jaxws/src/share/classes/com/sun/xml/internal/xsom/impl/scd/Axis.java - platform/libcore - Git at Google

 /*
  * Copyright 2005-2006 Sun Microsystems, Inc.  All Rights Reserved.
  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
  *
  * This code is free software; you can redistribute it and/or modify it
  * under the terms of the GNU General Public License version 2 only, as
  * published by the Free Software Foundation.  Sun designates this
  * particular file as subject to the "Classpath" exception as provided
  * by Sun in the LICENSE file that accompanied this code.
  *
  * This code is distributed in the hope that it will be useful, but WITHOUT
  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  * version 2 for more details (a copy is included in the LICENSE file that
  * accompanied this code).
  *
  * You should have received a copy of the GNU General Public License version
  * 2 along with this work; if not, write to the Free Software Foundation,
  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
  *
  * Please contact Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,
  * CA 95054 USA or visit www.sun.com if you need additional information or
  * have any questions.
  */
 package com.sun.xml.internal.xsom.impl.scd;

 import com.sun.xml.internal.xsom.XSAttContainer;
 import com.sun.xml.internal.xsom.XSAttGroupDecl;
 import com.sun.xml.internal.xsom.XSAttributeDecl;
 import com.sun.xml.internal.xsom.XSAttributeUse;
 import com.sun.xml.internal.xsom.XSComplexType;
 import com.sun.xml.internal.xsom.XSComponent;
 import com.sun.xml.internal.xsom.XSElementDecl;
 import com.sun.xml.internal.xsom.XSFacet;
 import com.sun.xml.internal.xsom.XSIdentityConstraint;
 import com.sun.xml.internal.xsom.XSListSimpleType;
 import com.sun.xml.internal.xsom.XSModelGroup;
 import com.sun.xml.internal.xsom.XSModelGroup.Compositor;
 import com.sun.xml.internal.xsom.XSModelGroupDecl;
 import com.sun.xml.internal.xsom.XSNotation;
 import com.sun.xml.internal.xsom.XSParticle;
 import com.sun.xml.internal.xsom.XSRestrictionSimpleType;
 import com.sun.xml.internal.xsom.XSSchema;
 import com.sun.xml.internal.xsom.XSSimpleType;
 import com.sun.xml.internal.xsom.XSType;
 import com.sun.xml.internal.xsom.XSUnionSimpleType;
 import com.sun.xml.internal.xsom.XSWildcard;

 import java.util.ArrayList;
 import java.util.HashSet;
 import java.util.Iterator;
 import java.util.List;
 import java.util.Set;

 /**
  * Axis of traversal.
  *
  * @param <T>
  *      The kind of components that this axis may return.
  *
  * @author Kohsuke Kawaguchi
  */
 public interface Axis<T extends XSComponent> {
     Iterator<T> iterator(XSComponent contextNode);

     Iterator<T> iterator(Iterator<? extends XSComponent> contextNodes);

     /**
      * Returns true if this is one of the model group axis.
      */
     boolean isModelGroup();


     /**
      * Pseudo-axis that selects all the {@link XSSchema}s in the current set.
      * Used to implement the absolute path expression
      */
     public static final Axis<XSSchema> ROOT = new Axis<XSSchema>() {
         public Iterator<XSSchema> iterator(XSComponent contextNode) {
             return contextNode.getRoot().iterateSchema();
         }

         public Iterator<XSSchema> iterator(Iterator<? extends XSComponent> contextNodes) {
             if(!contextNodes.hasNext())
                 return Iterators.empty();
             else
                 // this assumes that all current nodes belong to the same owner.
                 return iterator(contextNodes.next());
         }

         public boolean isModelGroup() {
             return false;
         }

         public String toString() {
             return "root::";
         }
     };

     /**
      * Pseudo-axis that visits all skipped intermediate steps.
      * Those are:
      * <ol>
      *  <li>complex type reachable from element
      *  <li>model groups
      *  <li>combination of above.
      * </ol>
      */
     public static final Axis<XSComponent> INTERMEDIATE_SKIP = new AbstractAxisImpl<XSComponent>() {
         public Iterator<XSComponent> elementDecl(XSElementDecl decl) {
             XSComplexType ct = decl.getType().asComplexType();
             if(ct==null)
                 return empty();
             else {
                 // also pick up model groups inside this complex type
                 return new Iterators.Union<XSComponent>(singleton(ct),complexType(ct));
             }
         }

         public Iterator<XSComponent> modelGroupDecl(XSModelGroupDecl decl) {
             return descendants(decl.getModelGroup());
         }

         public Iterator<XSComponent> particle(XSParticle particle) {
             return descendants(particle.getTerm().asModelGroup());
         }

