Refactoring:

o Renaming part.id to part.uri. Changing to URIs and use that as an
  identifier if the part is known. Schematic part does not have an URI.
o Merging <schema-reference> and <part-numbers> into <references>
o Creating <part-uri> as a possible <reference>. Used by order to point
  to other parts.

11 files changed, 510 insertions, 188 deletions

diff --git a/src/ee/digikey/normalize_facts.py b/src/ee/digikey/normalize_facts.py
index 91ad4db..d7546c3 100644
--- a/src/ee/digikey/normalize_facts.py
+++ b/src/ee/digikey/normalize_facts.py
@@ -153,4 +153,4 @@ def normalize_facts(in_path: Path, out_path: Path):
         out_parts.add_entry(part, True)
 
     print("Saving {} work parts".format(out_parts.size()))
-    save_db(out_path, out_parts)
+    save_db(out_path, out_parts, sort=True)
diff --git a/src/ee/digikey/search_parts.py b/src/ee/digikey/search_parts.py
index 4f637c7..3d271d5 100644
--- a/src/ee/digikey/search_parts.py
+++ b/src/ee/digikey/search_parts.py
@@ -10,15 +10,17 @@ __all__ = ["search_parts"]
 
 
 def resolved(p: DigikeyProduct) -> types.Part:
-    part = types.Part(id=p.part_number,
-                        distributor_info=types.DistributorInfo(),
-                        facts=types.FactList(),
-                        part_numbers=types.PartNumberList())
+    # TODO: fix uri
+    part = types.Part(uri="https://digikey.com/pn#{}".format(p.part_number),
+                      distributor_info=types.DistributorInfo(),
+                      facts=types.FactList(),
+                      references=types.ReferencesList())
     part.distributor_infoProp.stateProp = "resolved"
 
-    part_numbers = part.part_numbersProp.part_numberProp
+    supplier_part_numbers = part.referencesProp.supplier_part_numberProp
+    supplier_part_numbers.append(types.SupplierPartNumber(value=p.part_number, supplier=DIGIKEY_URI))
 
-    part_numbers.append(types.PartNumber(value=p.part_number, distributor=DIGIKEY_URI))
+    part_numbers = part.referencesProp.part_numberProp
     if p.mpn:
         part_numbers.append(types.PartNumber(value=p.mpn))
     facts: List[types.Fact] = part.factsProp.factProp
@@ -46,8 +48,8 @@ def search_parts(in_path: Path, out_path: Path, cache_dir: Path):
     client = DigikeyClient(cache_dir)
 
     for part in in_db.iterparts():
-        dpn = bom_file_utils.find_dpn(part, DIGIKEY_URI)
-        mpn = bom_file_utils.find_pn(part)
+        dpn = next((p.valueProp for p in bom_file_utils.supplier_part_numbers(part) if p.supplierProp == DIGIKEY_URI), None)
+        mpn = next((p.valueProp for p in bom_file_utils.part_numbers(part)), None)
 
         is_mpn = query = None
 
@@ -59,13 +61,14 @@ def search_parts(in_path: Path, out_path: Path, cache_dir: Path):
             is_mpn = True
 
         if query is None:
-            print("could not find pn or dpn: part.id={}".format(part.idProp))
+            # TODO: use schematic reference
+            print("could not find pn or dpn: part.uri={}".format(part.uriProp))
             continue
 
         out_id = query
-        out_part = types.Part(id=out_id,
-                                distributor_info=types.DistributorInfo(),
-                                part_numbers=part.part_numbersProp)
+        out_part = types.Part(uri=out_id,
+                              distributor_info=types.DistributorInfo(),
+                              references=part.referencesProp)
         di = out_part.distributor_infoProp
 
         text = client.search(query)
@@ -101,4 +104,4 @@ def search_parts(in_path: Path, out_path: Path, cache_dir: Path):
         out_parts.add_entry(out_part, True)
 
     print("Saving {} work parts".format(out_parts.size()))
-    save_db(out_path, out_parts)
+    save_db(out_path, out_parts, sort=True)
diff --git a/src/ee/element14/search_parts.py b/src/ee/element14/search_parts.py
index 55e8130..cfa1d34 100644
--- a/src/ee/element14/search_parts.py
+++ b/src/ee/element14/search_parts.py
@@ -14,9 +14,9 @@ def search_parts(in_path: Path, out_path: Path, cache_dir: Path, config: Element
     client = Element14Client(config, cache_dir)
 
     for part in in_db.iterparts():
-        mpn = bom_file_utils.find_pn(part)
+        mpn = bom_file_utils.first_pn(part)
 
-        query = mpn  # TODO: suppor dpn
+        query = mpn  # TODO: support dpn
 
         out_id = query
 
@@ -24,8 +24,8 @@ def search_parts(in_path: Path, out_path: Path, cache_dir: Path, config: Element
 
         out_part = types.Part(id=out_id,
                               distributor_info=types.DistributorInfo(),
-                              part_numbers=part.part_numbersProp)
+                              references=part.referencesProp)
         di = out_part.distributor_infoProp
 
     print("Saving {} work parts".format(out_parts.size()))
-    save_db(out_path, out_parts)
+    save_db(out_path, out_parts, sort=True)
diff --git a/src/ee/kicad/make_bom.py b/src/ee/kicad/make_bom.py
index 7dd5532..0a8f4bb 100644
--- a/src/ee/kicad/make_bom.py
+++ b/src/ee/kicad/make_bom.py
@@ -62,7 +62,7 @@ def mpn_strategy(component: Component, part: types.Part) -> types.Part:
     mpn = component.get_field("mpn")
     if mpn is not None:
         pn = types.PartNumber(value=mpn.value)
-        part.part_numbersProp.add_part_number(pn)
+        part.referencesProp.add_part_number(pn)
 
     return part
 
@@ -74,8 +74,8 @@ def dpn_strategy_factory(dpn_mappings: Mapping[str, str]) -> StrategyCallable:
             if s is None:
                 continue
 
-            pn = types.PartNumber(value=s.value, distributor=distributor)
-            part.part_numbersProp.add_part_number(pn)
+            pn = types.SupplierPartNumber(value=s.value, supplier=distributor)
+            part.referencesProp.add_part_number(pn)
 
         return part
 
@@ -111,17 +111,22 @@ def work(sch, out: Path, strategy: MakeBomStrategy, new_mode, pretty):
         parts = PartDb()
         components = to_bom(sch)
         for c in components:
-            part = types.Part(id=c.ref)
-            part.schema_reference = c.ref
-            part.part_numbersProp = types.PartNumberList()
+            part = types.Part()
+            part.referencesProp = types.ReferencesList()
+            part.referencesProp.schematic_reference.append(types.SchematicReference(reference=c.ref))
 
             part = strategy.process_part(c, part)
 
