An Error Occurred

The actual return type does not match the sequence type declared in the function's signature: local:intro() element(). Expected cardinality: exactly one, got 0. [at line 12, column 15]
In call to function:
local:intro() [12:15]
local:package(xs:string) [64:1]

org.apache.cocoon.ProcessingException: XMLDBException occurred: The actual return type does not match the sequence type declared in the function's signature: local:intro() element(). Expected cardinality: exactly one, got 0. [at line 12, column 15]
In call to function:
local:intro() [12:15]
local:package(xs:string) [64:1]: org.xmldb.api.base.XMLDBException: The actual return type does not match the sequence type declared in the function's signature: local:intro() element(). Expected cardinality: exactly one, got 0. [at line 12, column 15]
In call to function:
local:intro() [12:15]
local:package(xs:string) [64:1]

cause: org.exist.xquery.XPathException: The actual return type does not match the sequence type declared in the function's signature: local:intro() element(). Expected cardinality: exactly one, got 0. [at line 12, column 15]
In call to function:
local:intro() [12:15]
local:package(xs:string) [64:1]

full exception chain stacktrace[show]

org.apache.cocoon.ProcessingException: XMLDBException occurred: The actual return type does not match the sequence type declared in the function's signature: local:intro() element(). Expected cardinality: exactly one, got 0. [at line 12, column 15]
In call to function:
	local:intro() [12:15]
	local:package(xs:string) [64:1]: org.xmldb.api.base.XMLDBException: The actual return type does not match the sequence type declared in the function's signature: local:intro() element(). Expected cardinality: exactly one, got 0. [at line 12, column 15]
In call to function:
	local:intro() [12:15]
	local:package(xs:string) [64:1]
	at org.exist.cocoon.XQueryGenerator.generate(XQueryGenerator.java:339)
	at org.apache.cocoon.components.pipeline.AbstractProcessingPipeline.processXMLPipeline(AbstractProcessingPipeline.java:575)
	at org.apache.cocoon.components.pipeline.impl.AbstractCachingProcessingPipeline.processXMLPipeline(AbstractCachingProcessingPipeline.java:183)
	at org.apache.cocoon.components.pipeline.AbstractProcessingPipeline.process(AbstractProcessingPipeline.java:483)
	at org.apache.cocoon.components.treeprocessor.sitemap.SerializeNode.invoke(SerializeNode.java:120)
	at org.apache.cocoon.components.treeprocessor.AbstractParentProcessingNode.invokeNodes(AbstractParentProcessingNode.java:46)
	at org.apache.cocoon.components.treeprocessor.sitemap.PreparableMatchNode.invoke(PreparableMatchNode.java:130)
	at org.apache.cocoon.components.treeprocessor.AbstractParentProcessingNode.invokeNodes(AbstractParentProcessingNode.java:68)
	at org.apache.cocoon.components.treeprocessor.sitemap.PipelineNode.invoke(PipelineNode.java:138)
	at org.apache.cocoon.components.treeprocessor.AbstractParentProcessingNode.invokeNodes(AbstractParentProcessingNode.java:68)
	at org.apache.cocoon.components.treeprocessor.sitemap.PipelinesNode.invoke(PipelinesNode.java:92)
	at org.apache.cocoon.components.treeprocessor.ConcreteTreeProcessor.process(ConcreteTreeProcessor.java:234)
	at org.apache.cocoon.components.treeprocessor.ConcreteTreeProcessor.process(ConcreteTreeProcessor.java:176)
	at org.apache.cocoon.components.treeprocessor.TreeProcessor.process(TreeProcessor.java:243)
	at org.apache.cocoon.components.treeprocessor.sitemap.MountNode.invoke(MountNode.java:117)
	at org.apache.cocoon.components.treeprocessor.AbstractParentProcessingNode.invokeNodes(AbstractParentProcessingNode.java:46)
	at org.apache.cocoon.components.treeprocessor.sitemap.PreparableMatchNode.invoke(PreparableMatchNode.java:130)
