Control Service Life

Overview

The service life of an element is an appropriately reliable estimate of its durability in service. It describes the length of time that an element may be expected to perform its required function including the provision of any material, component, assembly or system maintenance or replacement that may be required.
An element may be an assembly or systematic grouping of other elements each of which may also have their own service life assessment. Within IFC, any subtype of IfcProduct may have a service life assigned as also may groups that are assets or systems.
Within the service life of a containing element (such as a building), the service life of contained elements may be significantly less and therefore such items may need to be replaced within the containing element lifecycle. Service life planning may need to include projections of the needs for, and timing of element replacement and end of life recovery.
These facts may all be used to determine life cycle cost profiles and estimate whole life costs. It is also information that informs environmental assessments. Service life planning is increasingly being linked with sustainable development and wholelife value.
Service life may be assessed in various ways depending on who is doing the assessing and the purpose of the assessment. These can include:

Actual Service Life	The service life that an artefact has given.
Design Service Life	The period of time during which the artefact is expected by its designers to work within its specified parameters; in other words, the life expectancy of the item. Note that for product artefacts, design life may also be designated as a mean time between failure (MTBF), which tells the user that they may expect the average product to last for the specified design time. However an MTBF rating is no guarantee that any single example of the product will not fail before the mean time specified.
Estimated Service Life	The service life that an artefact is expected to have under current operating conditions.
Optimistic Service Life	The best or most optimistic estimate of service life that is quoted for an artefact under reference operating conditions.
Pessimistic Service Life	The least or most pessimistic estimate of service life that is quoted for an artefact under reference operating conditions.
Reference Service Life	The typical service life that is quoted for an artefact under reference operating conditions.

Service Life Factors
Service life planning is typically carried out using a factor method such as is defined in ISO 15686. This is based on the assumption that several parameters have an impact on the service life of an artifact. These factors are:

A= Quality of components e.g. natural durability or preservative treatment
B = Design level e.g. protection by design
C= Work execution e.g. joints gaps
D= Indoor environment e.g. temp., RH, condensation
E= Outdoor Environment e.g. climate, driving rain, shadow
F= In use conditions e.g. wear, mechanical impacts
G= Maintenance level e.g. revisions, repainting

These parameters are brought together in the following general formula:
ESL = RSL * f(A,B,C,D,E,F,G)

Where:
ESL = estimated service life
RSL = reference service life
The function involved may be a simple multiplication, but in many cases the parameters may be interdependent, and more sophisticated combinations may be necessary. The parameter values may also be probabilistic in nature.
The ISO factor method is fully explained in ISO15686, which should be consulted for a broader understanding.
References
http://www.answers.com/topic/iso-15686
ISO 15686 Buildings and constructed assets - Service life planning (published parts)

Suggested modifications to IFC model and documentation
* Model currently refers to 'Expected Service Life'. This should be changed to Estimated Service Life
* Design Life should be introduced as a 'Service Life Type'
* IfcServiceLife.ServiceLifeType should be changed to PredefinedType to be similar to other type specifications. This will also allow a USERDEFINED/NOTDEFINED addition to the IfcServiceLifeTypeEnum
* IfcServiceLife.ServiceLifeDuration is an IfcTimeMeasure which is specified as a real value that is normally measured in seconds. Typically, service life (or mean time between failure) may be measured in much larger units (months/years for a typical building or building component). This fact has to be either dealt with in software (currently as indicated) or an alternative approach to measuring time measure determined for IFC.

Results

A service life specification is assigned to an artefact. Note that there are several types of service life that may be defined and it is possible to assign an instance of more than one type of service life to a particular artefact (so that, for instance, both design life and expected life may be captured).

