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Change Propagation

Cost Modelling and Change Propagation can be used together.

Change Propagation Rules providing input to the Cost Model​

Change Propagation rules may be used to provide values to all properties which are tagged with any of the following semantic tags:

  • Direct Runtime Cost
  • Direct License Cost
  • Direct Custom Cost
  • Purchase Cost
  • Depreciation Period
  • Direct Runtime Carbon Emissions
  • Direct Embodied Carbon Emissions
  • Direct Custom Carbon Emissions
  • Direct Runtime Energy Consumption
  • Direct Custom Energy Consumption

Overall, Change Propagation may provide values to all direct cost properties, except for Direct CAPEX Cost, since this value is computed by the cost model from the Purchase Cost and the Depreciation Period.

(Grand) Total Cost Properties cannot be written by Change Propagation

Since the Cost Model already provides values for all (Grand) Total Costs, Change Propagation rules may not select them as output properties. This equally applies to Financial Costs, Carbon Emissions and Energy Consumption.

Change Propagation rules reading from Cost Model Properties​

Txture 45 and below

The following information relates to Txture 46 and above. In Txture 45 and below, any property related to the Cost Model can not be used in a Change Propagation Rule script. Attempting to do so will result in a compilation error for the script. The technical reason is that a Change Propagation Rule which uses a Cost Model property as input creates a cyclic dependency between the Cost Model and the Change Propagation mechanism which could lead to an infinite loop.

Starting with Txture 46, it is possible to use an output property of the Cost Model as an input for a change propagation rule.

For example, let's assume there is a property called Grand Total Costs which is tagged with the semantic tag Grand Total Cost. The following change propagation rule script:

return asset.props.grandTotalCosts

... would have been illegal in Txture 45 and below because it depends on an output of the cost model. In Txture 46, this access is generally permitted and supported.

However, there is one important limitation. Each change propagation rule must belong to exactly one of the following three categories:

  • The rule does not interact with any cost model properties.
  • The rule provides input to the cost propagation by targeting a direct cost property, the depreciation period or the purchase cost.
  • The rule depends on the output of the cost model by either reading an output property or reading the output of another rule which depends on the output of the cost model.

In particular, this means that any given change propagation rule may...

  • either provide input to the cost model by targeting one of the input properties
  • or read the output of the cost model by accessing a cost model output property

Both behaviors at the same time are not allowed.

For example, let's assume that:

  • The property Grand Total Costs has the semantic tag Grand Total Cost
  • The property Direct Runtime Costs has the semantic tag Direct Runtime Cost

A rule which has the Direct Runtime Costs property as output and the following script:

return asset.props.grandTotalCosts

... would be invalid because it writes a cost model input property (Direct Runtime Cost) while depending on a cost model output property (Grand Total Costs). This forms an infinite loop with the cost model and is therefore forbidden. Txture validates your change propagation ruleset when it gets modified and notifies you if this problem occurs.

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