This is the javadoc for the class:

http://owlapi.sourceforge.net/javadoc/uk/ac/manchester/cs/owl/owlapi/OWLClassImpl.html

Here is the errors. 

Suggestions: Catch errors in print-object and print anyways, with flag if you really want to signal error.

-Alan


Inconsistent precedence graph.
   [Condition of type SIMPLE-ERROR]

Restarts:
 0: [RETRY] Retry SLIME REPL evaluation request.
 1: [ABORT] Return to SLIME's top level.
 2: [ABORT] Abort thread.

Backtrace:
  0: (ERROR "Inconsistent precedence graph.")
  1: (MOP::TOPOLOGICAL-SORT (#<BUILT-IN-CLASS T> #<STANDARD-CLASS STANDARD-OBJECT {F2FBFF}> #<JAVA-CLASS {163B1C}> #<JAVA-CLASS {82B591}> #<JAVA-CLASS {5E632A}> #<JAVA-CLASS {C069F9}> ...) ((#<STANDARD-CLA..
  2: (MOP::STD-COMPUTE-CLASS-PRECEDENCE-LIST #<JAVA-CLASS {79BBDF}>)
  3: (#<STANDARD-GENERIC-FUNCTION MOP::COMPUTE-CLASS-PRECEDENCE-LIST {B10995}> #<JAVA-CLASS {79BBDF}>)
  4: (MOP::STD-FINALIZE-INHERITANCE #<JAVA-CLASS {79BBDF}>)
  5: (#<STANDARD-GENERIC-FUNCTION MOP::FINALIZE-INHERITANCE {98068D}> #<JAVA-CLASS {79BBDF}>)
  6: (#<FUNCTION {C1F62E}> #<JAVA-CLASS {79BBDF}> :NAME #:|org.semanticweb.owlapi.model.OWLClassExpression| :DIRECT-SUPERCLASSES (#<JAVA-CLASS {C069F9}> #<JAVA-CLASS {5E632A}> #<JAVA-CLASS {82B591}>) ...)
  7: (APPLY #<FUNCTION {C1F62E}> #<JAVA-CLASS {79BBDF}> (:NAME #:|org.semanticweb.owlapi.model.OWLClassExpression| :DIRECT-SUPERCLASSES (# # #) :JAVA-CLASS #<java.lang.Class interface org.semanticweb.owlap..
  8: (#<FUNCTION {D182D6}> #<JAVA-CLASS {79BBDF}> :NAME #:|org.semanticweb.owlapi.model.OWLClassExpression| :DIRECT-SUPERCLASSES (#<JAVA-CLASS {C069F9}> #<JAVA-CLASS {5E632A}> #<JAVA-CLASS {82B591}>) ...)
  9: (APPLY #<FUNCTION {D182D6}> (#<JAVA-CLASS {79BBDF}> :NAME #:|org.semanticweb.owlapi.model.OWLClassExpression| :DIRECT-SUPERCLASSES (# # #) :JAVA-CLASS ...))
 10: (#<STANDARD-GENERIC-FUNCTION INITIALIZE-INSTANCE {318C29}> #<JAVA-CLASS {79BBDF}> :NAME #:|org.semanticweb.owlapi.model.OWLClassExpression| :DIRECT-SUPERCLASSES (#<JAVA-CLASS {C069F9}> #<JAVA-CLASS {5..
 11: (APPLY #<STANDARD-GENERIC-FUNCTION INITIALIZE-INSTANCE {318C29}> #<JAVA-CLASS {79BBDF}> (:NAME #:|org.semanticweb.owlapi.model.OWLClassExpression| :DIRECT-SUPERCLASSES (# # #) :JAVA-CLASS #<java.lang...
 12: (#<FUNCTION {E4B5A9}> #<STANDARD-CLASS JAVA-CLASS {67DCEF}> :NAME #:|org.semanticweb.owlapi.model.OWLClassExpression| :DIRECT-SUPERCLASSES (#<JAVA-CLASS {C069F9}> #<JAVA-CLASS {5E632A}> #<JAVA-CLASS {..
