ISO/IEC 19794-7:2021

INTERNATIONAL ISO/IEC
STANDARD 19794-7
Third edition
2021-10
Information technology — Biometric
data interchange formats —
Part 7:
Signature/sign time series data
Technologies de l'information — Formats d'échange de données
biométriques —
Partie 7: Données de série chronologique de signature/signe
Reference number
© ISO/IEC 2021
© ISO/IEC 2021
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Published in Switzerland
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Contents Page
Foreword .v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 2
4 Abbreviated terms . 3
5 Conformance . 4
6 Conventions . 4
6.1 Coordinate system . 4
6.2 Octet and bit order . 5
6.3 Registered format type identifiers . 5
7 Channels . 5
7.1 General . 5
7.2 Pen tip position channels: X, Y, Z . 6
7.3 Pen tip velocity channels: VX, VY . 6
7.4 Pen tip acceleration channels: AX, AY . 6
7.5 Time channel: T . 6
7.6 Time difference channel: DT . 7
7.7 Pen tip force channel: F . 7
7.8 Pen tip switch state channel: S . 7
7.9 Pen orientation channels: TX, TY, A, E, R . 7
8 Binary full format . 8
8.1 Record organization . 8
8.2 General header . 11
8.2.1 Structure . 11
8.2.2 Format identifier . 11
8.2.3 Version number . 11
8.2.4 Length of the data record . 11
8.2.5 Number of representations . 11
8.2.6 Certification flag . 11
8.3 Record body . 12
8.3.1 Structure .12
8.3.2 Representation header .12
8.3.3 Representation body . 17
9 Binary compact format .17
9.1 Record organization . 17
9.2 Comparison algorithm parameters template . 18
9.2.1 Structure . 18
9.2.2 Minimum and maximum number of sample points . 18
9.2.3 Channel descriptions . 19
9.3 Embedment in a CBEFF data structure . 20
9.4 Record body . 20
10 Binary compression format .20
10.1 Record organization . 20
10.2 General header . 21
10.3 Record body . 21
10.3.1 Structure . 21
10.3.2 Representation header . 21
10.3.3 Representation body . 24
11 XML encoding .25
Annex A (normative) Conformance testing methodology .26
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Annex B (informative) Best practices — Data acquisition .71
Annex C (informative) ASN.1 specification of the binary compact format .72
Annex D (informative) Binary signature/sign encoding examples .75
Annex E (normative) XML schema definition .77
Annex F (informative) XML signature/sign encoding example .81
Bibliography .84
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Foreword
ISO (the International Organization for Standardization) and IEC (the International Electrotechnical
Commission) form the specialized system for worldwide standardization. National bodies that are
members of ISO or IEC participate in the development of International Standards through technical
committees established by the respective organization to deal with particular fields of technical
activity. ISO and IEC technical committees collaborate in fields of mutual interest. Other international
organizations, governmental and non-governmental, in liaison with ISO and IEC, also take part in the
work.
The procedures used to develop this document and those intended for its further maintenance
are described in the ISO/IEC Directives, Part 1. In particular, the different approval criteria
needed for the different types of document should be noted. This document was drafted in
accordance with the editorial rules of the ISO/IEC Directives, Part 2 (see www.iso.org/directives or
www.iec.ch/members_experts/refdocs).
Attention is drawn to the possibility that some of the elements of this document may be the subject
of patent rights. ISO and IEC shall not be held responsible for identifying any or all such patent
rights. Details of any patent rights identified during the development of the document will be in the
Introduction and/or on the ISO list of patent declarations received (see www.iso.org/patents) or the IEC
list of patent declarations received (see patents.iec.ch).
Any trade name used in this document is information given for the convenience of users and does not
constitute an endorsement.
For an explanation of the voluntary nature of standards, the meaning of ISO specific terms and
expressions related to conformity assessment, as well as information about ISO's adherence to
the World Trade Organization (WTO) principles in the Technical Barriers to Trade (TBT) see
www.iso.org/iso/foreword.html. In the IEC, see www.iec.ch/understanding-standards.
This document was prepared by Joint Technical Committee ISO/IEC JTC 1, Information technology,
Subcommittee SC 37, Biometrics.
This third edition cancels and replaces the second edition (ISO/IEC 19794-7:2014), which has been
technically revised. It also incorporates the Amendment ISO/IEC 19794-7:2014/Amd 1:2015.
The main changes are as follows:
— inclusion of ISO/IEC 19794-7:2014/Amd 1:2015, XML encoding, and correction of technical defects
therein.
A list of all parts in the ISO/IEC 19794 series can be found on the ISO and IEC websites.
Any feedback or questions on this document should be directed to the user’s national standards
body. A complete listing of these bodies can be found at www.iso.org/members.html and
www.iec.ch/national-committees.
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© ISO/IEC 2021 – All rights reserved

