(B.) Up
Up Tack
(B.) Left
(B.) Right
Left Tack
Right Tack
(B.) Down
Down Tack
| Two Tack Conventions | ||||||
|---|---|---|---|---|---|---|
| Bosworth Convention | London Convention | |||||
| (B.) Up | Up Tack | |||||
| (B.) Left | (B.) Right | Left Tack | Right Tack | |||
| (B.) Down | Down Tack | |||||
| The Nine APL Tack Symbols | |||
|---|---|---|---|
| Symbol | UCS-2 Identifier | APL Name | UCS Name |
|
| U+22A2 | Right Tack | RIGHT TACK |
|
| U+22A3 | Left Tack | LEFT TACK |
|
| U+22A4 | Down Tack | DOWN TACK |
|
| U+22A5 | Up Tack | UP TACK |
| U+234A | Up Tack Underbar | APL FUNCTIONAL SYMBOL DOWN TACK UNDERBAR |
| U+234E | Up Tack Jot | APL FUNCTIONAL SYMBOL DOWN TACK JOT |
| U+2351 | Down Tack Overbar | APL FUNCTIONAL SYMBOL UP TACK OVERBAR |
| U+2355 | Down Tack Jot | APL FUNCTIONAL SYMBOL UP TACK JOT |
| U+2361 | Down Tack Diaeresis | APL FUNCTIONAL SYMBOL UP TACK DIAERESIS |
The problem is apparent in the fourth column, last five rows of the above table. The naming of the composite characters is not consistent with the naming of the tacks from which they are derived.
The Bosworth convention was used in the creation of "APL Characters for Workspace Interchange", (see References).
This list was registered as Set 68 by the Registration Authority for ISO 2475. This gave a home to a key subset of 94 APL characters. from which others may be obtained by "composition". All other characters in the APL Character Repertoire can be represented as combinations of pairs of these 94, but not all pairs are used, only certain ones.
The APL Working Group assisted SC 2 / WG x with the preparation ISO 10646. When the work started, there was an single block of positions, "Row 175" I think, set aside for APL characters. When was done, Registered Set 68 was at hand, and the Bosworth convention was used in the naming of the four tack characters and the five composite characters that use the tack.
We think it was Unicode who scuttled the APL block and saw fit to change the names of the four tack characters, using the London Convention for the names. However, they neglected to change the naming of the corresponding five composite characters that use tacks. This left Unicode (and UCS-2, because they tagged along) with internal nameing inconsistency.
Our problems are further complicated by the fact that SC2/WG2 has taken the position that it is the NAMES that are standarized and not the appearences of the glyphs.
Over time, members of WG3 recognized that the Bosworth Convention has become less widely accepted, and that most APL users and all of the members of the WG3 were personally using the London Convention. Perhaps this was because of the Unicode action mentioned above.
In the APL Character Repertoire, the subject of this note, give names that conform to the London Convention, and not the Bosworth Convention.
Because Committee Draft 1 (ISO-IEC / JTC1 / SC22 / N3067) was prepared while looking at Unicode tables, that same inconsistency crept into CD 1. This has been corrected in the tables of our Working Draft 2.
It is suggested that the APL Working Group (SC22/WG3) ask the UCS Working Group (SC2/WG2) to revise the UCS Names of the five compound symbols (named according to the Bosworth Convention) to agree with the names of the four tack symbols (named according to the London Convention). These changes are as follows:
It is proposed that The APL Working Group request that Registered Set Number 68 (which uses the Bosworth Convention) be revised so that the four tack symbols be renamed so that they agree with the the current names for the four tacks in UCS-2 (which uses the London Convention).
Last Updated on 2000/02/15
Last Updated on 2000/08/01