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See:
Description
Class Summary | |
DynamicAssociation | This class provides support to create dynamic two-way associations between any object types. |
DynamicObjectType | DynamicObjectType is a class that can be used to dynamically
create and modify ObjectType . |
Provides a set of classes to store metadata about data object types and the database schema used to persist data objects.
When the system starts up, the persistence layer reads the PDL
files into an Abstract Syntax Tree using the files within com.redhat.persistence.pdl.nodes
. The Abstract Syntax Tree then
populates the classes within this package. These classes are then
used by the operational persistence layer (the classes within the
com.arsdigita.persistence
package) to perform the standard
operations.
The resulting structure is a hierarchy as every item that can be
represented in PDL extends the Element
class. This class stores
general information about object models and is able to output itself
in the form of a PDL file.
The metadata is divided into Model
s. These models act as the
namespace for all of the metadata information (such as object types,
data queries, and data operations). The model itself is composed of
ModelElement
s.
There are two types of ModelElements: Association
and DataType
. The Association model
type holds information for associations between object types. The
DataType model contains both CompoundTypes and SimpleTypes.
SimpleType
s are used to
represent the primitive DataTypes that the persistence layer knows
how to store. For instance, there are SimpleTypes for BigDecimal,
Integer, Date, and String as well as many others. These are used
for describing Properties as well as Attributes defined
within MAP blocks.
A CompoundType
can
either be a ObjectType
ObjectTypes provide specific access special events that act on rows
within the tables. Each DataObject
contains a single ObjectType and that ObjectType is what contains
references to the events allowing the user to easily manipulate data
within the database. An ObjectType is made up of Attributes (columns
in the database), Associations (mappings between database tables), and
Events (A collection of Operations that dictate how information is
stored and retrieved within the database).
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