-            if len(part.part_numbersProp.get_part_number()) == 0:
-                part.part_numbersProp = None
+            if part is None:
+                continue
+
+            if len(part.referencesProp.schematic_reference) == 0 and \
+                    len(part.referencesProp.part_number) == 0 and \
+                    len(part.referencesProp.supplier_part_number) == 0:
+                # No need to dirty the xml with empty lists
+                part.referencesProp = None
 
-            if part is not None:
-                parts.add_entry(part, True)
+            parts.add_entry(part, True)
 
         save_db(out, parts)
 
diff --git a/src/ee/order/__init__.py b/src/ee/order/__init__.py
index 5350667..56d233f 100644
--- a/src/ee/order/__init__.py
+++ b/src/ee/order/__init__.py
@@ -2,6 +2,7 @@ from functools import total_ordering
 from pathlib import Path
 from typing import List, Tuple
 
+from ee import EeException
 from ee.part import PartDb, load_db, save_db
 from ee.xml import types, bom_file_utils
 
@@ -12,12 +13,17 @@ __all__ = ["create_order"]
 class PartInfo(object):
     def __init__(self, part: types.Part):
         self.part = part
-        self.id = part.id
-        self.pn = bom_file_utils.find_pn(part)
+        self.ref = next((ref.referenceProp for ref in bom_file_utils.schematic_references(part)), None)
+        self.pn = next((p.valueProp for p in bom_file_utils.part_numbers(part)), None)
         self.available_from: List[Tuple[str, types.Part]] = []
 
+        rl = part.referencesProp = part.referencesProp or types.ReferencesList()  # type: types.ReferencesList
+        rl.schematic_referenceProp = rl.schematic_referenceProp or []
+        rl.part_numberProp = rl.part_numberProp or []
+        rl.supplier_part_numberProp = rl.supplier_part_numberProp or []
+
     def __lt__(self, other: "PartInfo"):
-        return self.part.idProp == other.part.idProp
+        return self.ref == other.ref
 
 
 def create_order(schematic_path: Path, out_path: Path, part_db_dirs: List[Path], fail_on_missing_parts: bool):
@@ -30,28 +36,41 @@ def create_order(schematic_path: Path, out_path: Path, part_db_dirs: List[Path],
     infos = [PartInfo(sch) for sch in sch_db.iterparts()]
 
     for info in infos:
-        print("Resolving {}".format(info.id))
-
-        for distributor, db in dbs:
-            for p in db.iterparts(sort=True):
-                if info.pn:
-                    p_pn: str = bom_file_utils.find_pn(p)
-
-                    if info.pn == p_pn:
-                        info.available_from.append((distributor, p))
-
-                for sch_pn_ in bom_file_utils.part_numbers(info.part):
-                    sch_pn: types.PartNumber = sch_pn_
-
-                    for p_pn_ in bom_file_utils.part_numbers(p):
-                        p_pn: types.PartNumber = p_pn_
-
-                        if sch_pn.distributorProp == p_pn.distributorProp and sch_pn.value == p_pn.value:
-                            if p.idProp not in info.available_from:
-                                info.available_from.append((distributor, p))
+        print("Resolving {}".format(info.ref))
+
+        sch_part_numbers = info.part.referencesProp.part_number
+        sch_supplier_part_numbers: List[types.SupplierPartNumber] = info.part.referencesProp.supplier_part_number
+
+        for supplier, db in dbs:
+            for supplier_part in db.iterparts(sort=True):
+                found = None
+                for sch_pn in sch_part_numbers:
+                    for pn in bom_file_utils.part_numbers(supplier_part):
+                        if sch_pn.valueProp == pn.valueProp:
+                            found = supplier_part
+                            break
+                    if found:
+                        break
+
+                if found:
+                    info.available_from.append((supplier, found))
+                    break
+
+                found = None
+                for sch_spn in sch_supplier_part_numbers:
+                    for spn in bom_file_utils.supplier_part_numbers(supplier_part):
+                        if sch_spn.valueProp == spn.valueProp and sch_spn.supplierProp == spn.supplierProp:
+                            found = supplier_part
+                            break
+                    if found:
+                        break
+
+                if found:
+                    info.available_from.append((supplier, found))
+                    break
 
     for info in infos:
-        print("Resolved {} to {}".format(info.id, info.available_from))
+        print("Resolved {} to {}".format(info.ref, info.available_from))
 
     warnings = []
     has_missing_parts = False
@@ -59,28 +78,22 @@ def create_order(schematic_path: Path, out_path: Path, part_db_dirs: List[Path],
         if len(info.available_from) == 0:
             has_missing_parts = True
             warnings.append("Could not find {} in any database, part numbers: {}".
-                            format(info.id, ", ".join([p.value for p in bom_file_utils.part_numbers(info.part)])))
+                            format(info.ref, ", ".join([p.value for p in bom_file_utils.part_numbers(info.part)])))
 
     for w in sorted(warnings):
         print(w)
 
     if has_missing_parts and fail_on_missing_parts:
-        print("has missing parts")
-        return False
+        raise EeException("The order has parts that can't be found from any supplier")
 
     for info in infos:
-        part = types.Part(id=info.part.id,
-                            schema_reference=info.part.schema_reference,
-                            part_numbers=types.PartNumberList())
-
-        part_numbers = part.part_numbersProp.part_number
-
         if len(info.available_from) == 0:
             continue
 
-        distributor, distributor_part = info.available_from[0]
+        supplier, supplier_part = info.available_from[0]
 
-        part_numbers.append(types.PartNumber(value=distributor_part.id, distributor=distributor))
+        references = types.ReferencesList(schematic_reference=info.part.referencesProp.schematic_reference)
+        part = types.Part(uri=supplier_part.uri, references=references)
 
         out_parts.add_entry(part, True)
 
diff --git a/src/ee/part/__init__.py b/src/ee/part/__init__.py
index 45561ec..36a3d3c 100644
--- a/src/ee/part/__init__.py
+++ b/src/ee/part/__init__.py
@@ -1,9 +1,7 @@
 from pathlib import Path
 from typing import List, MutableMapping, Optional, Iterator
 
