+
+-- Local imports.
+import TSN.Team ( Team(..) )
+
+
+-- | Common associated type shared by 'FromXml' and 'FromXmlFk'. This
+-- basically just forces the client to define the \"database
+-- version\" of his type.
+--
+class ToDb a where
+ -- | Each instance @a@ must declare its associated database type @Db a@.
+ type Db a :: *
+
+-- | A typeclass for XML types that can be converted into an
+-- associated database type. The story behind this is long, but
+-- basically, we need to different types most XML thingies we're
+-- going to import: a database type and an XML type.
+--
+-- Both Groundhog and HXT are very particular about the types that
+-- they can use, and there's no way to reuse e.g. a type that HXT
+-- can pickle in Groundhog. This typeclass gives us a standard way
+-- to get the database type from the XML type that we have to define
+-- for HXT.
+--
+class (ToDb a) => FromXml a where
+ -- | A function for getting a @Db a@ out of an @a@.
+ from_xml :: a -> Db a
+
+
+-- | A class for XML representations which are children of other
+-- elements. The foal is to associate a child XML element with its
+-- parent element's database type. This is required to construct the
+-- database analogue of @a@ in the 'FromXmlFk' and 'FromXmlFkTeams'
+-- classes.
+--
+class Child a where
+ -- | The type of our parent object, i.e. to the type to whom our
+ -- foreign key will point.
+ type Parent a :: *
+
+
+-- | Some database types cannot be constructed from the XML type
+-- alone; they must be supplied a foreign key to a parent object
+-- first. Members of this class can be converted from an XML
+-- representation to a database representation in this manner.
+--
+class (Child a, ToDb a) => FromXmlFk a where
+ -- | The function that produces a @Db a@ out of a foreign key and an
+ -- @a@. The parameter order makes it easier to map this function
+ -- over a bunch of things.
+ from_xml_fk :: DefaultKey (Parent a) -> a -> Db a
+
+
+-- | A further refinement of 'FromXmlFk'. These types need not only a
+-- foreign key to a parent in order to make the XML -> DB
+-- conversion, but also two foreign keys to away/home teams (as
+-- represented in "TSN.Team").
+--
+class (Child a, ToDb a) => FromXmlFkTeams a where
+ -- | The function that produces a @Db a@ out of a parent foreign
+ -- key, two team foreign keys, and an @a@. The parameter order makes
+ -- it easier to map this function over a bunch of things.
+ from_xml_fk_teams :: DefaultKey (Parent a)
+ -> DefaultKey Team -- ^ The away team FK
+ -> DefaultKey Team -- ^ The home team FK
+ -> a
+ -> Db a
+
+
+-- | Represents the DTD filename (\"SYSTEM\") part of the DOCTYPE
+-- definition.
+newtype DtdName = DtdName String
+