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: Check for info in these links

Overview

Use a relationship diagram to represent the information that your application will use and how it is connected.

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.

Key concepts
Entity-Relationship Diagram	PhixFlow Relationship Diagram	Examples
A database table represents a thing or entity.	A stream represents a thing or entity. 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 the following relationships primary key → one to one → primary key primary key → one to many → foreign key foreign key → many to many → foreign key 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

Relationships are usually expressed as an action (verb) that follows the left-right flow of the diagram. For example:

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

How to

In PhixFlow, you can create a relationship diagram

either by dragging in existing streams and then adding relationships
or, as you add streams to the diagram, you can create the streams and their attributes.

Example

In a relationship diagram, a stream and its attributes looks like this:

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.

The green

The relationship connects identifiers in each stream. A unique identifier in a stream is it's primary key. It uniquely identifies the row (data record) in the stream. In some cases a unique attribute from one stream is represented in another stream - this is a foreign key . It uniquely identifies a row in a different stream.

For example Person has attributes

Name
Address
Employer - this contains the unique identifier of the company and is therefore a foreign key.

Relationships can be

1-1: primary key to primary key
1-to-many: primary key to foreign key
many-to-1: foreign key to primary key
many-to-many: foreign key to foreign key.

PhixFlow imposes no restrictions on naming relationships, but the relationship name must be unique. We recommend that you use an action word that represents the relationship, avoiding "has" or "contains".

The components of a diagram:

Each stream is displayed as a box
The box also lists all the attributes
Primary keys and foreign keys are highlighted in green
Relationships connect stream attribute primary and foreign keys.
You can collapse a stream box to show only the attributes that are primary or foreign keys.

TODO Invoice example

Invoice has the totals information. has attributes: custID, total, date etc.
Parent object - there are many
And it shows the invoice lines e.g. call breakdown - these are not the data records for the invoice
Children with their own attributes: invoice id -
Relationship is btwn ID field invoice - and the invoice id
Receipt is an invoice - individual lines - info

In PhixFlow, you can create a relationship diagram

either by dragging in existing streams and then adding relationships

or, as you add streams to the diagram, you can create the streams and their attributes.

To show the process flow of data, use a workflow diagram

Other affected pages: repository, toolbars

Properties

For information about the properties toolbar, and about the sections Parent Details, Analysis Models, Description and Audit Summary, see Common Properties. We recommend you always add a Description that explains the purpose of the item you are creating.

For a full list of all the PhixFlow property tabs and windows, see Properties, Windows, Menus and Toolbars.

Basic Settings

Field	Description
Name	Enter 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 Add New. 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 . PhixFlow opens a new Stream properties tab.
To add attributes to an entity/stream:
either, in the stream properties → Attributes section toolbar, click Add New
or, 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.

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