         /**
          * Iterate all descendant model groups of the given model group, including itself.
          */
         private Iterator<XSComponent> descendants(XSModelGroup mg) {
             // TODO: write a tree iterator
             // for now, we do it eagerly because I'm lazy
             List<XSComponent> r = new ArrayList<XSComponent>();
             visit(mg,r);
             return r.iterator();
         }

         private void visit(XSModelGroup mg, List<XSComponent> r) {
             // since model groups never form a cycle, no cycle check is needed
             r.add(mg);
             for (XSParticle p : mg) {
                 XSModelGroup child = p.getTerm().asModelGroup();
                 if(child!=null)
                     visit(child,r);
             }
         }

         public String toString() {
             return "(intermediateSkip)";
         }
     };

     /**
      * All descendants reachable via default axes. Used to implement the "//" semantics.
      *
      * So far the default axes together are guaranteed not to cause any cycle, so
      * no cycle check is needed (if it's needed, the life would be much harder!)
      */
     public static final Axis<XSComponent> DESCENDANTS = new Axis<XSComponent>() {
         public Iterator<XSComponent> iterator(XSComponent contextNode) {
             return new Visitor().iterator(contextNode);
         }
         public Iterator<XSComponent> iterator(Iterator<? extends XSComponent> contextNodes) {
             return new Visitor().iterator(contextNodes);
         }

         public boolean isModelGroup() {
             return false;
         }

         /**
          * Stateful visitor that remembers what's already traversed, to reduce the search space.
          */
         final class Visitor extends AbstractAxisImpl<XSComponent> {
             private final Set<XSComponent> visited = new HashSet<XSComponent>();

             /**
              * Recursively apply the {@link Axis#DESCENDANTS} axis.
              */
             final class Recursion extends Iterators.Map<XSComponent,XSComponent> {
                 public Recursion(Iterator<? extends XSComponent> core) {
                     super(core);
                 }

                 protected Iterator<XSComponent> apply(XSComponent u) {
                     return DESCENDANTS.iterator(u);
                 }
             }
             public Iterator<XSComponent> schema(XSSchema schema) {
                 if(visited.add(schema))
                     return ret( schema, new Recursion(schema.iterateElementDecls()));
                 else
                     return empty();
             }

             public Iterator<XSComponent> elementDecl(XSElementDecl decl) {
                 if(visited.add(decl))
                     return ret(decl, iterator(decl.getType()) );
                 else
                     return empty();
             }

             public Iterator<XSComponent> simpleType(XSSimpleType type) {
                 if(visited.add(type))
                     return ret(type, FACET.iterator(type));
                 else
                     return empty();
             }

             public Iterator<XSComponent> complexType(XSComplexType type) {
                 if(visited.add(type))
                     return ret(type, iterator(type.getContentType()));
                 else
                     return empty();
             }

             public Iterator<XSComponent> particle(XSParticle particle) {
                 if(visited.add(particle))
                     return ret(particle, iterator(particle.getTerm()));
                 else
                     return empty();
             }

             public Iterator<XSComponent> modelGroupDecl(XSModelGroupDecl decl) {
                 if(visited.add(decl))
                     return ret(decl, iterator(decl.getModelGroup()));
                 else
                     return empty();
             }

             public Iterator<XSComponent> modelGroup(XSModelGroup group) {
                 if(visited.add(group))
                     return ret(group, new Recursion(group.iterator()));
                 else
                     return empty();
             }

             public Iterator<XSComponent> attGroupDecl(XSAttGroupDecl decl) {
                 if(visited.add(decl))
                     return ret(decl, new Recursion(decl.iterateAttributeUses()));
                 else
                     return empty();
             }

             public Iterator<XSComponent> attributeUse(XSAttributeUse use) {
                 if(visited.add(use))
                     return ret(use, iterator(use.getDecl()));
                 else
                     return empty();
             }

             public Iterator<XSComponent> attributeDecl(XSAttributeDecl decl) {
                 if(visited.add(decl))
                     return ret(decl, iterator(decl.getType()));
                 else
                     return empty();
             }

             private Iterator<XSComponent> ret( XSComponent one, Iterator<? extends XSComponent> rest ) {
                 return union(singleton(one),rest);
             }
         }

         public String toString() {
             return "/";
         }
     };

     public static final Axis<XSSchema> X_SCHEMA = new Axis<XSSchema>() {
         public Iterator<XSSchema> iterator(XSComponent contextNode) {
             return Iterators.singleton(contextNode.getOwnerSchema());
         }

         public Iterator<XSSchema> iterator(Iterator<? extends XSComponent> contextNodes) {
             return new Iterators.Adapter<XSSchema,XSComponent>(contextNodes) {
                 protected XSSchema filter(XSComponent u) {
                     return u.getOwnerSchema();
                 }
             };
         }

