diff --git a/src/main/java/org/apache/sling/feature/extension/apiregions/api/config/PropertyDescription.java b/src/main/java/org/apache/sling/feature/extension/apiregions/api/config/PropertyDescription.java
index f07df67..584db9c 100644
--- a/src/main/java/org/apache/sling/feature/extension/apiregions/api/config/PropertyDescription.java
+++ b/src/main/java/org/apache/sling/feature/extension/apiregions/api/config/PropertyDescription.java
@@ -220,10 +220,18 @@
 
 	/**
 	 * Set the cardinality
-	 * @param cardinality the cardinality to set
+     * The default cardinality is {@code 1}. If the value is greater than zero
+     * the property can contain up to that number of values.
+     * If the cardinality is {@code -1} the property can hold an unlimited number
+     * of values.
+	 * @param value the cardinality to set
+     * @throws IllegalArgumentException If the value is {@code 0} or below {@code -1}.
 	 */
-	public void setCardinality(final int cardinality) {
-		this.cardinality = cardinality;
+	public void setCardinality(final int value) {
+        if ( value == 0 || value < -1 ) {
+            throw new IllegalArgumentException();
+        }
+		this.cardinality = value;
 	}
 
 	/**
diff --git a/src/main/java/org/apache/sling/feature/extension/apiregions/api/config/validation/PropertyValidator.java b/src/main/java/org/apache/sling/feature/extension/apiregions/api/config/validation/PropertyValidator.java
index a9d5554..ecfdb5a 100644
--- a/src/main/java/org/apache/sling/feature/extension/apiregions/api/config/validation/PropertyValidator.java
+++ b/src/main/java/org/apache/sling/feature/extension/apiregions/api/config/validation/PropertyValidator.java
@@ -26,6 +26,7 @@
 
 import org.apache.sling.feature.extension.apiregions.api.config.Option;
 import org.apache.sling.feature.extension.apiregions.api.config.PropertyDescription;
+import org.apache.sling.feature.extension.apiregions.api.config.PropertyType;
 
 /**
  * Validate a configuration property or framework property
@@ -122,61 +123,80 @@
 
     private static final List<String> PLACEHOLDERS = Arrays.asList("$[env:", "$[secret:", "$[prop:");
 
