SRC Forum - Message Replies
Forum: Reliability & Maintainability Questions and Answers
Topic: Reliability & Maintainability Questions and Answers
Topic Posted by: Reliability & Maintainability Forum
Organization: System Reliability Center
Date Posted: Mon Aug 31 12:47:36 US/Eastern 1998
Posted by: Luke Deng
Organization:Aerospace Industry Development Corp.
Date posted: Thu Mar 29 3:26:28 US/Eastern 2001
Subject: Maintenability Index
What's MAINTENABILITY INDEX meanning in physic and mathematic aspect?
Subject: Maintainability Index
Reply Posted by: Ned H. Criscimagna
Organization: Reliability Analysis Center
Date Posted: Thu Mar 29 14:21:09 US/Eastern 2001
The maintainability index is a term used in two different ways.
1. It is used as a measure of the maintainability of software.
> Maintainability Index - a measure of success
- Set of polynomial metrics developed at the University of Idaho
- Uses Halstead’s effort/module and McCabe’s cyclomatic complexity/module, plus other factors
- Validated in the field by HP
- Language independent
- Index is a number between 0 and 100
- Used primarily to determine if modules have a high, medium, or low degree of difficulty to maintain
> HP concluded “modules with a MI less than 65 are considered difficult to maintain”
For more information on MI used in this way, go to http://adaic.org/docs/present/ajpo/pll-cost/html/tsld054.htm or http://www.sei.cmu.edu/str/descriptions/mitmpm.html.
2. It is also used as a measure of the total maintenance effort required to maintain a product in operational status per unit operating time. It is expressed as (from MIL-HDBK-472, dated 24 May, 1986):
MI = (Summation (FRi) Mct Ti + Summation (FO) Mpt Tj)/T
MI = maintenance index
FRi = part failure rates (average part failure rates)
Mct = mean corrective maintenance time
Ti = operating time during calendar time Tj
FO = frequency of occurrences of preventive maintenance tasks
Mpt = mean preventive maintenance time
Tj = calendar time in operating inventory
T = total time