diff --git a/src/SemanticGraph.js b/src/SemanticGraph.js
index 2ade09b..c0190f0 100644
--- a/src/SemanticGraph.js
+++ b/src/SemanticGraph.js
@@ -3,7 +3,7 @@ const { readFileSync } = require('fs');
 const createRdfParser = require('n3').Parser;
 const {
   rdfIri, rdfsIri, owlIri, rdfsResource,
-  rdfType, rdfsLabel, rdfsComment, rdfsDomain, rdfsRange, rdfsSubClassOf, rdfsSubPropertyOf, owlInverseOf,
+  rdfType, rdfsLabel, rdfsComment, rdfsDomain, rdfsRange, rdfsSubClassOf, rdfsSubPropertyOf, owlInverseOf, owlUnionOf, rdfFirst, rdfRest
 } = require('./constants');
 const invariant = require('./utils/invariant');
 const isIri = require('./utils/isIri');
@@ -34,6 +34,9 @@ const workingPredicates = [
   rdfsSubClassOf,
   rdfsSubPropertyOf,
   owlInverseOf,
+  owlUnionOf,
+  rdfFirst,
+  rdfRest
 ];
 
 parseFileAndIndex(baseGraph, '../ontologies/rdf.ttl');
diff --git a/src/constants.js b/src/constants.js
index 368e402..4d0827a 100644
--- a/src/constants.js
+++ b/src/constants.js
@@ -17,6 +17,10 @@ x.rdfsSubClassOf = `${x.rdfsIri}subClassOf`;
 x.rdfsSubPropertyOf = `${x.rdfsIri}subPropertyOf`;
 x.owlFunctionalProperty = `${x.owlIri}FunctionalProperty`;
 x.owlInverseOf = `${x.owlIri}inverseOf`;
+x.owlUnionOf = `${x.owlIri}unionOf`;
+x.rdfFirst = `${x.rdfIri}first`;
+x.rdfRest = `${x.rdfIri}rest`;
+x.rdfNil = `${x.rdfIri}nil`;
 
 x._rdfType = `_${x.rdfType}`;
 x._rdfsDomain = `_${x.rdfsDomain}`;
diff --git a/src/graph/traversal.js b/src/graph/traversal.js
index cdb66ce..119290d 100644
--- a/src/graph/traversal.js
+++ b/src/graph/traversal.js
@@ -1,4 +1,5 @@
 const warn = require('../utils/warn');
+const { rdfsRange, owlUnionOf, rdfFirst, rdfRest, rdfNil  } = require('../constants');
 
 // Possible bug: stack overflow
 
@@ -36,7 +37,42 @@ function walklook(g, iri, walkIri, lookIri, s = new Set(), ws = new Set()) {
   return s;
 }
 
+// TODO: Possible bug: stack overflow - using recursive function without debounce (_walkLinkedList).
+// Resolves any resources that represent a Union of resources
+// The resource must contain an owl:unionOf predicate to be considered a union resource.
+// Additionally the object of the owl:unionOf must be an rdf linked list, having predicates rdf:first, rdf:rest and rdf:nil
+// Inputs: 
+// g : graph
+// resources : array[iri] 
+// returns: array[iri] after replacing all union iris with the resources in the union.
+function resolveUnionResources (g, resources) {
+  function _walkLinkedList(listNode) {
+    const head = g[listNode][rdfFirst]
+    if (listNode != rdfNil && head && head != rdfNil) {
+      const tail = g[listNode][rdfRest];
+      if (tail && tail != rdfNil) {
+        return [head].concat(_walkLinkedList(tail));
+      }
+      return [head];
+    }        
+    return [];
+  }
+
+  const unionResources = resources
+    .filter((iri) => g[iri][owlUnionOf])
+    // flatMap
+    .reduce((list, iri) => list.concat(g[iri][owlUnionOf]), [])
+    // flatMap
+    .reduce((list, listNode) => list.concat.apply(list,_walkLinkedList(listNode)), []);
+
+  const nonUnionResources = resources
+    .filter((iri) => !g[iri][owlUnionOf]);
+
+  return nonUnionResources.concat(unionResources).sort();
+}
+
 module.exports = {
   walkmap,
   walklook,
+  resolveUnionResources
 };
diff --git a/src/graphql/getGraphqlFieldConfig.js b/src/graphql/getGraphqlFieldConfig.js
index c930615..11e6f9f 100644
--- a/src/graphql/getGraphqlFieldConfig.js
+++ b/src/graphql/getGraphqlFieldConfig.js
@@ -1,7 +1,7 @@
 const { GraphQLList } = require('graphql');
-const { xsdIri, rdfsLiteral, rdfsSubPropertyOf, rdfsRange } = require('../constants');
+const { xsdIri, rdfsLiteral, rdfsSubPropertyOf, rdfsRange, owlUnionOf,rdfFirst,rdfRest,rdfNil } = require('../constants');
 const warn = require('../utils/warn');
-const { walklook } = require('../graph/traversal');
+const { walklook, resolveUnionResources } = require('../graph/traversal');
 const memorize = require('../graph/memorize');
 const requireGraphqlRelay = require('../requireGraphqlRelay');
 const isGraphqlList = require('./isGraphqlList');
@@ -21,7 +21,7 @@ function getGraphqlFieldConfig(g, iri) {
   // Otherwise for each super-property, look for a range,
   // if not found, check their super-properties and so on
   // TODO: check walklook, maybe test it
-  const ranges = [...walklook(g, iri, rdfsSubPropertyOf, rdfsRange)];
+  const ranges = resolveUnionResources(g, [...walklook(g, iri, rdfsSubPropertyOf, rdfsRange)]);
   const nRanges = ranges.length;
 