	at org.apache.cocoon.components.treeprocessor.AbstractParentProcessingNode.invokeNodes(AbstractParentProcessingNode.java:68)
	at org.apache.cocoon.components.treeprocessor.sitemap.PipelineNode.invoke(PipelineNode.java:138)
	at org.apache.cocoon.components.treeprocessor.AbstractParentProcessingNode.invokeNodes(AbstractParentProcessingNode.java:68)
	at org.apache.cocoon.components.treeprocessor.sitemap.PipelinesNode.invoke(PipelinesNode.java:92)
	at org.apache.cocoon.components.treeprocessor.ConcreteTreeProcessor.process(ConcreteTreeProcessor.java:234)
	at org.apache.cocoon.components.treeprocessor.ConcreteTreeProcessor.process(ConcreteTreeProcessor.java:176)
	at org.apache.cocoon.components.treeprocessor.TreeProcessor.process(TreeProcessor.java:243)
	at org.apache.cocoon.Cocoon.process(Cocoon.java:608)
	at org.apache.cocoon.servlet.CocoonServlet.service(CocoonServlet.java:1123)
	at javax.servlet.http.HttpServlet.service(HttpServlet.java:802)
	at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:237)
	at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:157)
	at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:214)
	at org.apache.catalina.core.StandardValveContext.invokeNext(StandardValveContext.java:104)
	at org.apache.catalina.core.StandardPipeline.invoke(StandardPipeline.java:520)
	at org.apache.catalina.core.StandardContextValve.invokeInternal(StandardContextValve.java:198)
	at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:152)
	at org.apache.catalina.core.StandardValveContext.invokeNext(StandardValveContext.java:104)
	at org.apache.catalina.core.StandardPipeline.invoke(StandardPipeline.java:520)
	at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:137)
	at org.apache.catalina.core.StandardValveContext.invokeNext(StandardValveContext.java:104)
	at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:118)
	at org.apache.catalina.core.StandardValveContext.invokeNext(StandardValveContext.java:102)
	at org.apache.catalina.core.StandardPipeline.invoke(StandardPipeline.java:520)
	at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:109)
	at org.apache.catalina.core.StandardValveContext.invokeNext(StandardValveContext.java:104)
	at org.apache.catalina.core.StandardPipeline.invoke(StandardPipeline.java:520)
	at org.apache.catalina.core.ContainerBase.invoke(ContainerBase.java:929)
	at org.apache.coyote.tomcat5.CoyoteAdapter.service(CoyoteAdapter.java:160)
	at org.apache.coyote.http11.Http11Processor.process(Http11Processor.java:799)
	at org.apache.coyote.http11.Http11Protocol$Http11ConnectionHandler.processConnection(Http11Protocol.java:705)
	at org.apache.tomcat.util.net.TcpWorkerThread.runIt(PoolTcpEndpoint.java:577)
	at org.apache.tomcat.util.threads.ThreadPool$ControlRunnable.run(ThreadPool.java:683)
	at java.lang.Thread.run(Thread.java:595)
Caused by: org.xmldb.api.base.XMLDBException: The actual return type does not match the sequence type declared in the function's signature: local:intro() element(). Expected cardinality: exactly one, got 0. [at line 12, column 15]
In call to function:
	local:intro() [12:15]
	local:package(xs:string) [64:1]
	at org.exist.xmldb.LocalXPathQueryService.execute(LocalXPathQueryService.java:200)
	at org.exist.cocoon.XQueryGenerator.generate(XQueryGenerator.java:330)
	... 50 more
Caused by: org.exist.xquery.XPathException: The actual return type does not match the sequence type declared in the function's signature: local:intro() element(). Expected cardinality: exactly one, got 0. [at line 12, column 15]
In call to function:
	local:intro() [12:15]
	local:package(xs:string) [64:1]
	at org.exist.xquery.DynamicCardinalityCheck.eval(DynamicCardinalityCheck.java:80)
