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of the toolbar icons are similar to the other tools in this chapter. However, instead of working with primarily with relationships and functions, you'll be using this tool to create or analyze the flow of data within your system.

Figure 32.5.
The Dataflow
Diagrammer.

Creating a Diagram

To create any dataflow diagram, you must follow certain steps. You should include functions and define dataflows, datastores, and external storage ”and you must save the diagram.

Using Functions

A dataflow diagram must contain functions, so you should create a functional hierarchy prior to using the tool in either RON or the Function Hierarchy Diagrammer. If you discover while using the Dataflow Diagrammer that you forgot a function, you can add it directly in the Dataflow Diagrammer. Select the Function icon. You will be prompted for a short name and a description (similar to when you use the Function Hierarchy Diagrammer). If you need to create an entire hierarchy, it is better to use the Function Hierarchy Diagrammer. When you create a new diagram, you will be prompted to select a function that will be the base for the diagram, generally a parent function. Next, add the children you want to depict in the diagram. To include an existing function from the application, use Edit Include Function from the menu bar. Then choose where you want to place it on the diagram.

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As in the other tools, remember to select multiple functions from the list, hold down the Ctrl key and click the functions you require or select a block of functions by holding down the Shift key. If you choose a large number, your diagram might become too difficult to follow for the initial editing, so keep this in mind when you make your selection.

After adding a function, you can edit it. The entities used in this function can be defined, as well as the attributes of the entities within this function. Double-click the function to edit it.

Adding Datastores

A datastore is a site in which data for entities or attributes can be stored for use by a function. For example, a paper timecard is temporarily the datastore for an employee's hours until the hours are entered into the system. Add the datastore by clicking the Datastore icon. After you decide where you want the datastore on the diagram, you can add the short name and description for the datastore. If a datastore is used when performing a function, place it inside the function.

After adding the datastore, you can edit it. The entities in the datastore can be defined, as well as the attributes of the entities. Double-click the datastore to edit it. From there, you can edit the description, any notes on the datastore, the entities, their attributes, and other data elements. Select an entity from the list. Then select an attribute or set of attributes by holding down the Ctrl key. Next, press the down arrow to insert them onto the dataflow list. To remove them from the dataflow list, press the up arrow. Data items are manually entered.

You can also include datastores from RON, if you entered them previously on another diagram. To select an existing datastore, choose Edit Include Datastore from the menu. Select an existing datastore from the list.

Adding Externals

Externals are repositories outside of the function in which entities, attributes, or data elements are stored. To add externals to the diagram, select the Datastore icon. Place the cursor where you want the external on the diagram. Enter the short name and description.

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If you want to create more than one external without having to select the button each time, hold down the Shift key when you select the external button. When you are ready to move on to another activity, press another button on the icon bar.

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After you add an external, you can edit it. To do so, double-click the external. On the screen you can edit the short name, description, information about whether it comes from outside the application (possibly from another application), a comment, and its representation. The representation signifies whether it is an entity or business unit. You can select a specific entity or business unit from the list of values.

You can also include externals from RON, if you entered them previously on another diagram. To select an existing external, select Edit Include Datastore from the menu. Select an existing external from the list.

Adding Dataflows

You can add dataflows to signify the flow of data from one element to another. To create a dataflow, select the Dataflow icon. Select the parent element for the flow and then select the child element. Enter a description for the flow. If no description is entered, the diagrammer will list the word none.

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If you want to create more than one dataflow without having to select the button each time, hold down the Shift key when you select the Dataflow button. When you are ready to move on to another activity, press another button on the icon bar.

After you add a dataflow, you can edit it by double-clicking the item. From there, you can edit the description, any notes on the dataflow, and the actual data flowing out of the parent element ”the entities, their attributes, and other data elements. Select an entity from the list. Then select an attribute or set of attributes by holding down the Ctrl key. Next, press the down arrow to insert them onto the dataflow list. To remove them from the dataflow list, hit the up arrow. Data items are manually entered.

You can also include dataflows from RON, if you entered them previously on another diagram. To select an existing dataflow, choose Edit Include Dataflow from the menu. Select an existing dataflow from the list.

Adding Resolved Flows

Resolved flows, or dataflows at levels lower than the functions displayed, can be added to the diagram to display the flow of data below the level of your diagram. To select an existing resolved flow, select Edit Include Resolved Flow from the menu. Select an existing dataflow from the list.

Modifying Dataflow Structure

After a diagram has been developed, you can return to analysis and discover that one dataflow actually represents multiple dataflows. You can then split or divide the dataflow.

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