-from ee import EeException
 from ee.xml import types, bom_file_utils
-from ee.xml.bom_file_utils import find_pn, find_dpn, find_root_tag
 
 __all__ = [
     "PartDb",
@@ -17,10 +15,10 @@ class Entry(object):
         self.new = new
         self.part = part
 
-        self.pn = find_pn(part)
+        self.pn = next((p.valueProp for p in bom_file_utils.part_numbers(part)), None)
 
     def dpn(self, uri: str):
-        return find_dpn(self.part, uri)
+        return [spn for spn in bom_file_utils.supplier_part_numbers(self.part) if spn.supplierProp == uri]
 
 
 class PartDb(object):
@@ -42,7 +40,7 @@ class PartDb(object):
 
     def iterparts(self, sort=False) -> Iterator[types.Part]:
         it = (e.part for e in self.parts)
-        return sorted(it, key=lambda p: p.idProp) if sort else it
+        return sorted(it, key=lambda p: p.uriProp) if sort else it
 
     def size(self) -> int:
         return len(self.parts)
@@ -51,16 +49,6 @@ class PartDb(object):
         entry = self.pn_index.get(pn, None)
         return entry.part if entry else None
 
-    def find_by_dpn(self, distributor: str, pn: str) -> types.Part:
-        idx = self.dpn_indexes.get(distributor)
-
-        if idx is None:
-            tmp = [(find_dpn(entry.part, distributor), entry) for entry in self.parts]
-            idx = {dpn: entry for dpn, entry in tmp if dpn is not None}
-            self.dpn_indexes[distributor] = idx
-
-        return idx[pn].part
-
 
 def load_db(path: Path) -> PartDb:
     db = PartDb()
@@ -76,10 +64,10 @@ def load_db(path: Path) -> PartDb:
     return db
 
 
-def save_db(path: Path, db: PartDb):
+def save_db(path: Path, db: PartDb, sort=False):
     part_db = types.PartDb()
     parts = part_db.parts = types.PartList()
-    parts.partProp.extend(db.iterparts(sort=True))
+    parts.partProp.extend(db.iterparts(sort=sort))
 
     with path.open("w") as f:
-        part_db.export(outfile=f, level=0, name_=find_root_tag(part_db))
+        part_db.export(outfile=f, level=0, name_=bom_file_utils.find_root_tag(part_db))
diff --git a/src/ee/part/create_distributor_search_list.py b/src/ee/part/create_distributor_search_list.py
index 88e5a10..10160d4 100644
--- a/src/ee/part/create_distributor_search_list.py
+++ b/src/ee/part/create_distributor_search_list.py
@@ -1,8 +1,7 @@
 from pathlib import Path
 
 from ee.part import PartDb, load_db, save_db
-from ee.xml import types
-from ee.xml.bom_file_utils import *
+from ee.xml import types, bom_file_utils
 
 __all__ = ["create_distributor_search_list"]
 
@@ -14,10 +13,11 @@ def create_distributor_search_list(in_path: Path, out_path: Path):
     print("loaded {} existing parts".format(in_parts.size()))
 
     for part in in_parts.iterparts():
-        pn_value = find_pn(part)
+        pn_value = next((p.valueProp for p in bom_file_utils.part_numbers(part)), None)
 
         if pn_value is None:
-            print("Skipping part with no part number: id={}".format(part.idProp))
+            # TODO: use schematic reference if found
+            print("Skipping part with no part number: uri={}".format(part.uriProp))
             continue
 
         entry = out_parts.find_by_pn(pn_value)
@@ -26,7 +26,7 @@ def create_distributor_search_list(in_path: Path, out_path: Path):
             continue
 
         new_part = types.Part(id=pn_value)
-        new_part.part_numbersProp = part.part_numbersProp
+        new_part.referencesProp = part.referencesProp
 
         out_parts.add_entry(new_part, True)
 
diff --git a/src/ee/tools/create_order.py b/src/ee/tools/create_order.py
index 8ca7e05..8941fcd 100644
--- a/src/ee/tools/create_order.py
+++ b/src/ee/tools/create_order.py
@@ -1,5 +1,4 @@
 import argparse
-import sys
 from pathlib import Path
 
 from ee.order import create_order
@@ -24,6 +23,4 @@ args = parser.parse_args()
 part_db_dirs = [Path(part_db) for part_db in args.part_db]
 fail_on_missing_parts = False
 
-ret = create_order(Path(args.schematic), Path(args.out), part_db_dirs, fail_on_missing_parts)
-
-sys.exit(1 if ret is False else 0)
+create_order(Path(args.schematic), Path(args.out), part_db_dirs, fail_on_missing_parts)
diff --git a/src/ee/xml/bom_file_utils.py b/src/ee/xml/bom_file_utils.py
index 59a9b0e..207ac5a 100644
--- a/src/ee/xml/bom_file_utils.py
+++ b/src/ee/xml/bom_file_utils.py
@@ -5,8 +5,9 @@ from ee.xml import types
 __all__ = [
     "facts",
     "find_root_tag",
-    "find_pn",
-    "find_dpn",
+    "schematic_references",
+    "part_numbers",
+    "supplier_part_numbers",
 ]
 
 
@@ -14,25 +15,19 @@ def find_root_tag(root):
     return next((tag for tag, klass in types.GDSClassesMapping.items() if klass == type(root)), None)
 
 
-def part_numbers(part: types.Part) -> List[types.PartNumber]:
-    pns = part.part_numbersProp  # type: types.PartNumberList
-
-    if pns is None:
-        return []
+def schematic_references(part: types.Part) -> List[types.SchematicReference]:
+    return [] if part.referencesProp is None or part.referencesProp.schematic_reference is None else \
+        part.referencesProp.schematic_reference
 
-    return pns.part_numberProp
 
-
-def find_pn(part: types.Part) -> Optional[str]:
-    for pn in part_numbers(part):
-        if pn.distributor is None:
-            return pn.value
+def part_numbers(part: types.Part) -> List[types.PartNumber]:
+    return [] if part.referencesProp is None or part.referencesProp.part_number is None else \
+        part.referencesProp.part_number
 
