diff --git a/asterixdb/asterix-algebra/src/main/java/org/apache/asterix/optimizer/rules/IntroduceDynamicTypeCastForExternalFunctionRule.java b/asterixdb/asterix-algebra/src/main/java/org/apache/asterix/optimizer/rules/IntroduceDynamicTypeCastForExternalFunctionRule.java
index 97e2174..a00933a 100644
--- a/asterixdb/asterix-algebra/src/main/java/org/apache/asterix/optimizer/rules/IntroduceDynamicTypeCastForExternalFunctionRule.java
+++ b/asterixdb/asterix-algebra/src/main/java/org/apache/asterix/optimizer/rules/IntroduceDynamicTypeCastForExternalFunctionRule.java
@@ -24,6 +24,7 @@
 import org.apache.asterix.om.functions.BuiltinFunctions;
 import org.apache.asterix.om.typecomputer.base.TypeCastUtils;
 import org.apache.asterix.om.types.ARecordType;
+import org.apache.asterix.om.types.ATypeTag;
 import org.apache.asterix.om.types.AUnionType;
 import org.apache.asterix.om.types.IAType;
 import org.apache.asterix.om.utils.NonTaggedFormatUtil;
@@ -71,36 +72,37 @@
         if (BuiltinFunctions.getBuiltinFunctionIdentifier(funcCallExpr.getFunctionIdentifier()) != null) {
             return changed;
         }
-        IAType inputRecordType;
-        ARecordType requiredRecordType;
-        for (int iter1 = 0; iter1 < funcCallExpr.getArguments().size(); iter1++) {
-            Mutable<ILogicalExpression> argExpr = funcCallExpr.getArguments().get(iter1);
-            inputRecordType = (IAType) op.computeOutputTypeEnvironment(context).getType(argExpr.getValue());
-            if (!(((ExternalScalarFunctionInfo) funcCallExpr.getFunctionInfo()).getArgumenTypes()
-                    .get(iter1) instanceof ARecordType)) {
-                continue;
+        IAType inputType;
+        IAType reqArgType;
+        boolean castFlag;
+        for (int i = 0; i < funcCallExpr.getArguments().size(); i++) {
+            Mutable<ILogicalExpression> argExpr = funcCallExpr.getArguments().get(i);
+            inputType = (IAType) op.computeOutputTypeEnvironment(context).getType(argExpr.getValue());
+            reqArgType = ((ExternalScalarFunctionInfo) funcCallExpr.getFunctionInfo()).getArgumentTypes().get(i);
+
+            if (reqArgType.getTypeTag() == ATypeTag.OBJECT) {
+                castFlag = !IntroduceDynamicTypeCastRule.compatible((ARecordType) reqArgType, inputType,
+                        argExpr.getValue().getSourceLocation());
+            } else {
+                castFlag = !reqArgType.equals(inputType);
             }
-            requiredRecordType = (ARecordType) ((ExternalScalarFunctionInfo) funcCallExpr.getFunctionInfo())
-                    .getArgumenTypes().get(iter1);
             /**
              * the input record type can be an union type
              * for the case when it comes from a subplan or left-outer join
              */
             boolean checkUnknown = false;
-            while (NonTaggedFormatUtil.isOptional(inputRecordType)) {
+            while (NonTaggedFormatUtil.isOptional(inputType)) {
                 /** while-loop for the case there is a nested multi-level union */
-                inputRecordType = ((AUnionType) inputRecordType).getActualType();
+                inputType = ((AUnionType) inputType).getActualType();
                 checkUnknown = true;
             }
-            boolean castFlag = !IntroduceDynamicTypeCastRule.compatible(requiredRecordType, inputRecordType,
-                    argExpr.getValue().getSourceLocation());
             if (castFlag || checkUnknown) {
                 AbstractFunctionCallExpression castFunc =
                         new ScalarFunctionCallExpression(FunctionUtil.getFunctionInfo(BuiltinFunctions.CAST_TYPE));
                 castFunc.setSourceLocation(argExpr.getValue().getSourceLocation());
                 castFunc.getArguments().add(argExpr);
-                TypeCastUtils.setRequiredAndInputTypes(castFunc, requiredRecordType, inputRecordType);
-                funcCallExpr.getArguments().set(iter1, new MutableObject<>(castFunc));
+                TypeCastUtils.setRequiredAndInputTypes(castFunc, reqArgType, inputType);
+                funcCallExpr.getArguments().set(i, new MutableObject<>(castFunc));
                 changed = true;
             }
         }
diff --git a/asterixdb/asterix-external-data/src/test/java/org/apache/asterix/external/library/SumFactory.java b/asterixdb/asterix-app/src/test/resources/runtimets/queries_sqlpp/external-library/my_array_sum/my_array_sum.1.ddl.sqlpp
similarity index 69%
copy from asterixdb/asterix-external-data/src/test/java/org/apache/asterix/external/library/SumFactory.java
copy to asterixdb/asterix-app/src/test/resources/runtimets/queries_sqlpp/external-library/my_array_sum/my_array_sum.1.ddl.sqlpp
index 5202093..76cc70d 100644
--- a/asterixdb/asterix-external-data/src/test/java/org/apache/asterix/external/library/SumFactory.java
+++ b/asterixdb/asterix-app/src/test/resources/runtimets/queries_sqlpp/external-library/my_array_sum/my_array_sum.1.ddl.sqlpp
@@ -16,16 +16,5 @@
  * specific language governing permissions and limitations
  * under the License.
  */
-package org.apache.asterix.external.library;
-
-import org.apache.asterix.external.api.IExternalScalarFunction;
-import org.apache.asterix.external.api.IFunctionFactory;
-
-public class SumFactory implements IFunctionFactory {
-
-    @Override
-    public IExternalScalarFunction getExternalFunction() {
-        return new SumFunction();
-    }
-
-}
+DROP DATAVERSE externallibtest if exists;
+CREATE DATAVERSE  externallibtest;
diff --git a/asterixdb/asterix-external-data/src/test/java/org/apache/asterix/external/library/SumFactory.java b/asterixdb/asterix-app/src/test/resources/runtimets/queries_sqlpp/external-library/my_array_sum/my_array_sum.2.lib.sqlpp
similarity index 69%
copy from asterixdb/asterix-external-data/src/test/java/org/apache/asterix/external/library/SumFactory.java
copy to asterixdb/asterix-app/src/test/resources/runtimets/queries_sqlpp/external-library/my_array_sum/my_array_sum.2.lib.sqlpp
index 5202093..d1e0e87 100644
--- a/asterixdb/asterix-external-data/src/test/java/org/apache/asterix/external/library/SumFactory.java
+++ b/asterixdb/asterix-app/src/test/resources/runtimets/queries_sqlpp/external-library/my_array_sum/my_array_sum.2.lib.sqlpp
@@ -16,16 +16,4 @@
  * specific language governing permissions and limitations
  * under the License.
  */
-package org.apache.asterix.external.library;
-
-import org.apache.asterix.external.api.IExternalScalarFunction;
-import org.apache.asterix.external.api.IFunctionFactory;
-
-public class SumFactory implements IFunctionFactory {
-
-    @Override
-    public IExternalScalarFunction getExternalFunction() {
-        return new SumFunction();
-    }
-
-}
+install externallibtest testlib target/data/externallib/asterix-external-data-testlib.zip
\ No newline at end of file
diff --git a/asterixdb/asterix-external-data/src/test/java/org/apache/asterix/external/library/SumFactory.java b/asterixdb/asterix-app/src/test/resources/runtimets/queries_sqlpp/external-library/my_array_sum/my_array_sum.3.query.sqlpp
similarity index 69%
copy from asterixdb/asterix-external-data/src/test/java/org/apache/asterix/external/library/SumFactory.java
copy to asterixdb/asterix-app/src/test/resources/runtimets/queries_sqlpp/external-library/my_array_sum/my_array_sum.3.query.sqlpp
index 5202093..f9ebecd 100644
--- a/asterixdb/asterix-external-data/src/test/java/org/apache/asterix/external/library/SumFactory.java
+++ b/asterixdb/asterix-app/src/test/resources/runtimets/queries_sqlpp/external-library/my_array_sum/my_array_sum.3.query.sqlpp
@@ -16,16 +16,6 @@
  * specific language governing permissions and limitations
  * under the License.
  */
-package org.apache.asterix.external.library;
+use externallibtest;
 
