diff --git a/asterixdb/asterix-app/src/test/resources/runtimets/queries_sqlpp/null-missing/is/is.1.query.sqlpp b/asterixdb/asterix-app/src/test/resources/runtimets/queries_sqlpp/null-missing/is/is.1.query.sqlpp
index 81f2a3f..77e8d91 100644
--- a/asterixdb/asterix-app/src/test/resources/runtimets/queries_sqlpp/null-missing/is/is.1.query.sqlpp
+++ b/asterixdb/asterix-app/src/test/resources/runtimets/queries_sqlpp/null-missing/is/is.1.query.sqlpp
@@ -41,5 +41,11 @@
   "21": 1 is valued,
   "22": null is not valued,
   "23": missing is not valued,
-  "24": 1 is not valued
+  "24": 1 is not valued,
+  "25": null is known,
+  "26": missing is known,
+  "27": 1 is known,
+  "28": null is not known,
+  "29": missing is not known,
+  "30": 1 is not known
 };
diff --git a/asterixdb/asterix-app/src/test/resources/runtimets/results/null-missing/is/is.1.adm b/asterixdb/asterix-app/src/test/resources/runtimets/results/null-missing/is/is.1.adm
index 920f7b4..cf13212 100644
--- a/asterixdb/asterix-app/src/test/resources/runtimets/results/null-missing/is/is.1.adm
+++ b/asterixdb/asterix-app/src/test/resources/runtimets/results/null-missing/is/is.1.adm
@@ -1 +1 @@
-{ "1": true, "3": false, "4": false, "6": true, "7": false, "8": true, "9": false, "10": true, "11": false, "12": true, "13": true, "14": true, "15": false, "16": false, "17": false, "18": true, "19": false, "20": false, "21": true, "22": true, "23": true, "24": false }
+{ "1": true, "3": false, "4": false, "6": true, "7": false, "8": true, "9": false, "10": true, "11": false, "12": true, "13": true, "14": true, "15": false, "16": false, "17": false, "18": true, "19": false, "20": false, "21": true, "22": true, "23": true, "24": false, "25": false, "26": false, "27": true, "28": true, "29": true, "30": false }
diff --git a/asterixdb/asterix-doc/src/main/markdown/sqlpp/2_expr.md b/asterixdb/asterix-doc/src/main/markdown/sqlpp/2_expr.md
index 93e2f5d..5c19566 100644
--- a/asterixdb/asterix-doc/src/main/markdown/sqlpp/2_expr.md
+++ b/asterixdb/asterix-doc/src/main/markdown/sqlpp/2_expr.md
@@ -103,16 +103,16 @@
 
 The following table enumerates all of SQL++'s comparison operators.
 
-| Operator       |  Purpose                                   | Example    |
-|----------------|--------------------------------------------|------------|
+| Operator       |  Purpose                                       | Example    |
+|----------------|------------------------------------------------|------------|
 | IS NULL        |  Test if a value is NULL                       | SELECT * FROM ChirpMessages cm <br/>WHERE cm.user.name IS NULL; |
 | IS NOT NULL    |  Test if a value is not NULL                   | SELECT * FROM ChirpMessages cm <br/>WHERE cm.user.name IS NOT NULL; |
 | IS MISSING     |  Test if a value is MISSING                    | SELECT * FROM ChirpMessages cm <br/>WHERE cm.user.name IS MISSING; |
 | IS NOT MISSING |  Test if a value is not MISSING                | SELECT * FROM ChirpMessages cm <br/>WHERE cm.user.name IS NOT MISSING;|
 | IS UNKNOWN     |  Test if a value is NULL or MISSING            | SELECT * FROM ChirpMessages cm <br/>WHERE cm.user.name IS UNKNOWN; |
 | IS NOT UNKNOWN |  Test if a value is neither NULL nor MISSING   | SELECT * FROM ChirpMessages cm <br/>WHERE cm.user.name IS NOT UNKNOWN;|
-| IS VALUED      |  Test if a value is neither NULL nor MISSING   | SELECT * FROM ChirpMessages cm <br/>WHERE cm.user.name IS VALUED; |
-| IS NOT VALUED  |  Test if a value is NULL or MISSING            | SELECT * FROM ChirpMessages cm <br/>WHERE cm.user.name IS NOT VALUED;|
+| IS KNOWN (IS VALUED) |  Test if a value is neither NULL nor MISSING | SELECT * FROM ChirpMessages cm <br/>WHERE cm.user.name IS KNOWN; |
+| IS NOT KNOWN (IS NOT VALUED) |  Test if a value is NULL or MISSING | SELECT * FROM ChirpMessages cm <br/>WHERE cm.user.name IS NOT KNOWN; |
 | BETWEEN        |  Test if a value is between a start value and <br/>a end value. The comparison is inclusive <br/>to both start and end values. |  SELECT * FROM ChirpMessages cm <br/>WHERE cm.chirpId BETWEEN 10 AND 20;|
 | =              |  Equality test                                 | SELECT * FROM ChirpMessages cm <br/>WHERE cm.chirpId=10; |
 | !=             |  Inequality test                               | SELECT * FROM ChirpMessages cm <br/>WHERE cm.chirpId!=10;|
@@ -134,8 +134,8 @@
 | IS NOT MISSING | TRUE | TRUE | FALSE |
 | IS UNKNOWN | FALSE | TRUE | TRUE |
 | IS NOT UNKNOWN | TRUE | FALSE | FALSE|
-| IS VALUED | TRUE | FALSE | FALSE |
-| IS NOT VALUED | FALSE | TRUE | TRUE |
+| IS KNOWN (IS VALUED) | TRUE | FALSE | FALSE |
+| IS NOT KNOWN (IS NOT VALUED) | FALSE | TRUE | TRUE |
 
 ### <a id="Logical_operators">Logical Operators</a>
 Logical operators perform logical `NOT`, `AND`, and `OR` operations over Boolean values (`TRUE` and `FALSE`) plus `NULL` and `MISSING`.
diff --git a/asterixdb/asterix-lang-sqlpp/src/main/javacc/SQLPP.jj b/asterixdb/asterix-lang-sqlpp/src/main/javacc/SQLPP.jj
index 9af114b..7f9149d 100644
--- a/asterixdb/asterix-lang-sqlpp/src/main/javacc/SQLPP.jj
+++ b/asterixdb/asterix-lang-sqlpp/src/main/javacc/SQLPP.jj
@@ -2018,7 +2018,7 @@
             <NULL> { fn = BuiltinFunctions.IS_NULL; } |
             <MISSING> { fn = BuiltinFunctions.IS_MISSING; } |
             <UNKNOWN> { fn = BuiltinFunctions.IS_UNKNOWN; } |
-            <VALUED> { not = !not; fn = BuiltinFunctions.IS_UNKNOWN; }
+            (<KNOWN> | <VALUED>) { not = !not; fn = BuiltinFunctions.IS_UNKNOWN; }
         )
       {
         FunctionSignature signature = new FunctionSignature(fn);
@@ -3252,6 +3252,7 @@
   | <JOIN : "join">
   | <KEYWORD : "keyword">
   | <KEY : "key">
+  | <KNOWN : "known">
   | <LEFT : "left">
   | <LETTING : "letting">
   | <LET : "let">