Model:
• Catalog (ID, SecondID, ThirdID). Primary key: (ID). Unique constraint: (SecondID, ThirdID)
• CatalogItem(ID,CatalogID, CatalogSecondID, CatalogThirdID)

Foreign key relation on Unique constraints, spanning two columns: CatalogItem(CatalogSecondID, CatalogThirdID)  Catalog(SecondID, ThirdID)

Expected in metadata DLL for CatalogItem:
CONSTRAINT FKI_SECOND_THIRD_ID FOREIGN KEY(CatalogSecondID, CatalogThirdID) REFERENCES Catalog(SecondID, ThirdID)

Actual:
CONSTRAINT FKI_SECOND_THIRD_ID FOREIGN KEY(CatalogSecondID, CatalogThirdID) REFERENCES Catalog(ID)