private XmlNameTable GetNameTable (NSResolver nss1, NSResolver nss2)
		{
			XmlNameTable nt = null;
			if (nss1 is XmlNamespaceManager)
				nt = ((XmlNamespaceManager) nss1).NameTable;
			if (nss2 is XmlNamespaceManager)
				nt = ((XmlNamespaceManager) nss2).NameTable;
			if (nt == null)
				nt = new NameTable ();
			return nt;
		}

		public RncWriter (TextWriter writer, NSResolver structureNamespaces, NSResolver dataNamespaces)
		{
			this.w = writer;
			this.nsmgr = structureNamespaces;
			this.datansmgr = dataNamespaces;
			XmlNameTable nt = GetNameTable (nsmgr, datansmgr);
			if (nsmgr == null)
				nsmgr = new XmlNamespaceManager (nt);
			if (datansmgr == null)
				datansmgr = new XmlNamespaceManager (nt);
		}

		internal bool EvaluateBoolean (XPathExpression expr, XPathNodeIterator context, NSResolver ctx)
		{
			CompiledExpression cexpr = (CompiledExpression) expr;
			if (ctx == null)
				ctx = cexpr.NamespaceManager;
			
			if (context == null)
				context = new NullIterator (this, cexpr.NamespaceManager);
			BaseIterator iterContext = ToBaseIterator (context, ctx);
			iterContext.NamespaceManager = ctx;
			return cexpr.EvaluateBoolean (iterContext);
		}

		// In this method, attributes are ignored.
		// It might throw Exception.
		public void ProcessMatch (bool isAttribute, ArrayList qnameStack, object sender, XmlNameTable nameTable, string sourceUri, object schemaType, NSResolver nsResolver, IXmlLineInfo li, int depth, string attrName, string attrNS, object attrValue, bool isXsiNil, ArrayList currentKeyFieldConsumers)
		{
			for (int i = 0; i < KeyFields.Count; i++) {
				XsdKeyEntryField keyField = KeyFields [i];
				XsdIdentityPath path = keyField.Matches (isAttribute, sender, nameTable, qnameStack, sourceUri, schemaType, nsResolver, li, depth, attrName, attrNS, attrValue);
				if (path == null)
					continue;

				if (keyField.FieldFound) {
					// HACK: This is not logical by nature. Attributes never be cosuming,
					// so I used it as a temporary mark to sign it is *just* validated now.
					if (!keyField.Consuming)
						throw new ValException ("Two or more matching field was found.",
							sender, sourceUri, this.OwnerSequence.SourceSchemaIdentity, null);
					else
						keyField.Consuming = false;
				}
				if (keyField.Consumed) 
					continue;

				if (isXsiNil && !keyField.SetIdentityField (Guid.Empty, true, XsdAnySimpleType.Instance, depth, li))
					throw new ValException ("Two or more identical field was found.", sender, sourceUri, OwnerSequence.SourceSchemaIdentity, null);
				XmlSchemaComplexType ct = schemaType as XmlSchemaComplexType;
				if (ct != null && 
					(ct.ContentType == XmlSchemaContentType.Empty || ct.ContentType == XmlSchemaContentType.ElementOnly) && 
					schemaType != XmlSchemaComplexType.AnyType)
					throw new ValException ("Specified schema type is complex type, which is not allowed for identity constraints.", sender, sourceUri, OwnerSequence.SourceSchemaIdentity, null);
				keyField.FieldFound = true;
				keyField.FieldFoundPath = path;
				keyField.FieldFoundDepth = depth;
				keyField.Consuming = true;
				if (li != null && li.HasLineInfo ()) {
					keyField.FieldHasLineInfo = true;
					keyField.FieldLineNumber = li.LineNumber;
					keyField.FieldLinePosition = li.LinePosition;
				}
				currentKeyFieldConsumers.Add (keyField);
			}
		}

		// if matchesAttr then check attributes; otherwise check elements.
		internal XsdIdentityPath Matches (bool matchesAttr, object sender, XmlNameTable nameTable, ArrayList qnameStack, string sourceUri, object schemaType, NSResolver nsResolver, IXmlLineInfo lineInfo, int depth, string attrName, string attrNS, object attrValue)
		{
			XsdIdentityPath matchedAttrPath = null;

			for (int i = 0; i < field.Paths.Length; i++) {
				XsdIdentityPath path = field.Paths [i];
				bool isAttribute = path.IsAttribute;
				if (matchesAttr != isAttribute)
					continue;
				XsdIdentityStep step;
				if (path.IsAttribute) {
					step = path.OrderedSteps [path.OrderedSteps.Length - 1];
					bool match = false;
					if (step.IsAnyName || step.NsName != null) {
						if (step.IsAnyName || attrNS == step.NsName)
							match = true;
					}
					else if (step.Name == attrName && step.Namespace == attrNS)
						match = true;
					if (!match)
						continue;
					// first -1 is to reduce attr path step, next -1 is to reduce Attribute's depth in XmlReader.
					if (entry.StartDepth + (path.OrderedSteps.Length - 1) != depth - 1)
						continue; // matched at different nest level
					matchedAttrPath = path;
				}
				if (FieldFound && (depth > this.FieldFoundDepth && this.FieldFoundPath == path))
					continue; // don't return; other fields might hit errorneously.

