2 Document XML structure

2.1 Overview 

<?xml version='1.0' encoding='utf-8'?>
<designspace format="5.1">
    <axes>
        <!-- define axes here -->
        <axis... />
        <mappings>
            <!-- define axis mappings here -->
            <!-- New in version 5.1 -->
            <mapping... />
        </mappings>
    </axes>
    <labels>
        <!-- define STAT format 4 labels here -->
        <!-- New in version 5.0 -->
        <label... />
    </labels>
    <sources>
        <!-- define masters here -->
        <source... />
    </sources>
    <variable-fonts>
        <!-- define variable fonts here -->
        <!-- New in version 5.0 -->
        <variable-font... />
    </variable-fonts>
    <instances>
        <!-- define instances here -->
        <instance... />
    </instances>
    <rules>
        <!-- define rules here -->
        <rule... />
    </rules>
    <lib>
        <dict>
            <!-- store custom data here -->
        </dict>
    </lib>
</designspace>

2.2 `<axes>` element 

The <axes> element contains one or more <axis> elements.

Attributes

elidedfallbackname: optional, string. STAT Style Attributes Header field elidedFallbackNameID. See: OTSpec STAT Style Attributes Header

Added in version 5.0.

2.2.1 `<axis>` element 

Define a single axis
Child element of axes
The axis can be either continuous (as in version 4.0) or discrete (new in version 5.0). Discrete axes have a list of values instead of a range minimum and maximum.

Attributes

name: required, string. Name of the axis that is used in the location elements.
tag: required, string, 4 letters. Some axis tags are registered in the OpenType Specification.
default: required, number. The default value for this axis, in user space coordinates.
hidden: optional, 0 or 1. Records whether this axis needs to be hidden in interfaces.

For a continuous axis:

minimum: required, number. The minimum value for this axis, in user space coordinates.
maximum: required, number. The maximum value for this axis, in user space coordinates.

For a discrete axis:

values: required, space-separated numbers. The exhaustive list of possible values along this axis.

Added in version 5.0.

Example

<axis name="weight" tag="wght" minimum="1" maximum="1000" default="400">

<!--
  Discrete axes provide a list of discrete values.
  No interpolation is allowed between these.
-->
<axis name="Italic" tag="ital" default="0" values="0 1">

2.2.1.1 `<labelname>` element (axis)

Defines a human readable name for UI use.
Optional for non-registered axis names.
Can be localised with xml:lang
Child element of <axis> or <label>

Attributes

xml:lang: required, string. XML language definition

Value

The natural language name of this axis or STAT label.

Example

<labelname xml:lang="fa-IR">قطر</labelname>
<labelname xml:lang="en">Wéíght</labelname>

2.2.1.2 `<map>` element 

Defines a single node in a series of input value (user space coordinate) to output value (designspace coordinate) pairs.
Together these values transform the designspace.
Child of <axis> element.

Example

<map input="1.0" output="10.0" />
<map input="400.0" output="66.0" />
<map input="1000.0" output="990.0" />

2.2.1.3 `<labels>` element (axis)

The <labels> element contains one or more <label> elements, and can indicate this axis’ STAT ordering.

Added in version 5.0.

Attributes

ordering: optional, int, default: natural position of this axis in the list of axes. STAT table field axisOrdering for this axis.

See: OTSpec STAT Axis Record

2.2.1.3.1 `<label>` element (axis)

Define STAT format 1, 2, 3 labels for the locations on this axis.
The axis can have several child <label> elements, one for each STAT entry.
This <label> element can have several <labelname> child elements, to provide translations of its name attribute.

Added in version 5.0.

Attributes

name: required, string. the name of this label
elidable: optional, boolean, default: false. STAT flag ELIDABLE_AXIS_VALUE_NAME.
oldersibling: optional, boolean, default: false. STAT flag OLDER_SIBLING_FONT_ATTRIBUTE.

