+All measured performance trend data is treated as time-series data
+that is modelled as a concatenation of groups,
+within each group the samples come (independently) from
+the same normal distribution (with some center and standard deviation).
+
+Center of the normal distribution for the group (equal to population average)
+is called a trend for the group.
+All the analysis is based on finding the right partition into groups
+and comparing their trends.
+
+Trend Compliance
+~~~~~~~~~~~~~~~~
+
+.. _Trend_Compliance:
+
+In the text below, "trend at time <t>", shorthand "Trend[t]"
+means "the group average of the group the sample at time <t> belongs to".
+Here, time is usually given as "last" or last with an offset,
+e.g. "last - 1week".
+
+Trend compliance metrics are targeted to provide an indication of trend
+changes over a short-term (i.e. weekly) and a long-term (i.e.
+quarterly), comparing the last group average Trend[last], to the one from week
+ago, Trend[last - 1week] and to the maximum of trend values over last
+quarter except last week, max(Trend[last - 3mths]..Trend[last - 1week]),
+respectively.
+
+This results in following trend compliance calculations:
+
++-------------------------+---------------------------------+-------------+-----------------------------------------------+
+| Trend Compliance Metric | Trend Change Formula | Value | Reference |
++=========================+=================================+=============+===============================================+
+| Short-Term Change | (Value - Reference) / Reference | Trend[last] | Trend[last - 1week] |
++-------------------------+---------------------------------+-------------+-----------------------------------------------+
+| Long-Term Change | (Value - Reference) / Reference | Trend[last] | max(Trend[last - 3mths]..Trend[last - 1week]) |
++-------------------------+---------------------------------+-------------+-----------------------------------------------+
+
+These metrics are displayed in the Dashboard table.
+
+Caveats
+-------
+
+Obviously, is result history is too short, the true Trend[t] value
+may not by available, we use the earliest Trend available instead.
+
+The current implementaton does not track time of the samples,
+it counts runs instead.
+For "- 1week" we use "10 runs ago, 5 runs for topo-arch with 1 TB",
+for "- 3mths" we use "180 days or 180 runs ago, whatever comes first".
+
+Anomalies in graphs
+~~~~~~~~~~~~~~~~~~~
+
+In graphs, the start of the following group is marked
+as a regression (red circle) or progression (green circle),
+if the new trend is lower (or higher respectively)
+then the previous group's.
+
+Implementation details
+~~~~~~~~~~~~~~~~~~~~~~
+
+Partitioning into groups
+------------------------
+
+While sometimes the samples within a group are far from being
+distributed normally, currently we do not have a better tractable model.