-import org.apache.asterix.external.api.IExternalScalarFunction;
-import org.apache.asterix.external.api.IFunctionFactory;
-
-public class SumFactory implements IFunctionFactory {
-
-    @Override
-    public IExternalScalarFunction getExternalFunction() {
-        return new SumFunction();
-    }
-
-}
+testlib#my_array_sum([8.9, 9.7, 1]);
diff --git a/asterixdb/asterix-app/src/test/resources/runtimets/queries_sqlpp/external-library/mysum/mysum.4.lib.sqlpp b/asterixdb/asterix-app/src/test/resources/runtimets/queries_sqlpp/external-library/my_array_sum/my_array_sum.6.lib.sqlpp
similarity index 100%
copy from asterixdb/asterix-app/src/test/resources/runtimets/queries_sqlpp/external-library/mysum/mysum.4.lib.sqlpp
copy to asterixdb/asterix-app/src/test/resources/runtimets/queries_sqlpp/external-library/my_array_sum/my_array_sum.6.lib.sqlpp
diff --git a/asterixdb/asterix-app/src/test/resources/runtimets/queries_sqlpp/external-library/mysum/mysum.5.ddl.sqlpp b/asterixdb/asterix-app/src/test/resources/runtimets/queries_sqlpp/external-library/my_array_sum/my_array_sum.7.ddl.sqlpp
similarity index 100%
copy from asterixdb/asterix-app/src/test/resources/runtimets/queries_sqlpp/external-library/mysum/mysum.5.ddl.sqlpp
copy to asterixdb/asterix-app/src/test/resources/runtimets/queries_sqlpp/external-library/my_array_sum/my_array_sum.7.ddl.sqlpp
diff --git a/asterixdb/asterix-external-data/src/test/java/org/apache/asterix/external/library/SumFactory.java b/asterixdb/asterix-app/src/test/resources/runtimets/queries_sqlpp/external-library/mysum/mysum.4.query.sqlpp
similarity index 69%
copy from asterixdb/asterix-external-data/src/test/java/org/apache/asterix/external/library/SumFactory.java
copy to asterixdb/asterix-app/src/test/resources/runtimets/queries_sqlpp/external-library/mysum/mysum.4.query.sqlpp
index 5202093..9fd6f94 100644
--- a/asterixdb/asterix-external-data/src/test/java/org/apache/asterix/external/library/SumFactory.java
+++ b/asterixdb/asterix-app/src/test/resources/runtimets/queries_sqlpp/external-library/mysum/mysum.4.query.sqlpp
@@ -16,16 +16,6 @@
  * specific language governing permissions and limitations
  * under the License.
  */
-package org.apache.asterix.external.library;
+use externallibtest;
 