 13: (APPLY #<FUNCTION {E4B5A9}> (#<STANDARD-CLASS JAVA-CLASS {67DCEF}> :NAME #:|org.semanticweb.owlapi.model.OWLClassExpression| :DIRECT-SUPERCLASSES (# # #) :JAVA-CLASS ...))
 14: (#<STANDARD-GENERIC-FUNCTION MAKE-INSTANCE {216D6D}> #<STANDARD-CLASS JAVA-CLASS {67DCEF}> :NAME #:|org.semanticweb.owlapi.model.OWLClassExpression| :DIRECT-SUPERCLASSES (#<JAVA-CLASS {C069F9}> #<JAVA..
 15: (APPLY #<STANDARD-GENERIC-FUNCTION MAKE-INSTANCE {216D6D}> #<STANDARD-CLASS JAVA-CLASS {67DCEF}> :NAME #:|org.semanticweb.owlapi.model.OWLClassExpression| (:DIRECT-SUPERCLASSES (# # #) :JAVA-CLASS #<j..
 16: (SYSTEM:ENSURE-CLASS #:|org.semanticweb.owlapi.model.OWLClassExpression| :METACLASS #<STANDARD-CLASS JAVA-CLASS {67DCEF}> :DIRECT-SUPERCLASSES (#<JAVA-CLASS {C069F9}> #<JAVA-CLASS {5E632A}> #<JAVA-CLA..
 17: (ENSURE-JAVA-CLASS #<java.lang.Class interface org.semanticweb.owlapi... {1D3D9D}>)
 18: (ENSURE-JAVA-CLASS #<java.lang.Class class uk.ac.manchester.cs.owl.ow... {B8486F}>)
 19: (PRINT-OBJECT #<uk.ac.manchester.cs.owl.owlapi.OWLClassImpl <http://ontology.neuinfo.org/NIF... {9B8B79}> #S(SYSTEM::STRING-OUTPUT-STREAM))
 20: (SYSTEM::OUTPUT-UGLY-OBJECT #<uk.ac.manchester.cs.owl.owlapi.OWLClassImpl <http://ontology.neuinfo.org/NIF... {9B8B79}> #S(SYSTEM::STRING-OUTPUT-STREAM))
 21: (SYSTEM::%PRINT-OBJECT #<uk.ac.manchester.cs.owl.owlapi.OWLClassImpl <http://ontology.neuinfo.org/NIF... {9B8B79}> #S(SYSTEM::STRING-OUTPUT-STREAM))
 22: (SYSTEM:OUTPUT-OBJECT #<uk.ac.manchester.cs.owl.owlapi.OWLClassImpl <http://ontology.neuinfo.org/NIF... {9B8B79}> #S(SYSTEM::STRING-OUTPUT-STREAM))
 23: (SYSTEM::OUTPUT-LIST (#<uk.ac.manchester.cs.owl.owlapi.OWLClassImpl <http://ontology.neuinfo.org/NIF... {9B8B79}> #<uk.ac.manchester.cs.owl.owlapi.OWLClassImpl <http://ccdb.ucsd.edu/NDPO/1.0/N... {E1F..
 24: (SYSTEM::OUTPUT-UGLY-OBJECT (#<uk.ac.manchester.cs.owl.owlapi.OWLClassImpl <http://ontology.neuinfo.org/NIF... {9B8B79}> #<uk.ac.manchester.cs.owl.owlapi.OWLClassImpl <http://ccdb.ucsd.edu/NDPO/1.0/N...
 25: (SYSTEM::%PRINT-OBJECT (#<uk.ac.manchester.cs.owl.owlapi.OWLClassImpl <http://ontology.neuinfo.org/NIF... {9B8B79}> #<uk.ac.manchester.cs.owl.owlapi.OWLClassImpl <http://ccdb.ucsd.edu/NDPO/1.0/N... {E..
 26: (SYSTEM:OUTPUT-OBJECT (#<uk.ac.manchester.cs.owl.owlapi.OWLClassImpl <http://ontology.neuinfo.org/NIF... {9B8B79}> #<uk.ac.manchester.cs.owl.owlapi.OWLClassImpl <http://ccdb.ucsd.edu/NDPO/1.0/N... {E1..
 27: (PRIN1-TO-STRING (#<uk.ac.manchester.cs.owl.owlapi.OWLClassImpl <http://ontology.neuinfo.org/NIF... {9B8B79}> #<uk.ac.manchester.cs.owl.owlapi.OWLClassImpl <http://ccdb.ucsd.edu/NDPO/1.0/N... {E1F4D8}..
