Changes between Initial Version and Version 1 of Prefs2

Timestamp:

Sep 8, 2019, 12:24:02 AM (6 years ago)

Author:

davea

Comment:

--

Prefs2

@@ +1 @@
+= Computing preferences, version 2 =
+
+== Static and dynamic prefs ==
+
+"Dynamic" prefs are parameters that limit BOINC activity,
+and that change in response to various factors.
+Examples include limits on #CPUs, RAM usage, network usage, etc.
+
+== Prefs dictionary ==
+
+The "prefs dictionary" is a name -> value map,
+containing values that can affect dynamic prefs.
+Examples:
+
+ * "idle_time": # seconds since last user input
+ * "time": time of day
+ * "on_batteries": whether system is running on batteries
+ * "exclusive_app_running": whether an exclusive app is running
+ * "non_boinc_cpu_usage": fraction of CPU used for non-BOINC apps recently
+
+These values are updated by the client.
+
+External programs can add items to the dictionary,
+and update their values, via GUI RPCs.
+Hence the prefs system is extensible without modifying the client.
+
+== Preference terms ==
+
+Preferences are expressed in terms of "conditions" that are the conjunction
+of a set of "terms".
+
+Each term is an assertion about a dictionary item.
+There are three types of terms:
+
+ * "greater than": the value of the item is greater than a threshold X.
+ * "nonzero": the value of the item is nonzero (i.e. a true Boolean)
+ * "time range": the value of the item (a time value) lies in a set of time intervals.
+
+A term can also have a "negate" flag, which if set reverses its sense.
+
+The XML representation of a term is
+{{{
+<prefs_term>
+   <item>item-name</item>
+   <term_type>x</term_type>     // 0 = greater than, 1 = nonzero, 2 = time range
+   [<negate/>]
+   [<thresh>x</thresh>]         // if greater than
+   [time range]                 // if time range
+</prefs_term>
+}}}
+and the representation of a time range is
+{{{
+<time_range>
+   <start_hour>x</start_hour>
+   <end_hour>y</end_hour>
+   [
+   <day>
+      <day_of_week>x</day_of_week>
+      <start_hour>x</start_hour>
+      <end_hour>y</end_hour>
+   <day>
+}}}
+== Conditions ==
+
+A "condition" is the conjunction ("and") of a set of terms, possibly negated.
+XML format:
+{{{
+<prefs_condition>
+   [<negate/>]
+   <prefs_term> ... </pref_term>
+   ...
+</prefs_condition>
+}}}
+
+== Clauses ==
+
+A "clause" is the combination of a condition and a set of dynamic prefs.
+XML format:
+{{{
+<prefs_clause>
+   <prefs_condition> ... </prefs_condition>
+   <dynamic_settings> ... </dynamic_settings>
+<prefs_clause>
+}}}
+
+== Preference sets ==
+
+A "preference set" is a list of clauses.
+XML format:
+{{{
+<computing_prefs>
+   <prefs_clause> ... </prefs_clause>
+   ...
+</computing_prefs>
+}}}
+
+The semantics are as follows.
+We maintain a set X of dynamic settings, initially empty.
+the clauses are processed in order.
+For each clause C, we evaluate its condition.
+If the condition is true, we overwrite X with C's dynamic settings.
+At the conclusion, X is the dynamic settings to be enforced.