   if (!nRanges) return;
diff --git a/src/graphql/getGraphqlPolymorphicObjectType.js b/src/graphql/getGraphqlPolymorphicObjectType.js
index a6fab3d..1bfb8fb 100644
--- a/src/graphql/getGraphqlPolymorphicObjectType.js
+++ b/src/graphql/getGraphqlPolymorphicObjectType.js
@@ -1,9 +1,64 @@
 const { rdfsResource } = require('../constants');
 const getGraphqlInterfaceType = require('./getGraphqlInterfaceType');
+const memorize = require('../graph/memorize');
+const { GraphQLUnionType } = require('graphql');
+const getGraphqlName = require('./getGraphqlName');
+const getGraphqlObjectType = require('./getGraphqlObjectType');
 
-function getGraphqlPolymorphicObjectType(g/*, ranges*/) {
-  // TODO
-  return getGraphqlInterfaceType(g, rdfsResource);
+// Generate an IRI that represents the Union of some resources
+function getUnionIri(g, iris) {
+  const gqlNames = iris.map(x => getGraphqlName(g,x)).sort().join(',');
+  return `union:${gqlNames}`;
 }
 
-module.exports = getGraphqlPolymorphicObjectType;
+// This adapter exists to compensate for the caller passing in a array of IRIs, and this breaks memorize.
+// So the idea is we create an IRI that represents the array(ranges) and pass that to memorize.
+// then we will receive that generated IRI in getGraphqlPolymorphicObjectType and have to 
+// reverse the process to get the ranges back from the generated IRI.
+function memorizeRangesAdapter(fn, key) {
+  return (g, ranges) => {
+    const unionUri = getUnionIri(g, ranges);
+    // make sure the IRI for for this range is in the graph
+    g[unionUri] = g[unionUri] || {ranges:ranges};
+    // and pass the IRI through, instead of the ranges
+    return memorize(fn,key)(g,unionUri);
+  }
+}
+
+// Creates a GraphQLUnionType from a collection of iris in ranges.
+// g : graph
+// iri : resource name of the range
+// ranges: array[resource:iri]
+function getGraphQlUnionObjectType(g, iri, ranges) {
+  const types = ranges.map(x => getGraphqlObjectType(g,x)).sort();
+  const typeMap = types.reduce((a,c,i) => {
+    return Object.assign(a, {[c.name]: c});
+  }, {});
+  const gqlNames   = ranges.map(x => getGraphqlName(g,x)).sort();
+  const unionName =  gqlNames.join('_');
+
+  return new GraphQLUnionType({
+    name: `U_${unionName}`,
+    types: types,
+    description: `Union of ${gqlNames.join(' and ')}`,
+    resolveType : (value) => typeMap[value.type]
+  });
+}
+
+// Responsible for determining which type of GraphQlPolymorphicObject is used.
+function getGraphqlPolymorphicObjectType(g, iri) {
+  const ranges = g[iri]["ranges"]; // this assumes memorizeRangesAdapter was used to wrap this call.
+  // Union strategy
+  if (ranges) {
+    return getGraphQlUnionObjectType(g, iri, ranges);
+  }
+  // TODO: other strategies.
+  return null;
+}
+
+module.exports = {
+  getUnionIri,
+  memorizeRangesAdapter,
+  getGraphQlUnionObjectType,
+  getGraphqlPolymorphicObjectType : memorizeRangesAdapter(getGraphqlPolymorphicObjectType, 'graphqlPolymorphicObjectType')
+};
diff --git a/test/index.js b/test/index.js
index aa816c0..7951928 100644
--- a/test/index.js
+++ b/test/index.js
@@ -6,11 +6,11 @@ const commonTurtlePrefixes = require('./utils/commonTurtlePrefixes');
 const castArrayShape = require('../src/utils/castArrayShape');
 const isNil = require('../src/utils/isNil');
 const capitalize = require('../src/utils/capitalize');
-const { walkmap, walklook } = require('../src/graph/traversal');
-const { rdfsClass, rdfType, _rdfsDomain } = require('../src/constants');
+const { walkmap, walklook, resolveUnionResources } = require('../src/graph/traversal');
+const { rdfsClass, rdfType, _rdfsDomain, rdfsRange, owlUnionOf, rdfFirst, rdfRest, rdfNil  } = require('../src/constants');
 const ArrayKeyedMap = require('../src/ArrayKeyedMap');
 const SemanticGraph = require('..');
-
+const { getUnionIri, getGraphqlPolymorphicObjectType} = require('../src/graphql/getGraphqlPolymorphicObjectType');
 // TODO: split this file
 
