Extension point for bundle to contribute Callout implementation. Use the {extension id}.{methodName} syntax in AD_Column.Callout to reference the extension that will provide the CalloutEngine instance (replace {extension id} with your actual extension id ). This extension point is provided to ease migration from pre-OSGi ADempiere code, new code is recommended to use the org.adempiere.base.IColumnCallout extension point. Implementation class name that extend org.compiere.model.CalloutEngine numeric priority value, higher value is of higher priority. 1.0.0 <pre> <extension point="org.compiere.model.Callout" id="org.compiere.model.CalloutOrder" name="Order Callout"> <callout class="org.compiere.model.CalloutOrder"> </callout> </extension> AD_Column.Callout="org.compiere.model.CalloutOrder.bPartner </pre> Class attribute must represent a subclass of org.compiere.model.CalloutEngine