	at org.exist.xquery.DynamicTypeCheck.eval(DynamicTypeCheck.java:66)
	at org.exist.xquery.FunctionCall.evalFunction(FunctionCall.java:223)
	at org.exist.xquery.FunctionCall.eval(FunctionCall.java:161)
	at org.exist.xquery.AbstractExpression.eval(AbstractExpression.java:59)
	at org.exist.xquery.PathExpr.eval(PathExpr.java:242)
	at org.exist.xquery.LetExpr.eval(LetExpr.java:150)
	at org.exist.xquery.BindingExpression.eval(BindingExpression.java:158)
	at org.exist.xquery.AbstractExpression.eval(AbstractExpression.java:59)
	at org.exist.xquery.PathExpr.eval(PathExpr.java:242)
	at org.exist.xquery.UserDefinedFunction.eval(UserDefinedFunction.java:122)
	at org.exist.xquery.DynamicCardinalityCheck.eval(DynamicCardinalityCheck.java:71)
	at org.exist.xquery.DynamicTypeCheck.eval(DynamicTypeCheck.java:66)
	at org.exist.xquery.FunctionCall.evalFunction(FunctionCall.java:223)
	at org.exist.xquery.FunctionCall.eval(FunctionCall.java:161)
	at org.exist.xquery.AbstractExpression.eval(AbstractExpression.java:59)
	at org.exist.xquery.PathExpr.eval(PathExpr.java:242)
	at org.exist.xquery.AbstractExpression.eval(AbstractExpression.java:59)
	at org.exist.xquery.XQuery.execute(XQuery.java:219)
	at org.exist.xquery.XQuery.execute(XQuery.java:186)
	at org.exist.xmldb.LocalXPathQueryService.execute(LocalXPathQueryService.java:190)
	... 51 more
org.xmldb.api.base.XMLDBException: The actual return type does not match the sequence type declared in the function's signature: local:intro() element(). Expected cardinality: exactly one, got 0. [at line 12, column 15]
In call to function:
	local:intro() [12:15]
	local:package(xs:string) [64:1]
	at org.exist.xmldb.LocalXPathQueryService.execute(LocalXPathQueryService.java:200)
	at org.exist.cocoon.XQueryGenerator.generate(XQueryGenerator.java:330)
	at org.apache.cocoon.components.pipeline.AbstractProcessingPipeline.processXMLPipeline(AbstractProcessingPipeline.java:575)
	at org.apache.cocoon.components.pipeline.impl.AbstractCachingProcessingPipeline.processXMLPipeline(AbstractCachingProcessingPipeline.java:183)
	at org.apache.cocoon.components.pipeline.AbstractProcessingPipeline.process(AbstractProcessingPipeline.java:483)
	at org.apache.cocoon.components.treeprocessor.sitemap.SerializeNode.invoke(SerializeNode.java:120)
	at org.apache.cocoon.components.treeprocessor.AbstractParentProcessingNode.invokeNodes(AbstractParentProcessingNode.java:46)
	at org.apache.cocoon.components.treeprocessor.sitemap.PreparableMatchNode.invoke(PreparableMatchNode.java:130)
	at org.apache.cocoon.components.treeprocessor.AbstractParentProcessingNode.invokeNodes(AbstractParentProcessingNode.java:68)
	at org.apache.cocoon.components.treeprocessor.sitemap.PipelineNode.invoke(PipelineNode.java:138)
	at org.apache.cocoon.components.treeprocessor.AbstractParentProcessingNode.invokeNodes(AbstractParentProcessingNode.java:68)
	at org.apache.cocoon.components.treeprocessor.sitemap.PipelinesNode.invoke(PipelinesNode.java:92)
	at org.apache.cocoon.components.treeprocessor.ConcreteTreeProcessor.process(ConcreteTreeProcessor.java:234)
	at org.apache.cocoon.components.treeprocessor.ConcreteTreeProcessor.process(ConcreteTreeProcessor.java:176)
	at org.apache.cocoon.components.treeprocessor.TreeProcessor.process(TreeProcessor.java:243)
	at org.apache.cocoon.components.treeprocessor.sitemap.MountNode.invoke(MountNode.java:117)
	at org.apache.cocoon.components.treeprocessor.AbstractParentProcessingNode.invokeNodes(AbstractParentProcessingNode.java:46)
	at org.apache.cocoon.components.treeprocessor.sitemap.PreparableMatchNode.invoke(PreparableMatchNode.java:130)
	at org.apache.cocoon.components.treeprocessor.AbstractParentProcessingNode.invokeNodes(AbstractParentProcessingNode.java:68)