 
-def find_dpn(part: types.Part, distributor: str) -> Optional[str]:
-    for pn in part_numbers(part):
-        if pn.distributor == distributor:
-            return pn.value
+def supplier_part_numbers(part: types.Part) -> List[types.SupplierPartNumber]:
+    return [] if part.referencesProp is None or part.referencesProp.supplier_part_number is None else \
+        part.referencesProp.supplier_part_number
 
 
 def facts(part: types.Part, create=False) -> Optional[types.FactList]:
diff --git a/src/ee/xml/types.py b/src/ee/xml/types.py
index fec6884..35cd664 100644
--- a/src/ee/xml/types.py
+++ b/src/ee/xml/types.py
@@ -807,13 +807,12 @@ class PartDb(GeneratedsSuper):
 class Part(GeneratedsSuper):
     subclass = None
     superclass = None
-    def __init__(self, id=None, schema_reference=None, part_type=None, part_numbers=None, distributor_info=None, facts=None, price_breaks=None, **kwargs_):
+    def __init__(self, uri=None, part_type=None, references=None, distributor_info=None, facts=None, price_breaks=None, **kwargs_):
         self.original_tagname_ = None
         self.parent_object_ = kwargs_.get('parent_object_')
-        self.id = _cast(None, id)
-        self.schema_reference = schema_reference
+        self.uri = _cast(None, uri)
         self.part_type = part_type
-        self.part_numbers = part_numbers
+        self.references = references
         self.distributor_info = distributor_info
         self.facts = facts
         self.price_breaks = price_breaks
@@ -828,21 +827,16 @@ class Part(GeneratedsSuper):
         else:
             return Part(*args_, **kwargs_)
     factory = staticmethod(factory)
-    def get_schema_reference(self):
-        return self.schema_reference
-    def set_schema_reference(self, schema_reference):
-        self.schema_reference = schema_reference
-    schema_referenceProp = property(get_schema_reference, set_schema_reference)
     def get_part_type(self):
         return self.part_type
     def set_part_type(self, part_type):
         self.part_type = part_type
     part_typeProp = property(get_part_type, set_part_type)
-    def get_part_numbers(self):
-        return self.part_numbers
-    def set_part_numbers(self, part_numbers):
-        self.part_numbers = part_numbers
-    part_numbersProp = property(get_part_numbers, set_part_numbers)
+    def get_references(self):
+        return self.references
+    def set_references(self, references):
+        self.references = references
+    referencesProp = property(get_references, set_references)
     def get_distributor_info(self):
         return self.distributor_info
     def set_distributor_info(self, distributor_info):
@@ -858,16 +852,15 @@ class Part(GeneratedsSuper):
     def set_price_breaks(self, price_breaks):
         self.price_breaks = price_breaks
     price_breaksProp = property(get_price_breaks, set_price_breaks)
-    def get_id(self):
-        return self.id
-    def set_id(self, id):
-        self.id = id
-    idProp = property(get_id, set_id)
+    def get_uri(self):
+        return self.uri
+    def set_uri(self, uri):
+        self.uri = uri
+    uriProp = property(get_uri, set_uri)
     def hasContent_(self):
         if (
-            self.schema_reference is not None or
             self.part_type is not None or
-            self.part_numbers is not None or
+            self.references is not None or
             self.distributor_info is not None or
             self.facts is not None or
             self.price_breaks is not None
@@ -897,22 +890,19 @@ class Part(GeneratedsSuper):
         else:
             outfile.write('/>%s' % (eol_, ))
     def exportAttributes(self, outfile, level, already_processed, namespaceprefix_='', name_='Part'):
-        if self.id is not None and 'id' not in already_processed:
-            already_processed.add('id')
-            outfile.write(' id=%s' % (self.gds_encode(self.gds_format_string(quote_attrib(self.id), input_name='id')), ))
+        if self.uri is not None and 'uri' not in already_processed:
+            already_processed.add('uri')
+            outfile.write(' uri=%s' % (self.gds_encode(self.gds_format_string(quote_attrib(self.uri), input_name='uri')), ))
     def exportChildren(self, outfile, level, namespaceprefix_='', namespacedef_='', name_='Part', fromsubclass_=False, pretty_print=True):
         if pretty_print:
             eol_ = '\n'
         else:
             eol_ = ''
-        if self.schema_reference is not None:
-            showIndent(outfile, level, pretty_print)
-            outfile.write('<%sschema-reference>%s</%sschema-reference>%s' % (namespaceprefix_ , self.gds_encode(self.gds_format_string(quote_xml(self.schema_reference), input_name='schema-reference')), namespaceprefix_ , eol_))
         if self.part_type is not None:
             showIndent(outfile, level, pretty_print)
             outfile.write('<%spart-type>%s</%spart-type>%s' % (namespaceprefix_ , self.gds_encode(self.gds_format_string(quote_xml(self.part_type), input_name='part-type')), namespaceprefix_ , eol_))
-        if self.part_numbers is not None:
-            self.part_numbers.export(outfile, level, namespaceprefix_, namespacedef_='', name_='part-numbers', pretty_print=pretty_print)
+        if self.references is not None:
+            self.references.export(outfile, level, namespaceprefix_, namespacedef_='', name_='references', pretty_print=pretty_print)
         if self.distributor_info is not None:
             self.distributor_info.export(outfile, level, namespaceprefix_, namespacedef_='', name_='distributor-info', pretty_print=pretty_print)
         if self.facts is not None:
@@ -927,24 +917,20 @@ class Part(GeneratedsSuper):
             self.buildChildren(child, node, nodeName_)
         return self
     def buildAttributes(self, node, attrs, already_processed):
-        value = find_attr_value_('id', node)
-        if value is not None and 'id' not in already_processed:
-            already_processed.add('id')
-            self.id = value
+        value = find_attr_value_('uri', node)
+        if value is not None and 'uri' not in already_processed:
+            already_processed.add('uri')
+            self.uri = value
     def buildChildren(self, child_, node, nodeName_, fromsubclass_=False):
-        if nodeName_ == 'schema-reference':
-            schema_reference_ = child_.text
-            schema_reference_ = self.gds_validate_string(schema_reference_, node, 'schema_reference')
-            self.schema_reference = schema_reference_
-        elif nodeName_ == 'part-type':
+        if nodeName_ == 'part-type':
             part_type_ = child_.text
             part_type_ = self.gds_validate_string(part_type_, node, 'part_type')
             self.part_type = part_type_
-        elif nodeName_ == 'part-numbers':
-            obj_ = PartNumberList.factory(parent_object_=self)
+        elif nodeName_ == 'references':
+            obj_ = ReferencesList.factory(parent_object_=self)
             obj_.build(child_)
-            self.part_numbers = obj_
-            obj_.original_tagname_ = 'part-numbers'
+            self.references = obj_
+            obj_.original_tagname_ = 'references'
         elif nodeName_ == 'distributor-info':
             obj_ = DistributorInfo.factory(parent_object_=self)
             obj_.build(child_)
@@ -1052,14 +1038,91 @@ class PartList(GeneratedsSuper):
 # end class PartList
 
