Oops, already had a SerializationContext stub.

src/org/perl6/nqp/runtime/GlobalContext.java

@@ -3,6 +3,7 @@
 import java.util.HashMap;
 
 import org.perl6.nqp.sixmodel.KnowHOWBootstrapper;
+import org.perl6.nqp.sixmodel.SerializationContext;
 import org.perl6.nqp.sixmodel.SixModelObject;
 
 public class GlobalContext {

src/org/perl6/nqp/sixmodel/SerializationContext.java

@@ -1,9 +1,31 @@
 package org.perl6.nqp.sixmodel;
 
+import java.util.ArrayList;
+import org.perl6.nqp.runtime.CodeRef;
+
 /**
  * A serialization context holds a list of objects and code references that live
  * within a serialization boundary.
  */
 public class SerializationContext {
-
+	/* The handle of this SC. */
+    public String handle;
+
+    /* Description (probably the file name) if any. */
+    public String description;
+
+    /* The root set of objects that live in this SC. */
+    public ArrayList<SixModelObject> root_objects;
+
+    /* The root set of STables that live in this SC. */
+    public ArrayList<STable> root_stables;
+
+    /* The root set of code refs that live in this SC. */
+    public ArrayList<CodeRef> root_codes;
+
+    /* Repossession info. The following lists have matching indexes, each
+     * representing the integer of an object in our root set along with the SC
+     * that the object was originally from. */
+    public ArrayList<Integer> rep_indexes;
+    public ArrayList<SerializationContext> rep_scs;
 }