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This page is for data modellers or application designers. It explains how to use a relationship diagram to understand how your system's data is connected.

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.

Overview

Use a relationship diagram to represent the information that your application will use and how it is connected. If you want to show a process, use a workflow diagram.

PhixFlow's relationship diagrams are simplified entity-relationship diagrams (ERD).  An ERD is commonly used to show the relationships between database tables. If you are not familiar with ERDs for databases, the concepts are explained in this article: ER Diagram Tutorial in DBMS.  


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Key concepts
Entity-Relationship DiagramPhixFlow Relationship DiagramExamples
A database table represents a thing or entity.

A stream represents a thing or entity.

Tip

Choose a stream name that reflects the entity it represents.


Entities:

  • Company
  • Employee
  • Department
  • Product
The column headers of a database table are the data attributes.

The stream attributes are the data attributes.

Employee attributes:

  • EmployeeID 
  • Name
  • Address
  • Phone
  • Department

A stream must include one unique attribute. This is usually an identifier, so has ID or UID in the name. The unique attribute is the primary key.

Primary Keys

  • Employee stream: EmployeeID
  • Department stream: DepartmentID
When the data from one stream's primary key also appears in a different stream, it is a foreign key.

Employee attributes:

  • EmployeeID (primary key)
  • Name
  • Address
  • Phone
  • Department = DepartmentID - foreign key

Department attributes

  • DepartmentID - primary key
  • Department Name
  • Purpose
  • Team members =  list of EmployeeID's = foreign key
Tables or attributes can have various relationships to each other

Attributes can have relationships, expressed as an action (verb) that follows the left-right flow of the diagram.

Relationships can be:

  • 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
Tip

Choose a relationship name that reflects the relationship


Relationships

  • one company → employs → many employee
  • one employee → works in → one department
  • one department → makes → many products


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.

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.

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


Relationship Diagrams and Relational Views

TODO - Add how ERDs and Relational vies interact.

Drawing Relationship Diagrams

Create a Relationship Diagram

  1. In the repository for your application, right-click on 
    Insert excerpt
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    .
  2. Click 
    Insert excerpt
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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.
Tip

When you make any changes to the diagram, remember to 

Insert excerpt
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Open a Relationship Diagram

To open an existing relationship diagram:

  • either, in the repository, right-click on its name and select Display.
  • or, in the properties toolbar, click the .
    Insert excerpt
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     icon.

Create a New Stream

  1. Drag the 
    Insert excerpt
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     icon from the toolbar into the diagram.
  2. In the pop-up, enter its name, for example "Customer" and click
    Insert excerpt
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    . PhixFlow opens a new Stream properties tab.
  3. PhixFlow adds a box to represent the data stream, and opens the properties tab for it.In
  4. To add attributes to the stream
    • either, in the properties tab on the right, In the Attributes section, click 
      Insert excerpt
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      .
    PhixFlow opens a properties
    • or right-click the stream and select Add New Stream Attribute.
  5. PhixFlow opens a Stream Attributes 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. PhixFlow adds the stream with a list of all of its attributes.
  3. If the stream has many attributes, click  to collapse the stream so that it only shows the primary and foreign keys.

Connect Attributes

ClickTo connect attributes in different streams, 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.

Tip

You can change which attributes are the Primary Key or a Foreign Key  using the tick boxes in the the Stream Attributes properties. TODO ADD the new properties to attributes)

PhixFlow automatically sets the 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

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Basic Settings

FieldDescription
NameEnter the name for the entity-relationship diagram. When yo press Return or save a new properties tab, PhixFlow opens an empty diagram in the workspace on the left.

Drawing Entity-Relationship Diagrams

To create an ERD, in the application repository, right-click ERD and select  Insert excerpt_add_addnopaneltrue. PhixFlow opens the properties for diagram, where you can add the name and a description for it. When you press Return or save a new properties tab, PhixFlow opens an empty diagram in the workspace on the left.

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.

  • from the toolbar, drag the stream icon (TODO add) into the diagram.
    • Enter a name for the new stream and click Insert excerpt_dialog_finish_dialog_finishnopaneltrue. PhixFlow opens a new Stream properties tab.
    To add attributes to an entity/stream:
    either, in the stream properties → Attributes section toolbar, click  Insert excerpt_add_addnopaneltrueor, right-click the stream and select Add New Stream Attribute.
  • 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

    TODO Same as Model Window Toolbar Icons

    Organise selected objects in a grid.

    Align all selected objects left.

    Align all selected objects right.

    Align all selected objects to top.

    Align all selected objects to bottom.

    Distribute all selected objects horizontally. Changed ICON TODO

    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