Information Needed	Entity/Pset/Functional Part	MAN	REC	OPT
CONCEPT: Control the service life of a product type or an occurrence of a product This is the assignment of a service life value to an instance of a product type or to an individual product occurrence as defined within the product structure of the IFC model. It may be a constructed or assembled product such as a building storey or a building or a physical product such as a pump or a window. Note that it is not expected that a service life would be applied to a product that is an IfcSpace.
Assert general attributes for the service life
Set the global unique identifier	IfcSeviceLife.GlobalId::fcGloballyUniqueId
Assert the owner history of the equipment type	IfcSeviceLife.OwnerHistory::fp_apply_owner_history
Specify a name for the service life declaration	IfcSeviceLife.Name::IfcLabel
Specify a description for the service life declaration	IfcSeviceLife.Description::IfcLabel
An object type could be asserted for the service life but is not considered appropriate. Therefore, this attribute should not be asserted.	IfcSeviceLife.ObjectType::IfcLabel	X	X	X
Select the type attributes for the service life
Select the predefined type of service life that is to be used for the service life. If the selection is made during the design stage, and prior to the actual product selection or definition, then it is probable that the selection will be DESIGNSERVICELIFE At product selection or definintion, the selection of service life type will probably be REFERENCESERVICELIFE (or an optimistic or pessimistic variety of this) At the time of construction or installation, then it is probable that the selection will be EXPECTEDSERVICELIFE. This is likely to continue during the operational stage until failure when an ACTUALSERVICWELIFE may be applied for historical purposes.	IfcServiceLife.ServiceLifeType::IfcServiceLifeTypeEnum
Set the duration of the service life IfcTimeMeasure is specified in IFC as a real value that is normally measured in seconds. Typically, service life (or mean time between failure) may be measured in much larger units (months/years for a typical building or building component). This fact has to be dealt with in software	IfcServiceLife.ServiceLifeDuration::IfcTimeMeasure
Set the Service Life Factor Values Several service life factor values may be defined for a given service life. For each factor, the following applies
Select the predefined type of service life factor that is to be defined. The predefined types of service life factor that are typically used are those defined in ISO 15686 and include: QUALITYOFCOMPONENTS DESIGNLEVEL WORKEXECUTIONLEVEL INDOORENVIRONMENT OUTDOORENVIRONMENT INUSECONDITIONS MAINTENANCELEVEL The reference letters used are the identities of the service life factors in ISO 15686. More complete specification of the service life factor name is used in IFC for semantic reasons	IfcServiceLifeFactor.PredefinedType::IfcServiceLifeFactorTypeEnum
Set the main or most used value of the service life factor being defined The most used value of a service life factor must be defined whether or not upper and lower values are used	IfcServiceLifeFactor.MostUsedValue::IfcParameterValue
Set the lower value of the service life factor being defined	IfcServiceLifeFactor.LowerValue::IfcParameterValue
Set the upper value of the service life factor being defined	IfcServiceLifeFactor.UpperValue::IfcParameterValue
Define the service life factors for the service life
Define each occurrence of service life factor that is to be applied within the service life	fp_define_by_propertikes
Assert the attributes of the relationship Note that it might be expected to a service life would be assigned to the product rather than vice versa as is the case in the description below. However, by assigning the products to the service that they may expect to have, the relationship between product and service life is easier to control within IFC
Assert the control element of the relationship relationship	IfcRelAssignsToControl.RelatingControl::IfcServiceLife
Assert the elements that are controlled in the relationship Note that element s that are to be controlled in te relationship may be any subtype of IfcObjectDefinition. This may include either a subtype of a type product or a product occurrence	IfcRelAssignsToControl.RelatedObjects::IfcObjectDefinition
Assert the type of related objects from the predefined list if required This value can be used to identify the parent supertype of related objects as e.g. product, group, process, control etc. If the related objects have mixed supertypes, then the value .NOTDEFINED. should be used.	IfcRelAssignsToControl.RelatedObjectsType::IfcObjectTypeEnum
Assert the identity of the relationship	IfcRelAssignsToControl.GlobalId::IfcGloballyUniqueId
Assert the owner history of the relationship	IfcRelAssignsToControl.OwnerHistory::fp_apply_owner_history
Specify a name of the relationship	IfcRelAssignsToControl.Name::IfcLabel
Specify a description of the relationship	IfcRelAssignsToControl.Description::IfcLabel