         public boolean isModelGroup() {
             return false;
         }

         public String toString() {
             return "x-schema::";
         }
     };

     public static final Axis<XSElementDecl> SUBSTITUTION_GROUP = new AbstractAxisImpl<XSElementDecl>() {
         public Iterator<XSElementDecl> elementDecl(XSElementDecl decl) {
             return singleton(decl.getSubstAffiliation());
         }

         public String toString() {
             return "substitutionGroup::";
         }
     };

     public static final Axis<XSAttributeDecl> ATTRIBUTE = new AbstractAxisImpl<XSAttributeDecl>() {
         public Iterator<XSAttributeDecl> complexType(XSComplexType type) {
             return attributeHolder(type);
         }

         public Iterator<XSAttributeDecl> attGroupDecl(XSAttGroupDecl decl) {
             return attributeHolder(decl);
         }

         private Iterator<XSAttributeDecl> attributeHolder(final XSAttContainer atts) {
             // TODO: check spec. is this correct?
             return new Iterators.Adapter<XSAttributeDecl,XSAttributeUse>(atts.iterateAttributeUses()) {
                 protected XSAttributeDecl filter(XSAttributeUse u) {
                     return u.getDecl();
                 }
             };
         }

         public Iterator<XSAttributeDecl> schema(XSSchema schema) {
             return schema.iterateAttributeDecls();
         }

         public String toString() {
             return "@";
         }
     };

     public static final Axis<XSElementDecl> ELEMENT = new AbstractAxisImpl<XSElementDecl>() {
         public Iterator<XSElementDecl> particle(XSParticle particle) {
             return singleton(particle.getTerm().asElementDecl());
         }

         public Iterator<XSElementDecl> schema(XSSchema schema) {
             return schema.iterateElementDecls();
         }

         public Iterator<XSElementDecl> modelGroupDecl(XSModelGroupDecl decl) {
             return modelGroup(decl.getModelGroup());
         }

         //public Iterator<XSElementDecl> modelGroup(XSModelGroup group) {
         //    return new Iterators.Map<XSElementDecl,XSParticle>(group.iterator()) {
         //        protected Iterator<XSElementDecl> apply(XSParticle p) {
         //            return particle(p);
         //        }
         //    };
         //}

         @Override
         public String getName() {
             return "";
         }

         public String toString() {
             return "element::";
         }
     };


     public static final Axis<XSType> TYPE_DEFINITION = new AbstractAxisImpl<XSType>() {
         public Iterator<XSType> schema(XSSchema schema) {
             return schema.iterateTypes();
         }

         public Iterator<XSType> attributeDecl(XSAttributeDecl decl) {
             return singleton(decl.getType());
         }

         public Iterator<XSType> elementDecl(XSElementDecl decl) {
             return singleton(decl.getType());
         }

         public String toString() {
             return "~";
         }
     };

     public static final Axis<XSType> BASETYPE = new AbstractAxisImpl<XSType>() {
         public Iterator<XSType> simpleType(XSSimpleType type) {
             return singleton(type.getBaseType());
         }

         public Iterator<XSType> complexType(XSComplexType type) {
             return singleton(type.getBaseType());
         }

         public String toString() {
             return "baseType::";
         }
     };

     public static final Axis<XSSimpleType> PRIMITIVE_TYPE = new AbstractAxisImpl<XSSimpleType>() {
         public Iterator<XSSimpleType> simpleType(XSSimpleType type) {
             return singleton(type.getPrimitiveType());
         }

         public String toString() {
             return "primitiveType::";
         }
     };

     public static final Axis<XSSimpleType> ITEM_TYPE = new AbstractAxisImpl<XSSimpleType>() {
         public Iterator<XSSimpleType> simpleType(XSSimpleType type) {
             XSListSimpleType baseList = type.getBaseListType();
             if(baseList==null)      return empty();
             return singleton(baseList.getItemType());
         }

         public String toString() {
             return "itemType::";
         }
     };

     public static final Axis<XSSimpleType> MEMBER_TYPE = new AbstractAxisImpl<XSSimpleType>() {
         public Iterator<XSSimpleType> simpleType(XSSimpleType type) {
             XSUnionSimpleType baseUnion = type.getBaseUnionType();
             if(baseUnion ==null)      return empty();
             return baseUnion.iterator();
         }

         public String toString() {
             return "memberType::";
         }
     };

     public static final Axis<XSComponent> SCOPE = new AbstractAxisImpl<XSComponent>() {
         public Iterator<XSComponent> complexType(XSComplexType type) {
             return singleton(type.getScope());
         }
         // TODO: attribute declaration has a scope, too.
         // TODO: element declaration has a scope

