diff --git a/go/analysis/analysis.go b/go/analysis/analysis.go
index 127f1d3f..8fa329c1 100644
--- a/go/analysis/analysis.go
+++ b/go/analysis/analysis.go
@@ -11,6 +11,9 @@
 //
 // The principal data types of this package are structs, not interfaces,
 // to permit later addition of optional fields as the API evolves.
+//
+// THIS INTERFACE IS EXPERIMENTAL AND SUBJECT TO CHANGE.
+// We aim to finalize it by November 2018.
 package analysis
 
 import (
@@ -67,14 +70,15 @@ type Analyzer struct {
 	// ResultType is the type of the optional result of the Run function.
 	ResultType reflect.Type
 
-	// UsesFacts indicates that this analyzer produces and consumes Facts.
+	// FactTypes indicates that this analyzer imports and exports
+	// Facts of the specified concrete types.
 	// An analyzer that uses facts may assume that its import
 	// dependencies have been similarly analyzed before it runs.
-	// Facts are pointers.
+	// Facts must be pointers.
 	//
-	// UsesFacts establishes a "vertical" dependency between
+	// FactTypes establishes a "vertical" dependency between
 	// analysis passes (same analyzer, different packages).
-	UsesFacts bool
+	FactTypes []Fact
 }
 
 func (a *Analyzer) String() string { return a.Name }
diff --git a/go/analysis/internal/checker/checker.go b/go/analysis/internal/checker/checker.go
index d4388c53..d9647c0e 100644
--- a/go/analysis/internal/checker/checker.go
+++ b/go/analysis/internal/checker/checker.go
@@ -188,7 +188,7 @@ func analyze(pkgs []*packages.Package, analyzers []*analysis.Analyzer) []*action
 
 			// An analysis that consumes/produces facts
 			// must run on the package's dependencies too.
-			if a.UsesFacts {
+			if len(a.FactTypes) > 0 {
 				paths := make([]string, 0, len(pkg.Imports))
 				for path := range pkg.Imports {
 					paths = append(paths, path)
@@ -374,7 +374,7 @@ func needFacts(analyzers []*analysis.Analyzer) bool {
 		q = q[1:]
 		if !seen[a] {
 			seen[a] = true
-			if a.UsesFacts {
+			if len(a.FactTypes) > 0 {
 				return true
 			}
 			q = append(q, a.Requires...)
diff --git a/go/analysis/passes/pkgfact/pkgfact.go b/go/analysis/passes/pkgfact/pkgfact.go
index 4c98cb7a..ddb18341 100644
--- a/go/analysis/passes/pkgfact/pkgfact.go
+++ b/go/analysis/passes/pkgfact/pkgfact.go
@@ -35,7 +35,7 @@ var Analyzer = &analysis.Analyzer{
 	Name:       "pkgfact",
 	Doc:        "gather name/value pairs from constant declarations",
 	Run:        run,
-	UsesFacts:  true, // *pairsFact
+	FactTypes:  []analysis.Fact{new(pairsFact)},
 	ResultType: reflect.TypeOf(map[string]string{}),
 }
 
diff --git a/go/analysis/validate.go b/go/analysis/validate.go
index e91729ca..ff176e48 100644
--- a/go/analysis/validate.go
+++ b/go/analysis/validate.go
@@ -2,38 +2,60 @@ package analysis
 
 import (
 	"fmt"
+	"reflect"
 	"unicode"
 )
 
 // Validate reports an error if any of the analyzers are misconfigured.
 // Checks include:
 // - that the name is a valid identifier;
-// - that analysis names are unique;
-// - that the Requires graph is acylic.
+// - that analyzer names are unique;
+// - that the Requires graph is acylic;
+// - that analyzer fact types are unique;
+// - that each fact type is a pointer.
 func Validate(analyzers []*Analyzer) error {
 	names := make(map[string]bool)
 
+	// Map each fact type to its sole generating analyzer.
+	factTypes := make(map[reflect.Type]*Analyzer)
+
 	// Traverse the Requires graph, depth first.
 	color := make(map[*Analyzer]uint8) // 0=white 1=grey 2=black
 	var visit func(a *Analyzer) error
 	visit = func(a *Analyzer) error {
 		if a == nil {
-			return fmt.Errorf("nil *Analysis")
+			return fmt.Errorf("nil *Analyzer")
 		}
 		if color[a] == 0 { // white
 			color[a] = 1 // grey
 
 			// names
 			if !validIdent(a.Name) {
-				return fmt.Errorf("invalid analysis name %q", a)
+				return fmt.Errorf("invalid analyzer name %q", a)
 			}
 			if names[a.Name] {
-				return fmt.Errorf("duplicate analysis name %q", a)
+				return fmt.Errorf("duplicate analyzer name %q", a)
 			}
 			names[a.Name] = true
 
 			if a.Doc == "" {
-				return fmt.Errorf("analysis %q is undocumented", a)
+				return fmt.Errorf("analyzer %q is undocumented", a)
+			}
+
+			// fact types
+			for _, f := range a.FactTypes {
+				if f == nil {
+					return fmt.Errorf("analyzer %s has nil FactType", a)
+				}
+				t := reflect.TypeOf(f)
+				if prev := factTypes[t]; prev != nil {
+					return fmt.Errorf("fact type %s registered by two analyzers: %v, %v",
+						t, a, prev)
+				}
+				if t.Kind() != reflect.Ptr {
+					return fmt.Errorf("%s: fact type %s is not a pointer", a, t)
+				}
+				factTypes[t] = a
 			}
 
 			// recursion