An IfcProcedure is a logical set of actions to be taken in response to an event or to cause an event to occur. 

IfcProcedure is used to capture information about stepped processes such as calibration, start/stop procedures for equipment items, designated actions to take in the event of an emergency etc. A procedure is not a task, but may describe a set of tasks and their order of occurrence in response to or to cause an event. As shown on the image below, IfcProcedure does not restrict anything but describes specific steps of how something should happen. While a procedure does control/restrict in the sense of indicating "this is how the task should be performed" by nature of describing inner detail, this is not different than parts of a product indicating "this is how the parts should be assembled". Consequently, it doesn't restrict the outer item as a whole but provides inner detail of the item. 

The Object Typing concept template applies to this entity as IfcProcedureType under RelatingType. IfcProcedure defines the anticipated or actual occurrence of any procedure; common information about procedure types is handled by IfcProcedureType. 

The IfcProcedure may be contained within an IfcTask or IfcProcedure using the IfcRelNests relationship. An IfcProcedure may in turn nest other IfcProcedure or IfcEvent entities. Such nesting indicates decomposed level of detail. 

The relationship IfcRelSequence is used to indicate control flow. An IfcProcedure as a successor to an IfcEvent indicates that the procedure should be performed in response to the event. An IfcProcedure as a predecessor to an IfcEvent indicates that the event should be triggered following the procedure. As procedures have arbitrary duration, the IfcRelSequence.SequenceType attribute has no effect on an IfcProcedure but still applies to the opposite end of the relationship if IfcTask is used. 

A particular type of IfcProcedure is a caution, warning or other form of advisory note. Typically, it is anticipated that such a procedure would be assigned to the specific IfcProcess for which it gives advice using IfcRelAssignsToProcess. 

An IfcProcedure may be assigned to an IfcWorkCalendar to indicate times when such procedure may be performed using IfcRelAssignsToControl; otherwise the effective calendar is determined by the nearest IfcProcess ancestor with a calendar assigned. Advisory notes should be assigned to the specific IfcProcess for which it gives advice using IfcRelAssignsToProcess. 

For building operation scenarios, IfcProcedure may be assigned to a product (IfcElement subtype) using IfcRelAssignsToProduct to indicate a specific product occurrence that performs the procedure.

• EXAMPLE: An IfcActuator may have a "Close" procedure. If the IfcProcedure is defined by an IfcProcedureType and the IfcProcedureType is assigned to a product type (using IfcRelAssignsToProduct), then the IfcProcedure must be assigned to one or more occurrences of the specified product type using IfcRelAssignsToProduct.

changes 

• IFC4 changes: Name of the attribute ProcedureType changed to PredefinedType and made optional (upward compatible).