         public String toString() {
             return "scope::";
         }
     };

     public static final Axis<XSAttGroupDecl> ATTRIBUTE_GROUP = new AbstractAxisImpl<XSAttGroupDecl>() {
         public Iterator<XSAttGroupDecl> schema(XSSchema schema) {
             return schema.iterateAttGroupDecls();
         }

         public String toString() {
             return "attributeGroup::";
         }
     };

     public static final Axis<XSModelGroupDecl> MODEL_GROUP_DECL = new AbstractAxisImpl<XSModelGroupDecl>() {
         public Iterator<XSModelGroupDecl> schema(XSSchema schema) {
             return schema.iterateModelGroupDecls();
         }

         public Iterator<XSModelGroupDecl> particle(XSParticle particle) {
             return singleton(particle.getTerm().asModelGroupDecl());
         }

         public String toString() {
             return "group::";
         }
     };

     public static final Axis<XSIdentityConstraint> IDENTITY_CONSTRAINT = new AbstractAxisImpl<XSIdentityConstraint>() {
         public Iterator<XSIdentityConstraint> elementDecl(XSElementDecl decl) {
             return decl.getIdentityConstraints().iterator();
         }

         public Iterator<XSIdentityConstraint> schema(XSSchema schema) {
             // TODO: iterate all elements in this schema (local or global!) and its identity constraints
             return super.schema(schema);
         }

         public String toString() {
             return "identityConstraint::";
         }
     };

     public static final Axis<XSIdentityConstraint> REFERENCED_KEY = new AbstractAxisImpl<XSIdentityConstraint>() {
         public Iterator<XSIdentityConstraint> identityConstraint(XSIdentityConstraint decl) {
             return singleton(decl.getReferencedKey());
         }

         public String toString() {
             return "key::";
         }
     };

     public static final Axis<XSNotation> NOTATION = new AbstractAxisImpl<XSNotation>() {
         public Iterator<XSNotation> schema(XSSchema schema) {
             return schema.iterateNotations();
         }

         public String toString() {
             return "notation::";
         }
     };

     public static final Axis<XSWildcard> WILDCARD = new AbstractAxisImpl<XSWildcard>() {
         public Iterator<XSWildcard> particle(XSParticle particle) {
             return singleton(particle.getTerm().asWildcard());
         }

         public String toString() {
             return "any::";
         }
     };

     public static final Axis<XSWildcard> ATTRIBUTE_WILDCARD = new AbstractAxisImpl<XSWildcard>() {
         public Iterator<XSWildcard> complexType(XSComplexType type) {
             return singleton(type.getAttributeWildcard());
         }

         public Iterator<XSWildcard> attGroupDecl(XSAttGroupDecl decl) {
             return singleton(decl.getAttributeWildcard());
         }

         public String toString() {
             return "anyAttribute::";
         }
     };

     public static final Axis<XSFacet> FACET = new AbstractAxisImpl<XSFacet>() {
         public Iterator<XSFacet> simpleType(XSSimpleType type) {
             // TODO: it's not clear if "facets" mean all inherited facets or just declared facets
             XSRestrictionSimpleType r = type.asRestriction();
             if(r!=null)
                 return r.iterateDeclaredFacets();
             else
                 return empty();
         }

         public String toString() {
             return "facet::";
         }
     };

     public static final Axis<XSModelGroup> MODELGROUP_ALL = new ModelGroupAxis(Compositor.ALL);
     public static final Axis<XSModelGroup> MODELGROUP_CHOICE = new ModelGroupAxis(Compositor.CHOICE);
     public static final Axis<XSModelGroup> MODELGROUP_SEQUENCE = new ModelGroupAxis(Compositor.SEQUENCE);
     public static final Axis<XSModelGroup> MODELGROUP_ANY = new ModelGroupAxis(null);

     static final class ModelGroupAxis extends AbstractAxisImpl<XSModelGroup> {
         private final XSModelGroup.Compositor compositor;

         ModelGroupAxis(Compositor compositor) {
             this.compositor = compositor;
         }

