diff --git a/js/compiler/compiler.js b/js/compiler/compiler.js
index cd65c43..2292d81 100644
--- a/js/compiler/compiler.js
+++ b/js/compiler/compiler.js
@@ -182,7 +182,7 @@ var modifiedSourceActions = {
                         buildOnEvent(true,
                                      'retracted',
                                      pattern.instantiatedSubscription,
-                                     'null',
+                                     pattern.instantiatedProjection,
                                      [],
                                      '{}') +
                         '.completeBuild(); }');
@@ -252,6 +252,12 @@ semantics.addAttribute('instantiatedSubscription', {
   }
 });
 
+semantics.addAttribute('instantiatedProjection', {
+  _default: function(children) {
+    return buildSubscription(children, null, 'instantiated');
+  }
+});
+
 semantics.addAttribute('projection', {
   _default: function(children) {
     return buildSubscription(children, null, 'projection');
diff --git a/js/compiler/demo-bankaccount.js b/js/compiler/demo-bankaccount.js
index 897dba4..aa70f37 100644
--- a/js/compiler/demo-bankaccount.js
+++ b/js/compiler/demo-bankaccount.js
@@ -1,4 +1,4 @@
-// node src/compiler.js src/demo-bankaccount.js | node
+// bin/syndicatec compiler/demo-bankaccount.js | node
 
 var Syndicate = require('./src/main.js');
 
diff --git a/js/compiler/demo-filesystem.js b/js/compiler/demo-filesystem.js
new file mode 100644
index 0000000..1542209
--- /dev/null
+++ b/js/compiler/demo-filesystem.js
@@ -0,0 +1,66 @@
+// bin/syndicatec compiler/demo-filesystem.js | node
+
+var Syndicate = require('./src/main.js');
+
+assertion type file(name, content) = "file";
+assertion type saveFile(name, content) = "save";
+assertion type deleteFile(name) = "delete";
+
+ground network {
+  ///////////////////////////////////////////////////////////////////////////
+  // The file system actor
+
+  actor {
+    this.files = {};
+    forever {
+      during Syndicate.observe(file($name, _)) {
+        init {
+          console.log("At least one reader exists for:", name);
+        }
+        assert file(name, this.files[name]);
+        done {
+          console.log("No remaining readers exist for:", name);
+        }
+      }
+      on message saveFile($name, $newcontent) {
+        this.files[name] = newcontent;
+      }
+      on message deleteFile($name) {
+        delete this.files[name];
+      }
+    }
+  }
+
+  ///////////////////////////////////////////////////////////////////////////
+  // A simple demo client of the file system
+
+  actor {
+    state {
+      on asserted file("hello.txt", $content) {
+        console.log("hello.txt has content", JSON.stringify(content));
+      }
+    } until {
+      case asserted file("hello.txt", "quit demo") {
+        console.log("The hello.txt file contained 'quit demo', so we will quit");
+      }
+    }
+
+    until {
+      case asserted Syndicate.observe(saveFile(_, _)) {
+        :: saveFile("hello.txt", "a");
+        :: deleteFile("hello.txt");
+        :: saveFile("hello.txt", "c");
+        :: saveFile("hello.txt", "quit demo");
+        :: saveFile("hello.txt", "final contents");
+        actor {
+          until {
+            case asserted file("hello.txt", $content) {
+              console.log("second observer sees that hello.txt content is",
+                          JSON.stringify(content));
+            }
+          }
+        }
+      }
+    }
+  }
+}
diff --git a/js/src/actor.js b/js/src/actor.js
index e2c9de2..3fa192f 100644
--- a/js/src/actor.js
+++ b/js/src/actor.js
@@ -99,7 +99,7 @@ Facet.prototype.onEvent = function(isTerminal, eventType, subscriptionFn, projec
                                            ? e.patch.added
                                            : e.patch.removed,
                                            compiledSpec);
-        if (objects) {
+        if (objects && objects.size > 0) {
           // console.log(objects.toArray());
           if (isTerminal) { facet.terminate(); }
           objects.forEach(function (o) { Util.kwApply(handlerFn, facet.actor.state, o); });
diff --git a/js/src/route.js b/js/src/route.js
index 854a93f..efdb218 100644
--- a/js/src/route.js
+++ b/js/src/route.js
@@ -17,7 +17,7 @@ function makeStructureConstructor(label, argumentNames) {
 }
 
 function isStructure(s) {
-  return !!(s.$SyndicateMeta$);
+  return (s !== null) && (typeof s === 'object') && ("$SyndicateMeta$" in s);
 }
 
 function structureToArray(s) {
@@ -138,7 +138,7 @@ function compilePattern(v, p) {
       return rseq(SOA, acc);
     }
 
-    if (p.$SyndicateMeta$) {
+    if (isStructure(p)) {
       var args = p.$SyndicateMeta$.arguments;
       acc = rseq(EOA, acc);
       for (var i = args.length - 1; i >= 0; i--) {
@@ -538,7 +538,7 @@ function matchValue(r, v) {
       } else {
 	r = rlookup(r, __);
       }
-    } else if (v.$SyndicateMeta$) {
+    } else if (isStructure(v)) {
       if (r.has(SOA)) {
         r = rlookup(r, SOA);
         stack.push(vs);
@@ -735,7 +735,7 @@ function compileProjection(/* projection, projection, ... */) {
       return;
     }
 
-    if (p.$SyndicateMeta$) {
+    if (isStructure(p)) {
       acc.push(SOA);
       acc.push(p.$SyndicateMeta$.label);
       var args = p.$SyndicateMeta$.arguments;
@@ -768,7 +768,7 @@ function projectionToPattern(p) {
       return result;
     }
 
-    if (p.$SyndicateMeta$) {
+    if (isStructure(p)) {
       var result = {"$SyndicateMeta$": p.$SyndicateMeta$};
       var args = p.$SyndicateMeta$.arguments;
       for (var i = 0; i < args.length; i++) {