diff --git a/lib/context.js b/lib/context.js
index 1a0161b5..5f0de789 100644
--- a/lib/context.js
+++ b/lib/context.js
@@ -1041,19 +1041,102 @@ function _expandIri(activeCtx, value, relativeTo, localCtx, defined, options) {
     }
   }
 
-  // prepend vocab
-  if(relativeTo.vocab && '@vocab' in activeCtx) {
-    return activeCtx['@vocab'] + value;
+  // A flag that captures whether the iri being expanded is
+  // the value for an @type
+  let typeExpansion = false;
+
+  if(options !== undefined && options.typeExpansion !== undefined) {
+    typeExpansion = options.typeExpansion;
   }
 
-  // prepend base
-  if(relativeTo.base && '@base' in activeCtx) {
-    if(activeCtx['@base']) {
-      // The null case preserves value as potentially relative
-      return prependBase(prependBase(options.base, activeCtx['@base']), value);
+  if(relativeTo.vocab && '@vocab' in activeCtx) {
+    // prepend vocab
+    const prependedResult = activeCtx['@vocab'] + value;
+    let expansionMapResult = undefined;
+    if(options && options.expansionMap) {
+      // if we are about to expand the value by prepending
+      // @vocab then call the expansion map to inform
+      // interested callers that this is occurring
+
+      // TODO: use `await` to support async
+      expansionMapResult = options.expansionMap({
+        prependedIri: {
+          type: '@vocab',
+          vocab: activeCtx['@vocab'],
+          value,
+          result: prependedResult,
+          typeExpansion,
+        },
+        activeCtx,
+        options
+      });
+
+    }
+    if(expansionMapResult !== undefined) {
+      value = expansionMapResult;
+    } else {
+      // the null case preserves value as potentially relative
+      value = prependedResult;
     }
   } else if(relativeTo.base) {
-    return prependBase(options.base, value);
+    // prepend base
+    let prependedResult;
+    let expansionMapResult;
+    let base;
+    if('@base' in activeCtx) {
+      if(activeCtx['@base']) {
+        base = prependBase(options.base, activeCtx['@base']);
+        prependedResult = prependBase(base, value);
+      } else {
+        base = activeCtx['@base'];
+        prependedResult = value;
+      }
+    } else {
+      base = options.base;
+      prependedResult = prependBase(options.base, value);
+    }
+    if(options && options.expansionMap) {
+      // if we are about to expand the value by pre-pending
+      // @base then call the expansion map to inform
+      // interested callers that this is occurring
+
+      // TODO: use `await` to support async
+      expansionMapResult = options.expansionMap({
+        prependedIri: {
+          type: '@base',
+          base,
+          value,
+          result: prependedResult,
+          typeExpansion,
+        },
+        activeCtx,
+        options
+      });
+    }
+    if(expansionMapResult !== undefined) {
+      value = expansionMapResult;
+    } else {
+      // the null case preserves value as potentially relative
+      value = prependedResult;
+    }
+  }
+
+  if(!_isAbsoluteIri(value) && options && options.expansionMap) {
+    // if the result of the expansion is not an absolute iri then
+    // call the expansion map to inform interested callers that
+    // the resulting value is a relative iri, which can result in
+    // it being dropped when converting to other RDF representations
+
+    // TODO: use `await` to support async
+    const expandedResult = options.expansionMap({
+      relativeIri: value,
+      activeCtx,
+      typeExpansion,
+      options
+    });
+    if(expandedResult !== undefined) {
+      value = expandedResult;
+    }
   }
 
   return value;
diff --git a/lib/expand.js b/lib/expand.js
index 44c5102f..737def7b 100644
--- a/lib/expand.js
+++ b/lib/expand.js
@@ -75,6 +75,10 @@ api.expand = async ({
   typeScopedContext = null,
   expansionMap = () => undefined
 }) => {
+
+  // add expansion map to the processing options
+  options = {...options, expansionMap};
+
   // nothing to expand
   if(element === null || element === undefined) {
     return null;
@@ -420,11 +424,14 @@ async function _expandObject({
   const nests = [];
   let unexpandedValue;
 
+  // add expansion map to the processing options
+  options = {...options, expansionMap};
+
   // Figure out if this is the type for a JSON literal
   const isJsonType = element[typeKey] &&
     _expandIri(activeCtx,
       (_isArray(element[typeKey]) ? element[typeKey][0] : element[typeKey]),
-      {vocab: true}, options) === '@json';
+      {vocab: true}, {...options, typeExpansion: true}) === '@json';
 
   for(const key of keys) {
     let value = element[key];
@@ -520,7 +527,8 @@ async function _expandObject({
         value = Object.fromEntries(Object.entries(value).map(([k, v]) => [
           _expandIri(typeScopedContext, k, {vocab: true}),
           _asArray(v).map(vv =>
-            _expandIri(typeScopedContext, vv, {base: true, vocab: true})
+            _expandIri(typeScopedContext, vv, {base: true, vocab: true},
+              {...options, typeExpansion: true})
           )
         ]));
       }
@@ -530,7 +538,8 @@ async function _expandObject({
         _asArray(value).map(v =>
           _isString(v) ?