 
+class PartUri(GeneratedsSuper):
+    subclass = None
+    superclass = None
+    def __init__(self, value=None, **kwargs_):
+        self.original_tagname_ = None
+        self.parent_object_ = kwargs_.get('parent_object_')
+        self.value = value
+    def factory(*args_, **kwargs_):
+        if CurrentSubclassModule_ is not None:
+            subclass = getSubclassFromModule_(
+                CurrentSubclassModule_, PartUri)
+            if subclass is not None:
+                return subclass(*args_, **kwargs_)
+        if PartUri.subclass:
+            return PartUri.subclass(*args_, **kwargs_)
+        else:
+            return PartUri(*args_, **kwargs_)
+    factory = staticmethod(factory)
+    def get_value(self):
+        return self.value
+    def set_value(self, value):
+        self.value = value
+    valueProp = property(get_value, set_value)
+    def hasContent_(self):
+        if (
+            self.value is not None
+        ):
+            return True
+        else:
+            return False
+    def export(self, outfile, level, namespaceprefix_='', namespacedef_='', name_='PartUri', pretty_print=True):
+        imported_ns_def_ = GenerateDSNamespaceDefs_.get('PartUri')
+        if imported_ns_def_ is not None:
+            namespacedef_ = imported_ns_def_
+        if pretty_print:
+            eol_ = '\n'
+        else:
+            eol_ = ''
+        if self.original_tagname_ is not None:
+            name_ = self.original_tagname_
+        showIndent(outfile, level, pretty_print)
+        outfile.write('<%s%s%s' % (namespaceprefix_, name_, namespacedef_ and ' ' + namespacedef_ or '', ))
+        already_processed = set()
+        self.exportAttributes(outfile, level, already_processed, namespaceprefix_, name_='PartUri')
+        if self.hasContent_():
+            outfile.write('>%s' % (eol_, ))
+            self.exportChildren(outfile, level + 1, namespaceprefix_, namespacedef_, name_='PartUri', pretty_print=pretty_print)
+            showIndent(outfile, level, pretty_print)
+            outfile.write('</%s%s>%s' % (namespaceprefix_, name_, eol_))
+        else:
+            outfile.write('/>%s' % (eol_, ))
+    def exportAttributes(self, outfile, level, already_processed, namespaceprefix_='', name_='PartUri'):
+        pass
+    def exportChildren(self, outfile, level, namespaceprefix_='', namespacedef_='', name_='PartUri', fromsubclass_=False, pretty_print=True):
+        if pretty_print:
+            eol_ = '\n'
+        else:
+            eol_ = ''
+        if self.value is not None:
+            showIndent(outfile, level, pretty_print)
+            outfile.write('<%svalue>%s</%svalue>%s' % (namespaceprefix_ , self.gds_encode(self.gds_format_string(quote_xml(self.value), input_name='value')), namespaceprefix_ , eol_))
+    def build(self, node):
+        already_processed = set()
+        self.buildAttributes(node, node.attrib, already_processed)
+        for child in node:
+            nodeName_ = Tag_pattern_.match(child.tag).groups()[-1]
+            self.buildChildren(child, node, nodeName_)
+        return self
+    def buildAttributes(self, node, attrs, already_processed):
+        pass
+    def buildChildren(self, child_, node, nodeName_, fromsubclass_=False):
+        if nodeName_ == 'value':
+            value_ = child_.text
+            value_ = self.gds_validate_string(value_, node, 'value')
+            self.value = value_
+# end class PartUri
+
+
 class PartNumber(GeneratedsSuper):
     subclass = None
     superclass = None
-    def __init__(self, value=None, distributor=None, **kwargs_):
+    def __init__(self, value=None, **kwargs_):
         self.original_tagname_ = None
         self.parent_object_ = kwargs_.get('parent_object_')
         self.value = value
-        self.distributor = distributor
     def factory(*args_, **kwargs_):
         if CurrentSubclassModule_ is not None:
             subclass = getSubclassFromModule_(
@@ -1076,15 +1139,9 @@ class PartNumber(GeneratedsSuper):
     def set_value(self, value):
         self.value = value
     valueProp = property(get_value, set_value)
-    def get_distributor(self):
-        return self.distributor
-    def set_distributor(self, distributor):
-        self.distributor = distributor
-    distributorProp = property(get_distributor, set_distributor)
     def hasContent_(self):
         if (
-            self.value is not None or
-            self.distributor is not None
+            self.value is not None
         ):
             return True
         else:
@@ -1120,9 +1177,6 @@ class PartNumber(GeneratedsSuper):
         if self.value is not None:
             showIndent(outfile, level, pretty_print)
             outfile.write('<%svalue>%s</%svalue>%s' % (namespaceprefix_ , self.gds_encode(self.gds_format_string(quote_xml(self.value), input_name='value')), namespaceprefix_ , eol_))
-        if self.distributor is not None:
-            showIndent(outfile, level, pretty_print)
-            outfile.write('<%sdistributor>%s</%sdistributor>%s' % (namespaceprefix_ , self.gds_encode(self.gds_format_string(quote_xml(self.distributor), input_name='distributor')), namespaceprefix_ , eol_))
     def build(self, node):
         already_processed = set()
         self.buildAttributes(node, node.attrib, already_processed)
@@ -1137,34 +1191,238 @@ class PartNumber(GeneratedsSuper):
             value_ = child_.text
             value_ = self.gds_validate_string(value_, node, 'value')
             self.value = value_
-        elif nodeName_ == 'distributor':
-            distributor_ = child_.text
-            distributor_ = self.gds_validate_string(distributor_, node, 'distributor')
-            self.distributor = distributor_
 # end class PartNumber
 