See: OTSpec STAT Flags

Depending on the intended target STAT format, use a combination of the following field, all in user coordinates. Check the following table for the format correspondences.

uservalue: (required) STAT field value (format 1, 3) or nominalValue (format 2).
userminimum: STAT field rangeMinValue (format 2).
usermaximum: STAT field rangeMaxValue (format 2).
linkeduservalue: STAT field linkedValue (format 3).

STAT Format	uservalue	userminimum	usermaximum	linkeduservalue
1	✅	❌	❌	❌
2	✅	✅	✅	❌
3	✅	❌	❌	✅

Example

<label userminimum="200" uservalue="200" usermaximum="250" name="Extra Light">
    <labelname xml:lang="de">Extraleicht</labelname>
    <labelname xml:lang="fr">Extra léger</labelname>
</label>
<label userminimum="350" uservalue="400" usermaximum="450" name="Regular" elidable="true" />

2.2.1.3.1.1 `<labelname>` element (axis STAT label)

User-facing translations of this STAT label. Keyed by xml:lang code.

Added in version 5.0.

Same attribute and value as the axis’ <labelname> element.

2.2.2 Example of all axis elements together 

<axes elidedfallbackname="Regular">
    <axis default="1" maximum="1000" minimum="0" name="weight" tag="wght">
        <labelname xml:lang="fa-IR">قطر</labelname>
        <labelname xml:lang="en">Wéíght</labelname>
        <labels>
            <label userminimum="200" uservalue="200" usermaximum="250" name="Extra Light">
                <labelname xml:lang="de">Extraleicht</labelname>
                <labelname xml:lang="fr">Extra léger</labelname>
            </label>
            <label userminimum="350" uservalue="400" usermaximum="450" name="Regular" elidable="true" />
        </labels>
    </axis>
    <axis default="100" maximum="200" minimum="50" name="width" tag="wdth">
        <map input="50.0" output="10.0" />
        <map input="100.0" output="66.0" />
        <map input="200.0" output="990.0" />
    </axis>
</axes>

2.2.3 `<mappings>` element 

Define an axis mappings group.
Child element of axes

Attributes

description: optional, string. the description of this mappings group

Added in version 5.2.

2.2.3.1 `<mapping>` element 

Defines an axis mapping.
Child element of <mappings>

Attributes

description: optional, string. the description of this mapping

Added in version 5.2.

2.2.3.1.1 `<input>` element 

Defines the input location of an axis mapping.
Child element of <mapping>
Contains one or more <dimension> elements with designspace locations.

Added in version 5.1.

2.2.3.1.2 `<output>` element 

Defines the output location of an axis mapping.
Child element of <mapping>
Contains one or more <dimension> elements with designspace locations.

Added in version 5.1.

2.2.4 Example of all mappings elements together 

<mappings>
    <mapping>
        <input>
            <dimension name="weight" xvalue="900"/>
            <dimension name="width" xvalue="150"/>
        </input>
        <output>
            <dimension name="weight" xvalue="870"/>
        </output>
    </mapping>
</mappings>

2.3 `<labels>` element (top-level)

The <labels> element contains one or more <label> elements.

Added in version 5.0.

2.3.1 `<label>` element (top-level)

Define STAT format 4 labels for a free-standing location.
The designspace can have several top-level <label> elements, one for each STAT format 4 entry.
This <label> element must have a child <location> element that represents the location to which the label applies.
This <label> element may have several child <labelname> elements to provide translations of its name attribute.

See: OTSpec STAT Axis value table, format 4

Added in version 5.0.

Attributes

name: required, string. the name of this label
elidable: optional, boolean, default: false. STAT flag ELIDABLE_AXIS_VALUE_NAME.
oldersibling: optional, boolean, default: false. STAT flag OLDER_SIBLING_FONT_ATTRIBUTE.

See: OTSpec STAT Flags

2.3.1.1 `<location>` element (top-level STAT label)

Defines a coordinate in either user or design space.
Encodes a dictionary of { axisname: axisvalue }.
Also used in <source>, <instance> and <glyph> elements.
This <location> element must have one or more child <dimension> elements.

2.3.1.1.1 `<dimension>` element 

Child element of <location>, input, or output elements

Attributes

name: required, string. Name of the axis.