	at org.apache.cocoon.components.treeprocessor.sitemap.PipelineNode.invoke(PipelineNode.java:138)
	at org.apache.cocoon.components.treeprocessor.AbstractParentProcessingNode.invokeNodes(AbstractParentProcessingNode.java:68)
	at org.apache.cocoon.components.treeprocessor.sitemap.PipelinesNode.invoke(PipelinesNode.java:92)
	at org.apache.cocoon.components.treeprocessor.ConcreteTreeProcessor.process(ConcreteTreeProcessor.java:234)
	at org.apache.cocoon.components.treeprocessor.ConcreteTreeProcessor.process(ConcreteTreeProcessor.java:176)
	at org.apache.cocoon.components.treeprocessor.TreeProcessor.process(TreeProcessor.java:243)
	at org.apache.cocoon.Cocoon.process(Cocoon.java:608)
	at org.apache.cocoon.servlet.CocoonServlet.service(CocoonServlet.java:1123)
	at javax.servlet.http.HttpServlet.service(HttpServlet.java:802)
	at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:237)
	at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:157)
	at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:214)
	at org.apache.catalina.core.StandardValveContext.invokeNext(StandardValveContext.java:104)
	at org.apache.catalina.core.StandardPipeline.invoke(StandardPipeline.java:520)
	at org.apache.catalina.core.StandardContextValve.invokeInternal(StandardContextValve.java:198)
	at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:152)
	at org.apache.catalina.core.StandardValveContext.invokeNext(StandardValveContext.java:104)
	at org.apache.catalina.core.StandardPipeline.invoke(StandardPipeline.java:520)
	at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:137)
	at org.apache.catalina.core.StandardValveContext.invokeNext(StandardValveContext.java:104)
	at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:118)
	at org.apache.catalina.core.StandardValveContext.invokeNext(StandardValveContext.java:102)
	at org.apache.catalina.core.StandardPipeline.invoke(StandardPipeline.java:520)
	at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:109)
	at org.apache.catalina.core.StandardValveContext.invokeNext(StandardValveContext.java:104)
	at org.apache.catalina.core.StandardPipeline.invoke(StandardPipeline.java:520)
	at org.apache.catalina.core.ContainerBase.invoke(ContainerBase.java:929)
	at org.apache.coyote.tomcat5.CoyoteAdapter.service(CoyoteAdapter.java:160)
	at org.apache.coyote.http11.Http11Processor.process(Http11Processor.java:799)
	at org.apache.coyote.http11.Http11Protocol$Http11ConnectionHandler.processConnection(Http11Protocol.java:705)
	at org.apache.tomcat.util.net.TcpWorkerThread.runIt(PoolTcpEndpoint.java:577)
	at org.apache.tomcat.util.threads.ThreadPool$ControlRunnable.run(ThreadPool.java:683)
	at java.lang.Thread.run(Thread.java:595)
Caused by: org.exist.xquery.XPathException: The actual return type does not match the sequence type declared in the function's signature: local:intro() element(). Expected cardinality: exactly one, got 0. [at line 12, column 15]
In call to function:
	local:intro() [12:15]
	local:package(xs:string) [64:1]
	at org.exist.xquery.DynamicCardinalityCheck.eval(DynamicCardinalityCheck.java:80)
	at org.exist.xquery.DynamicTypeCheck.eval(DynamicTypeCheck.java:66)
	at org.exist.xquery.FunctionCall.evalFunction(FunctionCall.java:223)
	at org.exist.xquery.FunctionCall.eval(FunctionCall.java:161)
	at org.exist.xquery.AbstractExpression.eval(AbstractExpression.java:59)
	at org.exist.xquery.PathExpr.eval(PathExpr.java:242)
	at org.exist.xquery.LetExpr.eval(LetExpr.java:150)
	at org.exist.xquery.BindingExpression.eval(BindingExpression.java:158)
	at org.exist.xquery.AbstractExpression.eval(AbstractExpression.java:59)
	at org.exist.xquery.PathExpr.eval(PathExpr.java:242)
