A symbolic link is *not* an alias. A symlink (symbolic link) is in the filesystem so all of the layers of the OS can use symlinks. This includes Carbon, Cocoa, Java, and BSD apps. Alias files are Finder-specific concept. Aliases are not used by the rest of the system. Only the Finder deals with aliases.
At the Finder level, aliases and symlinks are similar, but symlinks are far more versatile and used in pretty much every flavor of *nix.