Depending on whether you’re representing a location in user or design coordinates, provide one of the attributes below.

For user-space coordinates:

uservalue: required, number. The value on this axis in user coordinates.

Added in version 5.0.

For design-space coordinates:

xvalue: required, number. The value on this axis in design coordinates.
yvalue: optional, number. Separate value for anisotropic interpolations.

Example

<location>
    <dimension name="Width" uservalue="125" />
    <dimension name="Weight" xvalue="10" yvalue="20.5" />
</location>

2.3.1.2 `<labelname>` element (top-level STAT label)

User-facing translations of this STAT label. Keyed by xml:lang code.

Added in version 5.0.

Same attribute and value as the axis’ <labelname> element.

2.4 `<rules>` element 

The <rules> element contains one or more <rule> elements.

The rules are evaluated in this order.

Rules describe designspace areas in which one glyph should be replaced by another. A rule has a name and a number of conditionsets. The rule also contains a list of glyphname pairs: the glyphs that need to be substituted. For a rule to be triggered only one of the conditionsets needs to be true, OR. Within a conditionset all conditions need to be true, AND.

Attributes

processing: flag, optional. Valid values are [first, last]. This flag indicates whether the substitution rules should be applied before or after other glyph substitution features.
- If no processing attribute is given, interpret as first, and put the substitution rule in the rvrn feature.
- If processing is last, put it in rclt.
- The default is first. For new projects, you probably want last. See the following issues for more information: fontTools#1371 fontTools#2050
- If you want to use a different feature(s) altogether, e.g. calt, use the lib key com.github.fonttools.varLib.featureVarsFeatureTag.
```
<lib>
    <dict>
        <key>com.github.fonttools.varLib.featureVarsFeatureTag</key>
        <string>calt</string>
    </dict>
</lib>
```
  This can also take a comma-separated list of feature tags, e.g. salt,ss01, if you wish the same rules to be applied with several features.

2.4.1 `<rule>` element 

Defines a named rule.
Each <rule> element contains one or more <conditionset> elements.
Only one <conditionset> needs to be true to trigger the rule (logical OR). An empty condition set is considered to be true, as in, the rule will be always-on.
All conditions in a <conditionset> must be true to make the <conditionset> true. (logical AND)
For backwards compatibility a <rule> can contain <condition> elements outside of a conditionset. These are then understood to be part of a single, implied, <conditionset>. Note: these conditions should be written wrapped in a conditionset.
A rule element needs to contain one or more <sub> elements in order to be compiled to a variable font.
Rules without sub elements should be ignored when compiling a font.
For authoring tools it might be necessary to save designspace files without <sub> elements just because the work is incomplete.

Attributes

name: optional, string. A unique name that can be used to identify this rule if it needs to be referenced elsewhere. The name is not important for compiling variable fonts.

2.4.1.1 `<conditionset>` element 

Child element of <rule>
Contains zero or more <condition> elements.

2.4.1.1.1 `<condition>` element 

Child element of <conditionset>
Between the minimum and maximum this condition is True.
minimum and maximum are in designspace coordinates.
If minimum is not available, assume it is axis.minimum, mapped to designspace coordinates.
If maximum is not available, assume it is axis.maximum, mapped to designspace coordinates.
The condition must contain at least a minimum or maximum or both.

Attributes

name: string, required. Must match one of the defined axis name attributes.
minimum: number, required*. The low value, in design coordinates.
maximum: number, required*. The high value, in design coordinates.

2.4.1.2 `<sub>` element 

Child element of <rule>.
Defines which glyph to replace when the rule evaluates to True.
The <sub> element contains a pair of glyphnames. The name attribute is the glyph that should be visible when the rule evaluates to False. The with attribute is the glyph that should be visible when the rule evaluates to True.

Attributes

name: string, required. The name of the glyph this rule looks for.
with: string, required. The name of the glyph it is replaced with.

Example

Example with an implied <conditionset>. Here the conditions are not contained in a conditionset.