INTERNATIONAL STANDARD ISO/IEC 19794-7:2021(E)
Information technology — Biometric data interchange
formats —
Part 7:
Signature/sign time series data
1 Scope
This document specifies data interchange formats for signature/sign behavioural data captured in
the form of a multi-dimensional time series using devices such as digitizing tablets or advanced pen
systems. The data interchange formats are generic, in that they can be applied and used in a wide
range of application areas where handwritten signs or signatures are involved. No application-specific
requirements or features are addressed in this document.
This document contains:
— a description of what data can be captured;
— three binary data formats for containing the data: a full format for general use, a compression format
capable of holding the same amount of information as the full format but in compressed form, and
a compact format for use with smart cards and other tokens that does not require compression/
decompression but conveys less information than the full format;
— an XML schema definition; and
— examples of data record contents and best practices in capture.
Specifying which of the format types and which options defined in this document are to be applied in
a particular application is out of scope; this needs to be defined in application-specific requirements
specifications or application profiles.
It is advisable that cryptographic techniques be used to protect the authenticity, integrity, and
confidentiality of stored and transmitted biometric data; yet such provisions are beyond the scope of
this document.
This document also specifies elements of conformance testing methodology, test assertions and test
procedures as applicable to this document. It establishes test assertions on the structure and internal
consistency of the signature/sign time series data formats defined in this document (type A level 1
and 2 as defined in ISO/IEC 19794-1) and semantic test assertions (type A level 3 as defined in ISO/IEC
19794-1).
The conformance testing methodology specified in this document does not establish:
— tests of other characteristics of biometric products or other types of testing of biometric products
(e.g. acceptance, performance, robustness, security); or
— tests of conformance of systems that do not produce data records claimed to conform to the
requirements of this document.
2 Normative references
The following documents are referred to in the text in such a way that some or all of their content
constitutes requirements of this document. For dated references, only the edition cited applies. For
undated references, the latest edition of the referenced document (including any amendments) applies.
© ISO/IEC 2021 – All rights reserved

ISO/IEC 8825-1, Information technology — ASN.1 encoding rules — Part 1: Specification of Basic Encoding
Rules (BER), Canonical Encoding Rules (CER) and Distinguished Encoding Rules (DER)
ISO/IEC 19794-1, Information technology — Biometric data interchange formats — Part 1: Framework
3 Terms and definitions
For the purposes of this document, the terms and definitions given in ISO/IEC 19794-1 and the following
apply.
ISO and IEC maintain terminology databases for use in standardization at the following addresses:
— ISO Online browsing platform: available at https:// www .iso .org/ obp
— IEC Electropedia: available at https:// www .electropedia .org/
3.1
channel
data item (captured, intermediate, or processed) recorded in form of a time series
EXAMPLE Pen tip position x and y coordinates, pen tip force, pen tilt along the x-axis (3.7), pen tilt along the
y-axis (3.8), pen azimuth (3.3), pen elevation (3.5), pen rotation (3.6).
3.2
compression
process that reduces the size of a digital file with or without loss of information
Note 1 to entry: The compression format defined in Clause 10 includes data compressed by lossless compression
schemes.
3.3
pen azimuth
angle measured clockwise from the positive y-axis to the perpendicular projection of the pen onto the
writing plane
Note 1 to entry: The pen azimuth may range from 0° to 360°.
3.4
pen-down event
event from which on the pen tip is touching the writing plane
3.5
pen elevation
angle between the perpendicular projection of the pen onto the writing plane and the pen
Note 1 to entry: The pen elevation may range from 0° to 90°.
3.6
pen rotation
angle of the rotation of the pen about its longitudinal axis measured counter-clockwise from a device-
specific rotational reference position
Note 1 to entry: The pen rotation may range from 0° to 360°.
3.7
pen tilt along the x-axis
angle measured clockwise from the positive z-axis to the perpendicular projection of the pen onto the
xz plane
Note 1 to entry: The pen tilt along the x-axis may range from –90° to +90°.
© ISO/IEC 2021 – All rights reserved

