Hi Xavier,
If you need to update the training due to a new document type or a document not performing as desired, you will need to create a new model/retrain the existing model in full. Retraining is a little difficult though, as you can't simply delete the model and keep the name, nor can you simply upload new documents as training batches. In some respects it's best to start fresh.
You can have a document type to represent exceptions, you don't need to provide any examples or link it to a DFD. This would mean any documents that don't meet the confidence requirements can be manually assigned to it. You may want to include a DFD and set up some fields for the exception detail, which will help your BP process understand it. Make the fields unassignable and they won't create any document training.
PNG documents are supported in Decipher for both classification and data extraction. You can also use all types of PDF, JPG and BMP. Classification models are trained based on the common locations of key text values and string types. This will be done via OCR extraction or vector based extraction for PDF's with selectable text.
Thanks
Ben
Ben Lyons
Principal Product Specialist - Decipher
SS&C Blue Prism
UK based