diff --git a/packages/concerto-cli/index.js b/packages/concerto-cli/index.js
index 319cc8cec9..941ccab790 100755
--- a/packages/concerto-cli/index.js
+++ b/packages/concerto-cli/index.js
@@ -323,7 +323,7 @@ require('yargs')
             type: 'string'
         });
         yargs.option('namespace', {
-            describe: 'The namepspace for the output model',
+            describe: 'The namespace for the output model',
             type: 'string',
         });
         yargs.option('typeName', {
diff --git a/packages/concerto-cli/test/cli.js b/packages/concerto-cli/test/cli.js
index b414712465..c3ba893da4 100644
--- a/packages/concerto-cli/test/cli.js
+++ b/packages/concerto-cli/test/cli.js
@@ -563,8 +563,6 @@ describe('concerto-cli', () => {
             );
             obj.should.equal(`namespace concerto.test.jsonSchema
 
-import org.accordproject.time.* from https://models.accordproject.org/time@0.2.0.cto
-
 concept Root {
    o String name optional
    o Root[] children optional
@@ -582,8 +580,6 @@ concept Root {
             );
             obj.should.equal(`namespace petstore
 
-import org.accordproject.time.* from https://models.accordproject.org/time@0.2.0.cto
-
 concept Pet {
    o NewPet pet optional
 }
diff --git a/packages/concerto-tools/lib/codegen/fromJsonSchema/cto/inferModel.js b/packages/concerto-tools/lib/codegen/fromJsonSchema/cto/inferModel.js
index 5cf912c619..6830290c76 100644
--- a/packages/concerto-tools/lib/codegen/fromJsonSchema/cto/inferModel.js
+++ b/packages/concerto-tools/lib/codegen/fromJsonSchema/cto/inferModel.js
@@ -73,12 +73,13 @@ function parseIdUri(id) {
 
 /**
  * Infer a type name for a definition. Examines $id, title and parent declaration
- * @param {*} definition the input object
- * @param {*} context the processing context
+ * @param {object} definition - the input object
+ * @param {*} context - the processing context
+ * @param {boolean} [skipDictionary] - if true, this function will not use the dictionary help inference
  * @returns {string} A name for the definition
  * @private
  */
-function inferTypeName(definition, context) {
+function inferTypeName(definition, context, skipDictionary) {
     if (definition.$ref) {
         return normalizeType(definition.$ref);
     }
@@ -86,7 +87,12 @@ function inferTypeName(definition, context) {
     const name = context.parents.peek();
     const { type } = parseIdUri(definition.$id) ||
         { type: definition.title || name };
-    return normalizeType(type);
+
+    if (skipDictionary || context.dictionary.has(normalizeType(type))){
+        return normalizeType(type);
+    }
+    // We fallback to a stringified object representation. This is "untyped".
+    return 'String';
 }
 
 /**
@@ -122,7 +128,8 @@ function inferType(definition, context) {
                 if (definition.format === 'date-time' || definition.format === 'date') {
                     return 'DateTime';
                 } else {
-                    throw new Error(`Format '${definition.format}' in '${name}' is not supported`);
+                    console.warn(`Format '${definition.format}' in '${name}' is not supported. It has been ignored.`);
+                    return 'String';
                 }
             }
             return 'String';
@@ -143,13 +150,15 @@ function inferType(definition, context) {
 
     // Hack until we support union types.
     // https://github.com/accordproject/concerto/issues/292
-    if (definition.anyOf){
+    const alternative = definition.anyOf || definition.oneOf;
+    if (alternative){
+        const keyword = definition.anyOf ? 'anyOf' : 'oneOf';
         console.warn(
-            `Keyword 'anyOf' in definition '${name}' is not fully supported. Defaulting to first alternative.`
+            `Keyword '${keyword}' in definition '${name}' is not fully supported. Defaulting to first alternative.`
         );
 