<rules processing="last">
    <rule name="named.rule.1">
        <condition minimum="250" maximum="750" name="weight" />
        <condition minimum="50" maximum="100" name="width" />
        <sub name="dollar" with="dollar.alt"/>
    </rule>
</rules>

Example with <conditionsets>. All conditions in a conditionset must be true.

<rules>
    <rule name="named.rule.2">
        <conditionset>
            <condition minimum="250" maximum="750" name="weight" />
            <condition minimum="50" maximum="100" name="width" />
        </conditionset>
        <conditionset>
            <condition... />
            <condition... />
        </conditionset>
        <sub name="dollar" with="dollar.alt"/>
    </rule>
</rules>

2.5 `<sources>` element 

The <sources> element contains one or more <source> elements.

2.5.1 `<source>` element 

Defines a single font or layer that contributes to the designspace.
Child element of <sources>
Location in designspace coordinates.

Attributes

familyname: optional, string. The family name of the source font. While this could be extracted from the font data itself, it can be more efficient to add it here.
stylename: optional, string. The style name of the source font.
name: optional, string. A unique name that can be used to identify this font if it needs to be referenced elsewhere.
filename: required, string. A path to the source file, relative to the root path of this document. The path can be at the same level as the document or lower.
layer: optional, string. The name of the layer in the source file. If no layer attribute is given assume the foreground layer should be used.

2.5.1.1 `<familyname>` element: localised names for sources 

Localised family names for sources can be included with this <familyname> element with an xml:lang attribute: XML language definition

Added in version 5.0.

Example

<familyname xml:lang="fr">Montserrat</familyname>
<familyname xml:lang="ja">モンセラート</familyname>

2.5.1.2 `<location>` element (source)

Defines the coordinates of this source in the design space.

2.5.1.2.1 `<dimension>` element (source)

2.5.1.3 `<lib>` element (source)

Example: <lib copy="1" />
Child element of <source>
Defines if the instances can inherit the data in the lib of this source.
MutatorMath only.

Deprecated since version 5.0.

Note

Don’t confuse with other <lib> elements which allow storing arbitrary data. Sources don’t have such a <lib> because usually the backing UFO file has one itself.

2.5.1.4 `<info>` element 

Example: <info copy="1" />
Child element of <source>
Defines if the instances can inherit the non-interpolating font info from this source.
MutatorMath only.

Deprecated since version 5.0.

2.5.1.5 `<features>` element 

Example: <features copy="1" />
Defines if the instances can inherit opentype feature text from this source.
Child element of <source>
MutatorMath only.

Deprecated since version 5.0.

2.5.1.6 `<glyph>` element (source)

Example: <glyph mute="1" name="A"/>
In a <source> element this states if a glyph is to be excluded from the calculation.
MutatorMath only.

Attributes

mute: optional attribute, number 1 or 0. Indicate if this glyph should be ignored as a master.

Note

Do not confuse with the <glyph> element in instances, which achieves something different.

2.5.1.7 `<kerning>` element (source)

Example: <kerning mute="1" />
Can appear in <source> as well as in <instance> elements.
MutatorMath only.

Attributes

mute: required attribute, number 1 or 0. Indicate if the kerning data from this source is to be excluded from the calculation.
- If the kerning element is not present, assume mute=0, yes, include the kerning of this source in the calculation.

Example

<source familyname="MasterFamilyName" filename="masters/masterTest1.ufo" name="master.ufo1" stylename="MasterStyleNameOne">
    <location>
        <dimension name="width" xvalue="0.000000" />
        <dimension name="weight" xvalue="0.000000" />
    </location>
    <glyph mute="1" name="A" />
    <glyph mute="1" name="Z" />
</source>

2.6 `<variable-fonts>` element 

The <variable-fonts> element contains one or more <variable-font> elements.

Added in version 5.0.

2.6.1 `<variable-font>` element 

Child of <variable-fonts>
Describe a variable font that can be built from an interpolating subset of the design space.
The document may have zero to many variable fonts.
- If no variable fonts are defined, and all the axes are continuous, then we assume, as in version 4 of the format, that the whole document describes one variable font covering the whole space.
Each variable font covers a subset of the whole designspace, defined using <axis-subset> elements.
Each variable font can have custom associated data using a <lib> element.

