Operation

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An operation represents an activity: these consume and produce material, take time and also require capacity.

An operation consumes and produces material, modeled through flows.

An operation requires capacity, modeled through loads.

Different operation types exist:

  • operation_fixed_time:
    Models an operation with a duration that is independent of the quantity. A good example is a transport or a procurement operation.
  • operation_time_per:
    Models an operation where the duration increases linear with the quantity. A good example is a manufacturing operation where the duration is determined by the production rate of a machine.
  • operation_alternate:
    Models a choice between different operations.
  • operation_routing:
    Models a sequence a number of 'step' sub-operations, to be executed sequentially.

Fields

Field Type Description
name non-empty string Name of the operation.
This is the key field and a required attribute.
description string Free format description.
category normalizedString Free format category.
subcategory normalizedString Free format subcategory.
location location Location of the operation.
Default is null.
The working hours and holidays for the operation are taken from the 'available' calendar of the location.
owner operation Operations can be organized in a hierarchical tree.
This field defines the parent operation.
fence duration Time window from the current date of the plan during which all operationplans are expected to be frozen / released.
When the "FENCE" constraint is enabled in the solver, it won't create any new operation plans in this time fence. Only the externally supplied operationplans will then exist in this time window.
size_minimum Positive double A minimum size for operationplans.
A request for a lower quantity will be rounded up.
size_multiple Positive double A lotsize quantity for operationplans.
cost double The cost of executing this operation, per unit of the operation_plan. Depending on what the operation models, this represents transportation costs, manufacturing costs, material procurement costs, delivery costs, etc...
The default value is 1.0.
pretime duration A pre-operation time, used as a buffer for uncertain material supply.
The solver will try to position material supply for operation plans early by the time specified here. This is a soft constraint, ie it can be violated if required to meet the demand in time.
posttime duration A post-operation time, used as a buffer for uncertain capacity or operation duration.
The solver will try to respect this time as a soft constraint. Ie when required to meet demand on time the post-operation time can be violated.

This field is used to model time-based safety stock targets. It is typically set for the producing operation of a certain buffer.
If you want to model a safety stock quantity, you can use the minimum field on the buffer.

detectproblems boolean Set this field to false to skip problem detection on this operation.
The default value is true.
loads List of load A list of all resources loaded by this operation.
flows List of flow A list of all buffers where material is consumed from or produced into.
level integer Indication of how upstream/downstream this entity is situated in the supply chain.
Lower numbers indicate the entity is close to the end item, while a high number will be shown for components nested deep in a bill of material.
The field is export-only.
cluster integer The network of entities can be partitioned in completely independent parts. This field gives the index for the partition this entity belongs to.
The field is export-only.
action A
C
AC (default)
R 		Type of action to be executed:
  • A: Add an new entity, and report an error if the entity already exists.
  • C: Change an existing entity, and report an error if the entity doesn't exist yet.
  • AC: Change an entity or create a new one if it doesn't exist yet.
  • R: Remove an entity, and report an error if the entity doesn't exist.

operation_fixed_time

Models an operation with a fixed duration regardless of the quantity.
E.g. a transport operation.

This is the default operation type.

Field Type Description
duration duration Duration of the operation.
The default value is 0.

operation_time_per

Models an operation where the duration changes linear with the quantity.
E.g. a production operation.

The total duration of the operation plan is the sum of:

  • A fixed DURATION.
  • A variable duration, computed as the operationplan quantity multiplied by a DURATION_PER.
Field Type Description
duration duration Fixed component of the duration of the operationplan.
The default value is 0.
duration_per duration Variable component of the duration of the operationplan.
The default value is 0.

operation_alternate

Models a choice between different operations.
It has a list of alternate sub-operations listed, each with a priority.

Field Type Description
alternates List of alternate List of alternate sub-operations, each with their priority.

Alternate fields:

Field Type Description(:table border=1 width="100%":)
operation operation Sub-operation.
priority integer Priority of this alternate.
Lower numbers indicate higher priority.
When the priority is equal to 0, this alternate is considered unavailable and it can't be used for planning.
effective_start dateTime Earliest allowed start date for using this alternate.
effective_end dateTime Latest allowed end date for using this alternate.

operation_routing

Models a sequence a number of 'step' sub-operations, to be executed sequentially.

Field Type Description
steps List of operation Lists all sub-operations in the order of execution.

Example XML structures:

  • Adding or changing operations 
 <plan>
   <operations>
     <operation name="buy item X from supplier" 
       xsi:type="operation_fixed_time">
       <duration>P1D</duration>
     </operation>
     <operation name="make item X" 
       xsi:type="operation_time_per">
       <duration>PT1H</duration>
       <duration_per>PT5M</duration_per>
     </operation>
     <operation name="make or buy item X"
       xsi:type="operation_alternate">
       <alternates>
         <alternate>
           <operation name="make item X" />
           <priority>1</priority>
         </alternate>
         <alternate>
           <operation name="buy item X from supplier" />
           <priority>2</priority>
         </alternate>
       </alternates>
     </operation>
     <operation name="make subassembly"
       xsi:type="operation_routing">
       <steps>
          <operation name="make subassembly step 1" 
            duration="PT1H"/>
          <operation name="make subassembly step 2" 
            duration="PT5M"/>
       </steps>
     </operation>
   </operations>
 </plan>
  • Deleting an operation 
 <plan>
    <operations>
       <operation name="make item X" action="R"/>
    </operations>
 </plan>

Example Python code:

  • Adding or changing operations 
    op1 = frepple.operation_fixed_time(name="buy item X from supplier",
           duration=24*3600)
    op2 = frepple.operation_time_per(name="make item X", 
           duration=3600, duration_per=60*5)
    op3 = frepple.operation_alternate(name="make or buy item X")
    op3.addAlternate(operation=op1, priority=1)    
    op3.addAlternate(operation=op2, priority=2, 
      effective_end=datetime.datetime(2009,10,10))
    op4 = frepple.operation_routing(name="make subassembly")
    op4.addStep(
       frepple.operation_fixed_time(name="make subassembly step 1" 
            ,duration=3600),
       frepple.operation_fixed_time(name="make subassembly step 2" 
            ,duration=300)
       )
  • Deleting an operation 
    frepple.operation(name="make item X", action="R")
  • Iterate over operations, loads and flows 
    for o in frepple.operations():
      print "Operation:", o.name, o.description, o.category
      for l in o.loads:
        print "  Load:", l.resource.name, l.quantity, 
          l.effective_start, l.effective_end
      for l in o.flows:
        print "  Flow:", l.buffer.name, l.quantity, 
          l.effective_start, l.effective_end