diff --git a/schema/metaschema/metaschema-module-constraints.xml b/schema/metaschema/metaschema-module-constraints.xml
index c91a1e34..c0084ee7 100644
--- a/schema/metaschema/metaschema-module-constraints.xml
+++ b/schema/metaschema/metaschema-module-constraints.xml
@@ -5,37 +5,43 @@
     <context>
         <metapath target="/METASCHEMA"/>
         <constraints>
-            <let var="all-imports" expression="recurse-depth(.,'doc(resolve-uri(import/@href))/METASCHEMA')"/>
-            <index id="metaschema-short-name-unique" target="(.|$all-imports)" name="metaschema-metadata-short-name-index">
-                <formal-name>Unique Module Short Names</formal-name>
+            <let var="all-imports" expression="recurse-depth('doc(resolve-uri(import/@href))/METASCHEMA')"/>
+            <index id="module-short-name-unique" target="(.|$all-imports)" name="metaschema-metadata-short-name-index">
+                <formal-name>Index Module Short Names</formal-name>
                 <description>Ensures that the current and all imported modules have a unique short name.</description>
                 <key-field target="@short-name"/>
             </index>
+            <expect id="module-top-level-version-required" target=".[not(@abstract) or @abstract='yes']" test="@version">
+                <formal-name>Require Version for Top-Level Modules</formal-name>
+                <description>A top-level module, a module that is not marked as @abstract='yes', must have a version specified.</description>
+                <message>Unless marked as @abstract='yes', a Metaschema module (or an imported module) should have a version.</message>
+            </expect>
+            <expect id="module-top-level-root-required" target=".[not(@abstract) or @abstract='yes']" test="define-assembly/root-name">
+                <formal-name>Require Root Assembly for Top-Level Modules</formal-name>
+                <description>A top-level module, a module that is not marked as @abstract='yes', must have at least one assembly with a root-name.</description>
+                <message>Unless marked as @abstract='yes', a Metaschema module (or an imported module) should have at least one assembly with a root-name.</message>
+            </expect>
+            <is-unique id="module-namespace-unique-entry" target="namespace">
+                <formal-name>Require Unique Namespace Entries</formal-name>
+                <description>Ensures that all declared namespace entries are unique.</description>
+                <key-field target="@prefix"/>
+                <key-field target="@uri"/>
+            </is-unique>
+            <is-unique id="module-namespace-unique-prefix" target="namespace">
+                <formal-name>Require Unique Namespace Entry Prefixes</formal-name>
+                <description>Ensures that all declared namespace entries have a unique prefix.</description>
+                <key-field target="@prefix"/>
+            </is-unique>
         </constraints>
-        <context>
-            <metapath target=".[not(@abstract) or @abstract='yes']"/>
-            <constraints>
-                <expect id="metaschema-top-level-version-required" target="." test="@version">
-                    <formal-name>Require Version for Top-Level Modules</formal-name>
-                    <description>A top-level module, a module that is not marked as @abstract='yes', must have a version specified.</description>
-                    <message>Unless marked as @abstract='yes', a Metaschema module (or an imported module) should have a version.</message>
-                </expect>
-                <expect id="metaschema-top-level-root-required" target="." test="define-assembly/root-name">
-                    <formal-name>Require Root Assembly for Top-Level Modules</formal-name>
-                    <description>A top-level module, a module that is not marked as @abstract='yes', must have at least one assembly with a root-name.</description>
-                    <message>Unless marked as @abstract='yes', a Metaschema module (or an imported module) should have at least one assembly with a root-name.</message>
-                </expect>
-            </constraints>
-        </context>
         <context>
             <metapath target="import"/>
             <constraints>
-                <expect id="metaschema-import-href-available" target="." test="document-available(resolve-uri(import/@href))">
