tag:blogger.com,1999:blog-10280668.post112895019760753881..comments2023-09-22T06:05:17.495-05:00Comments on Brad Appleton's ACME Blog: The Single Configuration PrincipleBrad Appletonhttp://www.blogger.com/profile/15136106921504315995noreply@blogger.comBlogger1125tag:blogger.com,1999:blog-10280668.post-1129663982533305712005-10-18T14:33:00.000-05:002005-10-18T14:33:00.000-05:00A baseline consists of a configuration, a configur...A baseline consists of a configuration, a configuration consists of configuration items, a configuration item consists of (meta-)data elements and an element consists of 1 or more versions.<BR/><BR/>The <B>Single Configuration Principle</B> not only applies to baselines, but also to lower granularities, until "a baseline corresponds to (0 or) 1 instance of element" (0 is included because a baseline may be a subset of all controlled items). Note that I rather talk about <I>instance</I> than <I>version</I> because (1) versions may not apply to every level of granularity, and (2) versions suggests an order (1, 2, 3, ...) while we also must take parallel (partially ordered) instances into account.<BR/><BR/>Also the <B>Baseline Immutability Principle</B> is to specific. I rather see the <B>Instance Immutability Principle</B> that says that an instance cannot be changed once it is committed to the CM system. To make a "change" you can only add or destroy instances. This applies to elements, but also to a configuration. So to "change" a system, you add a new configuration consisting of different (possibly new) instances of the elements.<BR/><BR/>This way the <B>Baseline Identification Principle</B> can be generalized also: every instance is uniquely identified (relative to other instances). Thus a configuration identifier is (in principle) the union of all instance identifiers, and a baseline identifier is nothing more than a short representation of a configuration identifier.<BR/><BR/>Frank.Anonymoushttps://www.blogger.com/profile/05338420995938912564noreply@blogger.com