             _expandIri(typeScopedContext, v,
-              {base: true, vocab: true}, options) : v),
+              {base: true, vocab: true},
+              {...options, typeExpansion: true}) : v),
         {propertyIsArray: options.isFrame});
       continue;
     }
@@ -930,7 +939,8 @@ function _expandValue({activeCtx, activeProperty, value, options}) {
   if(expandedProperty === '@id') {
     return _expandIri(activeCtx, value, {base: true}, options);
   } else if(expandedProperty === '@type') {
-    return _expandIri(activeCtx, value, {vocab: true, base: true}, options);
+    return _expandIri(activeCtx, value, {vocab: true, base: true},
+      {...options, typeExpansion: true});
   }
 
   // get type definition from context
diff --git a/lib/util.js b/lib/util.js
index 77da8f61..1458005a 100644
--- a/lib/util.js
+++ b/lib/util.js
@@ -130,7 +130,7 @@ api.parseLinkHeader = header => {
     while((match = REGEX_LINK_HEADER_PARAMS.exec(params))) {
       result[match[1]] = (match[2] === undefined) ? match[3] : match[2];
     }
-    const rel = result['rel'] || '';
+    const rel = result.rel || '';
     if(Array.isArray(rval[rel])) {
       rval[rel].push(result);
     } else if(rval.hasOwnProperty(rel)) {
diff --git a/tests/misc.js b/tests/misc.js
index 1c3758e0..d9dae4fc 100644
--- a/tests/misc.js
+++ b/tests/misc.js
@@ -478,3 +478,531 @@ describe('literal JSON', () => {
     });
   });
 });
+
+describe('expansionMap', () => {
+  describe('unmappedProperty', () => {
+    it('should be called on unmapped term', async () => {
+      const docWithUnMappedTerm = {
+        '@context': {
+          'definedTerm': 'https://example.com#definedTerm'
+        },
+        definedTerm: "is defined",
+        testUndefined: "is undefined"
+      };
+
+      let expansionMapCalled = false;
+      const expansionMap = info => {
+        if(info.unmappedProperty === 'testUndefined') {
+          expansionMapCalled = true;
+        }
+      };
+
+      await jsonld.expand(docWithUnMappedTerm, {expansionMap});
+
+      assert.equal(expansionMapCalled, true);
+    });
+
+    it('should be called on nested unmapped term', async () => {
+      const docWithUnMappedTerm = {
+        '@context': {
+          'definedTerm': 'https://example.com#definedTerm'
+        },
+        definedTerm: {
+          testUndefined: "is undefined"
+        }
+      };
+
+      let expansionMapCalled = false;
+      const expansionMap = info => {
+        if(info.unmappedProperty === 'testUndefined') {
+          expansionMapCalled = true;
+        }
+      };
+
+      await jsonld.expand(docWithUnMappedTerm, {expansionMap});
+
+      assert.equal(expansionMapCalled, true);
+    });
+  });
+
+  describe('relativeIri', () => {
+    it('should be called on relative iri for id term', async () => {
+      const docWithRelativeIriId = {
+        '@context': {
+          'definedTerm': 'https://example.com#definedTerm'
+        },
+        '@id': "relativeiri",
+        definedTerm: "is defined"
+      };
+
+      let expansionMapCalled = false;
+      const expansionMap = info => {
+        if(info.relativeIri === 'relativeiri') {
+          expansionMapCalled = true;
+        }
+      };
+
+      await jsonld.expand(docWithRelativeIriId, {expansionMap});
+
+      assert.equal(expansionMapCalled, true);
+    });
+
+    it('should be called on relative iri for id term (nested)', async () => {
+      const docWithRelativeIriId = {
+        '@context': {
+          'definedTerm': 'https://example.com#definedTerm'
+        },
+        '@id': "urn:absoluteIri",
+        definedTerm: {
+          '@id': "relativeiri"
+        }
+      };
+
+      let expansionMapCalled = false;
+      const expansionMap = info => {
+        if(info.relativeIri === 'relativeiri') {
+          expansionMapCalled = true;
+        }
+      };
+
+      await jsonld.expand(docWithRelativeIriId, {expansionMap});
+
+      assert.equal(expansionMapCalled, true);
+    });
+
+    it('should be called on relative iri for aliased id term', async () => {
+      const docWithRelativeIriId = {
+        '@context': {
+          'id': '@id',
+          'definedTerm': 'https://example.com#definedTerm'
+        },
+        'id': "relativeiri",
+        definedTerm: "is defined"
+      };
+
+      let expansionMapCalled = false;