	at org.exist.xquery.UserDefinedFunction.eval(UserDefinedFunction.java:122)
	at org.exist.xquery.DynamicCardinalityCheck.eval(DynamicCardinalityCheck.java:71)
	at org.exist.xquery.DynamicTypeCheck.eval(DynamicTypeCheck.java:66)
	at org.exist.xquery.FunctionCall.evalFunction(FunctionCall.java:223)
	at org.exist.xquery.FunctionCall.eval(FunctionCall.java:161)
	at org.exist.xquery.AbstractExpression.eval(AbstractExpression.java:59)
	at org.exist.xquery.PathExpr.eval(PathExpr.java:242)
	at org.exist.xquery.AbstractExpression.eval(AbstractExpression.java:59)
	at org.exist.xquery.XQuery.execute(XQuery.java:219)
	at org.exist.xquery.XQuery.execute(XQuery.java:186)
	at org.exist.xmldb.LocalXPathQueryService.execute(LocalXPathQueryService.java:190)
	... 51 more
Caused by: org.exist.xquery.XPathException: The actual return type does not match the sequence type declared in the function's signature: local:intro() element(). Expected cardinality: exactly one, got 0. [at line 12, column 15]
In call to function:
	local:intro() [12:15]
	local:package(xs:string) [64:1]
	at org.exist.xquery.DynamicCardinalityCheck.eval(DynamicCardinalityCheck.java:80)
	at org.exist.xquery.DynamicTypeCheck.eval(DynamicTypeCheck.java:66)
	at org.exist.xquery.FunctionCall.evalFunction(FunctionCall.java:223)
	at org.exist.xquery.FunctionCall.eval(FunctionCall.java:161)
	at org.exist.xquery.AbstractExpression.eval(AbstractExpression.java:59)
	at org.exist.xquery.PathExpr.eval(PathExpr.java:242)
	at org.exist.xquery.LetExpr.eval(LetExpr.java:150)
	at org.exist.xquery.BindingExpression.eval(BindingExpression.java:158)
	at org.exist.xquery.AbstractExpression.eval(AbstractExpression.java:59)
	at org.exist.xquery.PathExpr.eval(PathExpr.java:242)
	at org.exist.xquery.UserDefinedFunction.eval(UserDefinedFunction.java:122)
	at org.exist.xquery.DynamicCardinalityCheck.eval(DynamicCardinalityCheck.java:71)
	at org.exist.xquery.DynamicTypeCheck.eval(DynamicTypeCheck.java:66)
	at org.exist.xquery.FunctionCall.evalFunction(FunctionCall.java:223)
	at org.exist.xquery.FunctionCall.eval(FunctionCall.java:161)
	at org.exist.xquery.AbstractExpression.eval(AbstractExpression.java:59)
	at org.exist.xquery.PathExpr.eval(PathExpr.java:242)
	at org.exist.xquery.AbstractExpression.eval(AbstractExpression.java:59)
	at org.exist.xquery.XQuery.execute(XQuery.java:219)
	at org.exist.xquery.XQuery.execute(XQuery.java:186)
	at org.exist.xmldb.LocalXPathQueryService.execute(LocalXPathQueryService.java:190)
	at org.exist.cocoon.XQueryGenerator.generate(XQueryGenerator.java:330)
	at org.apache.cocoon.components.pipeline.AbstractProcessingPipeline.processXMLPipeline(AbstractProcessingPipeline.java:575)
	at org.apache.cocoon.components.pipeline.impl.AbstractCachingProcessingPipeline.processXMLPipeline(AbstractCachingProcessingPipeline.java:183)
	at org.apache.cocoon.components.pipeline.AbstractProcessingPipeline.process(AbstractProcessingPipeline.java:483)
	at org.apache.cocoon.components.treeprocessor.sitemap.SerializeNode.invoke(SerializeNode.java:120)
	at org.apache.cocoon.components.treeprocessor.AbstractParentProcessingNode.invokeNodes(AbstractParentProcessingNode.java:46)
	at org.apache.cocoon.components.treeprocessor.sitemap.PreparableMatchNode.invoke(PreparableMatchNode.java:130)
	at org.apache.cocoon.components.treeprocessor.AbstractParentProcessingNode.invokeNodes(AbstractParentProcessingNode.java:68)
	at org.apache.cocoon.components.treeprocessor.sitemap.PipelineNode.invoke(PipelineNode.java:138)
	at org.apache.cocoon.components.treeprocessor.AbstractParentProcessingNode.invokeNodes(AbstractParentProcessingNode.java:68)
	at org.apache.cocoon.components.treeprocessor.sitemap.PipelinesNode.invoke(PipelinesNode.java:92)
