# Transmission of the calculation formula — MSB-MELO view The calculation formula is transmitted for all market locations, irrespective of the number of metering locations relevant for calculating the energy at market location level. For every market location of the location bundle, the NB transmits the calculation formula for determining the values of the respective market location to every MSB that is assigned to a metering location of the location bundle. The NB transmits the associated calculation formula to the LF that is assigned to a market location, even if no metering location and therefore no MSB is assigned to that market location. In the event that the calculation formula cannot be transmitted as part of the electronic data exchange, the corresponding contact of the NB is to be stated at this point so that a bilateral transmission of the calculation formula can be carried out. The calculation formula represents the formula for calculating the values of the market location, stating the required metering locations and their measurands. It specifies how the determined values of the individual metering locations are to be offset in order to form the values of the market location. ## Process flow from the perspective of the MSB (MSB-MELO) \nSystem diagram: Übermittlung der Berechnungsformel — view of MSB\n\n\nCustomer backend system\n\nMACO APP · MSB (entsprich…\n\nMarket partner\n\n\n\n1. Berechnungsformel\n\nNB\n\nAS4\n25001\n\nLoad data for the incoming\ncheck\n\n\n2 read APIs called\n\nAPI\nlisted at the step\n\nAPERAK check: Z10\n\n\nCreate transaction\n\n\nCreate process data\n\nAPI\n\nLoad data for the check\n\n\n2 read APIs called\n\nAPI\nlisted at the step\n\nTrigger follow-up process:\n25010\n\n\nTriggered by incoming\nmessage: 25001\n\n\n2. Antwort auf\nBerechnungsformel\n\n\nNB\n\nAS4\n25010\n\nUpdate transaction\n\n\nUpdate process data\n\nAPI\n"} gesamt={"\nSequence diagram: Übermittlung der Berechnungsformel — view of MSB\n\n\nBackend (customer)\n\n\nMACO APP · MSB (entsprich…\n\n\nNB\n\n\nLF\n\n\n1. Berechnungsformel\nAS4 · PI 25001\n\nCreate transaction\nCreate process data\n\n2. Antwort auf Berechnungsformel\nAS4 · PI 25010 · E_0218\nE_0218 — Berechnungsformel prüfen\n\nUpdate transaction\nUpdate process data\n\n4. Berechnungsformel\nAS4 · PI 25001\n"} titel="MSB-MELO" /> ## Process steps ### Calculation formula
**Check identifiers** - [25001](/en/schnittstellen/202610/pruefi/UTILTS/PI_25001) — Calculation formula · AS4
**Flow**
  1. Message from **NB** · AS4
  2. **Load data for the incoming check** - [Read market location](/en/api/202610/backend-lesen/getmarketlocationbasic#marktlokation-lesen) `GET /getMarketLocationBasic` Try it - [Read grid location](/en/api/202610/backend-lesen/getgridlocationbasic#netzlokation-lesen) `GET /getGridLocationBasic` Try it
  3. **APERAK checks** - `25001` → `Z10`
  4. **Write endpoint** - Transaction created — [Create process data](/en/api/202610/backend-schreiben-msb/createprocessdata#prozessdaten-erstellen) `POST /createProcessData` Try it out Creates a new transaction in the backend with the data of the incoming message.
  5. **Load data for the check** - [Read location bundle](/en/api/202610/backend-lesen/getlocationbundlebasic#lokationsbundel-lesen) `GET /getLocationBundleBasic` Try it - [Read metering location](/en/api/202610/backend-lesen/getmeterlocationbasic#messlokation-lesen) `GET /getMeterLocationBasic` Try it
  6. **Trigger follow-up process** - [25010](/en/schnittstellen/202610/pruefi/UTILTS/PI_25010) — Response to calculation formula After processing, the MACO APP starts this follow-up process itself.
### Response to calculation formula
**Check identifiers** - [25010](/en/schnittstellen/202610/pruefi/UTILTS/PI_25010) — Response to calculation formula · AS4
**Flow**
  1. **Triggered by incoming message** - [25001](/en/schnittstellen/202610/pruefi/UTILTS/PI_25001) — Calculation formula The MACO APP sends this message itself, as a follow-up process after this incoming message.
  2. Message to **NB** · AS4
    **Response per decision tree** - `25010` → [E_0218](/en/referenz/202610/ebd/E_0218) · MSB · Check calculation formula
  3. **Write endpoint** - Transaction updated — [Update process data](/en/api/202610/backend-schreiben-msb/updateprocessdata#prozessdaten-aktualiseren) `POST /updateProcessData` Try it out Updates the existing transaction in the backend once the message has been created.
### Calculation formula This step runs between other market partners and is not relevant for this view.
**Check identifiers** - [25001](/en/schnittstellen/202610/pruefi/UTILTS/PI_25001) — Calculation formula · AS4
Decision trees of this process | EBD | Name | |---|---| | [E_0218](/referenz/202610/ebd/E_0218) | Check calculation formula |
## Process information Wording of the consolidated version, profile ch. 2.3.1, pp. 16–17.
  1. ### Preconditions Precondition for sending the calculation formulas to a MSB: - The MSB is assigned to a metering location of the location bundle.
  2. ### Results - The MSB of the metering locations are able to provide the required values to the MSB of the market location at the required point in time. - The MSB of the market location is able to determine the values of the market location. - The LF of the market location is able to check the values of the market location transmitted to it.
  3. ### Error case #### Result in the error case If the rejection of the calculation formula by the MSB is caused by asynchronous master data of the NB, the NB has the option of correcting this by means of the use case master data change (here SD “[Master data change initiated by the NB (responsible)](/en/prozessdoku/202610/MSB/GPKE-Teil4-stammdatenaenderung-vom-nb-verantwortlich-ausgehend)”) (GPKE part 4) in order to then send the calculation formula to all authorised parties again. #### Error cases - Calculation formula is incorrect or incomplete - Missing calculation formula
  4. ### Trigger - Reassignment of MSB to a metering location of the location bundle or - when a calculation formula changes or - Extension of the location bundle by a market location. Precondition for sending the calculation formulas to LF: - The LF is assigned to the market location. Trigger: - Reassignment of LF to a market location or - when the calculation formula for the market location changes (whereby the calculation formula must be sent to the currently assigned LF as well as to all those assigned to the market location in the future).
  5. ### First message **NB** sends “Calculation formula” (step 1). From here on, it is the turn of the party involved on this page.
  6. ### Objective Every MSB assigned to the location bundle has the calculation formula for each market location of the location bundle. The LF has the valid calculation formula for the market locations assigned to it.
## Other views of the process The same process through the eyes of the other parties involved: the same steps, each read from their point of view. - [View LF](/en/prozessdoku/202610/LF/WiM-Teil2-uebermittlung-der-berechnungsformel) — LF - [View NB](/en/prozessdoku/202610/NB/WiM-Teil2-uebermittlung-der-berechnungsformel) — NB *The steps are the **possible** messages of this process, not a sequence — the source lists neither conditions nor alternatives. The small box on the step names the own view on the left: with **←** it receives, with **→** it sends. Collapsed steps run between other market partners. The numbers are those of the source; where one is missing, it is missing there.*