# Processing of Property and System Fields

Consider the following points when using system fields on input according to different message types.

## Standard Messages

Substation ES processes properties or system fields according to the message conversion rule definition.

## Multi-Container Messages

If values are specified in the properties panel, all other configuration options are ignored and only values from the properties configuration panel are selected for input.

## EMS Map and Rendezvous Messages

Substation ES processes system fields in the following order:

1. If the special indicator `S` in the conversion rule panel in the Trunc column is set and a property is defined for the recipe, Substation ES uses that property definition to process the system fields.
2. If the special indicator `S` is not set, or if there is no property defined for the recipe, Substation ES processes the fields according to the definition rules.
3. Any user properties that might be defined in the properties panel.
4. Any correlation_id options.
5. Any other system properties defined in the properties panel.

## EMS Bytes Messages

Substation ES first copies the message directly to the buffer area, ignoring any message and buffer options. Then Substation ES processes system fields in the following order:

1. Fields in the conversion rule panel
2. Any user properties that are defined in the properties panel
3. Any correlation_id options
4. Any other system properties defined in the properties panel

## EMS Text Messages

Substation ES processes system fields in the following order:

1. Only the first field in the buffer definition is used to hold the user payload
2. All fields in the conversion rule panel
3. Any user properties that are defined in the properties panel
4. Any correlation_id options
5. Any other system properties defined in the properties panel

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