	at org.apache.cocoon.components.treeprocessor.ConcreteTreeProcessor.process(ConcreteTreeProcessor.java:234)
	at org.apache.cocoon.components.treeprocessor.ConcreteTreeProcessor.process(ConcreteTreeProcessor.java:176)
	at org.apache.cocoon.components.treeprocessor.TreeProcessor.process(TreeProcessor.java:243)
	at org.apache.cocoon.components.treeprocessor.sitemap.MountNode.invoke(MountNode.java:117)
	at org.apache.cocoon.components.treeprocessor.AbstractParentProcessingNode.invokeNodes(AbstractParentProcessingNode.java:46)
	at org.apache.cocoon.components.treeprocessor.sitemap.PreparableMatchNode.invoke(PreparableMatchNode.java:130)
	at org.apache.cocoon.components.treeprocessor.AbstractParentProcessingNode.invokeNodes(AbstractParentProcessingNode.java:68)
	at org.apache.cocoon.components.treeprocessor.sitemap.PipelineNode.invoke(PipelineNode.java:138)
	at org.apache.cocoon.components.treeprocessor.AbstractParentProcessingNode.invokeNodes(AbstractParentProcessingNode.java:68)
	at org.apache.cocoon.components.treeprocessor.sitemap.PipelinesNode.invoke(PipelinesNode.java:92)
	at org.apache.cocoon.components.treeprocessor.ConcreteTreeProcessor.process(ConcreteTreeProcessor.java:234)
	at org.apache.cocoon.components.treeprocessor.ConcreteTreeProcessor.process(ConcreteTreeProcessor.java:176)
	at org.apache.cocoon.components.treeprocessor.TreeProcessor.process(TreeProcessor.java:243)
	at org.apache.cocoon.Cocoon.process(Cocoon.java:608)
	at org.apache.cocoon.servlet.CocoonServlet.service(CocoonServlet.java:1123)
	at javax.servlet.http.HttpServlet.service(HttpServlet.java:802)
	at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:237)
	at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:157)
	at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:214)
	at org.apache.catalina.core.StandardValveContext.invokeNext(StandardValveContext.java:104)
	at org.apache.catalina.core.StandardPipeline.invoke(StandardPipeline.java:520)
	at org.apache.catalina.core.StandardContextValve.invokeInternal(StandardContextValve.java:198)
	at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:152)
	at org.apache.catalina.core.StandardValveContext.invokeNext(StandardValveContext.java:104)
	at org.apache.catalina.core.StandardPipeline.invoke(StandardPipeline.java:520)
	at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:137)
	at org.apache.catalina.core.StandardValveContext.invokeNext(StandardValveContext.java:104)
	at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:118)
	at org.apache.catalina.core.StandardValveContext.invokeNext(StandardValveContext.java:102)
	at org.apache.catalina.core.StandardPipeline.invoke(StandardPipeline.java:520)
	at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:109)
	at org.apache.catalina.core.StandardValveContext.invokeNext(StandardValveContext.java:104)
	at org.apache.catalina.core.StandardPipeline.invoke(StandardPipeline.java:520)
	at org.apache.catalina.core.ContainerBase.invoke(ContainerBase.java:929)
	at org.apache.coyote.tomcat5.CoyoteAdapter.service(CoyoteAdapter.java:160)
	at org.apache.coyote.http11.Http11Processor.process(Http11Processor.java:799)
	at org.apache.coyote.http11.Http11Protocol$Http11ConnectionHandler.processConnection(Http11Protocol.java:705)
	at org.apache.tomcat.util.net.TcpWorkerThread.runIt(PoolTcpEndpoint.java:577)
	at org.apache.tomcat.util.threads.ThreadPool$ControlRunnable.run(ThreadPool.java:683)
	at java.lang.Thread.run(Thread.java:595)

stacktrace[show]

org.exist.xquery.XPathException: The actual return type does not match the sequence type declared in the function's signature: local:intro() element(). Expected cardinality: exactly one, got 0. [at line 12, column 15]
