0 
( 
/ 0 (
$
? Many TeX installations currently store large numbers of related | files in single directories. Frequently, for example, all TFM files go in a single directory and most, if not all,@ TeX input files (LaTeX style files, Plain TeX macro files, etc.) go in another single directory.
= This monolithic arrangement makes maintenance of a TeX system > difficult: it is difficult to determine what files are used byC which packages, what files need to be updated when a new version is C installed, or what files should be deleted if a package is removed. 9 It can also be the source of catastrophic error if two or < more packages happen to have input files with the same name.
3 Therefore, the TWG felt each package should be in a A separate directory. But we recognized that explicitly listing all D directories to be searched would be unbearable. There are dozens of0 packages a site may wish to install. Aside fromE anything else, listing that many directories would lead to paths many E thousands of characters long, overflowing the available space on some systems.
F Also, if all directories are explicitly listed, installing or removingA a new package would mean changing a path as well as installing or > removing the actual files. This would be a time-consuming andB error-prone operation, even with implementations that provide some= ability to specify the directories to search at runtime (in a # TEXINPUTS environment variable or a E system configuration file, for example). On systems without any form 6 of runtime configuration, it would require recompiling software, an intolerable burden.
@ As a result, the TWG concluded that a comprehensive TDS requiredK that implementations of TeX must support some form of implicit subdirectory D searching. In other words, it must be possible to specify that TeX,B METAFONT, and their companion utilities search in both a specified7 directory and recursively through all subdirectories of . that directory when looking for an input file. We encourageD implementors to provide subdirectory searching (at the option of the" installer and user) for all paths.
> The TDS does not specify the order in which subdirectories areG descended. It follows that two identically named files in a search path 8 leads to ambiguity. The TDS does not define which one isA found. In order to resolve this ambiguity, a search path must be B specified that lists the respective subtrees in the desired search order.
: The TDS does not specify a syntax for specifying recursiveD searching, but we encourage implementors to provide interoperability wherever possible. See Section A.4, Subdirectory Searching Syntax for a list.