Based on purpose reviews are classified as

1. Technical Review – Review of work products – Requirements, Design,
Code, Test Plans, etc.

2. Non-technical Review – Review of status (e.g. PMRs), Project Plan,
SCM Plan, etc. - ensuring process compliance and process adequacy

Based on extent of formality reviews are classified as

a. Informal Review - One on one with peers, no agenda or preparation
time. Informal reviews do not have the rigor of a formal review. The reviews may
not be planned, or metrics may not be captured to measure review effectiveness.
They are typically used to confirm understanding, test ideas, brainstorm, etc.

b. Semiformal Review - Author walks the participants through work
product, defects are pointed out by participants, solutions may be discussed for
defects found. This could be a one person review also. Semiformal / Informal
reviews shall be considered for agile based projects.

c. Formal Review - Meeting is planned in advance, facilitated by a
moderator, follows a proper process, participants come prepared for the meeting.
Reviewers are selected based on skill and knowledge.