         @Override
         public boolean isModelGroup() {
             return true;
         }

         public Iterator<XSModelGroup> particle(XSParticle particle) {
             return filter(particle.getTerm().asModelGroup());
         }

         public Iterator<XSModelGroup> modelGroupDecl(XSModelGroupDecl decl) {
             return filter(decl.getModelGroup());
         }

         private Iterator<XSModelGroup> filter(XSModelGroup mg) {
             if(mg==null)
                 return empty();
             if(mg.getCompositor() == compositor || compositor == null)
                 return singleton(mg);
             else
                 return empty();
         }

         public String toString() {
             if(compositor==null)
                 return "model::*";
             else
                 return "model::"+compositor;
         }
     }
 }
	/*
	* Copyright 2005-2006 Sun Microsystems, Inc. All Rights Reserved.
	* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
	*
	* This code is free software; you can redistribute it and/or modify it
	* under the terms of the GNU General Public License version 2 only, as
	* published by the Free Software Foundation. Sun designates this
	* particular file as subject to the "Classpath" exception as provided
	* by Sun in the LICENSE file that accompanied this code.
	*
	* This code is distributed in the hope that it will be useful, but WITHOUT
	* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
	* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
	* version 2 for more details (a copy is included in the LICENSE file that
	* accompanied this code).
	*
	* You should have received a copy of the GNU General Public License version
	* 2 along with this work; if not, write to the Free Software Foundation,
	* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
	*
	* Please contact Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,
	* CA 95054 USA or visit www.sun.com if you need additional information or
	* have any questions.
	*/
	package com.sun.xml.internal.xsom.impl.scd;

	import com.sun.xml.internal.xsom.XSAttContainer;
	import com.sun.xml.internal.xsom.XSAttGroupDecl;
	import com.sun.xml.internal.xsom.XSAttributeDecl;
	import com.sun.xml.internal.xsom.XSAttributeUse;
	import com.sun.xml.internal.xsom.XSComplexType;
	import com.sun.xml.internal.xsom.XSComponent;
	import com.sun.xml.internal.xsom.XSElementDecl;
	import com.sun.xml.internal.xsom.XSFacet;
	import com.sun.xml.internal.xsom.XSIdentityConstraint;
	import com.sun.xml.internal.xsom.XSListSimpleType;
	import com.sun.xml.internal.xsom.XSModelGroup;
	import com.sun.xml.internal.xsom.XSModelGroup.Compositor;
	import com.sun.xml.internal.xsom.XSModelGroupDecl;
	import com.sun.xml.internal.xsom.XSNotation;
	import com.sun.xml.internal.xsom.XSParticle;
	import com.sun.xml.internal.xsom.XSRestrictionSimpleType;
	import com.sun.xml.internal.xsom.XSSchema;
	import com.sun.xml.internal.xsom.XSSimpleType;
	import com.sun.xml.internal.xsom.XSType;
	import com.sun.xml.internal.xsom.XSUnionSimpleType;
	import com.sun.xml.internal.xsom.XSWildcard;

	import java.util.ArrayList;
	import java.util.HashSet;
	import java.util.Iterator;
	import java.util.List;
	import java.util.Set;

	/**
	* Axis of traversal.
	*
	* @param <T>
	* The kind of components that this axis may return.
	*
	* @author Kohsuke Kawaguchi
	*/
	public interface Axis<T extends XSComponent> {
	Iterator<T> iterator(XSComponent contextNode);

	Iterator<T> iterator(Iterator<? extends XSComponent> contextNodes);

	/**
	* Returns true if this is one of the model group axis.
	*/
	boolean isModelGroup();


	/**
	* Pseudo-axis that selects all the {@link XSSchema}s in the current set.
	* Used to implement the absolute path expression
	*/
	public static final Axis<XSSchema> ROOT = new Axis<XSSchema>() {
	public Iterator<XSSchema> iterator(XSComponent contextNode) {
	return contextNode.getRoot().iterateSchema();
	}

	public Iterator<XSSchema> iterator(Iterator<? extends XSComponent> contextNodes) {
	if(!contextNodes.hasNext())
	return Iterators.empty();
	else
	// this assumes that all current nodes belong to the same owner.
	return iterator(contextNodes.next());
	}

	public boolean isModelGroup() {
	return false;
	}

	public String toString() {
	return "root::";
	}
	};

	/**
	* Pseudo-axis that visits all skipped intermediate steps.
	* Those are:
	* <ol>
	* <li>complex type reachable from element
	* <li>model groups
	* <li>combination of above.
	* </ol>
	*/
	public static final Axis<XSComponent> INTERMEDIATE_SKIP = new AbstractAxisImpl<XSComponent>() {
	public Iterator<XSComponent> elementDecl(XSElementDecl decl) {
	XSComplexType ct = decl.getType().asComplexType();
	if(ct==null)
	return empty();
	else {
	// also pick up model groups inside this complex type
	return new Iterators.Union<XSComponent>(singleton(ct),complexType(ct));
	}
	}

	public Iterator<XSComponent> modelGroupDecl(XSModelGroupDecl decl) {
	return descendants(decl.getModelGroup());
	}

	public Iterator<XSComponent> particle(XSParticle particle) {
	return descendants(particle.getTerm().asModelGroup());
	}

