- Old bugs have been fixed. This is probably the one thing users can count on being true of every release.
- New bugs have been added. This too can usually be counted on, except sometimes in the case of security releases or other one-offs (see the section called “Security Releases” later in this chapter).
- New features may have been added.
- New configuration options may have been added, or the meanings of old options may have changed subtly. The installation procedures may have changed slightly since the last release too, though one always hopes not.
- Incompatible changes may have been introduced, such that the data formats used by older versions of the software are no longer useable without undergoing some sort of (possibly manual) one-way conversion step.
居然有一项是“引入新的bug”，好象各种软件（比如MS的Windows）都确实符合这一条件…这才注意到好象Release Notes里面都会包含一个Known Bug之类的