 
-class PartNumberList(GeneratedsSuper):
+class SupplierPartNumber(GeneratedsSuper):
     subclass = None
     superclass = None
-    def __init__(self, part_number=None, **kwargs_):
+    def __init__(self, value=None, supplier=None, **kwargs_):
         self.original_tagname_ = None
         self.parent_object_ = kwargs_.get('parent_object_')
+        self.value = value
+        self.supplier = supplier
+    def factory(*args_, **kwargs_):
+        if CurrentSubclassModule_ is not None:
+            subclass = getSubclassFromModule_(
+                CurrentSubclassModule_, SupplierPartNumber)
+            if subclass is not None:
+                return subclass(*args_, **kwargs_)
+        if SupplierPartNumber.subclass:
+            return SupplierPartNumber.subclass(*args_, **kwargs_)
+        else:
+            return SupplierPartNumber(*args_, **kwargs_)
+    factory = staticmethod(factory)
+    def get_value(self):
+        return self.value
+    def set_value(self, value):
+        self.value = value
+    valueProp = property(get_value, set_value)
+    def get_supplier(self):
+        return self.supplier
+    def set_supplier(self, supplier):
+        self.supplier = supplier
+    supplierProp = property(get_supplier, set_supplier)
+    def hasContent_(self):
+        if (
+            self.value is not None or
+            self.supplier is not None
+        ):
+            return True
+        else:
+            return False
+    def export(self, outfile, level, namespaceprefix_='', namespacedef_='', name_='SupplierPartNumber', pretty_print=True):
+        imported_ns_def_ = GenerateDSNamespaceDefs_.get('SupplierPartNumber')
+        if imported_ns_def_ is not None:
+            namespacedef_ = imported_ns_def_
+        if pretty_print:
+            eol_ = '\n'
+        else:
+            eol_ = ''
+        if self.original_tagname_ is not None:
+            name_ = self.original_tagname_
+        showIndent(outfile, level, pretty_print)
+        outfile.write('<%s%s%s' % (namespaceprefix_, name_, namespacedef_ and ' ' + namespacedef_ or '', ))
+        already_processed = set()
+        self.exportAttributes(outfile, level, already_processed, namespaceprefix_, name_='SupplierPartNumber')
+        if self.hasContent_():
+            outfile.write('>%s' % (eol_, ))
+            self.exportChildren(outfile, level + 1, namespaceprefix_, namespacedef_, name_='SupplierPartNumber', pretty_print=pretty_print)
+            showIndent(outfile, level, pretty_print)
+            outfile.write('</%s%s>%s' % (namespaceprefix_, name_, eol_))
+        else:
+            outfile.write('/>%s' % (eol_, ))
+    def exportAttributes(self, outfile, level, already_processed, namespaceprefix_='', name_='SupplierPartNumber'):
+        pass
+    def exportChildren(self, outfile, level, namespaceprefix_='', namespacedef_='', name_='SupplierPartNumber', fromsubclass_=False, pretty_print=True):
+        if pretty_print:
+            eol_ = '\n'
+        else:
+            eol_ = ''
+        if self.value is not None:
+            showIndent(outfile, level, pretty_print)
+            outfile.write('<%svalue>%s</%svalue>%s' % (namespaceprefix_ , self.gds_encode(self.gds_format_string(quote_xml(self.value), input_name='value')), namespaceprefix_ , eol_))
+        if self.supplier is not None:
+            showIndent(outfile, level, pretty_print)
+            outfile.write('<%ssupplier>%s</%ssupplier>%s' % (namespaceprefix_ , self.gds_encode(self.gds_format_string(quote_xml(self.supplier), input_name='supplier')), namespaceprefix_ , eol_))
+    def build(self, node):
+        already_processed = set()
+        self.buildAttributes(node, node.attrib, already_processed)
+        for child in node:
+            nodeName_ = Tag_pattern_.match(child.tag).groups()[-1]
+            self.buildChildren(child, node, nodeName_)
+        return self
+    def buildAttributes(self, node, attrs, already_processed):
+        pass
+    def buildChildren(self, child_, node, nodeName_, fromsubclass_=False):
+        if nodeName_ == 'value':
+            value_ = child_.text
+            value_ = self.gds_validate_string(value_, node, 'value')
+            self.value = value_
+        elif nodeName_ == 'supplier':
+            supplier_ = child_.text
+            supplier_ = self.gds_validate_string(supplier_, node, 'supplier')
+            self.supplier = supplier_
+# end class SupplierPartNumber
+
+
+class SchematicReference(GeneratedsSuper):
+    subclass = None
+    superclass = None
+    def __init__(self, reference=None, **kwargs_):
+        self.original_tagname_ = None
+        self.parent_object_ = kwargs_.get('parent_object_')
+        self.reference = reference
+    def factory(*args_, **kwargs_):
+        if CurrentSubclassModule_ is not None:
+            subclass = getSubclassFromModule_(
+                CurrentSubclassModule_, SchematicReference)
+            if subclass is not None:
+                return subclass(*args_, **kwargs_)
+        if SchematicReference.subclass:
+            return SchematicReference.subclass(*args_, **kwargs_)
+        else:
+            return SchematicReference(*args_, **kwargs_)
+    factory = staticmethod(factory)
+    def get_reference(self):
+        return self.reference
+    def set_reference(self, reference):
+        self.reference = reference
+    referenceProp = property(get_reference, set_reference)
+    def hasContent_(self):
+        if (
+            self.reference is not None
+        ):
+            return True
+        else:
+            return False
+    def export(self, outfile, level, namespaceprefix_='', namespacedef_='', name_='SchematicReference', pretty_print=True):
+        imported_ns_def_ = GenerateDSNamespaceDefs_.get('SchematicReference')
+        if imported_ns_def_ is not None:
+            namespacedef_ = imported_ns_def_
+        if pretty_print:
+            eol_ = '\n'
+        else:
+            eol_ = ''
+        if self.original_tagname_ is not None:
+            name_ = self.original_tagname_
+        showIndent(outfile, level, pretty_print)
+        outfile.write('<%s%s%s' % (namespaceprefix_, name_, namespacedef_ and ' ' + namespacedef_ or '', ))
+        already_processed = set()
+        self.exportAttributes(outfile, level, already_processed, namespaceprefix_, name_='SchematicReference')
+        if self.hasContent_():
+            outfile.write('>%s' % (eol_, ))
+            self.exportChildren(outfile, level + 1, namespaceprefix_, namespacedef_, name_='SchematicReference', pretty_print=pretty_print)
+            showIndent(outfile, level, pretty_print)
+            outfile.write('</%s%s>%s' % (namespaceprefix_, name_, eol_))
+        else:
+            outfile.write('/>%s' % (eol_, ))
+    def exportAttributes(self, outfile, level, already_processed, namespaceprefix_='', name_='SchematicReference'):
+        pass
+    def exportChildren(self, outfile, level, namespaceprefix_='', namespacedef_='', name_='SchematicReference', fromsubclass_=False, pretty_print=True):
+        if pretty_print:
+            eol_ = '\n'
+        else:
+            eol_ = ''
+        if self.reference is not None:
+            showIndent(outfile, level, pretty_print)
+            outfile.write('<%sreference>%s</%sreference>%s' % (namespaceprefix_ , self.gds_encode(self.gds_format_string(quote_xml(self.reference), input_name='reference')), namespaceprefix_ , eol_))
+    def build(self, node):
+        already_processed = set()
+        self.buildAttributes(node, node.attrib, already_processed)
+        for child in node:
+            nodeName_ = Tag_pattern_.match(child.tag).groups()[-1]
+            self.buildChildren(child, node, nodeName_)
+        return self
+    def buildAttributes(self, node, attrs, already_processed):
+        pass
+    def buildChildren(self, child_, node, nodeName_, fromsubclass_=False):
+        if nodeName_ == 'reference':
+            reference_ = child_.text
+            reference_ = self.gds_validate_string(reference_, node, 'reference')
+            self.reference = reference_
+# end class SchematicReference
+
+
+class ReferencesList(GeneratedsSuper):
+    subclass = None
+    superclass = None
+    def __init__(self, schematic_reference=None, part_uri=None, part_number=None, supplier_part_number=None, **kwargs_):
