I appreciate the explanations provided by Mr. Philip Melzer from Library
of Congress for my questions.  Mr. Melzer mentioned that "As with other
romanization schemes, Chinese romanization procedures have been adapted
for use in American libraries."  While the statement sounds reasonable, we
are not convinced that the two changes made on the use of umlaut and
apostrophe are necessary.  Since Hanyu Pinyin Fang'an has been adopted as
an international standard (ISO 7098), it should be followed as closely as
possible, for the sake of data storage and transmission and information
exchange.  Therefore, the Hong Kong University of Science and Technology
Library will apply the following rules as set in Hanyu Pinyin Fang'an in
its pinyin conversion: 

1. The umlaut shall be kept when  and e spelled with n or l.

While we understand the intention of using nue and lue instead of ne and
le to minimize the use of diacritics, since the characters involved are
in a very small number and they rarely appear in the library catalog, it
does not seem worthwhile to deviate from Hanyu Pinyin Fang'an.

2. The syllable-dividing mark (apostrophe) shall be used between syllables
beginning with a, o, e and the syllable preceding them if the division of
two syllables is obscure when they are aggregated. 

We believe that applying this rule is sufficient to clarify the confusion,
including the situation of two joined syllables with the former ending
with n and the latter beginning with g ("dang'an" [archives] and "dangan"
[work on one's own], "fang'an" [scheme] and "fangan" [aversion] are
examples in illustration of this rule).  Especially when the vast majority
of syllables are not aggregated in our catalogs, the case of confusion
will seldom happen. 

Sun Zehua
Principal Cataloger
Hong Kong University of Science and Technology Library