IFC Entities Required

IfcAsset
IfcCalendarDate
IfcControl
IfcCostValue
IfcElectricalCircuit
IfcElement
IfcElementType
IfcGroup
IfcObject
IfcObjectDefinition
IfcProduct
IfcPropertyDefinition
IfcPropertySetDefinition
IfcRelationship
IfcRelAssigns
IfcRelAssignsToActor
IfcRelAssignsToControl
IfcRelAssignsToProduct
IfcRoot
IfcServiceLife
IfcServiceLifeFactor
IfcSystem
IfcTypeObject
IfcTypeProduct

IFC Datatypes Required

IfcDayInMonthNumber
IfcGloballyUniqueId
IfcIdentifier
IfcLabel
IfcMonthInYearNumber
IfcParameterValue
IfcText
IfcTimeMeasure
IfcYearNumber
IfcObjectTypeEnum
IfcServiceLifeFactorTypeEnum
IfcServiceLifeTypeEnum

IFC Functions Required

-

IFC Property Sets Required

-

IDM Functional Parts Required

fp_apply_owner_history;
fp_define_by_properties;
fp_define_by_type;
fp_map_representation;
fp_measure_with_unit;
fp_place_object;
fp_represent_product;
fp_select_actor;
fp_select_date_time;

EXPRESS Schema

SCHEMA FP_CONTROL_SERVICE_LIFE;

  TYPE IfcDayInMonthNumber = INTEGER;
  END_TYPE;

  TYPE IfcGloballyUniqueId = STRING (22) FIXED;
  END_TYPE;

  TYPE IfcIdentifier = STRING;
  END_TYPE;

  TYPE IfcLabel = STRING;
  END_TYPE;

  TYPE IfcMonthInYearNumber = INTEGER;
    WHERE
      WR1 : { 1<= SELF <= 12 };
  END_TYPE;

  TYPE IfcParameterValue = REAL;
  END_TYPE;

  TYPE IfcText = STRING;
  END_TYPE;

  TYPE IfcTimeMeasure = REAL;
  END_TYPE;

  TYPE IfcYearNumber = INTEGER;
  END_TYPE;

  TYPE IfcObjectTypeEnum = ENUMERATION OF
    (PRODUCT,
     PROCESS,
     CONTROL,
     RESOURCE,
     ACTOR,
     GROUP,
     PROJECT,
     NOTDEFINED);
  END_TYPE;

  TYPE IfcServiceLifeFactorTypeEnum = ENUMERATION OF
    (A_QUALITYOFCOMPONENTS,
     B_DESIGNLEVEL,
     C_WORKEXECUTIONLEVEL,
     D_INDOORENVIRONMENT,
     E_OUTDOORENVIRONMENT,
     F_INUSECONDITIONS,
     G_MAINTENANCELEVEL,
     USERDEFINED,
     NOTDEFINED);
  END_TYPE;

  TYPE IfcServiceLifeTypeEnum = ENUMERATION OF
    (ACTUALSERVICELIFE,
     EXPECTEDSERVICELIFE,
     OPTIMISTICREFERENCESERVICELIFE,
     PESSIMISTICREFERENCESERVICELIFE,
     REFERENCESERVICELIFE);
  END_TYPE;

  ENTITY IfcCalendarDate;
      DayComponent   : IfcDayInMonthNumber;
      MonthComponent : IfcMonthInYearNumber;
      YearComponent  : IfcYearNumber;
    WHERE
      WR21 : IfcValidCalendarDate (SELF);
  END_ENTITY;

  ENTITY IfcCostValue;
      CostType  : IfcLabel;
      Condition : OPTIONAL IfcText;
  END_ENTITY;

  ENTITY IfcProduct
    ABSTRACT SUPERTYPE
    SUBTYPE OF(IfcObject);
      Representation  : OPTIONAL fp_represent_product;
      ObjectPlacement : OPTIONAL fp_place_object;
    INVERSE
      ReferencedBy    : SET OF IfcRelAssignsToProduct FOR RelatingProduct;
    WHERE
      WR1 : (EXISTS(Representation) AND EXISTS(ObjectPlacement))
            OR (EXISTS(Representation) AND
            (NOT('IFC2X2_FINAL.IFCPRODUCTDEFINITIONSHAPE' IN TYPEOF(Representation))))
            OR (NOT(EXISTS(Representation)));
  END_ENTITY;