+                <expect id="module-import-href-available" target="." test="document-available(resolve-uri(import/@href))">
                     <formal-name>Import is Resolvable</formal-name>
                     <description>Ensure each import has a resolvable @href.</description>
                     <message>Unable to access a Metaschema module at '{{ resolve-uri(@href) }}'.</message>
                 </expect>
-                <expect id="metaschema-import-href-is-module" target="." test="doc(resolve-uri(import/@href))/METASCHEMA ! exists(.)">
+                <expect id="module-import-href-is-module" target="." test="doc(resolve-uri(import/@href))/METASCHEMA ! exists(.)">
                     <formal-name>Import is Resolvable</formal-name>
                     <description>Ensure each import is a Metaschema module.</description>
                     <message>Unable the resource at '{{ resolve-uri(@href) }}' is not a Metaschema module.</message>
@@ -43,4 +49,20 @@
             </constraints>
         </context>
     </context>
+    <context>
+        <metapath target="/metaschema-meta-constraints"/>
+        <constraints>
+            <is-unique id="meta-constraints-namespace-unique-entry" target="namespace">
+                <formal-name>Require Unique Namespace Entries</formal-name>
+                <description>Ensures that all declared namespace entries are unique.</description>
+                <key-field target="@prefix"/>
+                <key-field target="@uri"/>
+            </is-unique>
+            <is-unique id="meta-constraints-namespace-unique-prefix" target="namespace">
+                <formal-name>Require Unique Namespace Entry Prefixes</formal-name>
+                <description>Ensures that all declared namespace entries have a unique prefix.</description>
+                <key-field target="@prefix"/>
+            </is-unique>
+        </constraints>
+    </context>
 </metaschema-meta-constraints>
\ No newline at end of file
diff --git a/schema/metaschema/metaschema-module-metaschema.xml b/schema/metaschema/metaschema-module-metaschema.xml
index 0cdd5915..0b9c143d 100644
--- a/schema/metaschema/metaschema-module-metaschema.xml
+++ b/schema/metaschema/metaschema-module-metaschema.xml
@@ -52,6 +52,9 @@
                     <description>A relative or absolute URI for retrieving an out-of-line Metaschema definition.</description>
                 </define-flag>
             </define-assembly>
+            <assembly ref="metapath-namespace" max-occurs="unbounded">
+                <group-as name="namespaces" />
+            </assembly>
             <choice-group max-occurs="unbounded">
                 <group-as name="definitions" in-json="ARRAY"/>
                 <discriminator>object-type</discriminator>
@@ -183,6 +186,21 @@
         </constraint>
     </define-assembly>
     
+    <define-assembly name="metapath-namespace">
+        <formal-name>Metapath Namespace Declaration</formal-name>
+        <description>Assigns a Metapath namespace to a prefix for use in a Metapath expression in a lexical qualified name.</description>
+        <use-name>namespace</use-name>
+        <define-flag name="uri" as-type="uri" required="yes">
+            <formal-name>Metapath Namespace URI</formal-name>
+            <description>The namespace URI to bind to the prefix.</description>
+        </define-flag>
+        <define-flag name="prefix" as-type="token" required="yes">
+            <formal-name>Metapath Namespace Prefix</formal-name>
+            <description>The prefix that is bound to the namespace.</description>
+        </define-flag>
+    </define-assembly>
+
+
     <define-assembly name="inline-define-assembly">
         <formal-name>Inline Assembly Definition</formal-name>
         <use-name>define-assembly</use-name>
@@ -1302,6 +1320,10 @@
         <description>Defines constraint rules to be applied to an existing set of Metaschema module-based models.</description>
         <root-name>metaschema-meta-constraints</root-name>
         <model>
+            <assembly ref="metapath-namespace" max-occurs="unbounded">
+                <group-as name="namespaces" />
+            </assembly>
+
             <define-assembly name="definition-context">
                 <define-flag name="name" as-type="token" required="yes"/>
                 <define-flag name="namespace" as-type="uri" required="yes"/>