-import org.apache.asterix.external.api.IExternalScalarFunction;
-import org.apache.asterix.external.api.IFunctionFactory;
-
-public class SumFactory implements IFunctionFactory {
-
-    @Override
-    public IExternalScalarFunction getExternalFunction() {
-        return new SumFunction();
-    }
-
-}
+testlib#mysum(9.7, 4);
diff --git a/asterixdb/asterix-external-data/src/test/java/org/apache/asterix/external/library/SumFactory.java b/asterixdb/asterix-app/src/test/resources/runtimets/queries_sqlpp/external-library/mysum/mysum.5.query.sqlpp
similarity index 69%
copy from asterixdb/asterix-external-data/src/test/java/org/apache/asterix/external/library/SumFactory.java
copy to asterixdb/asterix-app/src/test/resources/runtimets/queries_sqlpp/external-library/mysum/mysum.5.query.sqlpp
index 5202093..776f976 100644
--- a/asterixdb/asterix-external-data/src/test/java/org/apache/asterix/external/library/SumFactory.java
+++ b/asterixdb/asterix-app/src/test/resources/runtimets/queries_sqlpp/external-library/mysum/mysum.5.query.sqlpp
@@ -16,16 +16,6 @@
  * specific language governing permissions and limitations
  * under the License.
  */
-package org.apache.asterix.external.library;
+use externallibtest;
 
-import org.apache.asterix.external.api.IExternalScalarFunction;
-import org.apache.asterix.external.api.IFunctionFactory;
-
-public class SumFactory implements IFunctionFactory {
-
-    @Override
-    public IExternalScalarFunction getExternalFunction() {
-        return new SumFunction();
-    }
-
-}
+testlib#mysum("3",4);
diff --git a/asterixdb/asterix-app/src/test/resources/runtimets/queries_sqlpp/external-library/mysum/mysum.4.lib.sqlpp b/asterixdb/asterix-app/src/test/resources/runtimets/queries_sqlpp/external-library/mysum/mysum.6.lib.sqlpp
similarity index 100%
rename from asterixdb/asterix-app/src/test/resources/runtimets/queries_sqlpp/external-library/mysum/mysum.4.lib.sqlpp
rename to asterixdb/asterix-app/src/test/resources/runtimets/queries_sqlpp/external-library/mysum/mysum.6.lib.sqlpp
diff --git a/asterixdb/asterix-app/src/test/resources/runtimets/queries_sqlpp/external-library/mysum/mysum.5.ddl.sqlpp b/asterixdb/asterix-app/src/test/resources/runtimets/queries_sqlpp/external-library/mysum/mysum.7.ddl.sqlpp
similarity index 100%
rename from asterixdb/asterix-app/src/test/resources/runtimets/queries_sqlpp/external-library/mysum/mysum.5.ddl.sqlpp
rename to asterixdb/asterix-app/src/test/resources/runtimets/queries_sqlpp/external-library/mysum/mysum.7.ddl.sqlpp
diff --git a/asterixdb/asterix-app/src/test/resources/runtimets/results/external-library/my_array_sum/my_array_sum.1.adm b/asterixdb/asterix-app/src/test/resources/runtimets/results/external-library/my_array_sum/my_array_sum.1.adm
new file mode 100644
index 0000000..25bf17f
--- /dev/null
+++ b/asterixdb/asterix-app/src/test/resources/runtimets/results/external-library/my_array_sum/my_array_sum.1.adm
@@ -0,0 +1 @@
+18
\ No newline at end of file
diff --git a/asterixdb/asterix-app/src/test/resources/runtimets/results/external-library/mysum/mysum.2.adm b/asterixdb/asterix-app/src/test/resources/runtimets/results/external-library/mysum/mysum.2.adm
new file mode 100644
index 0000000..ca7bf83
--- /dev/null
+++ b/asterixdb/asterix-app/src/test/resources/runtimets/results/external-library/mysum/mysum.2.adm
@@ -0,0 +1 @@
+13
\ No newline at end of file
diff --git a/asterixdb/asterix-app/src/test/resources/runtimets/results/external-library/validate-default-library/validate-default-library.1.adm b/asterixdb/asterix-app/src/test/resources/runtimets/results/external-library/validate-default-library/validate-default-library.1.adm
index 13de599..ee90703 100644
--- a/asterixdb/asterix-app/src/test/resources/runtimets/results/external-library/validate-default-library/validate-default-library.1.adm
+++ b/asterixdb/asterix-app/src/test/resources/runtimets/results/external-library/validate-default-library/validate-default-library.1.adm
@@ -5,7 +5,8 @@
 { "Function": { "DataverseName": "externallibtest", "Name": "testlib#fnameDetector", "Arity": "1", "Params": [ "InputRecordType" ], "ReturnType": "DetectResultType", "Definition": "org.apache.asterix.external.library.KeywordsDetectorFactory", "Language": "JAVA", "Kind": "SCALAR", "Dependencies": [ [  ], [  ] ] } }
