More About Relationships

The name for the relationship should reflect its direction. For example:

• either company → employs → people
• or people→ work for → company
• but not company → work for→ people

PhixFlow imposes no restrictions on the names for relationships, but it must be unique in the repository. 

Example

In a relationship diagram, a stream and its attributes are displayed as a box. You can expand or collapse the  box using the icon in the top left. PhixFlow shows all the attributes when the stream is expanded, and only the primary and foreign keys when it is collapsed.

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The following diagram shows some relationships between streams that represent a company, its employees and departments, the products it makes and the customers who buy them.

Image Modified

The company "contains" many departments. An employee "works in" a department, and a department can have many team members. In this company, the department "makes" several products, which "ship to" many customers.

Relationship diagrams are useful because you can design relational views that use data from multiple streams. For example, you might want a view that shows the employee details by department. This will display data from the Employee stream and the Department stream. The relationship diagram shows these are connected by the DepartmentID attribute.

How to Draw a Relationship Diagram

Create the Diagram

1. In the repository for your application, right-click on 

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   .
2. Click 

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   .
3. In the pop-up, enter its name.
4. PhixFlow opens a properties tab on the right, and a new relationship diagram on the left. The relationship diagram has a toolbar at the top; see the Toolbar section below for details.

Create a New Stream

1. Drag the 

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    icon from the toolbar into the diagram.
2. In the pop-up, enter its name, for example "Customer".
3. PhixFlow adds a box to represent the data stream, and opens the properties tab for it.
4. In the properties tab on the right, In the Attributes section, click 

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   .
5. PhixFlow opens a properties tab where you can specify details for the attribute, such as its name, data type and length.
6. If this is the unique identifier, tick Primary Key. Remember to include ID or UID in the name.

Add an Existing Stream

1. In the repository, open the list of streams.
2. Drag a stream from the repository into the diagram.
3. If the stream has many attributes, click Image Modified to collapse the stream so that it only shows the primary and foreign keys.

Connect Attributes

Click-drag from one attribute to another, PhixFlow shows the currently selected destination in bold. Release the click to connect to the selected destination.

PhixFlow can only connect primary and foreign keys. If you connect standard attributes, PhixFlow automatically sets them to be foreign keys.

PhixFlow automatically sets type of relationship according to the keys:

• one to one: from primary key to primary key
• one to many: from primary key to foreign key
• many to one: from foreign key to primary key
• many to many: from foreign key to foreign key

Other affected pages: repository, toolbars

Properties

Basic Settings

Drawing Entity-Relationship Diagrams

To create an ERD, in the application repository, right-click ERD and select 

Adding Entities

To open an existing ERD:

• either, in the Repository, right-click the name and select Display.
• or, in the properties toolbar, click the ERD icon (TODO add).

Entities are represented by streams and their attributes.

To add an existing stream, from the repository, drag an existing stream into the diagram. PhixFlow adds the stream and all of its attributes.

To add a new stream.

1. from the toolbar, drag the stream icon (TODO add) into the diagram.
   
2. Enter a name for the new stream and click

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   . PhixFlow opens a new Stream properties tab.
   
3. To add attributes to an entity/stream:
   either, in the stream properties → Attributes section toolbar, click 

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   or, right-click the stream and select Add New Stream Attribute.
4. In the new attribute properties, enter details for the Stream Attributes.

As streams can contain many attributes, you can collapse the view to show only primary and foreign keys. TODO ADD screenshot

Adding Relationships

To add a relationship, click on one attribute and drag the mouse pointer to an attribute in another stream. PhixFlow extends a red arrow line. Stop dragging, or click on an attribute name to connect the two. PhixFlow displays an attribute in bold when it has focus.

When you create a relationship, PhixFlow:

• sets the origin attribute to be a Primary Key which must be unique.
• sets the destination attribute to be a Foreign Key
• creates a one-to-many relationship

The Primary Key and Foreign Key are properties of the Stream Attributes. (TODO ADD the new properties to attributes)

If both attributes are

primary keys, PhixFlow creates a one-to-one relationship.

foreigh keys, PhixFlow creates a many-to-many relationship.

If you connect two primary keys, PhixFlow creates a 1 to 1 relationship.

You cannot create a relationship between attributes if they are not a primary or foreign key. If you add a relationship between attributes, PhixFlow automatically sets them to be one of these.

ERDs and Relational Views

TODO - Add how ERDs and Relational vies interact.

TODO - Possibly bugs or possibly me...

• I ended up with 3 streams that did not appear until the diagram is saved - can I reproduce this
• relationship end points can be drawn a long way from the mouse. 
• I can untick keys and it keeps the relationship
• When entities are below each other PhixFlow gets confused.

Toolbar 

Anchor
toolbar toolbar

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TODO Same as Model Window Toolbar Icons

Image Modified	Organise selected objects in a grid.
Image Modified	Align all selected objects left.
Image Modified	Align all selected objects right.
Image Modified	Align all selected objects to top.
Image Modified	Align all selected objects to bottom.
Image Modified	Distribute all selected objects horizontally. Changed ICON TODO
Image Modified	Distribute all selected objects vertically. Changed ICON TODO
	Drag into the diagram to add a stream, or click to open the list of streams in the repository
	Save TODO
	Refresh TODO
	Help TODO