+      const expansionMap = info => {
+        if(info.relativeIri === 'relativeiri') {
+          expansionMapCalled = true;
+        }
+      };
+
+      await jsonld.expand(docWithRelativeIriId, {expansionMap});
+
+      assert.equal(expansionMapCalled, true);
+    });
+
+    it('should be called on relative iri for type term', async () => {
+      const docWithRelativeIriId = {
+        '@context': {
+          'definedTerm': 'https://example.com#definedTerm'
+        },
+        'id': "urn:absoluteiri",
+        '@type': "relativeiri",
+        definedTerm: "is defined"
+      };
+
+      let expansionMapCalled = false;
+      const expansionMap = info => {
+        if(info.relativeIri === 'relativeiri') {
+          expansionMapCalled = true;
+        }
+      };
+
+      await jsonld.expand(docWithRelativeIriId, {expansionMap});
+
+      assert.equal(expansionMapCalled, true);
+    });
+
+    it('should be called on relative iri for type\
+     term in scoped context', async () => {
+      const docWithRelativeIriId = {
+        '@context': {
+          'definedType': {
+            '@id': 'https://example.com#definedType',
+            '@context': {
+              'definedTerm': 'https://example.com#definedTerm'
+
+            }
+          }
+        },
+        'id': "urn:absoluteiri",
+        '@type': "definedType",
+        definedTerm: {
+          '@type': 'relativeiri'
+        }
+      };
+
+      let expansionMapCalled = false;
+      const expansionMap = info => {
+        if(info.relativeIri === 'relativeiri') {
+          expansionMapCalled = true;
+        }
+      };
+
+      await jsonld.expand(docWithRelativeIriId, {expansionMap});
+
+      assert.equal(expansionMapCalled, true);
+    });
+
+    it('should be called on relative iri for \
+    type term with multiple relative iri types', async () => {
+      const docWithRelativeIriId = {
+        '@context': {
+          'definedTerm': 'https://example.com#definedTerm'
+        },
+        'id': "urn:absoluteiri",
+        '@type': ["relativeiri", "anotherRelativeiri" ],
+        definedTerm: "is defined"
+      };
+
+      let expansionMapCalledTimes = 0;
+      const expansionMap = info => {
+        if(info.relativeIri === 'relativeiri' ||
+           info.relativeIri === 'anotherRelativeiri') {
+          expansionMapCalledTimes++;
+        }
+      };
+
+      await jsonld.expand(docWithRelativeIriId, {expansionMap});
+
+      assert.equal(expansionMapCalledTimes, 3);
+    });
+
+    it('should be called on relative iri for \
+    type term with multiple relative iri types in scoped context', async () => {
+      const docWithRelativeIriId = {
+        '@context': {
+          'definedType': {
+            '@id': 'https://example.com#definedType',
+            '@context': {
+              'definedTerm': 'https://example.com#definedTerm'
+
+            }
+          }
+        },
+        'id': "urn:absoluteiri",
+        '@type': "definedType",
+        definedTerm: {
+          '@type': ["relativeiri", "anotherRelativeiri" ]
+        }
+      };
+
+      let expansionMapCalledTimes = 0;
+      const expansionMap = info => {
+        if(info.relativeIri === 'relativeiri' ||
+           info.relativeIri === 'anotherRelativeiri') {
+          expansionMapCalledTimes++;
+        }
+      };
+
+      await jsonld.expand(docWithRelativeIriId, {expansionMap});
+
+      assert.equal(expansionMapCalledTimes, 3);
+    });
+
+    it('should be called on relative iri for \
+    type term with multiple types', async () => {
+      const docWithRelativeIriId = {
+        '@context': {
+          'definedTerm': 'https://example.com#definedTerm'
+        },
+        'id': "urn:absoluteiri",
+        '@type': ["relativeiri", "definedTerm" ],
+        definedTerm: "is defined"
+      };
+
+      let expansionMapCalled = false;
+      const expansionMap = info => {
+        if(info.relativeIri === 'relativeiri') {
+          expansionMapCalled = true;
+        }
+      };
+
+      await jsonld.expand(docWithRelativeIriId, {expansionMap});
+
+      assert.equal(expansionMapCalled, true);
+    });
+
+    it('should be called on relative iri for aliased type term', async () => {
+      const docWithRelativeIriId = {
+        '@context': {
+          'type': "@type",
