ALA Rules (2nd definitive edition):

American Library Association. ALA cataloging rules for author and title entries. - 2nd ed. / Clara Beetle, editor. - Chicago: American Library Association, 1949. The criticism of the 1941 draft code of ALA rules faulted the code in general and the descriptive rules part more in particular. The code needed revision, recasting and finalisation. 

This code (1949. ALA 2nd ed.) was limited to rules for entry and heading only. It represented somewhat an expansion and elaboration of the 1908 code. It did not state and apply any guiding principles. The code proved exceedingly complicated to use. For about a decade and a half (i.e., until the AACR I appeared) the arrangement of using the twin codes (the 1949 ALA 2nd ed. sand the 1949 LC rules) in conjunction as the American standards for cataloguing continued. But cataloguers always found it tedious and inconvenient to have to refer to one code for entry and heading work and another for description.

Since the LC code of descriptive rules covered printed material only, it required the use of other aids br standards for describing other non-print items (e.g., LC's Motion pictures and film strips, Phonorecords, and Picture designs and other two-dimensional representations - three separate booklets). 

Like the earlier preliminary draft second edition, the definitive second edition too was targeted for criticism. While the LC descriptive rules looked forward, the ALA code looked backward. A more coherent and unified code therefore .was demanded.