Information Technology Reference
In-Depth Information
7.8.2.1.3 Trees
In computer terms a tree is a data structure that emulates a tree structure with a set
of linked nodes, each of which has a single parent node - except the (single) root
node - and there are no closed “loop” structures (i.e. it is acyclic). A node with
no children is a “leaf” node. This type of structure is illustrated in Fig.
7.20
, and it
appears in many areas including XML structures. A variety of tree structures can be
created by associating different properties with the nodes.
The Java TreeModel interface [
75
] is an example of this.
7.8.2.1.4 Documents
Simple documents, i.e. something with text and images that can be displayed to
a user, can also be virtualised; an example of this is the Multivalent Browser
[
76
], which defines common access methods to documents in a number of formats
including scanned paper, HTML, UNIX manual pages, TeX, DVI and PDF. The
Multivalent browser central data structure is the document tree - a specialised ver-
sion of the tree structure described in
Sect. 5.2.1.1.3
. Another, simpler, document
model is provided by the W3C's Document Object Model (DOM) [
77
] and the Java
implementation [
78
].
7.8.3 Composite Objects
The concept Composite Object is a catch-all term which covers a variety of struc-
tured (tree-like) objects, which may contain other complex and simple objects. The
Root node
Get the Root
Get the number of children
for a node
Get child number “i”
Node 1
Node 2
Node 3
Node 4
Node 5
Node 6
Node 6
Node 7
Node 8
Node 9
Fig. 7.20
Tree structure