	/**
	* Iterate all descendant model groups of the given model group, including itself.
	*/
	private Iterator<XSComponent> descendants(XSModelGroup mg) {
	// TODO: write a tree iterator
	// for now, we do it eagerly because I'm lazy
	List<XSComponent> r = new ArrayList<XSComponent>();
	visit(mg,r);
	return r.iterator();
	}

	private void visit(XSModelGroup mg, List<XSComponent> r) {
	// since model groups never form a cycle, no cycle check is needed
	r.add(mg);
	for (XSParticle p : mg) {
	XSModelGroup child = p.getTerm().asModelGroup();
	if(child!=null)
	visit(child,r);
	}
	}

	public String toString() {
	return "(intermediateSkip)";
	}
	};

	/**
	* All descendants reachable via default axes. Used to implement the "//" semantics.
	*
	* So far the default axes together are guaranteed not to cause any cycle, so
	* no cycle check is needed (if it's needed, the life would be much harder!)
	*/
	public static final Axis<XSComponent> DESCENDANTS = new Axis<XSComponent>() {
	public Iterator<XSComponent> iterator(XSComponent contextNode) {
	return new Visitor().iterator(contextNode);
	}
	public Iterator<XSComponent> iterator(Iterator<? extends XSComponent> contextNodes) {
	return new Visitor().iterator(contextNodes);
	}

	public boolean isModelGroup() {
	return false;
	}

	/**
	* Stateful visitor that remembers what's already traversed, to reduce the search space.
	*/
	final class Visitor extends AbstractAxisImpl<XSComponent> {
	private final Set<XSComponent> visited = new HashSet<XSComponent>();

	/**
	* Recursively apply the {@link Axis#DESCENDANTS} axis.
	*/
	final class Recursion extends Iterators.Map<XSComponent,XSComponent> {
	public Recursion(Iterator<? extends XSComponent> core) {
	super(core);
	}

	protected Iterator<XSComponent> apply(XSComponent u) {
	return DESCENDANTS.iterator(u);
	}
	}
	public Iterator<XSComponent> schema(XSSchema schema) {
	if(visited.add(schema))
	return ret( schema, new Recursion(schema.iterateElementDecls()));
	else
	return empty();
	}

	public Iterator<XSComponent> elementDecl(XSElementDecl decl) {
	if(visited.add(decl))
	return ret(decl, iterator(decl.getType()) );
	else
	return empty();
	}

	public Iterator<XSComponent> simpleType(XSSimpleType type) {
	if(visited.add(type))
	return ret(type, FACET.iterator(type));
	else
	return empty();
	}

	public Iterator<XSComponent> complexType(XSComplexType type) {
	if(visited.add(type))
	return ret(type, iterator(type.getContentType()));
	else
	return empty();
	}

	public Iterator<XSComponent> particle(XSParticle particle) {
	if(visited.add(particle))
	return ret(particle, iterator(particle.getTerm()));
	else
	return empty();
	}

	public Iterator<XSComponent> modelGroupDecl(XSModelGroupDecl decl) {
	if(visited.add(decl))
	return ret(decl, iterator(decl.getModelGroup()));
	else
	return empty();
	}

	public Iterator<XSComponent> modelGroup(XSModelGroup group) {
	if(visited.add(group))
	return ret(group, new Recursion(group.iterator()));
	else
	return empty();
	}

	public Iterator<XSComponent> attGroupDecl(XSAttGroupDecl decl) {
	if(visited.add(decl))
	return ret(decl, new Recursion(decl.iterateAttributeUses()));
	else
	return empty();
	}

	public Iterator<XSComponent> attributeUse(XSAttributeUse use) {
	if(visited.add(use))
	return ret(use, iterator(use.getDecl()));
	else
	return empty();
	}

	public Iterator<XSComponent> attributeDecl(XSAttributeDecl decl) {
	if(visited.add(decl))
	return ret(decl, iterator(decl.getType()));
	else
	return empty();
	}

	private Iterator<XSComponent> ret( XSComponent one, Iterator<? extends XSComponent> rest ) {
	return union(singleton(one),rest);
	}
	}

	public String toString() {
	return "/";
	}
	};

	public static final Axis<XSSchema> X_SCHEMA = new Axis<XSSchema>() {
	public Iterator<XSSchema> iterator(XSComponent contextNode) {
	return Iterators.singleton(contextNode.getOwnerSchema());
	}

	public Iterator<XSSchema> iterator(Iterator<? extends XSComponent> contextNodes) {
	return new Iterators.Adapter<XSSchema,XSComponent>(contextNodes) {
	protected XSSchema filter(XSComponent u) {
	return u.getOwnerSchema();
	}
	};
	}

