diff --git a/doc/pdm.png b/doc/pdm.png
index 89dce07..8c811e4 100644
Binary files a/doc/pdm.png and b/doc/pdm.png differ
diff --git a/doc/pdm.puml b/doc/pdm.puml
index 706708f..b88ae87 100644
--- a/doc/pdm.puml
+++ b/doc/pdm.puml
@@ -14,13 +14,11 @@ skinparam class {
 !define rel(a,b,c,d,e) a c e
 !define pyk(n,t="MEDIUMINT NOT NULL UNSIGNED") <font color="red">PK:<b>n</b> <size:09>[t]</size></font>
 !define fnk(n,r,t="MEDIUMINT NOT NULL UNSIGNED") <font color="blue">FK:<b>n</b> <size:09>[t]</size></font>
-!define pfk(n,r,t="MEDIUMINT NOT NULL UNSIGNED") <font color="orangered">PFK:<b>n</b> <size:09>[t]</size></font>
 !define att(n,u,s) {field} <b>n</b> [s]
 
 /' = = = = = = = CLASSE = = = = = = = '/
 class product
 class category
-class prod_category <<assoc>>
 
 /' = = = = = = = RELATION = = = = = = = '/
 rel(product,1..,--,1..*,category)
@@ -28,28 +26,20 @@ rel(product,1..,--,1..*,category)
 /' = = = = = = = KEY = = = = = = = '/
 class product {
     pyk(id)
+    fnk(substitute_id,product.id)
     ..
 }
 class category {
     pyk(id)
     ..
 }
-class prod_category <<assoc>> {
-    pfk(category_id,category.id)
-    pfk(product_id,product.id)
-    ..
-}
 /' = = = = = = = ATTRIBUTE = = = = = = = '/
 class product {
     att(name,String,VARCHAR(200))
+    att(url,String,VARCHAR(255))
     att(nutrition_grades,String,VARCHAR(1))
 }
 class category {
     att(name,String,VARCHAR(200))
 }
-
-/' = = = = = = = ASSOCIATION = = = = = = = '/
-rel(product,.,--,.,prod_category)
-rel(category,.,-,.,prod_category)
-
 @enduml