 // NOTE: getIriLocalName and isIri will be imported from an external lib someday
@@ -40,6 +40,112 @@ describe('Utils', () => {
   });
 });
 
+describe('Graphql polymorphic Object Type', () => {
+
+  const graph = {
+    config: {
+      prefixes: { lllist:"list" }
+    },
+    a: {
+      x: ['b', 'c'],
+      y: ['d', 'e'],
+    },
+    b: {
+      x: ['a', 'c', 'd'],
+      z: ['a', 'f'],
+    },
+    c: {
+      x: ['c'],
+    },
+    d: {
+      y: ['a', 'b'],
+      z: ['c'],
+    },
+    e: {
+      z: ['c', 'd', 'g'],
+    },
+    f: {
+      x: ['g'],
+    },
+    g: {
+      y: ['a', 'f'],
+    },
+    h: {
+      [rdfsRange]: ['union:resource:1']
+    },
+    i: {
+      [rdfsRange]: ['union:resource:2']
+    },
+    'union:resource:empty': {
+      [owlUnionOf]: ['_:list:empty:node:1']
+    },
+    '_:list:empty:node:1': {
+      [rdfFirst]: [rdfNil],
+      [rdfRest]: [rdfNil]
+    },
+    'union:resource:single': {
+      [owlUnionOf]: ['_:list:_:node:1']
+    },
+    '_:list:_:node:1': {
+      [rdfFirst]: ['list:_:item:1'],
+      [rdfRest]: [rdfNil]
+    },
+    'union:resource:double': {
+      [owlUnionOf]: ['_:list:a:node:1']
+    },
+    '_:list:a:node:1': {
+      [rdfFirst]: ['list:a:item:1'],
+      [rdfRest]: ['_:list:a:node:2']
+    },
+    '_:list:a:node:2': {
+      [rdfFirst]: ['list:a:item:2'],
+      [rdfRest]: [rdfNil]
+    },
+    'union:resource:quad': {
+      [owlUnionOf]: ['_:list:b:node:1']
+    },
+    '_:list:b:node:1': {
+      [rdfFirst]: ['list:b:item:1'],
+      [rdfRest]: ['_:list:b:node:2']
+    },
+    '_:list:b:node:2': {
+      [rdfFirst]: ['list:b:item:2'],
+      [rdfRest]: '_:list:b:node:3'
+    },
+    '_:list:b:node:3': {
+      [rdfFirst]: ['list:b:item:3'],
+      [rdfRest]: '_:list:b:node:4'
+    },
+    '_:list:b:node:4': {
+      [rdfFirst]: ['list:b:item:4'],
+      [rdfRest]: [rdfNil]
+    },
+    'list:b;item;1': {
+      a: ['a']
+    },
+    'list:b;item;2': {
+      a: ['a']
+    },
+    'list:b;item;3': {
+      a: ['a']
+    },
+  };
+
+  it('Should Create a Union IRI from a range of resources', () => {
+    const unionIri = getUnionIri(graph, ['list:b;item;1','list:b;item;2','list:b;item;3']);
+    assert.deepEqual(unionIri, 'union:B_item_1,B_item_2,B_item_3');
+  })
+
+  it('Should Create a union type when given a range in IRI position', () => {
+    const unionResources = ['list:b;item;1','list:b;item;2','list:b;item;3'];
+    var createdType;
+    assert.doesNotThrow(() => {
+      createdType = getGraphqlPolymorphicObjectType(graph, unionResources);
+    });
+    assert.deepEqual(createdType._typeConfig.types.length, unionResources.length);
+  });
+})
+
 describe('Graph traversal', () => {
 