 { "Function": { "DataverseName": "externallibtest", "Name": "testlib#getCapital", "Arity": "1", "Params": [ "ASTRING" ], "ReturnType": "CountryCapitalType", "Definition": "org.apache.asterix.external.library.CapitalFinderFactory", "Language": "JAVA", "Kind": "SCALAR", "Dependencies": [ [  ], [  ] ] } }
 { "Function": { "DataverseName": "externallibtest", "Name": "testlib#lnameDetector", "Arity": "1", "Params": [ "InputRecordType" ], "ReturnType": "DetectResultType", "Definition": "org.apache.asterix.external.library.KeywordsDetectorFactory", "Language": "JAVA", "Kind": "SCALAR", "Dependencies": [ [  ], [  ] ] } }
-{ "Function": { "DataverseName": "externallibtest", "Name": "testlib#mysum", "Arity": "2", "Params": [ "AINT32", "AINT32" ], "ReturnType": "AINT32", "Definition": "org.apache.asterix.external.library.SumFactory", "Language": "JAVA", "Kind": "SCALAR", "Dependencies": [ [  ], [  ] ] } }
+{ "Function": { "DataverseName": "externallibtest", "Name": "testlib#my_array_sum", "Arity": "1", "Params": [ "[AINT32]" ], "ReturnType": "AINT32", "Definition": "org.apache.asterix.external.library.MyArraySumFactory", "Language": "JAVA", "Kind": "SCALAR", "Dependencies": [ [  ], [  ] ] } }
+{ "Function": { "DataverseName": "externallibtest", "Name": "testlib#mysum", "Arity": "2", "Params": [ "AINT32", "AINT32" ], "ReturnType": "AINT32", "Definition": "org.apache.asterix.external.library.MySumFactory", "Language": "JAVA", "Kind": "SCALAR", "Dependencies": [ [  ], [  ] ] } }
 { "Function": { "DataverseName": "externallibtest", "Name": "testlib#parseTweet", "Arity": "1", "Params": [ "TweetInputType" ], "ReturnType": "TweetOutputType", "Definition": "org.apache.asterix.external.library.ParseTweetFactory", "Language": "JAVA", "Kind": "SCALAR", "Dependencies": [ [  ], [  ] ] } }
 { "Function": { "DataverseName": "externallibtest", "Name": "testlib#toUpper", "Arity": "1", "Params": [ "TextType" ], "ReturnType": "TextType", "Definition": "org.apache.asterix.external.library.UpperCaseFactory", "Language": "JAVA", "Kind": "SCALAR", "Dependencies": [ [  ], [  ] ] } }
 { "Function": { "DataverseName": "externallibtest", "Name": "testlib#typeValidation", "Arity": "11", "Params": [ "AINT32", "AFLOAT", "ASTRING", "ADouble", "ABoolean", "APoint", "ADate", "ADatetime", "ALine", "ACircle", "ARectangle" ], "ReturnType": "AString", "Definition": "org.apache.asterix.external.library.TypeValidationFunctionFactory", "Language": "JAVA", "Kind": "SCALAR", "Dependencies": [ [  ], [  ] ] } }
diff --git a/asterixdb/asterix-app/src/test/resources/runtimets/testsuite_it_sqlpp.xml b/asterixdb/asterix-app/src/test/resources/runtimets/testsuite_it_sqlpp.xml
index 2121aae..71d0503 100644
--- a/asterixdb/asterix-app/src/test/resources/runtimets/testsuite_it_sqlpp.xml
+++ b/asterixdb/asterix-app/src/test/resources/runtimets/testsuite_it_sqlpp.xml
@@ -31,6 +31,12 @@
     <test-case FilePath="external-library">
       <compilation-unit name="mysum">
         <output-dir compare="Text">mysum</output-dir>
+        <expected-error>Type mismatch: function testlib#mysum expects its 1st input parameter to be of type integer</expected-error>
+      </compilation-unit>
+    </test-case>
+    <test-case FilePath="external-library">
+      <compilation-unit name="my_array_sum">
+        <output-dir compare="Text">my_array_sum</output-dir>
       </compilation-unit>
     </test-case>
     <test-case FilePath="external-library">
diff --git a/asterixdb/asterix-external-data/src/main/java/org/apache/asterix/external/library/ExternalFunction.java b/asterixdb/asterix-external-data/src/main/java/org/apache/asterix/external/library/ExternalFunction.java
index c5b9ad6..33fff14 100755
--- a/asterixdb/asterix-external-data/src/main/java/org/apache/asterix/external/library/ExternalFunction.java
+++ b/asterixdb/asterix-external-data/src/main/java/org/apache/asterix/external/library/ExternalFunction.java
@@ -28,9 +28,6 @@
 import org.apache.asterix.external.api.IFunctionFactory;
 import org.apache.asterix.external.api.IFunctionHelper;
 import org.apache.asterix.om.functions.IExternalFunctionInfo;
-import org.apache.asterix.om.types.ATypeTag;
-import org.apache.asterix.om.types.EnumDeserializer;
-import org.apache.asterix.om.types.hierachy.ATypeHierarchy;
 import org.apache.hyracks.algebricks.common.exceptions.AlgebricksException;
 import org.apache.hyracks.algebricks.runtime.base.IScalarEvaluator;
 import org.apache.hyracks.algebricks.runtime.base.IScalarEvaluatorFactory;
@@ -45,11 +42,10 @@
 