         // Just choose the first item
-        return inferType(definition.anyOf[0], context);
+        return inferType(alternative[0], context);
     }
 
     throw new Error(`Unsupported definition: ${JSON.stringify(definition)}`);
@@ -253,9 +262,13 @@ function inferDeclaration(definition, context) {
     } else if (definition.type) {
         if (definition.type === 'object') {
             inferConcept(definition, context);
+        } else if (definition.type === 'array') {
+            console.warn(
+                `Type keyword 'array' in definition '${name}' is not supported. It has been ignored.`
+            );
         } else {
             throw new Error(
-                `Type keyword '${definition.type}' in definition '${name}' not supported.`
+                `Type keyword '${definition.type}' in definition '${name}' is not supported.`
             );
         }
     } else {
@@ -265,7 +278,7 @@ function inferDeclaration(definition, context) {
             !key.startsWith('x-') // Ignore custom extensions
         );
         console.warn(
-            `Keyword(s) '${badKeys.join('\', \'')}' in definition '${name}' is not supported.`
+            `Keyword(s) '${badKeys.join('\', \'')}' in definition '${name}' are not supported.`
         );
     }
 }
@@ -304,18 +317,32 @@ function inferModelFile(defaultNamespace, defaultType, schema) {
     const context = {
         parents: new TypedStack(),
         writer: new Writer(),
+        dictionary: new Set(),
     };
 
     context.writer.writeLine(0, `namespace ${namespace}`);
     context.writer.writeLine(0, '');
 
-    // Add imports
-    // TODO we need some heuristic or metadata to identify Concerto dependencies rather than making assumptions
-    context.writer.writeLine(0, 'import org.accordproject.time.* from https://models.accordproject.org/time@0.2.0.cto');
-    context.writer.writeLine(0, '');
-
     // Create definitions
     const defs = schema.definitions || schema.$defs || schema?.components?.schemas ||[];
+
+    // Build a dictionary
+    context.dictionary.add(defaultType);
+    if (schema.$id) {
+        context.dictionary.add(normalizeType(parseIdUri(schema.$id).type));
+    }
+    Object.keys(defs).forEach((key) => {
+        context.parents.push(key);
+        const definition = defs[key];
+        const typeName = inferTypeName(definition, context, true);
+        if (context.dictionary.has(typeName)){
+            throw new Error(`Duplicate definition found for type '${typeName}'.`);
+        }
+        context.dictionary.add(typeName);
+        context.parents.pop();
+    });
+
+    // Visit each declaration
     Object.keys(defs).forEach((key) => {
         context.parents.push(key);
         const definition = defs[key];
diff --git a/packages/concerto-tools/test/codegen/fromJsonSchema/cto/data/full.cto b/packages/concerto-tools/test/codegen/fromJsonSchema/cto/data/full.cto
index de831413bd..3915974ffe 100644
--- a/packages/concerto-tools/test/codegen/fromJsonSchema/cto/data/full.cto
+++ b/packages/concerto-tools/test/codegen/fromJsonSchema/cto/data/full.cto
@@ -1,7 +1,5 @@
 namespace org.acme
 
-import org.accordproject.time.* from https://models.accordproject.org/time@0.2.0.cto
-
 concept Children {
    o String name
    o Integer age
@@ -16,6 +14,8 @@ concept Children {
    o String[] emptyArray
    o Pet[] favoritePets
    o Stuff[] stuff
+   o String json optional
+   o Double alternation optional
 }
 
 enum Color {
diff --git a/packages/concerto-tools/test/codegen/fromJsonSchema/cto/data/schema.json b/packages/concerto-tools/test/codegen/fromJsonSchema/cto/data/schema.json
index ac616390b2..96bde41110 100644
--- a/packages/concerto-tools/test/codegen/fromJsonSchema/cto/data/schema.json
+++ b/packages/concerto-tools/test/codegen/fromJsonSchema/cto/data/schema.json
@@ -142,6 +142,16 @@
                         },
                         "required": ["$class", "sku", "price", "product"]
                     }
+                },
+                "json": {
+                    "type": "object"
+                },
+                "alternation": {
+                    "oneOf": [
+                        { "type": "number" },
+                        { "type": "string" }
+                    ]
+
                 }
             },
             "required": [
diff --git a/packages/concerto-tools/test/codegen/fromJsonSchema/cto/inferModel.js b/packages/concerto-tools/test/codegen/fromJsonSchema/cto/inferModel.js
index a02bdcee1b..ca8b00a2e8 100644
--- a/packages/concerto-tools/test/codegen/fromJsonSchema/cto/inferModel.js
+++ b/packages/concerto-tools/test/codegen/fromJsonSchema/cto/inferModel.js
@@ -63,8 +63,6 @@ describe('inferModel', function () {
         });
         cto.should.equal(`namespace org.acme
 