+        self.original_tagname_ = None
+        self.parent_object_ = kwargs_.get('parent_object_')
+        if schematic_reference is None:
+            self.schematic_reference = []
+        else:
+            self.schematic_reference = schematic_reference
+        if part_uri is None:
+            self.part_uri = []
+        else:
+            self.part_uri = part_uri
         if part_number is None:
             self.part_number = []
         else:
             self.part_number = part_number
+        if supplier_part_number is None:
+            self.supplier_part_number = []
+        else:
+            self.supplier_part_number = supplier_part_number
     def factory(*args_, **kwargs_):
         if CurrentSubclassModule_ is not None:
             subclass = getSubclassFromModule_(
-                CurrentSubclassModule_, PartNumberList)
+                CurrentSubclassModule_, ReferencesList)
             if subclass is not None:
                 return subclass(*args_, **kwargs_)
-        if PartNumberList.subclass:
-            return PartNumberList.subclass(*args_, **kwargs_)
+        if ReferencesList.subclass:
+            return ReferencesList.subclass(*args_, **kwargs_)
         else:
-            return PartNumberList(*args_, **kwargs_)
+            return ReferencesList(*args_, **kwargs_)
     factory = staticmethod(factory)
+    def get_schematic_reference(self):
+        return self.schematic_reference
+    def set_schematic_reference(self, schematic_reference):
+        self.schematic_reference = schematic_reference
+    def add_schematic_reference(self, value):
+        self.schematic_reference.append(value)
+    def add_schematic_reference(self, value):
+        self.schematic_reference.append(value)
+    def insert_schematic_reference_at(self, index, value):
+        self.schematic_reference.insert(index, value)
+    def replace_schematic_reference_at(self, index, value):
+        self.schematic_reference[index] = value
+    schematic_referenceProp = property(get_schematic_reference, set_schematic_reference)
+    def get_part_uri(self):
+        return self.part_uri
+    def set_part_uri(self, part_uri):
+        self.part_uri = part_uri
+    def add_part_uri(self, value):
+        self.part_uri.append(value)
+    def add_part_uri(self, value):
+        self.part_uri.append(value)
+    def insert_part_uri_at(self, index, value):
+        self.part_uri.insert(index, value)
+    def replace_part_uri_at(self, index, value):
+        self.part_uri[index] = value
+    part_uriProp = property(get_part_uri, set_part_uri)
     def get_part_number(self):
         return self.part_number
     def set_part_number(self, part_number):
@@ -1178,15 +1436,31 @@ class PartNumberList(GeneratedsSuper):
     def replace_part_number_at(self, index, value):
         self.part_number[index] = value
     part_numberProp = property(get_part_number, set_part_number)
+    def get_supplier_part_number(self):
+        return self.supplier_part_number
+    def set_supplier_part_number(self, supplier_part_number):
+        self.supplier_part_number = supplier_part_number
+    def add_supplier_part_number(self, value):
+        self.supplier_part_number.append(value)
+    def add_supplier_part_number(self, value):
+        self.supplier_part_number.append(value)
+    def insert_supplier_part_number_at(self, index, value):
+        self.supplier_part_number.insert(index, value)
+    def replace_supplier_part_number_at(self, index, value):
+        self.supplier_part_number[index] = value
+    supplier_part_numberProp = property(get_supplier_part_number, set_supplier_part_number)
     def hasContent_(self):
         if (
-            self.part_number
+            self.schematic_reference or
+            self.part_uri or
+            self.part_number or
+            self.supplier_part_number
         ):
             return True
         else:
             return False
-    def export(self, outfile, level, namespaceprefix_='', namespacedef_='', name_='PartNumberList', pretty_print=True):
-        imported_ns_def_ = GenerateDSNamespaceDefs_.get('PartNumberList')
+    def export(self, outfile, level, namespaceprefix_='', namespacedef_='', name_='ReferencesList', pretty_print=True):
+        imported_ns_def_ = GenerateDSNamespaceDefs_.get('ReferencesList')
         if imported_ns_def_ is not None:
             namespacedef_ = imported_ns_def_
         if pretty_print:
@@ -1198,23 +1472,29 @@ class PartNumberList(GeneratedsSuper):
         showIndent(outfile, level, pretty_print)
         outfile.write('<%s%s%s' % (namespaceprefix_, name_, namespacedef_ and ' ' + namespacedef_ or '', ))
         already_processed = set()
-        self.exportAttributes(outfile, level, already_processed, namespaceprefix_, name_='PartNumberList')
+        self.exportAttributes(outfile, level, already_processed, namespaceprefix_, name_='ReferencesList')
         if self.hasContent_():
             outfile.write('>%s' % (eol_, ))
-            self.exportChildren(outfile, level + 1, namespaceprefix_, namespacedef_, name_='PartNumberList', pretty_print=pretty_print)
+            self.exportChildren(outfile, level + 1, namespaceprefix_, namespacedef_, name_='ReferencesList', pretty_print=pretty_print)
             showIndent(outfile, level, pretty_print)
             outfile.write('</%s%s>%s' % (namespaceprefix_, name_, eol_))
         else:
             outfile.write('/>%s' % (eol_, ))
-    def exportAttributes(self, outfile, level, already_processed, namespaceprefix_='', name_='PartNumberList'):
+    def exportAttributes(self, outfile, level, already_processed, namespaceprefix_='', name_='ReferencesList'):
         pass
-    def exportChildren(self, outfile, level, namespaceprefix_='', namespacedef_='', name_='PartNumberList', fromsubclass_=False, pretty_print=True):
+    def exportChildren(self, outfile, level, namespaceprefix_='', namespacedef_='', name_='ReferencesList', fromsubclass_=False, pretty_print=True):
         if pretty_print:
             eol_ = '\n'
         else:
             eol_ = ''
+        for schematic_reference_ in self.schematic_reference:
+            schematic_reference_.export(outfile, level, namespaceprefix_, namespacedef_='', name_='schematic-reference', pretty_print=pretty_print)
+        for part_uri_ in self.part_uri:
+            part_uri_.export(outfile, level, namespaceprefix_, namespacedef_='', name_='part-uri', pretty_print=pretty_print)
         for part_number_ in self.part_number:
             part_number_.export(outfile, level, namespaceprefix_, namespacedef_='', name_='part-number', pretty_print=pretty_print)
+        for supplier_part_number_ in self.supplier_part_number:
+            supplier_part_number_.export(outfile, level, namespaceprefix_, namespacedef_='', name_='supplier-part-number', pretty_print=pretty_print)
     def build(self, node):
         already_processed = set()
         self.buildAttributes(node, node.attrib, already_processed)
@@ -1225,12 +1505,27 @@ class PartNumberList(GeneratedsSuper):
     def buildAttributes(self, node, attrs, already_processed):
         pass
     def buildChildren(self, child_, node, nodeName_, fromsubclass_=False):
-        if nodeName_ == 'part-number':
+        if nodeName_ == 'schematic-reference':
+            obj_ = SchematicReference.factory(parent_object_=self)
+            obj_.build(child_)
+            self.schematic_reference.append(obj_)
+            obj_.original_tagname_ = 'schematic-reference'
+        elif nodeName_ == 'part-uri':
+            obj_ = PartUri.factory(parent_object_=self)
+            obj_.build(child_)
+            self.part_uri.append(obj_)
+            obj_.original_tagname_ = 'part-uri'
+        elif nodeName_ == 'part-number':
             obj_ = PartNumber.factory(parent_object_=self)
             obj_.build(child_)
             self.part_number.append(obj_)
             obj_.original_tagname_ = 'part-number'
-# end class PartNumberList
+        elif nodeName_ == 'supplier-part-number':
+            obj_ = SupplierPartNumber.factory(parent_object_=self)
+            obj_.build(child_)
+            self.supplier_part_number.append(obj_)
+            obj_.original_tagname_ = 'supplier-part-number'
+# end class ReferencesList
 