Added in version 5.0.

Attributes

name: string, required. Each variable font has a name, that can be used by build tools to refer to the font that gets built from this element.
filename: string, optional. This filename will be used by tools to decide where to store the built font on the disk. If not given, a filename can be computed from the name. The filename may include an extension (e.g. .ttf) and the build tools can replace that extension with another (e.g. .otf or .woff2) as needed.

Example

<variable-font name="MyFontVF_Italic">
  <axis-subsets>
    <axis-subset name="Weight"/>
    <axis-subset name="Italic" uservalue="1"/>
  </axis-subsets>
</variable-font>

2.6.1.1 `<axis-subsets>` element 

Child of <variable-font>
Defines the portion of the design space that this variable font covers.
Each axis that you want to include in the VF needs to be mentioned here.
Not mentioning an axis is equivalent to slicing the space at the default value of that axis.

Added in version 5.0.

2.6.1.1.1 `<axis-subset>` element 

Child of <axis-subsets>
Defines the subset of one axis, by name="", that the variable font covers.
If this axis is continuous, the VF can either cover:
1. the whole axis
```
<axis-subset name="Weight"/>
```
2. a sub-range of the full axis
```
<axis-subset name="Weight" userminimum="400" usermaximum="500" userdefault="400"/>
```
3. a specific value along that axis; then the axis is not functional in the VF but the design space is sliced at the given location. Note: While valid to have a specific value that doesn’t have a matching <source> at that value, currently there isn’t an implentation that supports this. See this fontmake issue.
```

<axis-subset name="Weight" uservalue="700"/>
```
If this axis is discrete, then only the third option above is possible: give one value along the axis.
```

<axis-subset name="Italic" uservalue="1"/>
```

Added in version 5.0.

Attributes

name: required, string. Name of the axis to subset.

When defining a range:

userminimum: optional, number. Lower end of the range, in user coordinates. If not mentioned, assume the axis’s minimum.
usermaximum: optional, number. Upper end of the range, in user coordinates. If not mentioned, assume the axis’s maximum.
userdefault: optional, number. New default value of subset axis, in user coordinates. If not mentioned, assume the axis’s default. If the axis’s default falls outside of the subset range, then the new default will be the extremum that is closest to the full axis’s default.

When defining a single value:

uservalue: required, number. Single value, in user coordinates, at which to snapshot the design space while building this VF.

2.6.1.2 `<lib>` element (variable font)

Arbitrary data about this variable font.

Added in version 5.0.

See also

2.8 <lib> element (top-level)

Here is an example of using the public.fontInfo lib key to gain more granular control over the font info of a variable font, in this case setting some names to reflect the fact that this is a Narrow variable font subset from the larger designspace. This lib key allows font info in variable fonts to be more specific than the font info of the sources.

Example

<variable-font name="MyFontNarrVF">
  <axis-subsets>
    <axis-subset name="Weight"/>
    <axis-subset name="Width" uservalue="75"/>
  </axis-subsets>
  <lib>
    <dict>
      <key>public.fontInfo</key>
      <dict>
        <key>familyName</key>
        <string>My Font Narrow VF</string>
        <key>styleName</key>
        <string>Regular</string>
        <key>postscriptFontName</key>
        <string>MyFontNarrVF-Regular</string>
        <key>trademark</key>
        <string>My Font Narrow VF is a registered trademark...</string>
      </dict>
    </dict>
  </lib>
</variable-font>

2.6.1.3 Instances included in the variable font 

A designspace version 5 lists many instances and variable fonts. Each variable font gets in its fvar table whichever instances fall within the bounds of the variable font's subset axes. — Illustration of instances included in a variable font.

2.7 `<instances>` element 

The <instances> element contains one or more <instance> elements.

