diff --git a/src/proc/control/command-impl.hpp b/src/proc/control/command-impl.hpp
index 58c906315..5aa4ce533 100644
--- a/src/proc/control/command-impl.hpp
+++ b/src/proc/control/command-impl.hpp
@@ -163,31 +163,30 @@ namespace control {
       /* === diagnostics === */
       
       bool
-      isValid()  const
+      isValid()  const    ///< validity self-check: is basically usable.
         {
-          UNIMPLEMENTED ("command validity self check");
+          return bool(pClo_) 
+              && HandlingPattern::get(defaultPatt_).isValid();
         }
       
       bool
-      canExec()  const
+      canExec()  const    ///< state check: sufficiently defined to be invoked 
         {
-          UNIMPLEMENTED ("state check: sufficiently defined to be invoked");
+          return isValid()
+              && *pClo_ && do_;
         }
       
       bool
-      canUndo()  const
+      canUndo()  const    ///< state check: has undo state been captured? 
         {
-          UNIMPLEMENTED ("state check: has undo state been captured?");
+          return isValid() && undo_;
         }
       
       
       
       
     protected:
-//     static Command& fetchDef (Symbol cmdID);
-     
-//     friend class CommandDef;
-
+      
     };
   ////////////////TODO currently just fleshing  out the API....
   
diff --git a/src/proc/control/handling-pattern.hpp b/src/proc/control/handling-pattern.hpp
index 67b326c81..09fad5b65 100644
--- a/src/proc/control/handling-pattern.hpp
+++ b/src/proc/control/handling-pattern.hpp
@@ -77,6 +77,7 @@ namespace control {
    * @todo Type-comment
    */
   class HandlingPattern
+    : public lib::BoolCheckable<HandlingPattern>
     {
       
     public:
@@ -106,6 +107,7 @@ namespace control {
       HandlingPattern const& howtoUNDO()  const;
       
       
+      virtual bool isValid()  const  =0;
       
     protected:
       
@@ -114,6 +116,7 @@ namespace control {
       virtual HandlingPattern const& defineUNDO()  const  =0;
       
       
+      
     };
   ////////////////TODO currently just fleshing  out the API....
   
diff --git a/src/proc/control/handling-patterns.hpp b/src/proc/control/handling-patterns.hpp
index b692aafae..f4f86313a 100644
--- a/src/proc/control/handling-patterns.hpp
+++ b/src/proc/control/handling-patterns.hpp
@@ -85,6 +85,12 @@ namespace control {
           {
             UNIMPLEMENTED ("yield a handling pattern suitable for UNDOing a command, according to this pattern");
           }
+        
+        bool
+        isValid()  const
+          {
+            UNIMPLEMENTED ("is this pattern currently able to handle commands?");
+          }
       };
     
     
@@ -107,6 +113,12 @@ namespace control {
           {
             UNIMPLEMENTED ("yield a handling pattern suitable for UNDOing a command, according to this pattern");
           }
+        
+        bool
+        isValid()  const
+          {
+            UNIMPLEMENTED ("is this pattern currently able to handle commands?");
+          }
       };
     
     
@@ -129,6 +141,12 @@ namespace control {
           {
             UNIMPLEMENTED ("yield a handling pattern suitable for UNDOing a command, according to this pattern");
           }
+        
+        bool
+        isValid()  const
+          {
+            UNIMPLEMENTED ("is this pattern currently able to handle commands?");
+          }
       };