can be accessed from the Planning or Analysis
workstations.
At the start, you will be queried as to the scope of the data model. You can create a data model for a separate process, function, or other part of the IS. This option is useful in the context of very large IS, wherein it becomes necessary to look at parts of the data model to manage the complexity. In the case of the projects that you will be working on, the scope is fairly restricted, and thus you can work on the data model for the entire IS at once. Therefore, you need to select The Entity Model radio button, and then click on Display. This brings up a data model for the entire IS, integrating any separate data models if they exist.
To create a data model, you need to add entities to the window. This is done through the Add option at the main menu, as depicted below.
As with any ADW Add menu, you can add several entities at a time. In case you wish to include entities already entered previously, you should use the Find option. However, in most cases you will be using the Create option.
This will put several entities (in red) on the screen in a fairly random layout. You can rearrange these objects by selecting them (left mouse click - they will appear highlighted in yellow), and then dragging then (keeping the right mouse button pressed) to the point where you wish them located (and then releasing the right mouse button). Note that this works differently than in Windows.
You can also expand the size of the diagram by moving an entity off the screen (either down or left). ADW will then redraw the diagram with a larger Overview window.
You are then presented with a screen that describes the relation, including two-way labels, and respective cardinalities.
In this case, it is assumed that the relationship of interest is labelled teaches and is taught by. The cardinalities are also straightforward, assuming that an instructor can teach none or many course sections, while each section is taught by one and only one instructor.
This gives you a different window that describes the entity in greater detail, specifying all native and inherited attributes, as well as native and inherited relationships.
Attributes are added through the Add menu. Key attributes need to be added slightly differently from regular attributes.
For all attributes, you need to specify a minimum and maximum representing the number of occurrences in each tuple. Since we are working with a relational model, no repeating groups are allowed, and hence these values are set to 1 each. In the case of a key attribute, the Max per value field needs to be set to 1, representing the maximum possible instance values of this attribute.
In this case, the COURSE-NO is designated as the key. Other attributes can be added, with a blank value for the Max per value field. The result of adding the relevant attributes is depicted below.
Note that the COURSE-NO attribute has a designated < Id > notation.
When you are done with adding attributes, you shut down the window by double clinking the folder icon. This will return you to the original entity-relationship diagram
It is also possible to depict the associated attributes (and also print them) on the diagram itself. To accomplish this, click on the four paned window in the bottom left of an entity, and all defined attributes will be displayed, with keys identified.
At this stage, the diagram can be easily printed.