     protected final IExternalFunctionInfo finfo;
     protected final IFunctionFactory externalFunctionFactory;
-    protected final IExternalFunction externalFunction;
+    protected final IExternalFunction externalFunctionInstance;
     protected final IScalarEvaluatorFactory[] evaluatorFactories;
     protected final IPointable inputVal = new VoidPointable();
     protected final ArrayBackedValueStorage resultBuffer = new ArrayBackedValueStorage();
-    protected final ArrayBackedValueStorage castBuffer = new ArrayBackedValueStorage();
     protected final IScalarEvaluator[] argumentEvaluators;
     protected final JavaFunctionHelper functionHelper;
 
@@ -75,7 +71,7 @@
         try {
             clazz = Class.forName(classname, true, libraryClassLoader);
             externalFunctionFactory = (IFunctionFactory) clazz.newInstance();
-            externalFunction = externalFunctionFactory.getExternalFunction();
+            externalFunctionInstance = externalFunctionFactory.getExternalFunction();
         } catch (Exception e) {
             throw new RuntimeDataException(ErrorCode.LIBRARY_EXTERNAL_FUNCTION_UNABLE_TO_LOAD_CLASS, e, classname);
         }
@@ -84,30 +80,18 @@
     public void setArguments(IFrameTupleReference tuple) throws AlgebricksException, IOException {
         for (int i = 0; i < evaluatorFactories.length; i++) {
             argumentEvaluators[i].evaluate(tuple, inputVal);
-
-            // Type-cast the source array based on the input type that this function wants to receive.
-            ATypeTag targetTypeTag = finfo.getArgumentList().get(i).getTypeTag();
-            ATypeTag sourceTypeTag = EnumDeserializer.ATYPETAGDESERIALIZER
-                    .deserialize(inputVal.getByteArray()[inputVal.getStartOffset()]);
-            if (sourceTypeTag != targetTypeTag) {
-                castBuffer.reset();
-                ATypeHierarchy.convertNumericTypeByteArray(inputVal.getByteArray(), inputVal.getStartOffset(),
-                        inputVal.getLength(), targetTypeTag, castBuffer.getDataOutput(), true);
-                functionHelper.setArgument(i, castBuffer);
-            } else {
-                functionHelper.setArgument(i, inputVal);
-            }
+            functionHelper.setArgument(i, inputVal);
         }
     }
 
     @Override
     public void deinitialize() {
-        externalFunction.deinitialize();
+        externalFunctionInstance.deinitialize();
     }
 
     @Override
     public void initialize(IFunctionHelper functionHelper) throws Exception {
-        externalFunction.initialize(functionHelper);
+        externalFunctionInstance.initialize(functionHelper);
     }
 
 }
diff --git a/asterixdb/asterix-external-data/src/main/java/org/apache/asterix/external/library/ExternalFunctionProvider.java b/asterixdb/asterix-external-data/src/main/java/org/apache/asterix/external/library/ExternalFunctionProvider.java
index 05124dd..83b60f1 100755
--- a/asterixdb/asterix-external-data/src/main/java/org/apache/asterix/external/library/ExternalFunctionProvider.java
+++ b/asterixdb/asterix-external-data/src/main/java/org/apache/asterix/external/library/ExternalFunctionProvider.java
@@ -77,7 +77,7 @@
     public void evaluate(IFunctionHelper argumentProvider) throws HyracksDataException {
         try {
             resultBuffer.reset();
-            ((IExternalScalarFunction) externalFunction).evaluate(argumentProvider);
+            ((IExternalScalarFunction) externalFunctionInstance).evaluate(argumentProvider);
             if (!argumentProvider.isValidResult()) {
                 throw new RuntimeDataException(ErrorCode.EXTERNAL_UDF_RESULT_TYPE_ERROR);
             }
diff --git a/asterixdb/asterix-external-data/src/test/java/org/apache/asterix/external/library/SumFactory.java b/asterixdb/asterix-external-data/src/test/java/org/apache/asterix/external/library/MyArraySumFactory.java
similarity index 91%
copy from asterixdb/asterix-external-data/src/test/java/org/apache/asterix/external/library/SumFactory.java
copy to asterixdb/asterix-external-data/src/test/java/org/apache/asterix/external/library/MyArraySumFactory.java
index 5202093..3f8c945 100644
--- a/asterixdb/asterix-external-data/src/test/java/org/apache/asterix/external/library/SumFactory.java
+++ b/asterixdb/asterix-external-data/src/test/java/org/apache/asterix/external/library/MyArraySumFactory.java
@@ -21,11 +21,11 @@
 import org.apache.asterix.external.api.IExternalScalarFunction;
 import org.apache.asterix.external.api.IFunctionFactory;
 
-public class SumFactory implements IFunctionFactory {
+public class MyArraySumFactory implements IFunctionFactory {
 
     @Override
     public IExternalScalarFunction getExternalFunction() {
-        return new SumFunction();
+        return new MyArraySumFunction();
     }
 
 }
diff --git a/asterixdb/asterix-external-data/src/test/java/org/apache/asterix/external/library/SumFunction.java b/asterixdb/asterix-external-data/src/test/java/org/apache/asterix/external/library/MyArraySumFunction.java
similarity index 78%
copy from asterixdb/asterix-external-data/src/test/java/org/apache/asterix/external/library/SumFunction.java
copy to asterixdb/asterix-external-data/src/test/java/org/apache/asterix/external/library/MyArraySumFunction.java
index e16d779..67c2889 100644
--- a/asterixdb/asterix-external-data/src/test/java/org/apache/asterix/external/library/SumFunction.java
+++ b/asterixdb/asterix-external-data/src/test/java/org/apache/asterix/external/library/MyArraySumFunction.java
@@ -21,8 +21,9 @@
 import org.apache.asterix.external.api.IExternalScalarFunction;
 import org.apache.asterix.external.api.IFunctionHelper;
 import org.apache.asterix.external.library.java.base.JInt;
+import org.apache.asterix.external.library.java.base.JOrderedList;
 
-public class SumFunction implements IExternalScalarFunction {
+public class MyArraySumFunction implements IExternalScalarFunction {
 
     private JInt result;
 
