A risk analysis typically focuses on a particular configuration of the target
 of analysis at a particular point in time, and the analysis results are valid
 under the assumptions made in the analysis. However, both the target
 and its environment change over time, and we therefore need methods
 and techniques for having these changes reflected in the risk analysis.

How we choose to deal with changes in a risk analysis depends on the
context and the types of changes we are addressing. We therefore
operate with various perspectives on change, where each perspective can
be placed within the following two dimensions:
\begin{itemize}
\item	The extent to which the changes are planned or not, i.e.
 whether the risk analysis is proactive or reactive, respectively.
\item	The extent to which the changes have the character of evolution
 or revolution: 
\begin{enumerate}
\item	Evolution: Smaller changes that accumulate over time.
\item	Revolution: Major changes that have large effects on the target.
\end{enumerate}
\end{itemize}

Using these two dimensions we identify three different viewpoints or
perspectives on change:
\begin{itemize}
\item The maintenance perspective (a posteriori perspective): Sometimes
 the target evolves over time, changes accumulate unnoticed, and risk
 analysis documentation and results may become outdated. Rather than
 conducting a new risk analysis from scratch, we want to address only the
 parts and aspects that have changed and thereby maintain the existing
 results. The maintenance perspective is a reactive evolution.
\item	The before-after perspective (a priori perspective): We often
 plan and anticipate changes, and major changes to the target may even
 be the motivation for a risk analysis. For comprehensive and substantial
 changes we need to understand both the risks of the target as-is and the
 target to-be, as well as risks that may arise during the transition in
 between. The before-after perspective is proactive revolution.
\item	The continuous perspective: There may be cases where we plan
 for the target to change over time, or where we can anticipate and predict
 gradual changes to the target and-or its environment. In those cases both
 the evolving target and the evolving risks can be described as a function
 of time, thereby giving a risk picture for any future point in time. The
 continuous perspective is proactive evolution.
\end{itemize}

For each of these three perspectives we present a conceptual model that
 describes language extensions required for a risk modeling language to
 have the expressiveness to document the relevant changes of the target
 and of the risks.