In call to function:
	local:intro() [12:15]
	local:package(xs:string) [64:1]
	at org.exist.xquery.DynamicCardinalityCheck.eval(DynamicCardinalityCheck.java:80)
	at org.exist.xquery.DynamicTypeCheck.eval(DynamicTypeCheck.java:66)
	at org.exist.xquery.FunctionCall.evalFunction(FunctionCall.java:223)
	at org.exist.xquery.FunctionCall.eval(FunctionCall.java:161)
	at org.exist.xquery.AbstractExpression.eval(AbstractExpression.java:59)
	at org.exist.xquery.PathExpr.eval(PathExpr.java:242)
	at org.exist.xquery.LetExpr.eval(LetExpr.java:150)
	at org.exist.xquery.BindingExpression.eval(BindingExpression.java:158)
	at org.exist.xquery.AbstractExpression.eval(AbstractExpression.java:59)
	at org.exist.xquery.PathExpr.eval(PathExpr.java:242)
	at org.exist.xquery.UserDefinedFunction.eval(UserDefinedFunction.java:122)
	at org.exist.xquery.DynamicCardinalityCheck.eval(DynamicCardinalityCheck.java:71)
	at org.exist.xquery.DynamicTypeCheck.eval(DynamicTypeCheck.java:66)
	at org.exist.xquery.FunctionCall.evalFunction(FunctionCall.java:223)
	at org.exist.xquery.FunctionCall.eval(FunctionCall.java:161)
	at org.exist.xquery.AbstractExpression.eval(AbstractExpression.java:59)
	at org.exist.xquery.PathExpr.eval(PathExpr.java:242)
	at org.exist.xquery.AbstractExpression.eval(AbstractExpression.java:59)
	at org.exist.xquery.XQuery.execute(XQuery.java:219)
	at org.exist.xquery.XQuery.execute(XQuery.java:186)
	at org.exist.xmldb.LocalXPathQueryService.execute(LocalXPathQueryService.java:190)
	at org.exist.cocoon.XQueryGenerator.generate(XQueryGenerator.java:330)
	at org.apache.cocoon.components.pipeline.AbstractProcessingPipeline.processXMLPipeline(AbstractProcessingPipeline.java:575)
	at org.apache.cocoon.components.pipeline.impl.AbstractCachingProcessingPipeline.processXMLPipeline(AbstractCachingProcessingPipeline.java:183)
	at org.apache.cocoon.components.pipeline.AbstractProcessingPipeline.process(AbstractProcessingPipeline.java:483)
	at org.apache.cocoon.components.treeprocessor.sitemap.SerializeNode.invoke(SerializeNode.java:120)
	at org.apache.cocoon.components.treeprocessor.AbstractParentProcessingNode.invokeNodes(AbstractParentProcessingNode.java:46)
	at org.apache.cocoon.components.treeprocessor.sitemap.PreparableMatchNode.invoke(PreparableMatchNode.java:130)
	at org.apache.cocoon.components.treeprocessor.AbstractParentProcessingNode.invokeNodes(AbstractParentProcessingNode.java:68)
	at org.apache.cocoon.components.treeprocessor.sitemap.PipelineNode.invoke(PipelineNode.java:138)
	at org.apache.cocoon.components.treeprocessor.AbstractParentProcessingNode.invokeNodes(AbstractParentProcessingNode.java:68)
	at org.apache.cocoon.components.treeprocessor.sitemap.PipelinesNode.invoke(PipelinesNode.java:92)
	at org.apache.cocoon.components.treeprocessor.ConcreteTreeProcessor.process(ConcreteTreeProcessor.java:234)
	at org.apache.cocoon.components.treeprocessor.ConcreteTreeProcessor.process(ConcreteTreeProcessor.java:176)
	at org.apache.cocoon.components.treeprocessor.TreeProcessor.process(TreeProcessor.java:243)
	at org.apache.cocoon.components.treeprocessor.sitemap.MountNode.invoke(MountNode.java:117)
	at org.apache.cocoon.components.treeprocessor.AbstractParentProcessingNode.invokeNodes(AbstractParentProcessingNode.java:46)
	at org.apache.cocoon.components.treeprocessor.sitemap.PreparableMatchNode.invoke(PreparableMatchNode.java:130)
	at org.apache.cocoon.components.treeprocessor.AbstractParentProcessingNode.invokeNodes(AbstractParentProcessingNode.java:68)
	at org.apache.cocoon.components.treeprocessor.sitemap.PipelineNode.invoke(PipelineNode.java:138)
	at org.apache.cocoon.components.treeprocessor.AbstractParentProcessingNode.invokeNodes(AbstractParentProcessingNode.java:68)
