diff --git a/kernel/is_valid.h b/kernel/is_valid.h
new file mode 100644
index 0000000..6101900
--- /dev/null
+++ b/kernel/is_valid.h
@@ -0,0 +1,35 @@
+/*
+Copyright (C) 2016-2019 The University of Notre Dame
+This software is distributed under the GNU General Public License.
+See the file LICENSE for details.
+*/
+
+#ifndef IS_VALID_H
+#define IS_VALID_H
+
+#include "kobject.h"
+
+// Does this string comprise a valid path?
+int is_valid_path(const char *s);
+
+// Does this string comprise a valid tag? 
+int is_valid_tag(const char *s);
+
+// Does this string point to a valid resource (i.e. is it a legitimate
+// tag-path concatenation)?
+int is_valid_location(const char *s);
+
+// Return true if file desciptor is in range and refers to a live object.
+int is_valid_object( int fd );
+
+// Return true if fd valid and object is also of indicated type.
+int is_valid_object_type( int fd, kobject_type_t type );
+
+// Return true if (ptr,length) describes a valid area in user space.
+int is_valid_pointer( void *ptr, int length );
+
+// Return true if string points to a valid area in user space.
+int is_valid_string( const char *str );
+
+
+#endif