2.7.1 `<instance>` element 

Defines a single font that can be calculated with the designspace.
Child element of <instances>
For use in varLib the instance element really only needs the names and the location. The <glyphs> element is not required.
MutatorMath uses the <glyphs> element to describe how certain glyphs need different masters, mainly to describe the effects of conditional rules in Superpolator.
Location in designspace coordinates.

Attributes

familyname: required, string. The family name of the instance font. Corresponds with font.info.familyName
stylename: required, string. The style name of the instance font. Corresponds with font.info.styleName
name: required, string. A unique name that can be used to identify this font if it needs to be referenced elsewhere.
filename: string. Required for MutatorMath. A path to the instance file, relative to the root path of this document. The path can be at the same level as the document or lower.
postscriptfontname: string. Optional for MutatorMath. Corresponds with font.info.postscriptFontName
stylemapfamilyname: string. Optional for MutatorMath. Corresponds with styleMapFamilyName
stylemapstylename: string. Optional for MutatorMath. Corresponds with styleMapStyleName
location: string. Optional. Describes the location of this instance, taking it from the root level <labels> (STAT format 4) element with the same name as the string.

Added in version 5.0.

2.7.1.1 `<location>` element (instance)

Defines the coordinates of this instance in the design space.

2.7.1.1.1 `<dimension>` element (instance)

2.7.1.2 `<lib>` element (instance)

Arbitrary data about this instance.

See also

2.8 <lib> element (top-level)

2.7.1.3 `<stylename>`, `<familyname>`, `<stylemapstylename>`, `<stylemapfamilyname>` elements: localised names for instances 

Localised names for instances can be included with these simple elements with an xml:lang attribute: XML language definition

<stylename>
<familyname>
<stylemapstylename>
<stylemapfamilyname>

Example

<stylename xml:lang="fr">Demigras</stylename>
<stylename xml:lang="ja">半ば</stylename>
<familyname xml:lang="fr">Montserrat</familyname>
<familyname xml:lang="ja">モンセラート</familyname>
<stylemapstylename xml:lang="de">Standard</stylemapstylename>
<stylemapfamilyname xml:lang="de">Montserrat Halbfett</stylemapfamilyname>
<stylemapfamilyname xml:lang="ja">モンセラート SemiBold</stylemapfamilyname>

2.7.1.4 Example for varLib 

<instance familyname="InstanceFamilyName" filename="instances/instanceTest2.ufo" name="instance.ufo2" postscriptfontname="InstancePostscriptName" stylemapfamilyname="InstanceStyleMapFamilyName" stylemapstylename="InstanceStyleMapStyleName" stylename="InstanceStyleName">
<location>
    <dimension name="width" xvalue="400" yvalue="300" />
    <dimension name="weight" xvalue="66" />
</location>
<lib>
    <dict>
        <key>com.coolDesignspaceApp.specimenText</key>
        <string>Hamburgerwhatever</string>
    </dict>
</lib>
</instance>

Here is an example using STAT format 4 labels to define the location of the instance directly.

<?xml version='1.0' encoding='utf-8'?>
<designspace format="5.0">
    <!-- ... -->
    <labels>
        <!-- define STAT format 4 labels here -->
        <!-- New in version 5.0 -->
        <label name="Extra Light">
            <location>
                <dimension name="weight" uservalue="123" />
            </location>
        </label>
    </labels>
    <!-- ... -->
    <instances>
        <instance filename="instances/labelled.ufo" location="Extra Light" />
    </instances>
</designspace>

Here is an example of using the public.fontInfo lib key to gain more granular control over the font info of the instances.

openTypeNameWWSFamilyName and openTypeNameWWSSubfamilyName are not able to be set by attributes on the <instance> element. The openTypeOS2WeightClass key is superseding the value that would have been set by the weight axis value. The trademark key is superseding the value that would have been set by UFO source at the origin. If the designer wishes to set name records for other encodings, platforms or laguages, they should do so using the openTypeNameRecords key, like they would in a UFO source.

See UFO3 fontinfo.plist specification.

