Model Northwind prices and deliveries with in-domain schema.org terms

Several schema.org properties were carrying values outside their declared
domains. Each is moved to the term the vocabulary actually provides:

- Order lines are now schema:OrderItem *and* schema:Offer. schema:OrderItem
  has no price properties at all, so schema:price/schema:priceCurrency were
  off-domain; typing the line as the offer that was accepted for it makes
  them legal without splitting the line across two nodes.
- schema:Offer's own schema:price is the price of the offer as a whole, so it
  replaces schema:totalPrice (a Reservation/Ticket property) as the line
  total. The historical unit price moves to a schema:UnitPriceSpecification
  with schema:priceType schema:ListPrice.
- schema:discount is dropped. It is an Order-level property in schema.org,
  and the list price, quantity and line total already pin the per-line rate
  exactly - unlike a stored rate, they cannot disagree with each other.
- Product prices move from schema:Product to a schema:Offer reached through
  schema:offers. A product is not an offer, so this one needs its own node.
- Freight moves off schema:ParcelDelivery, which has no price property, onto
  a schema:DeliveryChargeSpecification reached via schema:priceSpecification
  from a shipping schema:Offer.
- The dispatch date moves off schema:availableFrom (a DeliveryEvent property
  borrowed onto a ParcelDelivery, and meaning "available for pickup" rather
  than "dispatched") onto a real schema:DeliveryEvent hanging off
  schema:deliveryStatus. Orders never dispatched get no event at all.
- schema:orderedItem loses its rdfs:domain/rdfs:range. schema.org allows
  Order|OrderItem -> OrderItem|Product|Service, which a single domain/range
  pair cannot express; the narrowed pair entailed every OrderItem is a
  Product.

Also fixes a pre-existing import bug: shipPostalCode sat in the required BGP
but 19 orders have none, so those orders never entered the graph at all.
Making it OPTIONAL restores them, taking the import from 811 to 830 orders
and revenue from 1,215,812 to 1,265,792 - the canonical Northwind figure.

Consuming queries follow the new structure. The six revenue queries drop
their ?quantity * ?price * (1 - ?discount) recomputation for the materialised
line total, which also settles a 0.1 discrepancy between the carrier chart
and the rest. SelectProductsFromSupplier traverses schema:offers/schema:price.

Verified by running all eleven import queries over the real CSVs and all 28
view and chart queries against the resulting graph: 830 orders, 2155 lines,
freight totalling 64,943, and top product/employee/customer/category all
matching canonical Northwind.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01SYifJzEkGsTcJsuB4fGRAc

Author: namedgraph

demo/northwind-traders/admin/model/ns.ttl

@@ -44,6 +44,32 @@ schema:ParcelDelivery a owl:Class ;
     rdfs:label "Delivery" ;
     rdfs:isDefinedBy : .
 
+schema:DeliveryEvent a owl:Class ;
+    rdfs:label "Shipment" ;
+    rdfs:isDefinedBy : .
+
+schema:Offer a owl:Class ;
+    rdfs:label "Offer" ;
+    rdfs:isDefinedBy : .
+
+schema:PriceSpecification a owl:Class ;
+    rdfs:label "Price specification" ;
+    rdfs:isDefinedBy : .
+
+schema:DeliveryChargeSpecification a owl:Class ;
+    rdfs:label "Delivery charge" ;
+    rdfs:subClassOf schema:PriceSpecification ;
+    rdfs:isDefinedBy : .
+
+schema:UnitPriceSpecification a owl:Class ;
+    rdfs:label "Unit price" ;
+    rdfs:subClassOf schema:PriceSpecification ;
+    rdfs:isDefinedBy : .
+
+schema:DeliveryMethod a owl:Class ;
+    rdfs:label "Delivery method" ;
+    rdfs:isDefinedBy : .
+
 schema:OrderItem a owl:Class ;
     rdfs:label "Order item" ;
     rdfs:isDefinedBy : .
@@ -100,6 +126,53 @@ schema:orderDelivery a owl:ObjectProperty ;
     rdfs:range schema:ParcelDelivery ;
     rdfs:isDefinedBy : .
 
