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Tree Forms

Overview

This type of function is used to display a structure hierarchy in tree form, similar to that provided by the Explorer in Microsoft Windows. This contains objects known as NODES and LEAVES.

NODES can be arranged in hierarchies of any depth. Each NODE can have one parent and any number of children. A NODE which is at the top of the structure does not have a parent and is known as a ROOT NODE.

LEAVES are objects which are attached to NODES. A LEAF can be attached to one (and only one) NODE in the structure, but cannot have anything else attached to it.

In the context of Windows Explorer NODES are directories or folders, and LEAVES are files.

Any path (or branch) within the structure starts at a ROOT NODE and progresses down a different child NODE at each lower level until it terminates. A branch may terminate at a NODE or a LEAF.

When viewing a tree structure the user may open up any branch by clicking on the expand (+) symbol next to a node. Conversely, any branch may be closed by clicking on the collapse (-) symbol.

All the Tree templates described here were built using the database structure shown in Figure 1. This is described fully in a separate document called A Flexible Tree Structure.

Figure 1 - Database Structure

This database structure provides the following characteristics:-

• It is possible to define any number of Tree Types.
• Each Tree Type can have its own set of Tree Levels with custom descriptions.
• Each Tree Level can have its own set of Tree Nodes.
• Each Tree Node is related to another Tree Node at the next highest level, except for those at the top level (Level 1) which are known as Root Nodes.
• Each Tree Node can have any number of Leaves attached to it, where a Leaf can be any other object within the system.

Tree 1 - display Tree details, with navigation bar

Description

For an overview of all Tree forms please go here.

This type of form is used to display a hierarchical structure in tree form using the Two Pane view. Options on the navigation bar may allow the user to add, amend, or delete any node in the structure.

Upon initial entry the form will retrieve an occurrence of Tree Type using the primary key passed down from the parent form. The screen will then display the root node(s) for the selected structure. The user may traverse any branch of the structure as required.

The contents of the right-hand pane may be changed by selecting one of the radio buttons labelled List, Icon, or Details. These have the same effect as the options in the Windows Explorer.

Data for this form is obtained from two services:-

• A Node Service constructed from the Tree Service (Nodes) template.
• A Leaf Service constructed from the Tree Service (Leaves) template.

Buttons

Contents

Bound Objects

Local Constants (Refer to Local Constants)

Component Variables (Refer to Component Variables)

Tree 2 - display Tree details, without navigation bar

Description

For an overview of all Tree forms please go here.

This type of form is used to display a hierarchical structure in tree form using the Two Pane view.

Upon initial entry the form will retrieve an occurrence of Tree Type using the primary key passed down from the parent form. The screen will then display the root node(s) for the selected structure. The user may traverse any branch of the structure as required.

The contents of the right-hand pane may be changed by selecting one of the radio buttons labelled List, Icon, or Details. These have the same effect as the options in the Windows Explorer.

Data for this form is obtained from two services:-

• A Node Service constructed from the Tree Service (Nodes) template.
• A Leaf Service constructed from the Tree Service (Leaves) template.

Buttons

Contents

Bound Objects

Local Constants (Refer to Local Constants)

Component Variables (Refer to Component Variables)

Tree Popup 1 - Select a Tree Node

Description

For an overview of all Tree forms please go here.

This type of form is used to display the contents of a tree structure using only a single pane, the tree view.

The action taken upon initial entry depends on the existence of a parameter passed down by the parent process:-

• If a parameter is passed this will be used to retrieve an occurrence of Tree Type, then the contents of that structure will be automatically retrieved and displayed.
• If no parameter is passed the user will be required use the relevant popup screen in order to choose an entry from those which are currently available.

The screen will display the root node(s) for the selected Tree Type. The user may traverse any branch of the structure as required before selecting the desired node.

Data for this form is obtained from a Node Service which must be constructed from the Tree Service (Nodes) template.

Buttons

Contents

Bound Objects

Local Constants (Refer to Local Constants)

Name	Expression	Description
FORM_VERSION	01.000.000	To be incremented each time the component is changed.
NODE_SERVICE		The name of the service which will retrieve NODE details. This should be constructed from the Tree Service (Nodes) template.
POPUP_FORM		The name of the form that will be activated if the popup button is pressed.

Component Variables (Refer to Component Variables)

Tree Service (Nodes) - retrieve Node details

Description

For an overview of all Tree forms please go here.

This component will retrieve NODE details for a tree structure. It is used to supply data for one of the form components TREE1, TREE2 or TREE POPUP1.

This component has the following operations:-

• PROPERTIES - get the properties for this TREE TYPE, and the ROOT NODES.
• SELECT - get the details for the selected NODE.
• EXPAND - get the details for the child NODES of the selected NODE.

Buttons

N/A

Contents

Bound Objects

Local Constants (Refer to Local Constants)

Component Variables (Refer to Component Variables)

Tree Service (Leaves) - retrieve Leaf details

Description

For an overview of all Tree forms please go here.

This component will retrieve LEAF details for a selected NODE in a tree structure. It is used to supply data for one of the form components TREE1 or TREE2.

A LEAF entity can be any entity which contains a NODE_ID field which acts as a foreign key to the TREE_NODE table.

Buttons

N/A

Contents

Bound Objects

Local Constants (Refer to Local Constants)

Component Variables (Refer to Component Variables)

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