Auto-Calculations Based on Updated Nodes
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Auto-Calculations Based on Updated Nodes |
If you wish to create an Auto-Calculation (second Auto-Calculation) that uses a node updated by another Auto-Calculation (first Auto-Calculation), there are two possible situations:
| • | The two Auto-Calculations are in the same template templates. |
| • | The two Auto-Calculations are in different templates. |
Auto-Calculations in the same template
When two Auto-Calculations are in the same template, the SPS applies the following procedure:
| 1. | A node used in the XPath expression of the first Auto-Calculation is modified. |
| 2. | All node values in the XML document are read and all Auto-Calculations are executed. |
| 3. | Assuming that the first Auto-Calculation is executed correctly, it updates the specified XML node (call it Node-A). The second Auto-Calculation, which is based on Node-A, will be executed but will use the value of Node-A before Node-A was updated. This is because the value of Node-A was read before it was updated, and has not been read since then. |
| 4. | If the document is now edited in any way or if document views are changed (from and to Authentic View), then the values of nodes are read afresh and Auto-Calculations are executed. |
| 5. | The second Auto-Calculation is now carried out. (If this Auto-Calculation is intended to update a node, then, as is usual for node updates, a node used in the XPath expression will have to be changed before the update takes place.) |
The time lag between the updating of Node-A and the evaluation of the second Auto-Calculation with the updated value of Node-A could be confusing for the Authentic View user. To ensure that this situation does not occur, it is best that the XPath expression of the second Auto-Calculation contain the XPath expression of the first Auto-Calculation—not the updated node itself. As a result, the second Auto-Calculation will execute with the input to the first Auto-Calculation and perform that Auto-calculation as part of its own Auto-Calculation. This enables it to be evaluated independently of the contents of Node-A.
Example
The first Auto-Calculation calculates the VAT amount of a product using the nodes for (i) the net price, and (ii) the VAT rate; it updates the VAT-amount node. The second Auto-Calculation calculates the gross price, which is the sum of net price and VAT amount; it updates the gross price node.
| • | The Auto-Calculation to calculate the VAT amount is: NetPrice * VATRate div 100. When the VAT rate of the product is entered, the Auto-Calculation is executed and updates the VATAmount node. |
| • | If the Auto-Calculation to calculate the gross price is: NetPrice + VATAmount, then the Auto-Calculation will execute with the value of VATAmount that was read in before VATAmount was updated. |
| • | If, however, the Auto-Calculation to calculate the gross price is: NetPrice + (NetPrice * VATRate div 100), then the Auto-Calculation will execute with the value of VATRate and will update the GrossPrice node. The updated VatAmount node has been left out of the second Auto-Calculation. |
For a detailed example, see Example: An Invoice.
Auto-Calculations in different templates
When two Auto-Calculations are in different templates, a node updated by the first Auto-Calculation can be used by the second Auto-Calculation. This is because Auto-Calculations are calculated and nodes updated for each template separately. For an example of how this would work, see Example: An Invoice.
See also:
Editing and Moving Auto-Calculations, for a description of how to use Auto-Calculations.
Updating Nodes with Auto-Calculations, for the basics of updating nodes.
Example: An Invoice, for a detailed example of using Auto-Calculations.
XPath Dialog, for a description of the Edit XPath Expression dialog.
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