   const graph = {
@@ -67,6 +173,56 @@ describe('Graph traversal', () => {
     g: {
       y: ['a', 'f'],
     },
+    h: {
+      [rdfsRange]: ['union:resource:1']
+    },
+    i: {
+      [rdfsRange]: ['union:resource:2']
+    },
+    'union:resource:empty': {
+      [owlUnionOf]: ['_:list:empty:node:1']
+    },
+    '_:list:empty:node:1': {
+      [rdfFirst]: [rdfNil],
+      [rdfRest]: [rdfNil]
+    },
+    'union:resource:single': {
+      [owlUnionOf]: ['_:list:_:node:1']
+    },
+    '_:list:_:node:1': {
+      [rdfFirst]: ['list:_:item:1'],
+      [rdfRest]: [rdfNil]
+    },
+    'union:resource:double': {
+      [owlUnionOf]: ['_:list:a:node:1']
+    },
+    '_:list:a:node:1': {
+      [rdfFirst]: ['list:a:item:1'],
+      [rdfRest]: ['_:list:a:node:2']
+    },
+    '_:list:a:node:2': {
+      [rdfFirst]: ['list:a:item:2'],
+      [rdfRest]: [rdfNil]
+    },
+    'union:resource:quad': {
+      [owlUnionOf]: ['_:list:b:node:1']
+    },
+    '_:list:b:node:1': {
+      [rdfFirst]: ['list:b:item:1'],
+      [rdfRest]: ['_:list:b:node:2']
+    },
+    '_:list:b:node:2': {
+      [rdfFirst]: ['list:b:item:2'],
+      [rdfRest]: '_:list:b:node:3'
+    },
+    '_:list:b:node:3': {
+      [rdfFirst]: ['list:b:item:3'],
+      [rdfRest]: '_:list:b:node:4'
+    },
+    '_:list:b:node:4': {
+      [rdfFirst]: ['list:b:item:4'],
+      [rdfRest]: [rdfNil]
+    }
   };
 
   it('walkmap', () => {
@@ -88,6 +244,41 @@ describe('Graph traversal', () => {
     assert.deepEqual([...walklook(graph, 'g', 'x', 'z')], []);
     assert.deepEqual([...walklook(graph, 'c', 'x', 'z')], []);
   });
+
+  it('resolves UnionResources that are empty unions', () => {
+    // Resolves any resources that represent a Union of resources
+    // The resource must contain an owl:unionOf predicate to be considered a union resource.
+    // Additionally the object of the owl:unionOf must be an rdf linked list, having predicates rdf:first, rdf:rest and rdf:nil
+    assert.deepEqual(resolveUnionResources(graph, ['union:resource:empty']), []);
+  });
+
+  it('resolves UnionResources that contain 1 item', () => {
+    // Resolves any resources that represent a Union of resources
+    // The resource must contain an owl:unionOf predicate to be considered a union resource.
+    // Additionally the object of the owl:unionOf must be an rdf linked list, having predicates rdf:first, rdf:rest and rdf:nil
+    assert.deepEqual(resolveUnionResources(graph, ['union:resource:single']), ['list:_:item:1']);
+  });
+
+  it('resolves UnionResources that contain 2 items', () => {
+    // Resolves any resources that represent a Union of resources
+    // The resource must contain an owl:unionOf predicate to be considered a union resource.
+    // Additionally the object of the owl:unionOf must be an rdf linked list, having predicates rdf:first, rdf:rest and rdf:nil
+    assert.deepEqual(resolveUnionResources(graph, ['union:resource:double']), ['list:a:item:1','list:a:item:2']);
+  });
+
+  it('resolves UnionResources that contain 4 items', () => {
+    // Resolves any resources that represent a Union of resources
+    // The resource must contain an owl:unionOf predicate to be considered a union resource.
+    // Additionally the object of the owl:unionOf must be an rdf linked list, having predicates rdf:first, rdf:rest and rdf:nil
+    assert.deepEqual(resolveUnionResources(graph, ['union:resource:quad']), ['list:b:item:1','list:b:item:2','list:b:item:3','list:b:item:4']);
+  });
+
+  it('resolves UnionResources that contain [0 && 1 && 2 && 4] items', () => {
+    // Resolves any resources that represent a Union of resources
+    // The resource must contain an owl:unionOf predicate to be considered a union resource.
+    // Additionally the object of the owl:unionOf must be an rdf linked list, having predicates rdf:first, rdf:rest and rdf:nil
+    assert.deepEqual(resolveUnionResources(graph, ['union:resource:empty','union:resource:single','union:resource:double','union:resource:quad']), ['list:_:item:1','list:a:item:1','list:a:item:2','list:b:item:1','list:b:item:2','list:b:item:3','list:b:item:4']);
+  });
 });
 
 describe('ArrayKeyedMap', () => {