  ENTITY IfcObject
    ABSTRACT SUPERTYPE OF (ONEOF(IfcControl, IfcGroup, IfcProduct))
    SUBTYPE OF(IfcObjectDefinition);
      ObjectType : OPTIONAL IfcLabel;
    WHERE
      WR1 : SIZEOF(QUERY(temp <* IsDefinedBy | 'IFC2X2_FINAL.IFCRELDEFINESBYTYPE' IN TYPEOF(temp))) <= 1;
  END_ENTITY;

  ENTITY IfcRoot
    ABSTRACT SUPERTYPE OF (ONEOF(IfcPropertDdefinition, IfcRelationship, IfcObjectDefinition));
      GlobalId     : IfcGloballyUniqueId;
      Name         : OPTIONAL IfcLabel;
      Description  : OPTIONAL IfcText;
      OwnerHistory : fp_apply_owner_history;
    UNIQUE
      UR1 : GlobalId;
  END_ENTITY;

  ENTITY IfcPropertyDefinition
    ABSTRACT SUPERTYPE
    SUBTYPE OF(IfcRoot);
  END_ENTITY;

  ENTITY IfcPropertySetDefinition
    ABSTRACT SUPERTYPE
    SUBTYPE OF(IfcPropertDdefinition);
    INVERSE
      DefinesType : SET [0:1] OF IfcTypeObject FOR HasPropertySets;
  END_ENTITY;

  ENTITY IfcServiceLifeFactor
    SUBTYPE OF(IfcPropertySetDefinition);
      PredefinedType : IfcServiceLifeFactorTypeEnum;
      UpperValue     : OPTIONAL IfcParameterValue;
      MostUsedValue  : IfcParameterValue;
      LowerValue     : OPTIONAL IfcParameterValue;
    WHERE
      WR31 : NOT(PredefinedType = IfcServiceLifeFactorTypeEnum.USERDEFINED)
             OR EXISTS(SELF\IfcObject.ObjectType);
  END_ENTITY;

  ENTITY IfcTypeObject
    SUBTYPE OF(IfcObjectDefinition);
      ApplicableOccurrence : OPTIONAL IfcLabel;
      HasPropertySets      : OPTIONAL LIST [1:?] OF IfcPropertySetDefinition;
    WHERE
      WR1 : EXISTS(SELF\IfcRoot.Name);
  END_ENTITY;

  ENTITY IfcTypeProduct
    SUBTYPE OF(IfcTypeObject);
      Tag                : OPTIONAL IfcLabel;
      RepresentationMaps : SET [1:?] OF fp_map_representation;
    WHERE
      WR41 : NOT(EXISTS(SELF\IfcTypeObject.ObjectTypeOf[1])) OR
             (SIZEOF(QUERY(temp <* SELF\IfcTypeObject.ObjectTypeOf[1].RelatedObjects |
             NOT('IFC2X2_FINAL.IFCPRODUCT' IN TYPEOF(temp)))
             ) = 0);
  END_ENTITY;

  ENTITY IfcElementType
    ABSTRACT SUPERTYPE
    SUBTYPE OF(IfcTypeProduct);
      ElementType : OPTIONAL IfcLabel;
  END_ENTITY;

  ENTITY IfcRelationship
    ABSTRACT SUPERTYPE
    SUBTYPE OF(IfcRoot);
  END_ENTITY;

  ENTITY IfcRelAssigns
    ABSTRACT SUPERTYPE OF (ONEOF(IfcRelAssignsToActor, IfcRelAssignsToControl, IfcRelAssignsToProduct))
    SUBTYPE OF(IfcRelationship);
      RelatedObjects     : SET [1:?] OF IfcObjectDefinition;
      RelatedObjectsType : OPTIONAL IfcObjectTypeEnum;
    WHERE
      WR1 : IfcCorrectObjectAssignment(RelatedObjectsType, RelatedObjects);
  END_ENTITY;