				// Only "." hits.
				if (path.OrderedSteps.Length == 0) {
					if (depth == entry.StartDepth)
						return path;
					else
						continue;
				}
				// It does not hit as yet (too shallow to hit).
				if (depth - entry.StartDepth < path.OrderedSteps.Length - 1)
					continue;

				int iter = path.OrderedSteps.Length;
				if (isAttribute)
					iter--;
				if (path.Descendants && depth < entry.StartDepth + iter)
					continue;
				else if (!path.Descendants && depth != entry.StartDepth + iter)
					continue;

				iter--;

				for (; iter >= 0; iter--) {
					step = path.OrderedSteps [iter];
					if (step.IsCurrent || step.IsAnyName)
						continue;
					XmlQualifiedName qname = (XmlQualifiedName) qnameStack [entry.StartDepth + iter + (isAttribute ? 0 : 1)];
					if (step.NsName != null && qname.Namespace == step.NsName)
						continue;
					if ((step.Name == "*" || step.Name == qname.Name) &&
						step.Namespace == qname.Namespace)
						continue;
					else
						break;
				}
				if (iter >= 0)	// i.e. did not match against the path.
					continue;

				if (!matchesAttr)
					return path;
			}
			if (matchedAttrPath != null) {
				this.FillAttributeFieldValue (sender, nameTable, sourceUri, schemaType, nsResolver, attrValue, lineInfo, depth);
				if (this.Identity != null)
					return matchedAttrPath;
			}
			return null;
		}

		internal BaseIterator (BaseIterator other)
		{
			_nsm = other._nsm;
			position = other.position;
		}

		public NullIterator (XPathNavigator nav, NSResolver nsm) : base (nav, nsm) {}

		public WrapperIterator (XPathNodeIterator iter, NSResolver nsm)
			: base (nsm)
		{
			this.iter = iter;
		}

		internal override ValueType ParseValueType (string s, XmlNameTable nameTable, NSResolver nsmgr) 
		{
			return new StringValueType (ParseValue (s, nameTable, nsmgr) as string);
		}

		internal override ValueType ParseValueType (string s, XmlNameTable nameTable, NSResolver nsmgr) 
		{
			return DateTime.ParseExact (Normalize(s), "---dd", null);
		}

		internal override ValueType ParseValueType (string s, XmlNameTable nameTable, NSResolver nsmgr) 
		{
			return new UriValueType ((XmlSchemaUri) ParseValue (s, nameTable, nsmgr));
		}

		public override object ParseValue (string s,
			XmlNameTable nameTable, NSResolver nsmgr)
		{
			return new XmlSchemaUri (Normalize (s));
		}

		internal override ValueType ParseValueType (string s, XmlNameTable nameTable, NSResolver nsmgr) 
		{
			return new QNameValueType (ParseValue (s, nameTable, nsmgr) as XmlQualifiedName);
		}

		public void WriteCompact (TextWriter writer, NSResolver res)
		{
			WriteCompact (new RncWriter (writer, res));
		}

		public ListIterator (IList list, NSResolver nsm) : base (nsm)
		{
			_list = list;
		}

		public SimpleIterator (XPathNavigator nav, NSResolver nsm) : base (nsm)
		{
			_nav = nav.Clone ();
		}

		public ParentIterator (XPathNavigator nav, NSResolver nsm) : base (nav, nsm) {}

		internal override ValueType ParseValueType (string s, XmlNameTable nameTable, NSResolver nsmgr) 
		{
			return new StringArrayValueType (GetValidatedArray (s, nameTable));
		}

		private void FillAttributeFieldValue (object sender, XmlNameTable nameTable, string sourceUri, object schemaType, NSResolver nsResolver, object identity, IXmlLineInfo lineInfo, int depth)
		{
			if (this.FieldFound)
				throw new ValException (String.Format ("The key value was already found as '{0}'{1}.", Identity,
					(this.FieldHasLineInfo ?
						String.Format (CultureInfo.InvariantCulture, " at line {0}, position {1}", FieldLineNumber, FieldLinePosition) :
						"")),
					sender, sourceUri, entry.OwnerSequence.SourceSchemaIdentity, null);
			XmlSchemaDatatype dt = schemaType as XmlSchemaDatatype;
			XmlSchemaSimpleType st = schemaType as XmlSchemaSimpleType;
			if (dt == null && st != null)
				dt = st.Datatype;
			try {
				if (!this.SetIdentityField (identity, false, dt as XsdAnySimpleType, depth, lineInfo))
					throw new ValException ("Two or more identical field was found.",
						sender, sourceUri, entry.OwnerSequence.SourceSchemaIdentity, null);
				// HACK: This is not logical. Attributes will never be "cosuming",
				// so I used it as a temporary mark to sign it is validated *just now*.
				this.Consuming = true;
				this.FieldFound = true;
			} catch (Exception ex) {
				throw new ValException ("Failed to read typed value.", sender, sourceUri, entry.OwnerSequence.SourceSchemaIdentity, ex);
			}
		}

		internal override ValueType ParseValueType (string s, XmlNameTable nameTable, NSResolver nsmgr) 
		{
			decimal d = XmlConvert.ToDecimal (Normalize (s));
			if (Decimal.Floor (d) != d)
				throw new FormatException ("Integer contains point number.");
			return d;
		}