-- | General XML stuff.
--
module Xml (
+ Child(..),
DtdName(..),
FromXml(..),
FromXmlFk(..),
xunpickleVal,
yes )
+
+
-- | Common associated type shared by 'FromXml' and 'FromXmlFk'. This
-- basically just forces the client to define the \"database
-- version\" of his type.
from_xml :: a -> Db 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.
+-- | 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 'FromXmlFk'.
--
-class (ToDb a) => FromXmlFk a where
+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
+
-- | Represents the DTD filename (\"SYSTEM\") part of the DOCTYPE
-- definition.
newtype DtdName = DtdName String