1. Relationship Class What is a Relationship Class (3)
Geography, KHU,
Jinmu Choi
What is a Relationship Class (3)
Property of relationship class (8)
Name, Origin and destination tables, Keys, Cardinality, R_Type, Message, Labels, Attributes
Stacked Relationship and Rules (2)
Create and delete relationship class (2)
Relationship class in ArcCatalog (9)
Relationship class in ArcMap (3)
Relationship class vs. Join or Relate (2) Summary, Reviews and Next…
GIS Project

2. Physical Structure of GDB
Geodatabase
Feature datasets
Spatial Reference
Object classes, subtypes
Features classes, subtypes
Raster datasets
Rasters
Relationship classes
Geometric networks
TIN datasets
nodes, edges, faces
Planar topologies
Locators
Domains
Addresses, X.Y location
ZIP Codes, Place names
Validation rules
GIS Project

3. What is a relationship class?
Certain associations between objects in Geodatabase
In an electrical network, poles support transformers
In a parcel database, a parcel will have one or many owners
Relationships can exist between spatial and nonspatial objects
Relationships are stored in a relationship class
GIS Project

4. Anatomy of a Relationship
Once you have created a relationship between two tables, you can access data stored in one of the tables from the other
One obvious characteristic is the notion of cardinality
Cardinality describes how many objects of one type are related to the objects of another type
GIS Project

5. Relationship Properties
When you create a relationship class, you must define its properties
The properties tell ArcGIS exactly how the tables should relate to each other
Relationship properties
Name
Origin, destination tables
Relationship types
Labels
Message
Cardinality
Attributes
Keys
GIS Project

6. R-Property: Tables with Key
Primary table: origin table
Has primary key
Related table: destination table
Has foreign key
The key fields must store data of the same type
GIS Project

7. R-Property: Relationship Types
Two types of relationships
Simple and Composite
Simple relationships exist between two tables whose objects can exist independently of one another
Ex: if you delete a parcel record in the origin table, the related owner record in the destination table remains
Simple relationships can have any type of cardinality
In composite relationships, destination objects cannot exist without an origin object
Ex: electric transformers are mounted on a utility pole and, therefore, transformer features cannot exist without a pole feature
Composite relationships can have one-to-one or one-to-many cardinality
GIS Project

8. Relationship classes have forward and backward path labels
R-Property: Labels
Relationship classes have forward and backward path labels
The forward path label displays when you're navigating from the origin table to the destination table: a pole “support” a transformer
The backward path
label displays
when you're navigating
from the destination
to the origin table: “is mounted on”
GIS Project

9. R-Property: Messaging
No message with simple relationship
When related objects change, no messages are sent between the tables
EX: if you delete a parcel record in the origin table, the related owner record in the destination table remains
Only the value in the foreign key field is deleted, thus removing the owner's relationship with that parcel
Message with composite relationships
By default, composite relationship classes have forward messaging
If the origin object is deleted, rotated, or moved, related objects in the destination table are deleted, rotated, or moved with the origin object
GIS Project

10. R-Property: Cardinality
How records in two tables relate to one another
Each parcel is owned by only one person
One parcel is jointly owned by several people
Several parcels are owned by one person
Multiple parcels are jointly owned by multiple people
Four types of Cardinality
Cardinality is determined by the role that each table plays in the relationship
GIS Project

11. R-Property: Attribute
1-1, 1-M relationship classes may have attributes in a table
M-N relationship class requires a new table to store foreign keys to make the relationship
This table can also have other fields to store attribute describing the relationship itself
Ex: in a relationship between parcels and owners, an attribute of the relationship may be the percentage of ownership
GIS Project

12. Attributed Relationship
Attributed relationship can be specified during the creation of new relationship class
GIS Project

13. Stacked Relationship
To create a relationship between more than two tables, you can set up a stacked relationship
Table A is connected to table C through table B
To create a stacked relationship,
First, create a relationship class relating table A with table B
Then, create a second relationship class relating table B with table C
Example: Fire station – Personnel - Equipments
GIS Project

14. Relationship Rules After defining the properties, you can create rules
Which objects or subtypes from the origin table can be related to which objects or subtypes in the destination table
They can also be used to specify a valid cardinality range for related objects or subtypes
EX: wood poles may be able to support from 0 to 3 transformers, whereas steel poles may support 0 to 5 transformers
GIS Project

15. Create Relationship Relationship between two tables
is stored in a relationship class
Relationships persist for the life of the relationship class
Created in ArcCatalog
A relationship class can be created inside a feature dataset or at the root level of the geodatabase
Tables participating in the relationship class must be in the same geodatabase
GIS Project

16. Delete Relationship
Once you have created a relationship class, you cannot modify its properties
If you delete a feature class or nonspatial table that participates in a relationship class, then the relationship class is also deleted
Only two tables can be related in a single relationship class
GIS Project

17. Relationship class in ArcCatalog
Relationship classes can exist both inside feature datasets and at the root level of the geodatabase
To examine relationship, use Relationship tab in the Feature Class Property or Table Property
ArcCatalog contains
tools to create,
delete, and manage
relationship classes
GIS Project

18. Relationship class in ArcCatalog
For detain property, click Properties… button
GIS Project

19. Creating a simple Relationship
In ArcCatalog, right-click geodatabase
Point to New
Select Relationship Class
GIS Project

20. Creating a simple Relationship
GIS Project

21. Creating a Composite Relationship
Same steps with simple relationship class for name, origin and destination tables
GIS Project

22. GIS Project

23. Creating Attributed Relationship
Whether simple or composite, a relationship class can have attributes
GIS Project

24. Creating Relationship Rule
Right click the relationship class
Click Properties (Relationship Class Properties)
Click Rule tab
GIS Project

25. Managing Relationship Class
Renaming
Deleting
GIS Project

26. Relationship Class in ArcMap
Once the relationship between feature classes and tables are created, you can use the relationship in ArcMap
When you identity a feature, it will open all the related objects with the feature attributes
You can use related table’s attribute for labeling and symbolization
For editing, when you select a feature, you can edit the properties of its related objects
With ArcMap, you can add or delete a relationship in existing relationship class
GIS Project

27. Exploring related object of a feature
GIS Project

28. Exploring related object of an object
GIS Project

29. Rel.-classes vs. Join or Relate
Relationship classes
Stored with the data in a geodatabase
Allow greater interaction in editing among related objects
Allow to build behavior into the relationship
Deletion of one feature could delete related feature
Join or Relate
Performed without influencing the data in a geodatabase
Stored with the map document and are not geodatabase specific
Can establish relationships among data in different geodatabases or outside of the geodatabase
GIS Project

30. Using related Field in ArcMap
GIS Project

31. Summary Create and delete relationship class Stacked Relationship
Property of relationship class
Name, Origin and destination tables, Keys, Cardinality, R_Type, Message, Labels, Attributes
Relationship rules
Relationship class in ArcCatalog
Relationship class in ArcMap
Relationship class vs. Join or Relate
GIS Project

32. Next… Lab: Working with Relationships Geometry of Features
Read: Modeling our World Ch6
GIS Project