<instance familyname="My Font" stylename="Text Light" filename="instances/MyFont-TextLight.ufo" postscriptfontname="MyFont-TextLight" stylemapfamilyname="My Font Text Light" stylemapstylename="regular">
    <location>
        <dimension name="optical" xvalue="6"/>
        <dimension name="weight" xvalue="325"/>
    </location>
    <lib>
        <dict>
            <key>public.fontInfo</key>
            <dict>
                <key>openTypeNameWWSFamilyName</key>
                <string>My Font Text</string>
                <key>openTypeNameWWSSubfamilyName</key>
                <string>Light</string>
                <key>openTypeOS2WeightClass</key>
                <integer>300</integer>
                <key>trademark</key>
                <string>My Font Text Light is a registered trademark...</string>
                <key>openTypeNameRecords</key>
                <array>
                    <dict>
                        <key>encodingID</key>
                        <integer>1</integer>
                        <key>languageID</key>
                        <integer>1031</integer>
                        <key>nameID</key>
                        <integer>7</integer>
                        <key>platformID</key>
                        <integer>3</integer>
                        <key>string</key>
                        <string>Meine Schrift Text Leicht ist eine registrierte Marke...</string>
                    </dict>
                </array>
            </dict>
        </dict>
    </lib>
</instance>

2.7.1.5 `<glyphs>` element (instance)

Container for <glyph> elements.
Optional
MutatorMath only.

Deprecated since version 5.0.

2.7.1.5.1 `<glyph>` element (instance)

Child element of <glyphs>
May contain a <location> element.

Deprecated since version 5.0.

Attributes

name: string. The name of the glyph.
unicode: string. Unicode values for this glyph, in hexadecimal. Multiple values should be separated with a space.
mute: optional attribute, number 1 or 0. Indicate if this glyph should be supressed in the output.

2.7.1.5.1.1 `<note>` element 

String. The value corresponds to glyph.note in UFO.

Deprecated since version 5.0.

2.7.1.5.1.2 `<masters>` element 

Container for <master> elements
These <master> elements define an alternative set of glyph masters for this glyph.

Deprecated since version 5.0.

2.7.1.5.1.2.1 `<master>` element 

Defines a single alternative master for this glyph.

Deprecated since version 5.0.

Attributes

glyphname: the name of the alternate master glyph.
source: the identifier name of the source this master glyph needs to be loaded from

2.7.1.5.2 Example for MutatorMath 

<instance familyname="InstanceFamilyName" filename="instances/instanceTest2.ufo" name="instance.ufo2" postscriptfontname="InstancePostscriptName" stylemapfamilyname="InstanceStyleMapFamilyName" stylemapstylename="InstanceStyleMapStyleName" stylename="InstanceStyleName">
<location>
    <dimension name="width" xvalue="400" yvalue="300" />
    <dimension name="weight" xvalue="66" />
</location>
<glyphs>
    <glyph name="arrow2" />
    <glyph name="arrow" unicode="0x4d2 0x4d3">
    <location>
        <dimension name="width" xvalue="100" />
        <dimension name="weight" xvalue="120" />
    </location>
    <note>A note about this glyph</note>
    <masters>
        <master glyphname="BB" source="master.ufo1">
        <location>
            <dimension name="width" xvalue="20" />
            <dimension name="weight" xvalue="20" />
        </location>
        </master>
    </masters>
    </glyph>
</glyphs>
<kerning />
<info />
<lib>
    <dict>
        <key>com.coolDesignspaceApp.specimenText</key>
        <string>Hamburgerwhatever</string>
    </dict>
</lib>
</instance>

2.8 `<lib>` element (top-level)

The <lib> element contains arbitrary data.

Child element of <designspace>, <variable-font> and <instance>
If present, content must be an XML Property List (plist). <https://en.wikipedia.org/wiki/Property_list>__
Contains arbitrary data about the whole document or about a specific variable font or instance.
Items in the dict need to use reverse domain name notation <https://en.wikipedia.org/wiki/Reverse_domain_name_notation>__

Example:

<lib>
    <dict>
        <key>com.company.fontEditor.myString</key>
        <string>The contents use the PLIST format.</string>
    </dict>
</lib>