-	void validateValue(final PropertyDescription prop, final Object value, final PropertyValidationResult result) {
+	void validateValue(final PropertyDescription desc, final Object value, final PropertyValidationResult result) {
         final List<String> messages = result.getErrors();
 		if ( value != null ) {
             // check for placeholder
-            boolean checkValue = true;
+            boolean hasPlaceholder = false;
             if ( value instanceof String ) {
                 final String strVal = (String)value;
                 for(final String p : PLACEHOLDERS) {
                     if ( strVal.contains(p) ) {
-                        checkValue = false;
+                        hasPlaceholder = true;
                         break;
                     }
                 }
             }
-            if ( checkValue ) {
-                switch ( prop.getType() ) {
-                    case BOOLEAN : validateBoolean(prop, value, messages);
+            if ( !hasPlaceholder ) {
+                switch ( desc.getType() ) {
+                    case BOOLEAN : validateBoolean(desc, value, messages);
                                 break;
-                    case BYTE : validateByte(prop, value, messages);
+                    case BYTE : validateByte(desc, value, messages);
                                 break;
-                    case CHARACTER : validateCharacter(prop, value, messages);
+                    case CHARACTER : validateCharacter(desc, value, messages);
                                 break;
-                    case DOUBLE : validateDouble(prop, value, messages); 
+                    case DOUBLE : validateDouble(desc, value, messages); 
                                 break;
-                    case FLOAT : validateFloat(prop, value, messages); 
+                    case FLOAT : validateFloat(desc, value, messages); 
                                 break;
-                    case INTEGER : validateInteger(prop, value, messages);
+                    case INTEGER : validateInteger(desc, value, messages);
                                 break;
-                    case LONG : validateLong(prop, value, messages);
+                    case LONG : validateLong(desc, value, messages);
                                 break;
-                    case SHORT : validateShort(prop, value, messages);
+                    case SHORT : validateShort(desc, value, messages);
                                 break;
-                    case STRING : // no special validation for string
+                    case STRING : validateRequired(desc, value, messages);
                                 break;
-                    case EMAIL : validateEmail(prop, value, messages); 
+                    case EMAIL : validateEmail(desc, value, messages); 
                                 break;
-                    case PASSWORD : validatePassword(prop, value, messages);
+                    case PASSWORD : validatePassword(desc, value, messages, false);
                                 break;
-                    case URL : validateURL(prop, value, messages);
+                    case URL : validateURL(desc, value, messages);
                             break;
-                    case PATH : validatePath(prop, value, messages);
+                    case PATH : validatePath(desc, value, messages);
                                 break;
-                    default : messages.add("Unable to validate value - unknown property type : " + prop.getType());
+                    default : messages.add("Unable to validate value - unknown property type : " + desc.getType());
                 }
-                validateRegex(prop, value, messages);
-                validateOptions(prop, value, messages);                
+                validateRegex(desc, value, messages);
+                validateOptions(desc, value, messages);                
             } else {
-                result.markSkipped();
+                // placeholder is present
+                if ( desc.getType() == PropertyType.PASSWORD ) {
+                    validatePassword(desc, value, messages, true);
+                } else if ( desc.getType() == PropertyType.STRING ) {
+                    // any string is valid, we only mark the result as skipped if a regex or options are set
+                    if ( desc.getRegex() != null || desc.getOptions() != null || desc.isRequired() ) {
+                        result.markSkipped();
+                    }
+                } else {
+                    result.markSkipped();
+                }
             }
         } else {
 			messages.add("Null value provided for validation");
 		}
 	}
 	
-	void validateBoolean(final PropertyDescription prop, final Object value, final List<String> messages) {
+	void validateRequired(final PropertyDescription prop, final Object value, final List<String> messages) {
+        if ( prop.isRequired() ) {
+            final String val = value.toString();
+            if ( val.isEmpty() ) {
+                messages.add("Value is required");
+            }
+        }
+    }
+
+    void validateBoolean(final PropertyDescription prop, final Object value, final List<String> messages) {
         if ( ! (value instanceof Boolean) ) {
 			if ( value instanceof String ) {
 				final String v = (String)value;
@@ -333,10 +353,10 @@
 		}
 	}
 
-	void validatePassword(final PropertyDescription prop, final Object value, final List<String> messages) {
-		if ( prop.getVariable() == null ) {
-			messages.add("Value for a password must use a variable");
-		}
+	void validatePassword(final PropertyDescription desc, final Object value, final List<String> messages, final boolean hasPlaceholder) {
+        if ( !hasPlaceholder ) {
+            messages.add("Value for a password must use a placeholder");
+        }
 	}
 
 	void validatePath(final PropertyDescription prop, final Object value, final List<String> messages) {
diff --git a/src/test/java/org/apache/sling/feature/extension/apiregions/api/config/PropertyDescriptionTest.java b/src/test/java/org/apache/sling/feature/extension/apiregions/api/config/PropertyDescriptionTest.java
index d9b50c2..5e64e62 100644
--- a/src/test/java/org/apache/sling/feature/extension/apiregions/api/config/PropertyDescriptionTest.java
+++ b/src/test/java/org/apache/sling/feature/extension/apiregions/api/config/PropertyDescriptionTest.java
@@ -22,6 +22,7 @@
 import static org.junit.Assert.assertNotNull;
 import static org.junit.Assert.assertNull;
 import static org.junit.Assert.assertTrue;
+import static org.junit.Assert.fail;
 
