The network is created on the screen using the palette of tools (icons) contained in the tool strip in the window. To create a network, select a node tool from the toolstrip by clicking it. The cursor shape now changes to a node object symbol indicating a node is being created. Clicking in the window now defines the position of the node and creates it and gives it a unique name. The display attributes of the new node (colour and thickness) are the same as those in the toolstrip.
Next, create the links between nodes, selecting the link tool and then clicking on the nodes you wish to connect. The cursor shape again changes to link object symbol indicating a link is being created. A link is directed from the first to the second nodes clicked upon indicating the direction of flow from upstream to downstream. An arrow is placed on the downstream end of the link indicating the direction of positive flow. The position of the second end of the link (the end towards which flows are directed) is indicated by a dotted outline which tracks the mouse movement. A default unique name is automatically created for any object requiring a name.
You may create a polylink (bent link) by holding down the <Ctrl> key as you click with the mouse. This will create a vertex at each point at which you click.
You may change an existing link to a polylink by holding the <Ctrl> key down and clicking at the locations where you want a vertex.
You may remove a vertex by holding down the <Shift> and <Ctrl> keys and clicking on the vertex you wish to delete.
XP performs a series of validity checks to verify that a valid network is being created and, if the connection satisfies all of the rules, the link is created.
An additional feature of the link tool is the provision of a default end node. If the link tool is selected and you attempt to create a link in free space, i.e. you do not click on an existing node, a default node will be created. In this manner it is not necessary to first create nodes and then join them with links, but rather perform both operations simultaneously.