@@ -33,9 +34,12 @@
 
     @Override
     public void evaluate(IFunctionHelper functionHelper) throws Exception {
-        int arg0 = ((JInt) functionHelper.getArgument(0)).getValue();
-        int arg1 = ((JInt) functionHelper.getArgument(1)).getValue();
-        result.setValue(arg0 + arg1);
+        JOrderedList arg0 = (JOrderedList) (functionHelper.getArgument(0));
+        int sum = 0;
+        for (int iter1 = 0; iter1 < arg0.size(); iter1++) {
+            sum += ((JInt) arg0.getValue().get(iter1)).getValue();
+        }
+        result.setValue(sum);
         functionHelper.setResult(result);
     }
 
diff --git a/asterixdb/asterix-external-data/src/test/java/org/apache/asterix/external/library/SumFactory.java b/asterixdb/asterix-external-data/src/test/java/org/apache/asterix/external/library/MySumFactory.java
similarity index 92%
rename from asterixdb/asterix-external-data/src/test/java/org/apache/asterix/external/library/SumFactory.java
rename to asterixdb/asterix-external-data/src/test/java/org/apache/asterix/external/library/MySumFactory.java
index 5202093..0e071e4 100644
--- a/asterixdb/asterix-external-data/src/test/java/org/apache/asterix/external/library/SumFactory.java
+++ b/asterixdb/asterix-external-data/src/test/java/org/apache/asterix/external/library/MySumFactory.java
@@ -21,11 +21,11 @@
 import org.apache.asterix.external.api.IExternalScalarFunction;
 import org.apache.asterix.external.api.IFunctionFactory;
 
-public class SumFactory implements IFunctionFactory {
+public class MySumFactory implements IFunctionFactory {
 
     @Override
     public IExternalScalarFunction getExternalFunction() {
-        return new SumFunction();
+        return new MySumFunction();
     }
 
 }
diff --git a/asterixdb/asterix-external-data/src/test/java/org/apache/asterix/external/library/SumFunction.java b/asterixdb/asterix-external-data/src/test/java/org/apache/asterix/external/library/MySumFunction.java
similarity index 96%
rename from asterixdb/asterix-external-data/src/test/java/org/apache/asterix/external/library/SumFunction.java
rename to asterixdb/asterix-external-data/src/test/java/org/apache/asterix/external/library/MySumFunction.java
index e16d779..26abee8 100644
--- a/asterixdb/asterix-external-data/src/test/java/org/apache/asterix/external/library/SumFunction.java
+++ b/asterixdb/asterix-external-data/src/test/java/org/apache/asterix/external/library/MySumFunction.java
@@ -22,7 +22,7 @@
 import org.apache.asterix.external.api.IFunctionHelper;
 import org.apache.asterix.external.library.java.base.JInt;
 
-public class SumFunction implements IExternalScalarFunction {
+public class MySumFunction implements IExternalScalarFunction {
 
     private JInt result;
 
diff --git a/asterixdb/asterix-external-data/src/test/resources/library_descriptor.xml b/asterixdb/asterix-external-data/src/test/resources/library_descriptor.xml
index acbc003..720c003 100644
--- a/asterixdb/asterix-external-data/src/test/resources/library_descriptor.xml
+++ b/asterixdb/asterix-external-data/src/test/resources/library_descriptor.xml
@@ -73,7 +73,15 @@
       <function_type>SCALAR</function_type>
       <argument_type>AINT32,AINT32</argument_type>
       <return_type>AINT32</return_type>
-      <definition>org.apache.asterix.external.library.SumFactory
+      <definition>org.apache.asterix.external.library.MySumFactory
+      </definition>
+    </libraryFunction>
+    <libraryFunction>
+      <name>my_array_sum</name>
+      <function_type>SCALAR</function_type>
+      <argument_type>[AINT32]</argument_type>
+      <return_type>AINT32</return_type>
+      <definition>org.apache.asterix.external.library.MyArraySumFactory
       </definition>
     </libraryFunction>
     <libraryFunction>
diff --git a/asterixdb/asterix-metadata/src/main/java/org/apache/asterix/metadata/functions/ExternalFunctionCompilerUtil.java b/asterixdb/asterix-metadata/src/main/java/org/apache/asterix/metadata/functions/ExternalFunctionCompilerUtil.java
index 01d0af7..e203c36 100644
--- a/asterixdb/asterix-metadata/src/main/java/org/apache/asterix/metadata/functions/ExternalFunctionCompilerUtil.java
+++ b/asterixdb/asterix-metadata/src/main/java/org/apache/asterix/metadata/functions/ExternalFunctionCompilerUtil.java
@@ -29,28 +29,24 @@
 import org.apache.asterix.metadata.entities.Datatype;
 import org.apache.asterix.metadata.entities.Function;
 import org.apache.asterix.om.typecomputer.base.IResultTypeComputer;
-import org.apache.asterix.om.typecomputer.impl.ABinaryTypeComputer;
-import org.apache.asterix.om.typecomputer.impl.ADoubleTypeComputer;
-import org.apache.asterix.om.typecomputer.impl.AFloatTypeComputer;
-import org.apache.asterix.om.typecomputer.impl.AInt32TypeComputer;
-import org.apache.asterix.om.typecomputer.impl.AStringTypeComputer;
 import org.apache.asterix.om.types.AOrderedListType;
 import org.apache.asterix.om.types.AUnorderedListType;
 import org.apache.asterix.om.types.BuiltinType;
 import org.apache.asterix.om.types.IAType;
 import org.apache.hyracks.algebricks.common.exceptions.AlgebricksException;
-import org.apache.hyracks.algebricks.core.algebra.base.ILogicalExpression;
 import org.apache.hyracks.algebricks.core.algebra.expressions.AbstractFunctionCallExpression.FunctionKind;
-import org.apache.hyracks.algebricks.core.algebra.expressions.IVariableTypeEnvironment;
 import org.apache.hyracks.algebricks.core.algebra.functions.FunctionIdentifier;
 import org.apache.hyracks.algebricks.core.algebra.functions.IFunctionInfo;
-import org.apache.hyracks.algebricks.core.algebra.metadata.IMetadataProvider;
 
 public class ExternalFunctionCompilerUtil {
 
     private static Pattern orderedListPattern = Pattern.compile("\\[*\\]");
     private static Pattern unorderedListPattern = Pattern.compile("[{{*}}]");
 
