diff --git a/clang/include/clang/Analysis/FlowSensitive/DataflowAnalysis.h b/clang/include/clang/Analysis/FlowSensitive/DataflowAnalysis.h
--- a/clang/include/clang/Analysis/FlowSensitive/DataflowAnalysis.h
+++ b/clang/include/clang/Analysis/FlowSensitive/DataflowAnalysis.h
@@ -136,6 +136,26 @@
   return BlockStates;
 }
 
+/// Virtual base class for "dataflow models": reusable analysis components that
+/// model a particular aspect of program semantics, with respect to a specific
+/// lattice. Models are very similar to analyses, except:
+///
+/// a) Models implement a typed dynamic (that is, virtual) interface (with
+///    respect to the lattice type), while analyses implement an untyped dynamic
+///    interface.
+///
+/// b) Models should focus on _modeling_ a particular aspect of program
+///    semantics -- for example, a type and its related functions, and should be
+///    composable with other models over the same lattice.
+///
+/// c) Models do not provide an initial element -- that is the responsibility of
+///    the analysis.
+template <typename Lattice>
+class DataflowModel : public Environment::ValueModel {
+public:
+  virtual void transfer(const Stmt *Stmt, Lattice &L, Environment &Env) = 0;
+};
+
 } // namespace dataflow
 } // namespace clang