The IfcFontWeight type defines the weight of the font. Values are:

NOTE  Definition according to Cascading Style Sheets, level 1
The values '100' to '900' form an ordered sequence, where each number indicates a weight that is at least as dark as its predecessor. The keyword 'normal' is synonymous with '400', and 'bold' is synonymous with '700'. Keywords other than 'normal' and 'bold' have been shown to be often confused with font names and a numerical scale was therefore chosen for the 9-value list.
Fonts (the font data) typically have one or more properties whose values are names that are descriptive of the "weight" of a font. There is no accepted, universal meaning to these weight names. Their primary role is to distinguish faces of differing darkness within a single font family. Usage across font families is quite variant; for example a font that you might think of as being bold might be described as being Regular, Roman, Book, Medium, Semi- or DemiBold, Bold, or Black, depending on how black the "normal" face of the font is within the design. Because there is no standard usage of names, the weight property values in CSS1 are given on a numerical scale in which the value '400' (or 'normal') corresponds to the "normal" text face for that family. The weight name associated with that face will typically be Book, Regular, Roman, Normal or sometimes Medium.
The association of other weights within a family to the numerical weight values is intended only to preserve the ordering of darkness within that family. However, the following heuristics tell how the assignment is done in typical cases:
The following two examples illustrate the process. Assume four weights in the "Example1" family, from lightest to darkest: Regular, Medium, Bold, Heavy. And assume six weights in the "Example2" family: Book, Medium, Bold, Heavy, Black, ExtraBlack. Note how in the second example it has been decided not to assign "Example2 ExtraBlack" to anything.
Available faces       | Assignments   | Filling the holes
"Example1 Regular" | 400 | 100, 200, 300
"Example1 Medium" | 500 |
"Example1 Bold" | 700 | 600
"Example1 Heavy" | 800 | 900
Available faces       | Assignments   | Filling the holes
"Example2 Book" | 400 | 100, 200, 300
"Example2 Medium" | 500 |
"Example2 Bold" | 700 | 600
"Example2 Heavy" | 800 |
"Example2 Black" | 900 |
"Example2 ExtraBlack" | (none) |
NOTE  Type adopted from font-weight defined in CSS-1.
HISTORY  New type in IFC2x2 Add2.

XSD Specification:

 <xs:simpleType name="IfcFontWeight">
  <xs:restriction base="xs:normalizedString"/>
 <xs:element name="IfcFontWeight-wrapper" nillable="true">
    <xs:extension base="ifc:IfcFontWeight">
     <xs:attributeGroup ref="ifc:instanceAttributes"/>

EXPRESS Specification:

TYPE IfcFontWeight = STRING;
WR1 : SELF IN ['normal','small-caps','100','200','300','400','500','600','700','800','900']

Link to EXPRESS-G diagram EXPRESS-G diagram

Formal Propositions:

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