	public boolean isModelGroup() {
	return false;
	}

	public String toString() {
	return "x-schema::";
	}
	};

	public static final Axis<XSElementDecl> SUBSTITUTION_GROUP = new AbstractAxisImpl<XSElementDecl>() {
	public Iterator<XSElementDecl> elementDecl(XSElementDecl decl) {
	return singleton(decl.getSubstAffiliation());
	}

	public String toString() {
	return "substitutionGroup::";
	}
	};

	public static final Axis<XSAttributeDecl> ATTRIBUTE = new AbstractAxisImpl<XSAttributeDecl>() {
	public Iterator<XSAttributeDecl> complexType(XSComplexType type) {
	return attributeHolder(type);
	}

	public Iterator<XSAttributeDecl> attGroupDecl(XSAttGroupDecl decl) {
	return attributeHolder(decl);
	}

	private Iterator<XSAttributeDecl> attributeHolder(final XSAttContainer atts) {
	// TODO: check spec. is this correct?
	return new Iterators.Adapter<XSAttributeDecl,XSAttributeUse>(atts.iterateAttributeUses()) {
	protected XSAttributeDecl filter(XSAttributeUse u) {
	return u.getDecl();
	}
	};
	}

	public Iterator<XSAttributeDecl> schema(XSSchema schema) {
	return schema.iterateAttributeDecls();
	}

	public String toString() {
	return "@";
	}
	};

	public static final Axis<XSElementDecl> ELEMENT = new AbstractAxisImpl<XSElementDecl>() {
	public Iterator<XSElementDecl> particle(XSParticle particle) {
	return singleton(particle.getTerm().asElementDecl());
	}

	public Iterator<XSElementDecl> schema(XSSchema schema) {
	return schema.iterateElementDecls();
	}

	public Iterator<XSElementDecl> modelGroupDecl(XSModelGroupDecl decl) {
	return modelGroup(decl.getModelGroup());
	}

	//public Iterator<XSElementDecl> modelGroup(XSModelGroup group) {
	// return new Iterators.Map<XSElementDecl,XSParticle>(group.iterator()) {
	// protected Iterator<XSElementDecl> apply(XSParticle p) {
	// return particle(p);
	// }
	// };
	//}

	@Override
	public String getName() {
	return "";
	}

	public String toString() {
	return "element::";
	}
	};


	public static final Axis<XSType> TYPE_DEFINITION = new AbstractAxisImpl<XSType>() {
	public Iterator<XSType> schema(XSSchema schema) {
	return schema.iterateTypes();
	}

	public Iterator<XSType> attributeDecl(XSAttributeDecl decl) {
	return singleton(decl.getType());
	}

	public Iterator<XSType> elementDecl(XSElementDecl decl) {
	return singleton(decl.getType());
	}

	public String toString() {
	return "~";
	}
	};

	public static final Axis<XSType> BASETYPE = new AbstractAxisImpl<XSType>() {
	public Iterator<XSType> simpleType(XSSimpleType type) {
	return singleton(type.getBaseType());
	}

	public Iterator<XSType> complexType(XSComplexType type) {
	return singleton(type.getBaseType());
	}

	public String toString() {
	return "baseType::";
	}
	};

	public static final Axis<XSSimpleType> PRIMITIVE_TYPE = new AbstractAxisImpl<XSSimpleType>() {
	public Iterator<XSSimpleType> simpleType(XSSimpleType type) {
	return singleton(type.getPrimitiveType());
	}

	public String toString() {
	return "primitiveType::";
	}
	};

	public static final Axis<XSSimpleType> ITEM_TYPE = new AbstractAxisImpl<XSSimpleType>() {
	public Iterator<XSSimpleType> simpleType(XSSimpleType type) {
	XSListSimpleType baseList = type.getBaseListType();
	if(baseList==null) return empty();
	return singleton(baseList.getItemType());
	}

	public String toString() {
	return "itemType::";
	}
	};

	public static final Axis<XSSimpleType> MEMBER_TYPE = new AbstractAxisImpl<XSSimpleType>() {
	public Iterator<XSSimpleType> simpleType(XSSimpleType type) {
	XSUnionSimpleType baseUnion = type.getBaseUnionType();
	if(baseUnion ==null) return empty();
	return baseUnion.iterator();
	}

	public String toString() {
	return "memberType::";
	}
	};

	public static final Axis<XSComponent> SCOPE = new AbstractAxisImpl<XSComponent>() {
	public Iterator<XSComponent> complexType(XSComplexType type) {
	return singleton(type.getScope());
	}
	// TODO: attribute declaration has a scope, too.
	// TODO: element declaration has a scope

	public String toString() {
	return "scope::";
	}
	};

