is defined as exactly an instance of 'information content entity' that 'describes' some 'maintenance process' p and that 'is input of' p
operating state
running at desired speed, producing required power, pumping desired volume
In defining the state of an item as being able to perform a required function, we are assuming that the external resources, if required, are provided
Note that in an operating state the item may be functional (so in the operating state) and not currently operating (performing in the functioning process)
state of an item being able to perform a required function
generally speaking, the determination of maintenance state is determined from outside of the ontology, e.g., through analytics, other reasoning mechanims, or by reports from the device or control system, and so is not determinable from the ontology alone. The required constructs for creation of a formal definition are not available in this release.
if x is a 'operating state' then x is a 'maintenance state'
qualification specification
electrical trade qualification, welding qualification, registered engineer
QualificationSpecification(x) → RequirementSpecification(x)
requirement specification that identifies the need for a person to have an assessed skill for a specific task
detailed analysis of this concept is incomplete and, hence, the required constructs for creation of a formal definition are not available in this release.
if x is a 'qualification specification' then x is a 'requirement specification'
qualified maintenance person
Qualified person on its own is not particularly useful unless reasoning is constrained to only the individuals of interest at some time. Specific subtypes of qualified person are necessary to determine if specific qualification types are satisfied. Still, care must be taken when reasoning over temporal information as, if the critieria are met at some time, the classification will hold.
QualifiedMaintenancePerson(x) ↔ Person(x) ∧ ∃y(MaintenanceActivity(y) ∧ partcipatesInAtSomeTime(x,y) ∧ ∃z(QualificationSpecification(z) ∧ prescribedBy(y, z) ∧ satisfiesRequirement(x,z)))
person who is qualified to perform a specified specified maintenance activity
every instance of ‘qualified maintenance person’ is defined as exactly an instance of 'person' that 'participates in at some time' some 'maintenance activity' p and that 'satifies' some 'qualification specification' that 'prescribes' p
required function
to sense, to store, to process information, to control
the function can be a combination of functions
RequiredFunction(x) ↔ Function(x) ∧ ∃y,z(MaintainableMaterialItem(y) ∧ FunctioningProcess(z) ∧ participatesInAtSomeTime(y,z) ∧ functionOf(x,y))
function of a maintainable material item which is considered necessary to fulfil a process requirement
no sufficient conditions are defined for this class
every instance of 'required function' is defined as an instance of 'function' that is the 'function of' some 'maintainable material item' that 'participates in at some time' some 'functioning process'
supporting maintenance activity
activities that do not change the state of the asset but are done by maintenance personnel such as reporting activity, isolate activity, move activity, training activity
SupportingMaintenanceActivity(x) → PlannedProcess(x)
single action in support of the execution of a maintenance process
if x is a 'supporting maintenance activity' then x is a 'planned process'
undesireable disposition
disposition to leak, disposition to overheat, disposition to vibrate
There are two subclasses, disposition to fail and disposition to exhibit undesirable behavior. We need to distinguish between the disposition to leak which is realised in a leaking process (regarded as a failure) and the disposition to overheat realised in a heating process (which, in this example) is not a failure process). We asset that disposition to exhibit undesirable behavior is the disposition of an item that would not be expected under normal operating conditions but may occur such as vibration or overheating.
UndesirableDisposition(x) ↔ DispositionToFail(x) ∨ DispositionToExhibitUndesirableBehavior(x)
disposition of an item to undergo a process that leads to undesirable outcomes
every instance of 'undesirable disposition' is defined as exactly an instance of 'disposition to fail' or exactly an instance of 'disposition to exhibit undesirable behavior'
has maintenance state
has partial function or loss of function
inverse of 'stateOf'
initiates
comes before an event or process in time and results in beginning or creation of the event or process
maintenance state of
relation that describes the maintenance state of a maintainable item