A custom character entity defined by a publisher, or a custom character from the Unicode Private Use Area for which a bitmap is submitted for the glyph.
This DTD Suite has been designed with Unicode as the basic representation of all special characters. The use of combining characters is supported and encouraged, as is the use of entities defined by the STIX project (http://www.ams.org/STIX/). Unicode values in planes other than Plane 0 may be freely used. Use of private publisher entities and the Unicode Private Use Area is discouraged but supported with the <private-char> element, for which a corresponding bitmap must be submitted using the <glyph-data> element. In cases where an entity name has been generally accepted with a corresponding Unicode number and the entity has not been added to the ISO standard entity sets, a named entity may be defined in the %chars.ent; module (e.g., the Euro €). Because of the potential for conflicts in assignments by different publishers, this DTD Suite does not support assignment of values in the Unicode Private Use Area. Publishers who have defined characters in the Private Use Area must remap those characters to existing Unicode values (using combining characters for special accented characters where appropriate) or must submit bitmaps of those characters using one of the two methods supported under the <private-char> element. Those custom publisher entities for which corresponding Unicode values have not been determined must be tagged with the <private-char> element.
Special characters defined by publishers as custom entities or in the Unicode Private Use Area may not be deposited as is. If they cannot be remapped to existing Unicode values, each must be submitted as a bitmap using the <private-char> element. The most repository-friendly technique is the element <glyph-data>, although individual bitmap files may be submitted with Graphic, Inline. We thank the APS (American Physical Society) for providing us with this technique.
Because there are no completely standard/public agreements on how such characters are to be named and displayed, this technique is to be used instead of a custom general entity reference to provide complete information on the intended character. A document should contain a Private Character (Custom or Unicode) element at each location where a private character is used within the document. The corresponding image for the glyph may be given in the <glyph-data> element, as a <glyph-ref> reference to a <glyph-data> elsewhere in the document, or as an external bitmap file referenced by an Graphic, Inline element.
The attributes for this element supply a human-readable description of the character, for example, “Arrow, normal weight, single line, two-headed, Northwest to Southeast” and a unique name for the character in all uppercase ASCII, similar to names found in the Unicode standard (e.g., “NORTHWEST SOUTHEAST ARROW”).
Any one of:
... <p>...The map symbol indicating these conditions will be a <private-char name="NORTHWEST SOUTHEAST ARROW" description="Arrow, normal weight, single line, two-headed, Northwest to Southeast"> <glyph-data id="NWSEArr" format="PBM" resolution="300" x-size="34" y-size="34"> 0000000000000000000000000000000000 0111111111111100000000000000000000 0111111111111100000000000000000000 0111110000000000000000000000000000 0111110000000000000000000000000000 0111111000000000000000000000000000 0110111100000000000000000000000000 0110011110000000000000000000000000 0110001111000000000000000000000000 0110000111100000000000000000000000 0110000011110000000000000000000000 0110000001111000000000000000000000 0110000000111100000000000000000000 0110000000011110000000000000000000 0110000000001111000000000000000000 0110000000000111100000000000000000 0110000000000011110000000000000000 0000000000000001111000000000000000 0000000000000000111100000000000110 0000000000000000011110000000000110 0000000000000000001111000000000110 0000000000000000000111100000000110 0000000000000000000011110000000110 0000000000000000000001111000000110 0000000000000000000000111100000110 0000000000000000000000011110000110 0000000000000000000000001111000110 0000000000000000000000000111100110 0000000000000000000000000011110110 0000000000000000000000000001111110 0000000000000000000000000001111110 0000000000000000011111111111111110 0000000000000000011111111111111110 0000000000000000000000000000000000 </glyph-data></private-char>. The NOAA 1993 standard definition of <private-char name="NORTHWEST SOUTHEAST ARROW" description="Arrow, normal weight, single line, two-headed, Northwest to Southeast"> <glyph-ref glyph-data="NWSEArr"/></private-char> will apply. </p> ...