3.8
pen tilt along the y-axis
angle measured clockwise from the positive z-axis to the perpendicular projection of the pen onto the
yz plane
Note 1 to entry: The pen tilt along the y-axis may range from –90° to +90°.
3.9
pen-up event
event from which on the pen tip is not touching the writing plane, after a pen-down event (3.4)
3.10
sampling rate
number of samples per second (or per another unit) taken from a continuous signal to make a discrete
signal
3.11
signature/sign representation
data recorded from a single signature/sign
3.12
x jitter
sample standard deviation of at least 100 x-coordinate samples from a stationary pen
3.13
y jitter
sample standard deviation of at least 100 y-coordinate samples from a stationary pen
3.14
x pixel density
number of dots per millimetre that the capture device resolves in the x (horizontal) direction
3.15
y pixel density
number of dots per millimetre that the capture device resolves in the y (vertical) direction
4 Abbreviated terms
ASCII American Standard Code for Information Interchange
BDB biometric data block
BDIR biometric data interchange record
BHT biometric header template
BIR biometric information record
BIT biometric information template
CBEFF Common Biometric Exchange Formats Framework
IBIA International Biometrics & Identification Association
ICS implementation conformance statement
lsb least significant bit
msb most significant bit
© ISO/IEC 2021 – All rights reserved

5 Conformance
A binary biometric data record conforms to this document if it satisfies the format requirements with
respect to its structure, with respect to relations among its fields, and with respect to relations between
its fields and the underlying input that are specified within Clauses 6 to 10 of this document.
An XML document conforms to this document if it satisfies the format requirements with respect to its
structure, relations among its fields, and relations between its fields and the underlying input that are
specified within Annex E.
Biometric data interchange format conformance tests conform to this document if they satisfy all of the
normative requirements set forth in Annex A. Specifically, all level-1, level-2, and level-3 tests shall use
the test assertions defined in Table A.2, Table A.3, and Table A.4 of this document in conformity with
the concept and rules set out in ISO/IEC 19794-1.
Implementations of this document tested according to the specified methodology shall be able to claim
conformance only to those biometric data record requirements specified in this document that are
tested by the test methods established by this methodology.
Implementations of this document are not necessarily required to conform to all possible aspects of
this document, but only to those requirements that are claimed to be supported by the implementation
in an implementation conformance statement (ICS), filled out in accordance with ISO/IEC 19794-1 and
Table A.1 of this document.
6 Conventions
6.1 Coordinate system
The coordinate system used to express the pen position shall be a three-dimensional Cartesian
coordinate system. The x-axis shall be the horizontal axis of the writing plane, with x-coordinates
increasing to the right. The y-axis shall be the vertical axis of the writing plane, with y-coordinates
increasing upwards. The z-axis shall be the axis perpendicular to the writing plane, with z-coordinates
increasing upwards out of the writing plane starting from 0. For an illustration see Figure 1.
Key
P writing plane
Figure 1 — Coordinate system
NOTE The origin of x and y-coordinates is not specified here. Depending on the used technology, it can be,
for instance, in the centre of the writing pad, at its lower left corner, or at the pen position at the first pen-down
event.
© ISO/IEC 2021 – All rights reserved

