Explain that updates are required to produce short queries. Fixes #244

interactive-workload-definition.tex

@@ -31,7 +31,7 @@
 short read in the sequence is determined at run time, and is based on the
 completion time of the complex read it depends on. 
 The substitution parameters for short reads are taken from the results of previously
-executed queries.
+executed queries, including both complex and short reads:
 
 \begin{itemize}
 \item Complex reads:
@@ -72,3 +72,5 @@
 frequencies (see \autoref{table:freqs}).  Therefore, different
 throughputs can be tested while maintaining the relative ratios between the
 different query types.
+
+\emph{\textbf{Warning.} Note that in the current implementation of SNB Interactive v1, short queries are only produced if updates are enabled. In the absence of updates, no short queries will be executed.}