Constraints

Constraints0

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Constraints

AHaving accepted the necessity for subdirectory searching, the TWGAturned its attention next to other constraints placed on the TDS.>The other constraints arise because it must be possible to usethe TDS on any platform.D

Alphabetic Case in Filenames

FMany, but not all, operating systems disregard the distinction between?upper- and lowercase letters in filenames. The ISO-9660 format@(described below) does not allow mixed-case names. The TDS does<not require monocase names, although it is clear that=mixed-case filenames may cause problems in some environments.=Filenames which are identical except with respect to case are&particularly likely to be troublesome./

CD-ROMs

<One use of the TDS will be the creation of mountable genericATeX-related distributions on CD-ROM. CD-ROM vendors will want toAuse ISO-9660 format because it is the only universally acceptable6file system format for CD-ROMs. ISO-9660 is portable,>but it imposes strict limitations on file and directory names:

File and directory names, not including any directory path or extension* part, may not exceed eight characters.K
Filenames may have a single extension. Extensions may not exceed three characters.=
Names and extensions may consist of only the& characters A--Z,, 0--9, and underscore. 2
A period separates the filename from the1 extension. It is always present, even if the! name or extension is missing . (e.g., FILENAME., .EXT).;
A version number, ranging from 1--32767, is found? at the end of the file extension, separated by a semicolon $ (e.g., FILENAME.EXT;1).<
Only eight directory levels are allowed, including9 the top-level (mounted) directory. Thus, the deepest valid TDS path is:
```
$texmf/L2/L3/L4/L5/L6/L7/L8/FOO.BAR;11     2  3  4  5  6  7  8
```
A Here is the deepest TDS example, which needs only seven levels:
```
+texmf/fonts/pk/cx/public/cm/dpi300/cmr10.pk1     2     3  4      5  6  7  
```

%Note: Some systems display a modified:format of ISO-9660 names, mapping alphabetic characters to>lowercase, removing version numbers and trailing periods, etc.>This does not affect the format of names on the CD-ROM itself.