6.2 Octet and bit order
The more significant bytes of any multi-byte quantity are stored at lower addresses in memory than
(and are transmitted before) less significant bytes.
Within a byte, the bits are numbered from 8 to 1, where bit 8 is the ‘most significant bit’ (msb) and bit 1
the ‘least significant bit’ (lsb).
6.3 Registered format type identifiers
The data records specified in this document may be embedded in a CBEFF-compliant biometric
information record (BIR) (see ISO/IEC 19785-1). This subclause lists the BDB (biometric data block)
format owner identifier and the BDB format type identifiers that shall be used if embedded in a CBEFF
BIR. These identifiers are registered with IBIA, the CBEFF Registration authority (see ISO/IEC 19785-
2).
The format owner of the formats defined in the ISO/IEC 19794 series is ISO/IEC JTC 1/SC 37. The format
owner identifier is 257 (0101 ). Table 1 lists the format type identifiers for the formats defined in this
Hex
document.
Table 1 — Format type identifiers
CBEFF BDB format Short name Full object identifier
type identifier
14 (000e ) signature-sign-time- {iso(1) registration-authority(1) cbeff(19785) biometric-organ-
Hex
series-full ization(0) jtc1-sc37(257) bdbs(0) signature-sign-time-series-
full(14)}
15 (000f ) signature-sign-time- {iso(1) registration-authority(1) cbeff(19785) biometric-organi-
Hex
series-compact zation(0) jtc1-sc37(257) bdbs(0) signature-sign-time-series-com-
pact(15)}
30 (001e ) signature-sign-time- {iso(1) registration-authority(1) cbeff(19785) biometric-organi-
Hex
series-compression zation(0) jtc1-sc37(257) bdbs(0) signature-sign-time-series-com-
pression(30)}
38 (0026 ) {iso(1) registration-authority(1) cbeff(19785) biometric-organ-
Hex
XML-signature-sign-
ization(0) jtc1-sc37(257) bdbs(0) XML-signature-sign-time-se-
time-series
ries(38)}
NOTE 1 The format type identifier for the full format defined in this document (ISO/IEC 19794-7:2021) is the
same as the one for the full format defined in ISO/IEC 19794-7:2007. An indication of which version of the full
format applies can be determined from the version number included in the general header.
NOTE 2 The compact format defined in this document (ISO/IEC 19794-7:2021) is the same as the one defined
in ISO/IEC 19794-7:2007. Hence, the format type identifier for the compact format defined in this edition of ISO/
IEC 19794-7 is also the same as the one for the compact format defined in ISO/IEC 19794-7:2007.
7 Channels
7.1 General
Table 2 lists the channel names and their meanings. Signature/sign time series data captured with
different capture devices or used in different applications may contain data from different channels.
Either the T channel or the DT channel shall be present, or uniform sampling (constant time difference
between adjacent sample points) shall be indicated (see 7.6). Inclusion of at least one other channel is
mandatory.
Annex B provides recommendations for ensuring the quality of signature/sign time series data.
© ISO/IEC 2021 – All rights reserved

Table 2 — Channels
Channel name Description
X x-coordinate (horizontal pen position)
Y y-coordinate (vertical pen position)
Z z-coordinate (height of pen above the writing plane)
VX velocity in x-direction
VY velocity in y-direction
AX acceleration in x-direction
AY acceleration in y-direction
T time
DT time difference
F pen tip force
S pen tip switch state (touching/not touching the writing plane)
TX pen tilt along the x-axis
TY pen tilt along the y-axis
A pen azimuth
E pen elevation
R pen rotation
7.2 Pen tip position channels: X, Y, Z
There are three channels defined for recording pen tip position data in the three-dimensional space.
The X channel is for recording the x-coordinate of the projection of the pen tip on the writing plane. The
Y channel is for recording the y-coordinate of the projection of the pen tip on the writing plane. The Z
channel is for recording the height of the pen tip above the writing plane.
The unit of measurement is millimetres (mm). To restore the actual values, the integer values given
in the record body are to be divided by a scaling value given in the channel description. By choosing
appropriate scaling values, different degrees of accuracy can be expressed.
7.3 Pen tip velocity channels: VX, VY
The VX channel is for recording the pen tip velocity along the x-axis. The VY channel is for recording the
pen tip velocity along the y-axis.
The unit of measurement is millimetres per second (mm/s). To restore the actual values, the integer
values given in the record body are to be divided by a scaling value given in the channel description. By
choosing appropriate scaling values, different degrees of accuracy can be expressed.
7.4 Pen tip acceleration channels: AX, AY
The AX channel is for recording the pen tip acceleration along the x-axis. The AY channel is for recording
the pen tip acceleration along the y-axis.
The unit of measurement is millimetres per square second (mm/s ). To restore the actual values,
the integer values given in the record body are to be divided by a scaling value given in the channel
description. By choosing appropriate scaling values, different degrees of accuracy can be expressed.
7.5 Time channel: T
The T channel is for recording the time elapsed since the first sample.
© ISO/IEC 2021 – All rights reserved

