Mike Gerwitz

Activist for User Freedom

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authorMike Gerwitz <gerwitzm@lovullo.com>2017-03-23 09:50:59 -0400
committerMike Gerwitz <gerwitzm@lovullo.com>2017-03-23 12:16:52 -0400
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doc/liza.texi: Add predicate system documentation
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-rw-r--r--doc/design.texi112
1 files changed, 112 insertions, 0 deletions
diff --git a/doc/design.texi b/doc/design.texi
index a0277ff..5e23622 100644
--- a/doc/design.texi
+++ b/doc/design.texi
@@ -64,6 +64,7 @@ The main components of the system are:
These data are used to determine what assertions are performed,
what questions and groups display,
and more.
+ @xref{Predicate System}.
@cindex Program
@item Program
@@ -112,6 +113,7 @@ More information about each can be found in their respective section.
* Assertions::
* Bucket::
* Client::
+* Predicate System::
* Program::
* Program UI::
* Program XML::
@@ -248,6 +250,74 @@ Error state is managed by
@srcref{src/validate/ValidStateMonitor.js, ValidStateMonitor}.
+
+@node Predicate System
+@section Predicate System
+@maintstart
+@footnote{
+ New programs (using the old incarnation of TAME) use the classifier
+ embedded into the rater by TAME.
+ Old ones, however, still use the @dfn{Global Classifier}.
+ This system isn't as well tested as TAME's@mdash{
+ }which needs to work properly for the sake of calculating premium@mdash{
+ }and has suffered from a number of bugs in the past.
+
+ The solution is to migrate all programs to TAME and remove that old
+ code.}
+@maintend
+
+@tip{
+ For a practical application of these concepts, see its use in the
+ Program@tie{}XML (@pxref{Specifying Predicates}).}
+
+@cindex Predicate
+@cindex Classifier
+@cindex Applicability
+@cindex Domain of discourse, Predicate
+The @dfn{predicate system} determines the @dfn{applicability} of
+ certain objects (like questions and assertions) by associating them
+ with predicates.
+The domain of discourse (variables which may be quantified) is listed
+ in @ref{t:predicate-dod}.
+
+What it means for some object to be applicable depends on the context.
+
+@float Table, t:predicate-dod
+@multitable @columnfractions 0.25 0.10 0.65
+ @headitem Type @tab Prefix @tab Description
+
+ @item Classifications
+ @tab @emph{None}
+ @tab Results of applying an external @dfn{classifier} to the bucket
+ (@pxref{Bucket}).
+
+ @item Bucket Truth Predicate
+ @tab @code{q:}
+ @tab
+ Whether the given name in the bucket (@pxref{Bucket}) is
+ non-empty and non-zero.
+ The prefix @samp{q:} refers to its most common use
+ case---questions (@pxref{Program UI,,Program@tie{}UI}).
+@end multitable
+@caption{Predicate system domain of discourse}
+@end float
+
+This system is limited to universal quantification over the domain of
+ discourse.
+For other quantifiers and higher-order logic,
+ defer to one of the systems that contributes to the domain of
+ discourse,
+ like the classifier.@footnote{
+ This is usually TAME.
+ The Program XML also supports inline classifications
+ with TAME's syntax (@pxref{Specifying Predicates}).}
+
+Predicates are usually specified in the Program XML
+ (@pxref{Specifying Predicates}) and compiled into the program
+ (@pxref{Program}).
+
+
+
@node Program
@section Program
@maintstart
@@ -420,6 +490,48 @@ Groups support a number of @dfn{group styles} that determine how
@section Program XML
@helpwanted
+@menu
+* Specifying Predicates::
+@end menu
+
+
+@node Specifying Predicates
+@subsection Specifying Predicates
+
+Object predicates (@pxref{Predicate System}) are specified using the
+ @xmlattr{when} attribute of certain nodes.
+It must contain a string of references understood by the system
+ (see domain of discourse, @ref{Predicate System}),
+ all of which much match for the predicate to be true.
+
+@float Figure, f:pred-when
+@example
+ <question id="describe" type="noyes"
+ label="Any special notes for this location?" />
+
+ <question id="vacant_desc" type="textarea"
+ when="q:describe vacant property"
+ label="Show only when a vacant property with the
+ question 'describe' non-empty and non-zero" />
+@end example
+@caption{Using the @xmlattr{when} attribute}
+@end float
+
+In @ref{f:pred-when} above,
+ question @samp{vacant_desc} will be applicable when @emph{all} of
+ the values of @samp{vacant}, @samp{property},
+ and@tie{}@samp{q:describe} are true.@footnote{
+ @xref{Predicate System} for what ``true'' means for a particular
+ variable in the domain of discourse.}
+Within the context of the @progxml,
+ this concretely means that the classifications
+ @samp{vacant} and@tie{}@samp{property} are true,
+ and that the question @samp{describe} is answered ``yes''.
+It reads as a sentence:
+ ``@samp{vacant_desc}'' is applicable when we should @tie{}``describe
+ a vacant property''.
+
+
@node Validation
@section Validation