 28: (SWANK::PRESENT-REPL-RESULTS ((#<uk.ac.manchester.cs.owl.owlapi.OWLClassImpl <http://ontology.neuinfo.org/NIF... {9B8B79}> #<uk.ac.manchester.cs.owl.owlapi.OWLClassImpl <http://ccdb.ucsd.edu/NDPO/1.0/..
 29: (#<FUNCTION {68B350}>)
 30: (SWANK::TRACK-PACKAGE #<FUNCTION {68B350}>)
 31: (#<FUNCTION {D47FC3}>)
 32: (SWANK::CALL-WITH-RETRY-RESTART "Retry SLIME REPL evaluation request." #<FUNCTION {D47FC3}>)
 33: (#<FUNCTION {101CC5}>)
 34: (FUNCALL #<FUNCTION {101CC5}>)
 35: (#<FUNCTION (LAMBDA (SWANK-BACKEND::FN)) {4616CA}> #<FUNCTION {101CC5}>)
 36: (APPLY #<FUNCTION (LAMBDA (SWANK-BACKEND::FN)) {4616CA}> #<FUNCTION {101CC5}> NIL)
 37: (SWANK-BACKEND:CALL-WITH-SYNTAX-HOOKS #<FUNCTION {101CC5}>)
 38: (SWANK::CALL-WITH-BUFFER-SYNTAX NIL #<FUNCTION {101CC5}>)
 39: (SWANK::REPL-EVAL "(imports-declarations @)
     ")
 40: (SWANK:LISTENER-EVAL "(imports-declarations @)
     ")
 41: (SYSTEM::%EVAL (SWANK:LISTENER-EVAL "(imports-declarations @)
     "))
 42: (EVAL (SWANK:LISTENER-EVAL "(imports-declarations @)
     "))
 43: (SWANK::EVAL-FOR-EMACS (SWANK:LISTENER-EVAL "(imports-declarations @)
     ") "COMMON-LISP-USER" 712)
 44: (APPLY #<FUNCTION SWANK::EVAL-FOR-EMACS {825BB7}> ((SWANK:LISTENER-EVAL "(imports-declarations @)
     ") "COMMON-LISP-USER" 712))
 45: (SWANK::PROCESS-REQUESTS NIL)
 46: (#<FUNCTION {D0F6AE}>)
 47: (FUNCALL #<FUNCTION {D0F6AE}>)
 48: ((FLET SWANK-BACKEND:CALL-WITH-DEBUGGER-HOOK) #<FUNCTION SWANK:SWANK-DEBUGGER-HOOK {E26AA1}> #<FUNCTION {D0F6AE}>)
 49: (APPLY #<FUNCTION (FLET SWANK-BACKEND:CALL-WITH-DEBUGGER-HOOK) {F31E8A}> #<FUNCTION SWANK:SWANK-DEBUGGER-HOOK {E26AA1}> #<FUNCTION {D0F6AE}> NIL)
 50: (SWANK-BACKEND:CALL-WITH-DEBUGGER-HOOK #<FUNCTION SWANK:SWANK-DEBUGGER-HOOK {E26AA1}> #<FUNCTION {D0F6AE}>)
 51: (#<FUNCTION {5A3285}>)
 52: (SWANK::CALL-WITH-BINDINGS ((*STANDARD-OUTPUT* . #S(SLIME-OUTPUT-STREAM)) (*STANDARD-INPUT* . #S(SLIME-INPUT-STREAM)) (*TRACE-OUTPUT* . #S(SLIME-OUTPUT-STREAM)) (*ERROR-OUTPUT* . #S(SLIME-OUTPUT-STREA..
 53: (#<FUNCTION {5F32BE}>)
 54: (JRUN-EXCEPTION-PROTECTED #<FUNCTION {5F32BE}>)
 55: (#<FUNCTION {FC7979}>)
 56: (JRUN-EXCEPTION-PROTECTED #<FUNCTION {FC7979}>)
 57: (SWANK::CALL-WITH-CONNECTION #S(SWANK::CONNECTION :SOCKET #<java.net.ServerSocket ServerSocket[addr=0.0.0.0/0.0.0.... {8B2078}> :SOCKET-IO #<TWO-WAY-STREAM {DF7E}> :DEDICATED-OUTPUT NIL :USER-INPUT #S..
 58: (JRUN-EXCEPTION-PROTECTED #<FUNCTION {50D4FE}>)
 59: (#<FUNCTION {CF8D9B}>)