The unit of measurement is seconds (s). To restore the actual values, the integer values given in
the record body are to be divided by a scaling value given in the channel description. By choosing
appropriate scaling values, different degrees of accuracy can be expressed.
7.6 Time difference channel: DT
The DT channel is for recording the time elapsed since the previous sample point.
The unit of measurement is seconds (s). To restore the actual values, the integer values given in
the record body are to be divided by a scaling value given in the channel description. By choosing
appropriate scaling values, different degrees of accuracy can be expressed.
In case of uniform sampling, the channel inclusion field (see 8.3.2.8.1) in the representation header
should indicate the DT channel as present, but the DT channel values should be absent in the
representation body while the channel description preamble (see 8.3.2.8.2) for the DT channel indicates
the time differences between adjacent sample points as constant.
7.7 Pen tip force channel: F
The F channel is for recording the magnitude of the pen tip force.
The unit of measurement is Newton (N). To restore the actual values, the integer values given in
the record body are to be divided by a scaling value given in the channel description. By choosing
appropriate scaling values, different degrees of accuracy can be expressed.
NOTE The direction of the pen-tip force depends on the capture device technology, which is identified by the
capture device technology identifier.
7.8 Pen tip switch state channel: S
The S channel is for recording whether the pen tip touches the writing plane or not. The value shall be 0
in the case that the pen tip does not touch the writing plane. In case of pen-down events, the value shall
also be 0. The value shall be 1 in the case that the pen tip touches the writing plane. In case of pen-up
events, the value shall also be 1.
NOTE Temporarily maintaining a value of 0 when the pen tip starts touching the writing plane allows a
recognition of pen-down events even if the capture device provides no sample points for pen-up strokes.
7.9 Pen orientation channels: TX, TY, A, E, R
There are five channels defined for recording pen orientation data. The A channel is for recording the
pen azimuth. The E channel is for recording the pen elevation. The TX channel is for recording the pen
tilt along the x-axis. The TY channel is for recording the pen tilt along the y-axis. The R channel is for
recording the rotation of the pen about its longitudinal axis. It may be chosen to use:
— pen azimuth and pen elevation, or
— pen tilt along the x and y-axes,
with or without the pen rotation. For illustrations see Figure 2 and Figure 3.
The unit of measurement for the pen orientation angles is degree (°). To restore the actual values,
the integer values given in the record body are to be divided by a scaling value given in the channel
description. By choosing appropriate scaling values, different degrees of accuracy can be expressed.
© ISO/IEC 2021 – All rights reserved

Key
A pen azimuth
E pen elevation
TX pen tilt along the x-axis
TY pen tilt along the y-axis
Figure 2 — Pen orientation angles
Key
R rotation of the pen about its longitudinal axis
Figure 3 — Pen rotation
8 Binary full format
8.1 Record organization
A signature/sign time series data record in the full format shall consist of the following data elements
in the given order:
— a general header, containing descriptive information about the structure and contents of the data
record, and
— a record body, containing at least one signature/sign representation.
© ISO/IEC 2021 – All rights reserved

Figure 4 depicts a signature/sign time series data record in full format. The solid boxes indicate fields
that shall be present. The dashed boxes indicate optional fields. The length of each field in bytes is
indicated in parentheses at the bottom of the corresponding box. The ellipses indicate that more fields
of the same format may follow.
D.1 contains an encoding example in binary full format.
© ISO/IEC 2021 – All rights reserved