+    private ExternalFunctionCompilerUtil() {
+        // do nothing
+    }
+
     public static IFunctionInfo getExternalFunctionInfo(MetadataTransactionContext txnCtx, Function function)
             throws AlgebricksException {
 
@@ -72,24 +68,27 @@
             throws AlgebricksException {
         FunctionIdentifier fid =
                 new FunctionIdentifier(function.getDataverseName(), function.getName(), function.getArity());
-        IResultTypeComputer typeComputer = getResultTypeComputer(txnCtx, function);
-        List<IAType> arguments = new ArrayList<>();
-        IAType returnType;
-        List<String> argumentTypes = function.getArguments();
-        for (String argumentType : argumentTypes) {
-            arguments.add(getTypeInfo(argumentType, txnCtx, function));
+        List<IAType> argumentTypes = new ArrayList<>();
+        IAType returnType = getTypeInfo(function.getReturnType(), txnCtx, function);;
+        for (String argumentType : function.getArguments()) {
+            argumentTypes.add(getTypeInfo(argumentType, txnCtx, function));
         }
-
-        returnType = getTypeInfo(function.getReturnType(), txnCtx, function);
+        IResultTypeComputer typeComputer = new ExternalTypeComputer(returnType, argumentTypes);
 
         return new ExternalScalarFunctionInfo(fid.getNamespace(), fid.getName(), fid.getArity(), returnType,
-                function.getFunctionBody(), function.getLanguage(), arguments, typeComputer);
+                function.getFunctionBody(), function.getLanguage(), argumentTypes, typeComputer);
     }
 
     private static IAType getTypeInfo(String paramType, MetadataTransactionContext txnCtx, Function function)
             throws AlgebricksException {
-        if (paramType.equalsIgnoreCase(BuiltinType.AINT32.getDisplayName())) {
+        if (paramType.equalsIgnoreCase(BuiltinType.AINT8.getDisplayName())) {
+            return BuiltinType.AINT8;
+        } else if (paramType.equalsIgnoreCase(BuiltinType.AINT16.getDisplayName())) {
+            return BuiltinType.AINT16;
+        } else if (paramType.equalsIgnoreCase(BuiltinType.AINT32.getDisplayName())) {
             return BuiltinType.AINT32;
+        } else if (paramType.equalsIgnoreCase(BuiltinType.AINT64.getDisplayName())) {
+            return BuiltinType.AINT64;
         } else if (paramType.equalsIgnoreCase(BuiltinType.AFLOAT.getDisplayName())) {
             return BuiltinType.AFLOAT;
         } else if (paramType.equalsIgnoreCase(BuiltinType.ASTRING.getDisplayName())) {
@@ -144,59 +143,6 @@
         return null;
     }
 
-    private static IResultTypeComputer getResultTypeComputer(final MetadataTransactionContext txnCtx,
-            final Function function) throws AlgebricksException {
-
-        final IAType type = getTypeInfo(function.getReturnType(), txnCtx, function);
-        switch (type.getTypeTag()) {
-            case INTEGER:
-                return AInt32TypeComputer.INSTANCE;
-            case FLOAT:
-                return AFloatTypeComputer.INSTANCE;
-            case DOUBLE:
-                return ADoubleTypeComputer.INSTANCE;
-            case BINARY:
-                return ABinaryTypeComputer.INSTANCE;
-            case STRING:
-                return AStringTypeComputer.INSTANCE;
-            case ARRAY:
-                return new ExternalTypeComputer() {
-                    private static final long serialVersionUID = 1L;
-
-                    @Override
-                    public IAType computeType(ILogicalExpression expression, IVariableTypeEnvironment env,
-                            IMetadataProvider<?, ?> metadataProvider) throws AlgebricksException {
-
-                        return new AOrderedListType(((AOrderedListType) type).getItemType(),
-                                ((AOrderedListType) type).getItemType().getTypeName());
-                    }
-
-                };
-            case MULTISET:
-                return new ExternalTypeComputer() {
-                    private static final long serialVersionUID = 1L;
-
-                    @Override
-                    public IAType computeType(ILogicalExpression expression, IVariableTypeEnvironment env,
-                            IMetadataProvider<?, ?> metadataProvider) throws AlgebricksException {
-                        return new AUnorderedListType(((AUnorderedListType) type).getItemType(), type.getTypeName());
-                    }
-
-                };
-            default:
-                return new ExternalTypeComputer() {
-                    private static final long serialVersionUID = 1L;
-
-                    @Override
-                    public IAType computeType(ILogicalExpression expression, IVariableTypeEnvironment env,
-                            IMetadataProvider<?, ?> mp) throws AlgebricksException {
-                        return type;
-                    }
-                };
-        }
-
-    }
-
     private static IFunctionInfo getUnnestFunctionInfo(MetadataTransactionContext txnCtx, Function function) {
         return null;
     }
diff --git a/asterixdb/asterix-metadata/src/main/java/org/apache/asterix/metadata/functions/ExternalTypeComputer.java b/asterixdb/asterix-metadata/src/main/java/org/apache/asterix/metadata/functions/ExternalTypeComputer.java
index d50f4cb..2f5742e 100644
--- a/asterixdb/asterix-metadata/src/main/java/org/apache/asterix/metadata/functions/ExternalTypeComputer.java
+++ b/asterixdb/asterix-metadata/src/main/java/org/apache/asterix/metadata/functions/ExternalTypeComputer.java
@@ -18,10 +18,40 @@
  */
 package org.apache.asterix.metadata.functions;
 
-import java.io.Serializable;
+import java.util.List;
 
