Overview
ISO/IEC 19794-4:2011/Amd 2:2015 is an amendment to the international standard for biometric data interchange - Part 4: Finger image data. Amendment 2 adds XML encoding support and clarifies defects and conformance rules for finger image records. The amendment specifies that implementations may use either binary or XML encodings to exchange finger image biometric data, and it provides normative guidance (Annex F) and an example (Annex G) for XML-encoded records.
Key technical topics and requirements
- Dual encoding support: The standard now explicitly supports both binary and XML encodings to suit modern IT architectures (XML) and bandwidth- or storage-constrained environments (binary).
- XML schema and example: Annex F contains the XML schema that XML-encoded finger image records must conform to; Annex G gives a valid example.
- Conformance definitions:
- Binary records must meet the structural and field-value requirements in clause 8.
- XML documents must meet structure and field-relationship requirements specified in Annex F.
- Systems declare supported features in an Implementation Conformance Statement (ICS) and may claim conformance only to the features they support and test.
- Representation and header rules:
- Each finger image representation has a header (minimum 41 bytes for binary) followed by image data; multiple representations are concatenated.
- The representation length field records the full length of a representation including header and data.
- Quality and certification blocks:
- Quality information is recorded in five-byte blocks; quality score values range from 0–100 (higher is better) or 255 indicating failure to compute.
- Certification records (when present) include authority and scheme identifiers; certification flags in the general header control presence.
- Conformance testing: Annex A defines normative requirements for conformance tests and levels (Level-1, Level-2, Level-3) and uses specific assertions and test tables.
Practical applications and users
This amendment is directly applicable to:
- Biometric system vendors and fingerprint device manufacturers implementing interchange formats.
- Software developers and integrators building biometric enrollment, matching, and exchange solutions.
- Government agencies and border control systems requiring interoperable finger image records for identification and verification.
- Testing laboratories and QA teams performing conformance testing against the standard.
- Registries and authorities (e.g., IBIA) for vendor and product IDs used in records.
Benefits include improved interoperability, clearer conformance criteria, and flexible encoding choices for deployment constraints.
Related standards
Keywords: ISO/IEC 19794-4, biometric data interchange, finger image data, XML encoding, biometric interoperability, conformance, quality score, fingerprint image standard.