Figure 4 — Binary full format
© ISO/IEC 2021 – All rights reserved

8.2 General header
8.2.1 Structure
The general header shall contain information applicable to all signature/sign representations. The
general header shall consist of the following data elements in the given order:
— a format identifier,
— a version number,
— the length of the data record,
— a field indicating the number of subsequent signature/sign representations, and
— a certification flag.
8.2.2 Format identifier
The format identifier shall be recorded in four bytes. The format identifier shall consist of the three
ASCII characters “SDI” (534449 ) followed by Null (00 ) as a string terminator.
Hex Hex
8.2.3 Version number
The number of the version of this document shall be placed in four bytes. This version number shall
consist of three ASCII characters followed by Null (00 ) as a string terminator. The first and second
Hex
characters represent the major revision number and the third character represents the minor revision
number.
In a signature/sign time series data record following the second edition of this document, the version
number shall be 3032 3000 , i.e. “020” (an ASCII ‘0’ followed by an ASCII ‘2’ and an ASCII ‘0’) followed
Hex
by Null (00 ) as a string terminator.
Hex
In a signature/sign time series data record following this third edition of this document, the version
number shall be 3032 3100 , i.e. “021” (an ASCII ‘0’ followed by an ASCII ‘2’ and an ASCII ‘1’) followed
Hex
by Null (00 ) as a string terminator.
Hex
8.2.4 Length of the data record
The length in bytes of the entire BDIR (biometric data interchange record) shall be recorded in four
bytes. This count shall be the total length of the BDIR including the general header and one or more
representation records.
8.2.5 Number of representations
The total number of representation records contained in the BDIR shall be recorded in two bytes. A
minimum of one representation is required.
8.2.6 Certification flag
The one-byte certification flag indicates whether each representation header includes a certification
record. Its value shall be 00 to indicate that no representation contains a certification record.
Hex
NOTE The certification flag has been added for upward compatibility with later versions of the full format in
which representation headers can contain certification records.
© ISO/IEC 2021 – All rights reserved

8.3 Record body
8.3.1 Structure
The record body shall consist of a sequence of at least one signature/sign representation. Each
signature/sign representation shall consist of the following data elements in the given order:
— a representation header, and
— a representation body.
8.3.2 Representation header
8.3.2.1 Structure
A signature/sign representation header shall contain representation-specific descriptive information.
A representation header shall consist of the following data elements in the given order:
— a representation-length field,
— the capture date and time,
— a capture device technology identifier,
— a capture device vendor identifier,
— a capture device type identifier,
— a quality record,
— a sequence of channel descriptions, and
— a field indicating the number of sample points.
8.3.2.2 Length of the signature/sign representation
The four-byte representation-length field denotes the length in bytes of the representation including
the representation header.
8.3.2.3 Capture date and time
The capture date and time field shall indicate when the capture of this representation started in
Coordinated Universal Time (UTC). The capture date and time field shall consist of 9 bytes. Its value
shall be encoded in the form given in ISO/IEC 19794-1.
8.3.2.4 Capture device technology identifier
The capture device technology ID shall be encoded in one byte. This field shall indicate the class of
capture device technology used to acquire the captured biometric sample. A value of 00 indicates
Hex
unknown or unspecified technology. See Table 3 for the list of possible values.
Table 3 — Signature/sign capture device technology identifiers
Identifier Capture device technology
00 Unknown or unspecified
Hex
01 Electromagnetic
Hex
02 Semiconductor
Hex
04 Special pen with acceleration sensors
Hex
© ISO/IEC 2021 – All rights reserved

Table 3 (continued)
Identifier Capture device technology
08 Special pen with optical sensors
Hex
all others Reserved by ISO/IEC JTC 1/SC 37 for future use
8.3.2.5 Capture device vendor identifier
The capture device vendor identifier shall identify the biometric organization that owns the product
that created the BDIR. The capture device vendor identifier shall be encoded in two bytes carrying a
CBEFF biometric organization identifier (registered by IBIA or other approved registration authority).
A value of all zeros shall indicate that the capture device vendor is unreported.
8.3.2.6 Capture device type identifier
The capture device type identifier shall identify the product type that created the BDIR. It shall be
assigned by the registered product owner or other approved registration authority. Registered product
types shall include all valid combinations of writing tablet and pen as a single product where applicable.
A value of all zeros shall indicate that the capture device type is unreported. If the capture device
vendor identifier is 0000 , then also the capture device type identifier shall be 0000 .
Hex Hex
8.3.2.7 Quality record
The quality record shall consist of a length field followed by zero or more quality blocks. The length
field shall consist of one byte. It shall represent the number of quality blocks as an unsigned integer.
Each quality block shall consist of:
— a quality score,
— a quality algorithm vendor identifier, and
— a quality algorithm identifier.
A quality score should express the predicted comparison performance of a representation. A quality
score shall be encoded in one byte as an unsigned integer. Allowed values are:
— 0 to 100 with higher values indicating better quality,
— 255, i.e. ff , for indicating that an attempt to calculate a quality score failed.
Hex
The quality algorithm vendor identifier shall identify the provider of the quality algorithm. The quality
algorithm vendor identifier shall be encoded in two bytes carrying a CBEFF biometric organization
identifier (registered by IBIA or other approved registration authority). A value of all zeros shall
indicate that the quality algorithm vendor is unreported.
The quality algorithm identifier shall identify the vendor's quality algorithm that created the quality
score. It shall be assigned by the provider of the quality algorithm or an approved registration authority.
The quality algorithm identifier shall be encoded in two bytes. A value of all zeros shall indicate that the
quality algorithm is unreported.
8.3.2.8 Channel descriptions
8.3.2.8.1 Channel inclusion field
The channel descriptions field shall begin with a channel inclusion field indicating the presence or
absence of channels.
© ISO/IEC 2021 – All rights reserved