+          'definedTerm': 'https://example.com#definedTerm'
+        },
+        'id': "urn:absoluteiri",
+        'type': "relativeiri",
+        definedTerm: "is defined"
+      };
+
+      let expansionMapCalled = false;
+      const expansionMap = info => {
+        if(info.relativeIri === 'relativeiri') {
+          expansionMapCalled = true;
+        }
+      };
+
+      await jsonld.expand(docWithRelativeIriId, {expansionMap});
+
+      assert.equal(expansionMapCalled, true);
+    });
+
+    it("should be called on relative iri when \
+    @base value is './'", async () => {
+      const docWithRelativeIriId = {
+        '@context': {
+          "@base": "./",
+        },
+        '@id': "relativeiri",
+      };
+
+      let expansionMapCalled = false;
+      const expansionMap = info => {
+        if(info.relativeIri === '/relativeiri') {
+          expansionMapCalled = true;
+        }
+      };
+
+      await jsonld.expand(docWithRelativeIriId, {expansionMap});
+
+      assert.equal(expansionMapCalled, true);
+    });
+
+    it("should be called on relative iri when \
+    @base value is './'", async () => {
+      const docWithRelativeIriId = {
+        '@context': {
+          "@base": "./",
+        },
+        '@id': "relativeiri",
+      };
+
+      let expansionMapCalled = false;
+      const expansionMap = info => {
+        if(info.relativeIri === '/relativeiri') {
+          expansionMapCalled = true;
+        }
+      };
+
+      await jsonld.expand(docWithRelativeIriId, {expansionMap});
+
+      assert.equal(expansionMapCalled, true);
+    });
+
+    it("should be called on relative iri when \
+    @vocab value is './'", async () => {
+      const docWithRelativeIriId = {
+        '@context': {
+          "@vocab": "./",
+        },
+        '@type': "relativeiri",
+      };
+
+      let expansionMapCalled = false;
+      const expansionMap = info => {
+        if(info.relativeIri === '/relativeiri') {
+          expansionMapCalled = true;
+        }
+      };
+
+      await jsonld.expand(docWithRelativeIriId, {expansionMap});
+
+      assert.equal(expansionMapCalled, true);
+    });
+  });
+
+  describe('prependedIri', () => {
+    it("should be called when property is \
+    being expanded with `@vocab`", async () => {
+      const doc = {
+        '@context': {
+          "@vocab": "http://example.com/",
+        },
+        'term': "termValue",
+      };
+
+      let expansionMapCalled = false;
+      const expansionMap = info => {
+        assert.deepStrictEqual(info.prependedIri, {
+          type: '@vocab',
+          vocab: 'http://example.com/',
+          value: 'term',
+          typeExpansion: false,
+          result: 'http://example.com/term'
+        });
+        expansionMapCalled = true;
+      };
+
+      await jsonld.expand(doc, {expansionMap});
+
+      assert.equal(expansionMapCalled, true);
+    });
+
+    it("should be called when '@type' is \
+    being expanded with `@vocab`", async () => {
+      const doc = {
+        '@context': {
+          "@vocab": "http://example.com/",
+        },
+        '@type': "relativeIri",
+      };
+
+      let expansionMapCalled = false;
+      const expansionMap = info => {
+        assert.deepStrictEqual(info.prependedIri, {
+          type: '@vocab',
+          vocab: 'http://example.com/',
+          value: 'relativeIri',
+          typeExpansion: true,
+          result: 'http://example.com/relativeIri'
+        });
+        expansionMapCalled = true;
+      };
+
+      await jsonld.expand(doc, {expansionMap});
+
+      assert.equal(expansionMapCalled, true);
+    });
+
+    it("should be called when aliased '@type' is \
+    being expanded with `@vocab`", async () => {
+      const doc = {
+        '@context': {
+          "@vocab": "http://example.com/",
+          "type": "@type"
+        },
+        'type': "relativeIri",
+      };
+
+      let expansionMapCalled = false;
+      const expansionMap = info => {
+        assert.deepStrictEqual(info.prependedIri, {
+          type: '@vocab',
+          vocab: 'http://example.com/',
+          value: 'relativeIri',
+          typeExpansion: true,
+          result: 'http://example.com/relativeIri'
+        });
+        expansionMapCalled = true;
+      };
+
+      await jsonld.expand(doc, {expansionMap});