-import org.accordproject.time.* from https://models.accordproject.org/time@0.2.0.cto
-
 enum Root {
    o one
    o two
@@ -86,13 +84,11 @@ enum Root {
                 }
             }
         });
-        // TODO This is not a valid CTO model, because we don't generate definitions for inline sub-schemas.
+        // TODO Generate definitions for inline sub-schemas.
         cto.should.equal(`namespace org.acme
 
-import org.accordproject.time.* from https://models.accordproject.org/time@0.2.0.cto
-
 concept Root {
-   o Xs[] xs optional
+   o String[] xs optional
 }
 
 `);
@@ -112,8 +108,6 @@ concept Root {
         );
         cto.should.equal(`namespace org.acme
 
-import org.accordproject.time.* from https://models.accordproject.org/time@0.2.0.cto
-
 concept Root {
    o String name optional
    o Root[] children optional
@@ -127,8 +121,6 @@ concept Root {
         const cto = inferModel('org.acme', 'Root', schema);
         cto.should.equal(`namespace com.example
 
-import org.accordproject.time.* from https://models.accordproject.org/time@0.2.0.cto
-
 concept Veggie {
    o String veggieName
    o Boolean veggieLike
@@ -147,8 +139,6 @@ concept Arrays {
         const cto = inferModel('org.acme', 'Root', schema);
         cto.should.equal(`namespace com.example
 
-import org.accordproject.time.* from https://models.accordproject.org/time@0.2.0.cto
-
 concept Geographical_location {
    o String name default="home" regex=/[\\w\\s]+/ optional
    o Double latitude
@@ -190,23 +180,28 @@ concept Geographical_location {
         }).should.throw('\'additionalProperties\' are not supported in Concerto');
     });
 
-    it('should not generate when unsupported formats are used', async () => {
-        (function () {
-            inferModel('org.acme', 'Root', {
-                $schema: 'http://json-schema.org/draft-07/schema#',
-                definitions: {
-                    Foo: {
-                        type: 'object',
-                        properties: {
-                            email: {
-                                type: 'string',
-                                format: 'email'
-                            }
+    it('should quietly accept unsupported formats', async () => {
+        const cto = inferModel('org.acme', 'Root', {
+            $schema: 'http://json-schema.org/draft-07/schema#',
+            definitions: {
+                Foo: {
+                    type: 'object',
+                    properties: {
+                        email: {
+                            type: 'string',
+                            format: 'email'
                         }
                     }
                 }
-            });
-        }).should.throw('Format \'email\' in \'email\' is not supported');
+            }
+        });
+        cto.should.equal(`namespace org.acme
+
+concept Foo {
+   o String email optional
+}
+
+`);
     });
 
     it('should not generate when unsupported type keywords are used', async () => {
@@ -219,7 +214,7 @@ concept Geographical_location {
                     }
                 }
             });
-        }).should.throw('Type keyword \'null\' in definition \'Foo\' not supported.');
+        }).should.throw('Type keyword \'null\' in definition \'Foo\' is not supported.');
     });
 
     it('should not generate when unsupported type keywords are used in an object', async () => {
@@ -240,11 +235,36 @@ concept Geographical_location {
         }).should.throw('Type keyword \'null\' in \'email\' is not supported');
     });
 
-    it('should not fail for unsupported keywords', async () => {
-        inferModel('org.acme', 'Root', {
+    it('should not generate when duplicate definitions are found', async () => {
+        (function () {
+            inferModel('org.acme', 'Foo', {
+                $schema: 'http://json-schema.org/draft-07/schema#',
+                definitions: {
+                    'Foo': {
+                        'type': 'object',
+                    },
+                }
+            });
+        }).should.throw('Duplicate definition found for type \'Foo\'');
+    });
+
+    it('should quietly accept array definitions', async () => {
+        const cto = inferModel('org.acme', 'Root', {
+            type: 'array'
+        });
+        cto.should.equal(`namespace org.acme
+
+`);
+    });
+
+    it('should quietly accept unsupported definitions', async () => {
+        const cto = inferModel('org.acme', 'Root', {
             'allOf': [
                 { 'type': 'string' }
             ]
         });
+        cto.should.equal(`namespace org.acme
+
+`);
     });
 });