The channel inclusion field shall consist of two bytes. Each bit shall correspond to a channel as shown
in Table 4. A bit value of 1 shall encode the presence of the corresponding channel; a bit value of 0 shall
encode the absence of the corresponding channel.
Table 4 — Format of the channel inclusion field
Channel name Octet Bit position
X 8 (msb)
Y 7
Z 6
VX 5
VY 4
AX 3
AY 2
T 1 (lsb)
DT 8 (msb)
F 7
S 6
TX 5
TY 4
A 3
E 2
R 1 (lsb)
The channel inclusion field shall be followed by a sequence of channel descriptions for the channels
indicated as present in the channel inclusion field. The order of the channel descriptions is determined
by the order of indicated inclusion within the channel inclusion field starting with the X channel. The
channel descriptions are mandatory for all channels present in the signature/sign time series data
record.
EXAMPLE Figure 5 shows the channel inclusion field for signature/sign time series data including the
channels X, Y, T, F, S, A, E and R.
Figure 5 — Example of a channel inclusion field
8.3.2.8.2 Channel description preamble
Each channel description shall begin with a preamble. Each channel description preamble shall consist
of one byte.
Each of the bits 4 through 8 of a channel description preamble shall correspond to a channel attribute
as shown in Table 5. A bit value of 1 shall encode the presence of the corresponding channel attribute;
a bit value of 0 shall encode the absence of the corresponding channel attribute. If any of the bits 4
through 8 of a channel description preamble are set to 1, the preamble shall be followed by a sequence
of channel attributes in the same order as indicated in the preamble starting with the scaling value.
Table 5 — Format of a channel description preamble
Channel attribute Bit position
Scaling value 8 (msb)
© ISO/IEC 2021 – All rights reserved

Table 5 (continued)
Channel attribute Bit position
Minimum possible channel value 7
Maximum possible channel value 6
Average of the channel values 5
Standard deviation of the channel values 4
Constant value 3
Removal of the linear component with respect to time 2
Reserved by ISO/IEC JTC 1/SC 37 for future use 1 (lsb)
A value of 1 for bit 3 of a channel description preamble shall indicate that the value of this channel is
constant. If bit 3 of a channel description preamble is set to 1, then this channel shall be absent in the
representation body even though the representation header indicates the presence of the channel. If the
channel description contains a scaling value, then the constant value of this channel shall be 1 divided
by the scaling value.
EXAMPLE 1 Bit 3 of the DT channel description preamble can be used to indicate a uniform sampling rate.
NOTE 1 For all other channels except the DT channel, bit 3 of the channel description preamble is usually 0.
A value of 1 for bit 2 of a channel description preamble shall indicate that the linear component of the
regression line for this channel has been removed from this channel.
EXAMPLE 2 Bit 2 of the X channel description preamble can be used to indicate that the linear component of
the X-on-T regression line (which can be present due to writing along a horizontal line) has been removed from
the X channel in order to map the X values to a smaller range.
NOTE 2 Since the removal of a linear trend with respect to time is not practically relevant for the time channel,
the value of 1 should not be used for bit 2 of the channel description preamble of the T channel.
The unused tra
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