+schema:acceptedOffer a owl:ObjectProperty ;
+    rdfs:label "Accepted offer" ;
+    rdfs:domain schema:Order ;
+    rdfs:range schema:Offer ;
+    rdfs:isDefinedBy : .
+
+schema:offers a owl:ObjectProperty ;
+    rdfs:label "Offer" ;
+    rdfs:domain schema:Product ;
+    rdfs:range schema:Offer ;
+    rdfs:isDefinedBy : .
+
+schema:priceType a owl:ObjectProperty ;
+    rdfs:label "Price type" ;
+    rdfs:domain schema:UnitPriceSpecification ;
+    rdfs:isDefinedBy : .
+
+schema:itemOffered a owl:ObjectProperty ;
+    rdfs:label "Product" ;
+    rdfs:domain schema:Offer ;
+    rdfs:range schema:Product ;
+    rdfs:isDefinedBy : .
+
+schema:priceSpecification a owl:ObjectProperty ;
+    rdfs:label "Price specification" ;
+    rdfs:domain schema:Offer ;
+    rdfs:range schema:PriceSpecification ;
+    rdfs:isDefinedBy : .
+
+schema:appliesToDeliveryMethod a owl:ObjectProperty ;
+    rdfs:label "Delivery method" ;
+    rdfs:domain schema:DeliveryChargeSpecification ;
+    rdfs:range schema:DeliveryMethod ;
+    rdfs:isDefinedBy : .
+
+schema:deliveryStatus a owl:ObjectProperty ;
+    rdfs:label "Shipment" ;
+    rdfs:domain schema:ParcelDelivery ;
+    rdfs:range schema:DeliveryEvent ;
+    rdfs:isDefinedBy : .
+
+schema:partOfOrder a owl:ObjectProperty ;
+    rdfs:label "Order" ;
+    rdfs:domain schema:ParcelDelivery ;
+    rdfs:range schema:Order ;
+    rdfs:isDefinedBy : .
+
 schema:deliveryAddress a owl:ObjectProperty ;
     rdfs:label "Delivery address" ;
     rdfs:domain schema:ParcelDelivery ;
@@ -131,8 +204,6 @@ schema:sponsor a owl:ObjectProperty ;
 
 schema:orderedItem a owl:ObjectProperty ;
     rdfs:label "Ordered item" ;
-    rdfs:domain schema:Order ;
-    rdfs:range schema:Product ;
     rdfs:isDefinedBy : .
 
 schema:orderStatus a owl:ObjectProperty ;
@@ -220,22 +291,19 @@ schema:orderQuantity a owl:DatatypeProperty ;
     rdfs:domain schema:OrderItem ;
     rdfs:isDefinedBy : .
 
-schema:discount a owl:DatatypeProperty ;
-    rdfs:label "Discount" ;
-    rdfs:domain schema:OrderItem ;
-    rdfs:isDefinedBy : .
-
+# left without an rdfs:domain on purpose: schema:price is carried both by the order
+# lines (as schema:Offer) and by the freight charge (as schema:DeliveryChargeSpecification)
 schema:price a owl:DatatypeProperty ;
     rdfs:label "Price" ;
     rdfs:isDefinedBy : .
 
-schema:totalPrice a owl:DatatypeProperty ;
-    rdfs:label "Total price" ;
+schema:priceCurrency a owl:DatatypeProperty ;
+    rdfs:label "Currency" ;
     rdfs:isDefinedBy : .
 
-schema:availableFrom a owl:DatatypeProperty ;
-    rdfs:label "Shipped date" ;
-    rdfs:domain schema:ParcelDelivery ;
+schema:startDate a owl:DatatypeProperty ;
+    rdfs:label "Shipped" ;
+    rdfs:domain schema:DeliveryEvent ;
     rdfs:isDefinedBy : .
 