	public static final Axis<XSAttGroupDecl> ATTRIBUTE_GROUP = new AbstractAxisImpl<XSAttGroupDecl>() {
	public Iterator<XSAttGroupDecl> schema(XSSchema schema) {
	return schema.iterateAttGroupDecls();
	}

	public String toString() {
	return "attributeGroup::";
	}
	};

	public static final Axis<XSModelGroupDecl> MODEL_GROUP_DECL = new AbstractAxisImpl<XSModelGroupDecl>() {
	public Iterator<XSModelGroupDecl> schema(XSSchema schema) {
	return schema.iterateModelGroupDecls();
	}

	public Iterator<XSModelGroupDecl> particle(XSParticle particle) {
	return singleton(particle.getTerm().asModelGroupDecl());
	}

	public String toString() {
	return "group::";
	}
	};

	public static final Axis<XSIdentityConstraint> IDENTITY_CONSTRAINT = new AbstractAxisImpl<XSIdentityConstraint>() {
	public Iterator<XSIdentityConstraint> elementDecl(XSElementDecl decl) {
	return decl.getIdentityConstraints().iterator();
	}

	public Iterator<XSIdentityConstraint> schema(XSSchema schema) {
	// TODO: iterate all elements in this schema (local or global!) and its identity constraints
	return super.schema(schema);
	}

	public String toString() {
	return "identityConstraint::";
	}
	};

	public static final Axis<XSIdentityConstraint> REFERENCED_KEY = new AbstractAxisImpl<XSIdentityConstraint>() {
	public Iterator<XSIdentityConstraint> identityConstraint(XSIdentityConstraint decl) {
	return singleton(decl.getReferencedKey());
	}

	public String toString() {
	return "key::";
	}
	};

	public static final Axis<XSNotation> NOTATION = new AbstractAxisImpl<XSNotation>() {
	public Iterator<XSNotation> schema(XSSchema schema) {
	return schema.iterateNotations();
	}

	public String toString() {
	return "notation::";
	}
	};

	public static final Axis<XSWildcard> WILDCARD = new AbstractAxisImpl<XSWildcard>() {
	public Iterator<XSWildcard> particle(XSParticle particle) {
	return singleton(particle.getTerm().asWildcard());
	}

	public String toString() {
	return "any::";
	}
	};

	public static final Axis<XSWildcard> ATTRIBUTE_WILDCARD = new AbstractAxisImpl<XSWildcard>() {
	public Iterator<XSWildcard> complexType(XSComplexType type) {
	return singleton(type.getAttributeWildcard());
	}

	public Iterator<XSWildcard> attGroupDecl(XSAttGroupDecl decl) {
	return singleton(decl.getAttributeWildcard());
	}

	public String toString() {
	return "anyAttribute::";
	}
	};

	public static final Axis<XSFacet> FACET = new AbstractAxisImpl<XSFacet>() {
	public Iterator<XSFacet> simpleType(XSSimpleType type) {
	// TODO: it's not clear if "facets" mean all inherited facets or just declared facets
	XSRestrictionSimpleType r = type.asRestriction();
	if(r!=null)
	return r.iterateDeclaredFacets();
	else
	return empty();
	}

	public String toString() {
	return "facet::";
	}
	};

	public static final Axis<XSModelGroup> MODELGROUP_ALL = new ModelGroupAxis(Compositor.ALL);
	public static final Axis<XSModelGroup> MODELGROUP_CHOICE = new ModelGroupAxis(Compositor.CHOICE);
	public static final Axis<XSModelGroup> MODELGROUP_SEQUENCE = new ModelGroupAxis(Compositor.SEQUENCE);
	public static final Axis<XSModelGroup> MODELGROUP_ANY = new ModelGroupAxis(null);

	static final class ModelGroupAxis extends AbstractAxisImpl<XSModelGroup> {
	private final XSModelGroup.Compositor compositor;

	ModelGroupAxis(Compositor compositor) {
	this.compositor = compositor;
	}

	@Override
	public boolean isModelGroup() {
	return true;
	}

	public Iterator<XSModelGroup> particle(XSParticle particle) {
	return filter(particle.getTerm().asModelGroup());
	}

	public Iterator<XSModelGroup> modelGroupDecl(XSModelGroupDecl decl) {
	return filter(decl.getModelGroup());
	}

	private Iterator<XSModelGroup> filter(XSModelGroup mg) {
	if(mg==null)
	return empty();
	if(mg.getCompositor() == compositor \|\| compositor == null)
	return singleton(mg);
	else
	return empty();
	}

	public String toString() {
	if(compositor==null)
	return "model::*";
	else
	return "model::"+compositor;
	}
	}
	}