-import org.apache.asterix.om.typecomputer.base.IResultTypeComputer;
+import org.apache.asterix.om.exceptions.TypeMismatchException;
+import org.apache.asterix.om.typecomputer.base.AbstractResultTypeComputer;
+import org.apache.asterix.om.types.IAType;
+import org.apache.asterix.om.types.hierachy.ATypeHierarchy;
+import org.apache.hyracks.algebricks.common.exceptions.AlgebricksException;
+import org.apache.hyracks.algebricks.core.algebra.base.ILogicalExpression;
+import org.apache.hyracks.algebricks.core.algebra.functions.FunctionIdentifier;
+import org.apache.hyracks.api.exceptions.SourceLocation;
 
-public interface ExternalTypeComputer extends IResultTypeComputer, Serializable {
+public class ExternalTypeComputer extends AbstractResultTypeComputer {
 
+    private IAType resultType;
+    private List<IAType> argTypes;
+
+    @Override
+    protected void checkArgType(FunctionIdentifier funcId, int argIndex, IAType type, SourceLocation sourceLoc)
+            throws AlgebricksException {
+        IAType reqArgType = argTypes.get(argIndex);
+        if (!type.equals(argTypes.get(argIndex))
+                && !ATypeHierarchy.isCompatible(type.getTypeTag(), reqArgType.getTypeTag())) {
+            throw new TypeMismatchException(sourceLoc, funcId, argIndex, type.getTypeTag(),
+                    argTypes.get(argIndex).getTypeTag());
+        }
+    }
+
+    public ExternalTypeComputer(IAType resultType, List<IAType> argTypes) {
+        this.resultType = resultType;
+        this.argTypes = argTypes;
+    }
+
+    @Override
+    protected IAType getResultType(ILogicalExpression expr, IAType... strippedInputTypes) {
+        return resultType;
+    }
 }
diff --git a/asterixdb/asterix-metadata/src/test/java/org/apache/asterix/metadata/functions/ExternalFunctionCompilerUtilTest.java b/asterixdb/asterix-metadata/src/test/java/org/apache/asterix/metadata/functions/ExternalFunctionCompilerUtilTest.java
index b4bae90..78145c1 100644
--- a/asterixdb/asterix-metadata/src/test/java/org/apache/asterix/metadata/functions/ExternalFunctionCompilerUtilTest.java
+++ b/asterixdb/asterix-metadata/src/test/java/org/apache/asterix/metadata/functions/ExternalFunctionCompilerUtilTest.java
@@ -42,11 +42,9 @@
         // when
         ExternalScalarFunctionInfo info =
                 (ExternalScalarFunctionInfo) ExternalFunctionCompilerUtil.getExternalFunctionInfo(txnCtx, function);
-        IAType type = info.getResultTypeComputer().computeType(null, null, null);
 
         // then
         IAType expectedType = new AUnorderedListType(BuiltinType.ASTRING, "AUnorderedList");
         Assert.assertEquals(expectedType, info.getReturnType());
-        Assert.assertEquals(expectedType, type);
     }
 }
diff --git a/asterixdb/asterix-om/src/main/java/org/apache/asterix/om/functions/ExternalFunctionInfo.java b/asterixdb/asterix-om/src/main/java/org/apache/asterix/om/functions/ExternalFunctionInfo.java
index af1bc7c..2c80470 100644
--- a/asterixdb/asterix-om/src/main/java/org/apache/asterix/om/functions/ExternalFunctionInfo.java
+++ b/asterixdb/asterix-om/src/main/java/org/apache/asterix/om/functions/ExternalFunctionInfo.java
@@ -50,7 +50,7 @@
         return rtc;
     }
 
-    public List<IAType> getArgumenTypes() {
+    public List<IAType> getArgumentTypes() {
         return argumentTypes;
     }
 
diff --git a/asterixdb/asterix-server/src/test/resources/integrationts/library/results/library-functions/my_array_sum/my_array_sum.1.adm b/asterixdb/asterix-server/src/test/resources/integrationts/library/results/library-functions/my_array_sum/my_array_sum.1.adm
new file mode 100644
index 0000000..25bf17f
--- /dev/null
+++ b/asterixdb/asterix-server/src/test/resources/integrationts/library/results/library-functions/my_array_sum/my_array_sum.1.adm
@@ -0,0 +1 @@
+18
\ No newline at end of file
diff --git a/asterixdb/asterix-server/src/test/resources/integrationts/library/results/library-functions/mysum/mysum.2.adm b/asterixdb/asterix-server/src/test/resources/integrationts/library/results/library-functions/mysum/mysum.2.adm
new file mode 100644
index 0000000..ca7bf83
--- /dev/null
+++ b/asterixdb/asterix-server/src/test/resources/integrationts/library/results/library-functions/mysum/mysum.2.adm
@@ -0,0 +1 @@
+13
\ No newline at end of file
diff --git a/asterixdb/asterix-server/src/test/resources/integrationts/library/testsuite.xml b/asterixdb/asterix-server/src/test/resources/integrationts/library/testsuite.xml
index babf911..76b74ef 100644
--- a/asterixdb/asterix-server/src/test/resources/integrationts/library/testsuite.xml
+++ b/asterixdb/asterix-server/src/test/resources/integrationts/library/testsuite.xml
@@ -28,6 +28,12 @@
     <test-case FilePath="library-functions">
       <compilation-unit name="mysum">
         <output-dir compare="Text">mysum</output-dir>
+        <expected-error>Type mismatch: function testlib#mysum expects its 1st input parameter to be of type integer</expected-error>
+      </compilation-unit>
+    </test-case>
+    <test-case FilePath="external-library">
+      <compilation-unit name="my_array_sum">
+        <output-dir compare="Text">my_array_sum</output-dir>
       </compilation-unit>
     </test-case>
     <test-case FilePath="library-functions">