  ENTITY IfcRelAssignsToActor
    SUBTYPE OF(IfcRelAssigns);
      ActingRole : OPTIONAL fp_select_actor;
    WHERE
      WR1 : SIZEOF(QUERY(Temp <* SELF\IfcRelAssigns.RelatedObjects | RelatingActor :=: Temp)) = 0;
  END_ENTITY;

  ENTITY IfcRelAssignsToControl
    SUBTYPE OF(IfcRelAssigns);
      RelatingControl : IfcControl;
    WHERE
      WR1 : SIZEOF(QUERY(Temp <* SELF\IfcRelAssigns.RelatedObjects | RelatingControl :=: Temp)) = 0;
  END_ENTITY;

  ENTITY IfcControl
    ABSTRACT SUPERTYPE
    SUBTYPE OF(IfcObject);
    INVERSE
      Controls : SET OF IfcRelAssignsToControl FOR RelatingControl;
  END_ENTITY;

  ENTITY IfcServiceLife
    SUBTYPE OF(IfcControl);
      ServiceLifeType     : IfcServiceLifeTypeEnum;
      ServiceLifeDuration : IfcTimeMeasure;
  END_ENTITY;

  ENTITY IfcGroup
    SUPERTYPE OF (ONEOF(IfcSystem, IfcAsset))
    SUBTYPE OF(IfcObject);
  END_ENTITY;

  ENTITY IfcAsset
    SUBTYPE OF(IfcGroup);
      AssetId              : IfcIdentifier;
      OriginalValue        : IfcCostValue;
      CurrentValue         : IfcCostValue;
      TotalReplacementCost : IfcCostValue;
      Owner                : fp_select_actor;
      User                 : fp_select_actor;
      IncorporationDate    : IfcCalendarDate;
      DepreciatedValue     : IfcCostValue;
    WHERE
      WR1 : SIZEOF(QUERY(Temp <* SELF\IfcGroup.IsGroupedBy.RelatedObjects | NOT('IFC2X2_FINAL.IFCELEMENT' IN TYPEOF(Temp)))) = 0;
  END_ENTITY;

  ENTITY IfcSystem
    SUBTYPE OF(IfcGroup);
    WHERE
      WR1 : SIZEOF (QUERY (temp <* SELF\IfcGroup.IsGroupedBy.RelatedObjects |  NOT('IFC2X2_FINAL.IFCELEMENT' IN TYPEOF(temp)))) = 0;
  END_ENTITY;

  ENTITY IfcElement
    ABSTRACT SUPERTYPE
    SUBTYPE OF(IfcProduct);
      Tag : OPTIONAL IfcIdentifier;
  END_ENTITY;

  ENTITY IfcElectricalCircuit
    SUBTYPE OF(IfcSystem);
  END_ENTITY;

  ENTITY IfcRelAssignsToProduct
    SUBTYPE OF(IfcRelAssigns);
      RelatingProduct : IfcProduct;
    WHERE
      WR1 : SIZEOF(QUERY(Temp <* SELF\IfcRelAssigns.RelatedObjects | RelatingProduct :=: Temp)) = 0;
  END_ENTITY;

  ENTITY IfcObjectDefinition
    SUPERTYPE OF (ONEOF(IfcObject, IfcTypeObject))
    SUBTYPE OF(IfcRoot);
    INVERSE
      HasAssignments : SET OF IfcRelAssigns FOR RelatedObjects;
  END_ENTITY;

  ENTITY fp_apply_owner_history;
  END_ENTITY;

  ENTITY fp_define_by_properties;
  END_ENTITY;

  ENTITY fp_define_by_type;
  END_ENTITY;

  ENTITY fp_map_representation;
  END_ENTITY;

  ENTITY fp_measure_with_unit;
  END_ENTITY;

  ENTITY fp_place_object;
  END_ENTITY;

  ENTITY fp_represent_product;
  END_ENTITY;

  ENTITY fp_select_actor;
  END_ENTITY;

  ENTITY fp_select_date_time;
  END_ENTITY;

END_SCHEMA;

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