 import java.io.IOException;
 import java.util.Arrays;
@@ -133,4 +134,27 @@
 
         assertEquals(ext.getJSONStructure().asJsonObject(), entity.toJSONObject());
     }
+
+    @Test public void testSetCardinality() {
+        final PropertyDescription desc = new PropertyDescription();
+        desc.setCardinality(5);
+        assertEquals(5, desc.getCardinality());
+        desc.setCardinality(1);
+        assertEquals(1, desc.getCardinality());
+        desc.setCardinality(-1);
+        assertEquals(-1, desc.getCardinality());
+
+        try {
+            desc.setCardinality(0);
+            fail();
+        } catch ( final IllegalArgumentException iae) {
+            // expected
+        }
+        try {
+            desc.setCardinality(-2);
+            fail();
+        } catch ( final IllegalArgumentException iae) {
+            // expected
+        }
+    }
 }
\ No newline at end of file
diff --git a/src/test/java/org/apache/sling/feature/extension/apiregions/api/config/validation/PropertyValidatorTest.java b/src/test/java/org/apache/sling/feature/extension/apiregions/api/config/validation/PropertyValidatorTest.java
index fd8d1c0..dd544bd 100644
--- a/src/test/java/org/apache/sling/feature/extension/apiregions/api/config/validation/PropertyValidatorTest.java
+++ b/src/test/java/org/apache/sling/feature/extension/apiregions/api/config/validation/PropertyValidatorTest.java
@@ -21,6 +21,7 @@
 import static org.junit.Assert.assertTrue;
 
 import java.util.ArrayList;
+import java.util.Collections;
 import java.util.List;
 
 import org.apache.sling.feature.extension.apiregions.api.config.Option;
@@ -278,8 +279,10 @@
         assertTrue(result.isValid());
         assertFalse(result.isSkipped());
 
-        prop.setVariable("secret");
-        result = validator.validate(null, prop);
+        result = validator.validate("secret", prop);
+        assertFalse(result.isValid());
+
+        result = validator.validate("$[secret:dbpassword]", prop);
         assertTrue(result.isValid());
         assertFalse(result.isSkipped());
     }
@@ -299,6 +302,52 @@
         assertFalse(result.isSkipped());
     }
     
+    @Test public void testValidateString() {
+        final PropertyDescription desc = new PropertyDescription();
+        PropertyValidationResult result;
+
+        result = validator.validate("hello world", desc);
+        assertTrue(result.isValid());
+        assertFalse(result.isSkipped());
+
+        result = validator.validate("$[prop:KEY]", desc);
+        assertTrue(result.isValid());
+        assertFalse(result.isSkipped());
+
+        // skip if required
+        desc.setRequired(true);
+        result = validator.validate("$[prop:KEY]", desc);
+        assertTrue(result.isValid());
+        assertTrue(result.isSkipped());
+        desc.setRequired(false);
+
+        // skip if options
+        desc.setOptions(Collections.singletonList(new Option()));
+        result = validator.validate("$[prop:KEY]", desc);
+        assertTrue(result.isValid());
+        assertTrue(result.isSkipped());
+        desc.setOptions(null);
+
+        // skip if regexp
+        desc.setRegex(".*");        
+        result = validator.validate("$[prop:KEY]", desc);
+        assertTrue(result.isValid());
+        assertTrue(result.isSkipped());
+        desc.setRegex(null);
+
+        // empty string - not required
+        result = validator.validate("", desc);
+        assertTrue(result.isValid());
+        assertFalse(result.isSkipped());
+
+        // empty string - required
+        desc.setRequired(true);
+        result = validator.validate("", desc);
+        assertFalse(result.isValid());
+        assertFalse(result.isSkipped());
+        desc.setRequired(false);
+    }
+
     @Test public void testValidateRange() {
         final List<String> messages = new ArrayList<>();
         final PropertyDescription prop = new PropertyDescription();
@@ -510,6 +559,7 @@
 
     @Test public void testPlaceholdersString() {
         final PropertyDescription desc = new PropertyDescription();
+        desc.setType(PropertyType.PATH);
 
         PropertyValidationResult result = null;