 
 class Fact(GeneratedsSuper):
@@ -1911,7 +2206,10 @@ __all__ = [
     "PartDb",
     "PartList",
     "PartNumber",
-    "PartNumberList",
+    "PartUri",
     "PriceBreak",
-    "PriceBreakList"
+    "PriceBreakList",
+    "ReferencesList",
+    "SchematicReference",
+    "SupplierPartNumber"
 ]
diff --git a/xsd/ee.xsd b/xsd/ee.xsd
index 3e0d024..64d0f11 100644
--- a/xsd/ee.xsd
+++ b/xsd/ee.xsd
@@ -31,7 +31,7 @@ TODO: rename 'id' to 'url'.
         targetNamespace="http://purl.org/ee/bom-file"
         xmlns="http://purl.org/ee/bom-file">
 
-    <xs:attribute name="id" type="xs:string"/>
+    <xs:attribute name="uri" type="xs:anyURI"/>
 
     <xs:element name="part-db" type="PartDb"/>
     <xs:element name="part" type="Part"/>
@@ -44,14 +44,14 @@ TODO: rename 'id' to 'url'.
 
     <xs:complexType name="Part">
         <xs:sequence>
-            <xs:element name="schema-reference" type="xs:string"/>
+            <!-- TODO: this should be a fact -->
             <xs:element name="part-type" type="xs:anyURI"/>
-            <xs:element name="part-numbers" type="PartNumberList"/>
+            <xs:element name="references" type="ReferencesList"/>
             <xs:element name="distributor-info" type="DistributorInfo"/>
             <xs:element name="facts" type="FactList"/>
             <xs:element name="price-breaks" type="PriceBreakList"/>
         </xs:sequence>
-        <xs:attribute ref="id" use="required"/>
+        <xs:attribute ref="uri"/>
     </xs:complexType>
 
     <xs:complexType name="PartList">
@@ -60,16 +60,39 @@ TODO: rename 'id' to 'url'.
         </xs:sequence>
     </xs:complexType>
 
+    <xs:complexType name="PartUri">
+        <xs:sequence>
+            <xs:element name="value" type="xs:anyURI"/>
+        </xs:sequence>
+    </xs:complexType>
+
     <xs:complexType name="PartNumber">
         <xs:sequence>
             <xs:element name="value" type="xs:string"/>
-            <xs:element name="distributor" type="xs:anyURI"/>
         </xs:sequence>
     </xs:complexType>
 
-    <xs:complexType name="PartNumberList">
+    <xs:complexType name="SupplierPartNumber">
+        <xs:sequence>
+            <xs:element name="value" type="xs:string"/>
+            <xs:element name="supplier" type="xs:anyURI"/>
+        </xs:sequence>
+    </xs:complexType>
+
+    <xs:complexType name="SchematicReference">
+        <xs:sequence>
+            <xs:element name="reference" type="xs:string"/>
+        </xs:sequence>
+    </xs:complexType>
+
+    <xs:complexType name="ReferencesList">
         <xs:sequence>
-            <xs:element name="part-number" type="PartNumber" maxOccurs="unbounded"/>
+            <xs:choice maxOccurs="unbounded">
+                <xs:element name="schematic-reference" type="SchematicReference"/>
+                <xs:element name="part-uri" type="PartUri"/>
+                <xs:element name="part-number" type="PartNumber"/>
+                <xs:element name="supplier-part-number" type="SupplierPartNumber"/>
+            </xs:choice>
         </xs:sequence>
     </xs:complexType>