What is XFS?
XFS (eXtensions for Financial Services) is the standard interface between the software in a self-service banking machine and the devices inside it. A CEN Workshop of manufacturers, software companies and banks writes it. CEN publishes it as CEN Workshop Agreements, which are free to download.
The problem it solves
An ATM, a kiosk or a branch terminal is a computer with special devices attached: a cash dispenser, a card reader, an encrypting PIN pad, a receipt printer, sensors, a camera. Each manufacturer builds these differently. A bank wants one application across machines from different makers and different years, and wants to replace a machine without rewriting the application.
XFS defines, for each kind of device, the commands an application may send, the data it gets back, and the events the device reports on its own. The application is written against the standard. Each manufacturer supplies the software that maps the standard onto its own hardware.
The parts of an XFS system
- The application — the bank's or software house's program: screens, transactions, the host connection. It talks XFS and nothing vendor-specific.
- The XFS manager — a thin layer that routes each request to the right device and keeps the rules of the conversation (who has the device, timeouts, events).
- Service providers — one per device, supplied by the device's manufacturer. They implement the standard's commands on the real hardware.
- The devices — the hardware itself.
In XFS 3.x all of this runs on one Windows PC inside the machine. XFS4IoT keeps the same roles but exchanges messages over a network connection, so the parts can run on any operating system and on different computers. See XFS 3.x and XFS4IoT.
The device classes
The standard has one part per kind of device, called a device class, and a first part that defines the programming interface itself. The 3.50 edition has 17 device classes:
| Class | Code | In the standard since |
|---|---|---|
| Alarm Device Class Interface | ALM | 3.00 |
| Barcode Reader Device Class Interface | BCR | 3.10 |
| Biometrics Device Class Interface Proposal | BIO | 3.40 |
| Camera Device Class Interface | CAM | 2.00 |
| Card Dispenser Device Class Interface | CRD | 3.10 |
| Card Embossing Unit Device Class Interface | CEU | 3.00 |
| Cash Dispenser Module Class Interface | CDM | 2.00 |
| Cash-In Module Device Class Interface | CIM | 3.00 |
| Check Reader/Scanner Device Class Interface | CHK | 2.00 |
| Depository Device Class Interface | DEP | 2.00 |
| Identification Card Device Class Interface | IDC | 2.00 |
| Item Processing Module Device Class Interface | IPM | 3.10 |
| PIN Keypad Device Class Interface | PIN | 2.00 |
| Printer and Scanning Device Class Interface | PTR | 2.00 |
| Sensors and Indicators Unit Device Class Interface | SIU | 2.00 |
| Text Terminal Unit Device Class Interface | TTU | 2.00 |
| Vendor Dependent Mode Device Class Interface | VDM | 2.00 |
Who publishes it
XFS is published as a CEN Workshop Agreement (CWA). A CEN Workshop is an open group of companies, banks and consultants that meets under the European Committee for Standardization. A CWA is quicker to produce and to revise than a European Standard. The XFS Workshop was opened by a public call in 1998. It has published 7 editions of XFS 3.x (CWA 13449, 14050, 15748, 16374 and 16926) and, since 2021, XFS4IoT (CWA 17852). CEN publishes the documents free of charge; the XFS4IoT specification is also maintained in a public repository on GitHub.
The organisations that took part are listed in each document's foreword. The editions are listed with their numbers and dates.
A short history
XFS began in the early 1990s as WOSA/XFS, for the Windows PCs that were replacing proprietary controllers in ATMs. In 1998 the work moved to CEN, where the Workshop published release 2.00 as CWA 13449 with ten device classes. Release 3.00 (2000) restructured the interface and added cash-in, alarms and card embossing. Release 3.10 (2008) added barcode readers, card dispensers and item processing. Release 3.40 (2020) added biometrics, the seventeenth class. The editions in between revised what was already there. In 2021 the Workshop published the first release of XFS4IoT. The editions page has the numbers and dates.