 schema:orderDate a owl:DatatypeProperty ;
@@ -354,7 +422,7 @@ WHERE
       { ?product a schema:Product ;
                  schema:provider $about ;
                  schema:category ?category ;
-                 schema:price ?price
+                 schema:offers/schema:price ?price
       }
   }
 ORDER BY ?product
@@ -440,8 +508,7 @@ WHERE
       { $about schema:orderedItem ?item .
         ?item schema:orderedItem ?product ;
               schema:orderQuantity ?quantity ;
-              schema:price ?price ;
-              schema:totalPrice ?lineTotal
+              schema:price ?lineTotal
       }
   }
 ORDER BY ?item

demo/northwind-traders/categories.ttl

@@ -57,10 +57,7 @@ WHERE {
     GRAPH ?orderGraph {
         ?order schema:orderedItem ?orderItem .
         ?orderItem schema:orderedItem ?product ;
-                   schema:orderQuantity ?quantity ;
-                   schema:price ?price ;
-                   schema:discount ?discount .
-        BIND(?quantity * ?price * (1 - ?discount) AS ?sale)
+                   schema:price ?sale .
     }
     GRAPH ?productGraph {
         ?product schema:category ?category .

demo/northwind-traders/customers.ttl

@@ -47,10 +47,7 @@ WHERE {
     GRAPH ?orderGraph {
         ?order schema:customer ?customer ;
                schema:orderedItem ?orderItem .
-        ?orderItem schema:orderQuantity ?quantity ;
-                   schema:price ?price ;
-                   schema:discount ?discount .
-        BIND(?quantity * ?price * (1 - ?discount) AS ?sale)
+        ?orderItem schema:price ?sale .
     }
     GRAPH ?customerGraph {
         ?customer schema:legalName ?companyName .

demo/northwind-traders/employees.ttl

@@ -55,10 +55,7 @@ WHERE {
     GRAPH ?orderGraph {
         ?order schema:broker ?employee ;
                schema:orderedItem ?orderItem .
-        ?orderItem schema:orderQuantity ?quantity ;
-                   schema:price ?price ;
-                   schema:discount ?discount .
-        BIND(?quantity * ?price * (1 - ?discount) AS ?sale)
+        ?orderItem schema:price ?sale .
     }
     GRAPH ?employeeGraph {
         ?employee schema:givenName ?givenName ;

demo/northwind-traders/orders.ttl

@@ -174,7 +174,7 @@ WHERE {
                schema:orderDate ?orderDate ;
                schema:orderDelivery ?delivery ;
                schema:orderedItem ?orderItem .
-        ?orderItem schema:totalPrice ?lineTotal .
+        ?orderItem schema:price ?lineTotal .
         ?delivery schema:provider ?shipper .
     }
     GRAPH ?shipperGraph {

demo/northwind-traders/orders/order_details.rq

@@ -7,16 +7,32 @@ CONSTRUCT
 {
     GRAPH ?graph
     {
-        ?graph foaf:topic ?orderItem .
+        ?graph foaf:topic ?orderItem, ?listPrice .
 
         ?order schema:orderedItem ?orderItem .
 
-        ?orderItem a schema:OrderItem ;
+        # schema:OrderItem carries no price in schema.org - its only properties are
+        # orderedItem, orderQuantity, orderItemNumber, orderItemStatus and orderDelivery.
+        # Prices belong to schema:Offer, so the line is both: the item that was ordered
+        # and the offer that was accepted for it. schema:Offer's own schema:price is the
+        # price of the offer as a whole, i.e. what this line came to.
+        ?orderItem a schema:OrderItem, schema:Offer ;
             schema:orderedItem ?product ;
+            schema:itemOffered ?product ;
             schema:orderQuantity ?quantity ;
-            schema:discount ?discount ;
+            schema:price ?lineTotal ;
+            schema:priceCurrency "USD" ;
+            schema:priceSpecification ?listPrice .
+
+        # Northwind's per-line discount rate has no home in schema.org - schema:discount
+        # is an Order-level property. Nothing is lost by dropping it: the undiscounted
+        # unit price below, the quantity above and the line total pin the rate exactly,
+        # and unlike a stored rate they cannot disagree with each other.
+        ?listPrice a schema:UnitPriceSpecification ;
+            dct:title "List price" ;
+            schema:priceType schema:ListPrice ;
             schema:price ?price ;
-            schema:totalPrice ?lineTotal .
+            schema:priceCurrency "USD" .
     }
 }
 WHERE
@@ -30,6 +46,7 @@ WHERE
     BIND(uri(concat(str($base), "orders/", encode_for_uri(?orderID), "/")) AS ?graph)
     BIND(uri(concat(str(?graph), "#this")) AS ?order)
     BIND(uri(concat(str(?graph), "#", STRUUID())) AS ?orderItem)
+    BIND(uri(concat(str(?orderItem), "-list-price")) AS ?listPrice)
     BIND(uri(concat(str($base), "products/", encode_for_uri(?productID), "/#this")) AS ?product)
     BIND (STRDT(?unitPrice, xsd:float) AS ?price)
     BIND (STRDT(?quantityString, xsd:integer) AS ?quantity)

