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Data::Grove(3)		       User Contributed Perl Documentation		   Data::Grove(3)

       Data::Grove -- support for deeply nested structures

	use Data::Grove;

	$object = MyPackage->new;

	package MyPackage;
	@ISA = qw{Data::Grove};

       "Data::Grove" provides support for deeply nested tree or graph structures.  "Data::Grove"
       is intended primarily for Perl module authors writing modules with many types or classes
       of objects that need to be manipulated and extended in a consistent and flexible way.

       "Data::Grove" is best used by creating a core set of ``data'' classes and then incremen-
       tally adding functionality to the core data classes by using ``extension'' modules.  One
       reason for this design is so that the data classes can be swapped out and the extension
       modules can work with new data sources.	For example, these other data sources could be
       disk-based, network-based or built on top of a relational database.

       Two extension modules that come with "Data::Grove" are "Data::Grove::Parent" and
       "Data::Grove::Visitor".	"Data::Grove::Parent" adds a `"Parent"' property to grove objects
       and implements a `"root"' method to grove objects to return the root node of the tree from
       anywhere in the tree and a `"rootpath"' method to return a list of nodes between the root
       node and ``this'' node.	"Data::Grove::Visitor" adds callback methods `"accept"' and
       `"accept_name"' that call your handler or receiver module back by object type name or the
       object's name.

       "Data::Grove" objects do not contain parent references, Perl garbage collection will
       delete them when no longer referenced and sub-structures can be shared among several
       structures.  "Data::Grove::Parent" is used to create temporary objects with parent point-

       Properties of data classes are accessed directly using Perl's hash functions (i.e.
       `"$object->{Property}"').  Extension modules may also define properties that they support
       or use, for example Data::Grove::Parent adds `"Parent"' and `"Raw"' properties and Visitor
       depends on `"Name"' and `"Content"' properties.

       See the module "XML::Grove" for an example implementation of "Data::Grove".

       new( PROPERTIES )
	   Return a new object blessed into the SubClass, with the given properties.  PROPERTIES
	   may either be a list of key/value pairs, a single hash containing key/value pairs, or
	   an existing "Data::Grove" object.  If an existing "Data::Grove" is passed to
	   `"new()"', a shallow copy of that object will be returned.  A shallow copy means that
	   you are returned a new object, but all of the objects underneath still refer to the
	   original objects.

       Ken MacLeod, ken@bitsko.slc.ut.us


perl v5.8.0				    2000-02-22				   Data::Grove(3)
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