	at org.apache.cocoon.components.treeprocessor.sitemap.PipelinesNode.invoke(PipelinesNode.java:92)
	at org.apache.cocoon.components.treeprocessor.ConcreteTreeProcessor.process(ConcreteTreeProcessor.java:234)
	at org.apache.cocoon.components.treeprocessor.ConcreteTreeProcessor.process(ConcreteTreeProcessor.java:176)
	at org.apache.cocoon.components.treeprocessor.TreeProcessor.process(TreeProcessor.java:243)
	at org.apache.cocoon.Cocoon.process(Cocoon.java:608)
	at org.apache.cocoon.servlet.CocoonServlet.service(CocoonServlet.java:1123)
	at javax.servlet.http.HttpServlet.service(HttpServlet.java:802)
	at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:237)
	at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:157)
	at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:214)
	at org.apache.catalina.core.StandardValveContext.invokeNext(StandardValveContext.java:104)
	at org.apache.catalina.core.StandardPipeline.invoke(StandardPipeline.java:520)
	at org.apache.catalina.core.StandardContextValve.invokeInternal(StandardContextValve.java:198)
	at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:152)
	at org.apache.catalina.core.StandardValveContext.invokeNext(StandardValveContext.java:104)
	at org.apache.catalina.core.StandardPipeline.invoke(StandardPipeline.java:520)
	at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:137)
	at org.apache.catalina.core.StandardValveContext.invokeNext(StandardValveContext.java:104)
	at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:118)
	at org.apache.catalina.core.StandardValveContext.invokeNext(StandardValveContext.java:102)
	at org.apache.catalina.core.StandardPipeline.invoke(StandardPipeline.java:520)
	at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:109)
	at org.apache.catalina.core.StandardValveContext.invokeNext(StandardValveContext.java:104)
	at org.apache.catalina.core.StandardPipeline.invoke(StandardPipeline.java:520)
	at org.apache.catalina.core.ContainerBase.invoke(ContainerBase.java:929)
	at org.apache.coyote.tomcat5.CoyoteAdapter.service(CoyoteAdapter.java:160)
	at org.apache.coyote.http11.Http11Processor.process(Http11Processor.java:799)
	at org.apache.coyote.http11.Http11Protocol$Http11ConnectionHandler.processConnection(Http11Protocol.java:705)
	at org.apache.tomcat.util.net.TcpWorkerThread.runIt(PoolTcpEndpoint.java:577)
	at org.apache.tomcat.util.threads.ThreadPool$ControlRunnable.run(ThreadPool.java:683)
	at java.lang.Thread.run(Thread.java:595)

If you need help and this information is not enough, you are invited to read the Cocoon FAQ.
If you still don't find the answers you need, can send a mail to the Cocoon users mailing list, remembering to:

• specify the version of Cocoon you're using, or we'll assume that you are talking about the latest released version;
• specify the platform-operating system-version-servlet container version;
• send any pertinent error message;
• send pertinent log snippets;
• send pertinent sitemap snippets;
• send pertinent parts of the page that give you problems.

For more detailed technical information, take a look at the log files in the log directory of Cocoon, which is placed by default in the WEB-INF/logs/ folder of your cocoon webapp context.
If the logs don't give you enough information, you might want to increase the log level by changing the Logging configuration which is by default the WEB-INF/logkit.xconf file.

If you think you found a bug, please report it to Apache's Bugzilla; a message will automatically be sent to the developer mailing list and you'll be kept in contact automatically with the further progress on that bug.

Thanks, and sorry for the trouble if this is our fault.

The Apache Cocoon Project