demo/northwind-traders/orders/orders.rq

@@ -9,7 +9,8 @@ CONSTRUCT
     {
         ?graph dct:title ?orderID ;
             foaf:primaryTopic ?order ;
-            foaf:topic ?orderDelivery, ?deliveryAddress .
+            foaf:topic ?orderDelivery, ?deliveryAddress, ?shipment,
+                ?shippingOffer, ?freightCharge .
 
         ?order a schema:Order ;
             schema:identifier ?orderID ;
@@ -18,16 +19,41 @@ CONSTRUCT
             schema:broker ?employee ;
             schema:orderDate ?orderDate ;
             schema:orderStatus ?status ;
+            schema:acceptedOffer ?shippingOffer ;
             schema:orderDelivery ?orderDelivery .
 
         ?orderDelivery a schema:ParcelDelivery ;
             foaf:page ?graph ;
+            schema:partOfOrder ?order ;
             schema:expectedArrivalUntil ?requiredDate ;
-            schema:availableFrom ?shippedDate ;
-            schema:price ?freight ;
+            schema:deliveryStatus ?shipment ;
             schema:deliveryAddress ?deliveryAddress ;
             schema:provider ?shipper .
 
+        # schema:ParcelDelivery has no price property either. A delivery charge is a
+        # schema:DeliveryChargeSpecification, and the only way into a PriceSpecification
+        # is schema:priceSpecification from an Offer - so the freight the customer
+        # accepted is spelled out as exactly that.
+        ?shippingOffer a schema:Offer ;
+            foaf:page ?graph ;
+            dct:title "Shipping" ;
+            schema:priceSpecification ?freightCharge .
+
+        ?freightCharge a schema:DeliveryChargeSpecification ;
+            foaf:page ?graph ;
+            dct:title "Freight" ;
+            schema:price ?freight ;
+            schema:priceCurrency "USD" ;
+            schema:appliesToDeliveryMethod schema:ParcelService .
+
+        # schema:ParcelDelivery has no date of its own for "when did this leave the warehouse".
+        # The vocabulary models the journey as a series of schema:DeliveryEvent legs hanging
+        # off schema:deliveryStatus; Northwind knows exactly one leg, the dispatch.
+        ?shipment a schema:DeliveryEvent ;
+            foaf:page ?graph ;
+            dct:title ?shipmentTitle ;
+            schema:startDate ?shippedDate .
+
         ?deliveryAddress a schema:PostalAddress ;
             foaf:page ?graph ;
             schema:addressCountry ?shipCountry ;
@@ -49,22 +75,35 @@ WHERE
         <#shipName> ?shipName ;
         <#shipAddress> ?shipAddress ;
         <#shipCity> ?shipCity ;
-        <#shipPostalCode> ?shipPostalCode ;
         <#shipCountry> ?shipCountry .
 