+
+      assert.equal(expansionMapCalled, true);
+    });
+
+    it("should be called when '@id' is being \
+    expanded with `@base`", async () => {
+      const doc = {
+        '@context': {
+          "@base": "http://example.com/",
+        },
+        '@id': "relativeIri",
+      };
+
+      let expansionMapCalled = false;
+      const expansionMap = info => {
+        if(info.prependedIri) {
+          assert.deepStrictEqual(info.prependedIri, {
+            type: '@base',
+            base: 'http://example.com/',
+            value: 'relativeIri',
+            typeExpansion: false,
+            result: 'http://example.com/relativeIri'
+          });
+          expansionMapCalled = true;
+        }
+      };
+
+      await jsonld.expand(doc, {expansionMap});
+
+      assert.equal(expansionMapCalled, true);
+    });
+
+    it("should be called when aliased '@id' \
+    is being expanded with `@base`", async () => {
+      const doc = {
+        '@context': {
+          "@base": "http://example.com/",
+          "id": "@id"
+        },
+        'id': "relativeIri",
+      };
+
+      let expansionMapCalled = false;
+      const expansionMap = info => {
+        if(info.prependedIri) {
+          assert.deepStrictEqual(info.prependedIri, {
+            type: '@base',
+            base: 'http://example.com/',
+            value: 'relativeIri',
+            typeExpansion: false,
+            result: 'http://example.com/relativeIri'
+          });
+          expansionMapCalled = true;
+        }
+      };
+
+      await jsonld.expand(doc, {expansionMap});
+
+      assert.equal(expansionMapCalled, true);
+    });
+
+    it("should be called when '@type' is \
+    being expanded with `@base`", async () => {
+      const doc = {
+        '@context': {
+          "@base": "http://example.com/",
+        },
+        '@type': "relativeIri",
+      };
+
+      let expansionMapCalled = false;
+      const expansionMap = info => {
+        if(info.prependedIri) {
+          assert.deepStrictEqual(info.prependedIri, {
+            type: '@base',
+            base: 'http://example.com/',
+            value: 'relativeIri',
+            typeExpansion: true,
+            result: 'http://example.com/relativeIri'
+          });
+          expansionMapCalled = true;
+        }
+      };
+
+      await jsonld.expand(doc, {expansionMap});
+
+      assert.equal(expansionMapCalled, true);
+    });
+
+    it("should be called when aliased '@type' is \
+    being expanded with `@base`", async () => {
+      const doc = {
+        '@context': {
+          "@base": "http://example.com/",
+          "type": "@type"
+        },
+        'type': "relativeIri",
+      };
+
+      let expansionMapCalled = false;
+      const expansionMap = info => {
+        if(info.prependedIri) {
+          assert.deepStrictEqual(info.prependedIri, {
+            type: '@base',
+            base: 'http://example.com/',
+            value: 'relativeIri',
+            typeExpansion: true,
+            result: 'http://example.com/relativeIri'
+          });
+          expansionMapCalled = true;
+        }
+      };
+
+      await jsonld.expand(doc, {expansionMap});
+
+      assert.equal(expansionMapCalled, true);
+    });
+  });
+});
diff --git a/tests/test-common.js b/tests/test-common.js
index b9982182..9cc520c7 100644
--- a/tests/test-common.js
+++ b/tests/test-common.js
@@ -398,7 +398,7 @@ function addManifest(manifest, parent) {
  */
 function addTest(manifest, test, tests) {
   // expand @id and input base
-  const test_id = test['@id'] || test['id'];
+  const test_id = test['@id'] || test.id;
   //var number = test_id.substr(2);
   test['@id'] =
     manifest.baseIri +
@@ -958,10 +958,10 @@ function createDocumentLoader(test) {
         }
 
         // If not JSON-LD, alternate may point there
-        if(linkHeaders['alternate'] &&
-          linkHeaders['alternate'].type == 'application/ld+json' &&
+        if(linkHeaders.alternate &&
+          linkHeaders.alternate.type == 'application/ld+json' &&
           !(contentType || '').match(/^application\/(\w*\+)?json$/)) {
-          doc.documentUrl = prependBase(url, linkHeaders['alternate'].target);
+          doc.documentUrl = prependBase(url, linkHeaders.alternate.target);
         }
       }
     }