Basic features of NCES Editor


The user interface of NCES Editor comprises two windows. The figure below shows the windows.
NCES Editor

Overview of the user interface

The NCES Editor window is divided into two main components which are the tool bar and the draw area. The draw area contains the edited NCES. It is here where the actual drawing is done. To select which operation to perform in the draw area you must use the tool bar.

The Properties window shown on the right in the previous figure allows editing the properties of individual elements. The window shows the properties of the currently selected element. An element can be selected either by clicking on it with the mouse or selecting it from the combo box that is on the top of the window. The combo box contains all selectable individual elements that are on the draw area.

The properties of the currently selected element can be changed by typing new values to them in the Properties window. The selected element can be deleted either by pressing the Delete button on the keyboard or clicking on the Remove button in the Properties window.

Elements in the draw area can be moved either by setting new values for their x and y coordinates in the Properties window or by dragging them with the mouse. To drag an element place the mouse cursor over it. Then with the left mouse button pressed move the element to its new location and release the mouse button. The coordinate values in the dragged element's Properties window will be updated accordingly. Several elements can be dragged simulataneously provided that they are first selected using the selection tool in the toolbar.

Although one can use the Properties window to move or resize modules it is often more convenient to do these operations with the mouse. For example to move a transition, place or module click and hold on the element and drag it to the desired location. To resize a module move the mouse over one of its borders. The mouse cursor will change shape indicating that you can now move the border by dragging with the left mouse button pressed. Note that dragging or resizing elements in this manner is possible only when no tool bar action is selected. Only modules can be resized in this way, for other element types you must use the Properties window.

Whenever elements are resized or moved the size of the draw area will be automatically adjusted so that all elements can be displayed. This is indicated by the scroll bars.

Drawing NCES elements

To draw an NCES element you must first select the appropriate element type from the toolbar. The mouse cursor will change to a crosshair to indicate that you can select the location for the new element. When creating a new NCES from scratch the first element one needs to draw is a NCES module (Note that places, transitions and other elements cannot exist outside modules).

An NCES module can be drawn by clicking on the NCES toolbar button, moving the mouse cursor to the location where the new modules upper left corner should be and then drag the mouse with the left mouse button pressed. When the module is of the right size release the mouse button. If the location where the module was inserted is inside another module then the new module will become a submodule of that module. At any time there can be only one top level module, i.e. a module which is not contained in any other module. If you try to add another module outside the current top level module then a new top level module will be automatically created which contains both the old top level module and the new module.

Places and transitions can be placed anywhere inside modules. However, they cannot be placed in a module which contains submodules. Similarly modules cannot be placed in a module which contains places and transitions. To add a place or transition click on the corresponding toolbar button and then click on the location where to add the new element.

IOs (event inputs, event outputs, condition inputs and condition outputs) are created the same way as places and transitions. However, IOs are automatically placed at the borders of the module. Inputs are placed on the left border and outputs on the right border.

Arcs are placed by first selecting the appropriate toolbar button (flow arc, condition arc or event arc). Then click on the source element for the arc. After selecting the source a line will be drawn from the source. You can now specify the intermiate points for the arc. Once you click on the destination element the arc will be created. Note that there are restrictions regarding the acceptable source and destination for arcs which depend on the type of the arc. In addition arcs cannot go through module boundaries. The intermediate points, also called nails, of an arc are highlighted as light green ovals when the arc is selected. These points can be dragged with the mouse to new locations. New nails can be added and old ones removed in the editor popup menu.

In many cases an error dialog will be displayed if you try to insert an invalid element. To cancel adding a new element after clicking on a toolbar button press the ESC key on the keyboard and the mouse cursor will change to an arrow again.