+    # ?shipment is bound inside the OPTIONAL so that the 21 orders that were never
+    # dispatched get no DeliveryEvent at all, rather than an empty one. It is built from
+    # $base (a constant, substituted before execution) and a re-matched ?orderID rather
+    # than from ?graph: an OPTIONAL group is evaluated standalone, so variables BINDed in
+    # the enclosing group are not in scope inside it.
     OPTIONAL {
-        ?order_row <#shippedDate> ?shippedDateString
+        ?order_row <#orderID> ?orderID ;
+            <#shippedDate> ?shippedDateString .
         BIND(strdt(?shippedDateString, xsd:date) AS ?shippedDate)
+        BIND(uri(concat(str($base), "orders/", encode_for_uri(?orderID), "/#shipment")) AS ?shipment)
+        BIND(concat("Shipped ", ?shippedDateString) AS ?shipmentTitle)
     }
     OPTIONAL {
         ?order_row <#shipRegion> ?shipRegion
     }
+    # 19 orders carry no postal code; requiring one here dropped them from the import
+    OPTIONAL {
+        ?order_row <#shipPostalCode> ?shipPostalCode
+    }
 
     BIND(uri(concat(str($base), "orders/")) AS ?container)
     BIND(uri(concat(str(?container), encode_for_uri(?orderID), "/")) AS ?graph)
     BIND(uri(concat(str(?graph), "#this")) AS ?order)
     BIND(uri(concat(str(?graph), "#delivery")) AS ?orderDelivery)
     BIND(uri(concat(str(?graph), "#delivery-address")) AS ?deliveryAddress)
+    BIND(uri(concat(str(?graph), "#shipping")) AS ?shippingOffer)
+    BIND(uri(concat(str(?graph), "#freight")) AS ?freightCharge)
     BIND(uri(concat(str($base), "employees/", encode_for_uri(?employeeID), "/#this")) AS ?employee)
     BIND(uri(concat(str($base), "customers/", encode_for_uri(?customerID), "/#this")) AS ?customer)
     BIND(uri(concat(str($base), "shippers/", encode_for_uri(?shipVia), "/#this")) AS ?shipper)

demo/northwind-traders/products.ttl

@@ -58,10 +58,7 @@ WHERE
   { GRAPH ?orderGraph
       { ?order    schema:orderedItem    ?orderItem .
         ?orderItem  schema:orderedItem  ?product ;
-                  schema:orderQuantity  ?quantity ;
-                  schema:price          ?price ;
-                  schema:discount       ?discount
-      BIND (?quantity * ?price * (1 - ?discount) AS ?sale)
+                  schema:price          ?sale
       }
     GRAPH ?productGraph
       { ?product  schema:name  ?productName }

demo/northwind-traders/products/products.rq

@@ -8,7 +8,8 @@ CONSTRUCT
     GRAPH ?graph
     {
         ?graph dct:title ?productName ;
-            foaf:primaryTopic ?product .
+            foaf:primaryTopic ?product ;
+            foaf:topic ?offer .
 
         ?product a schema:Product ;
             schema:identifier ?productID ;
@@ -17,11 +18,21 @@ CONSTRUCT
             schema:provider ?supplier ;
             schema:category ?category ;
             schema:description ?quantityPerUnit ;
-            schema:price ?unitPrice .
+            schema:offers ?offer .
             # ?unitsInStock ;
             # ?unitsOnOrder ;
             # ?reorderLevel ;
             # ?discontinued - schema:Discontinued
+
+        # schema:Product has no price of its own - schema:price belongs to schema:Offer,
+        # which a product reaches through schema:offers. This is the catalogue price;
+        # what a given order line was actually billed at lives on that line's own offer.
+        ?offer a schema:Offer ;
+            foaf:page ?graph ;
+            dct:title "List price" ;
+            schema:itemOffered ?product ;
+            schema:price ?unitPrice ;
+            schema:priceCurrency "USD" .
     }
 }
 WHERE
@@ -40,6 +51,7 @@ WHERE
     BIND (uri(concat(str($base), "products/")) AS ?container)
     BIND(uri(concat(str(?container), encode_for_uri(?productID), "/")) AS ?graph)
     BIND(uri(concat(str(?graph), "#this")) AS ?product)
+    BIND(uri(concat(str(?graph), "#offer")) AS ?offer)
     BIND(uri(concat(str($base), "suppliers/", encode_for_uri(?supplierID), "/#this")) AS ?supplier)
     BIND(uri(concat(str($base), "categories/", encode_for_uri(?categoryID), "/#this")) AS ?category)
     BIND (STRDT(?unitPriceString, xsd:float) AS ?unitPrice)