Geodatabase Relationships & Relationship Classes by q4tg9N


									Geodatabase Relationships &
Relationship Classes

           GIS 458
         Spring 2006
         Larry Clamp
Geodatabase Relationships
   Relationships are associations between
    geodatabase objects
   Can exist between spatial objects
       Features in feature classes
   Can exist between non-spatial objects
       Rows in tables
Major Types of Relationships
   Topological
       Built into data when networks or topologies are
   Spatial
       Operations that help determine locations
            Intersect, coincidence, overlap, inside of…
   General
       Explicitly defined to form a persistent tie between
       Our topic tonight
Relationship Classes
   Feature Classes: Spatial Objects
   Tables: Non-Spatial Objects
   Relationship Classes: Relationships
Relationship Classes
   Link objects between classes in GDB
       All combinations of tables & FCs supported
       RCs are persisted in GDB
       Joins & relates only in map document
   Have advanced capabilities
       Read-write access
       All cardinalities
       Simple or composite
       Relationship rules
       Referential integrity
       Versioning supported
Advanced Capabilities
   Read-write access
       Can edit attributes in related classes
   All cardinalities
       1-1, 1-many, many-many
       May have attributes
   Simple or composite
       Simple: peer-to-peer
       Composite: parent-to-child
   Relationship Rules
       Rules to refine cardinality based on subtypes
   Referential integrity
       Performs “cascade delete”
   Versioning supported
       Allows multiple users in ArcSDE environment
Table Relationships
   One is the “Origin”
   One is the “Destination” – the one linked to
   Key Fields
       Matching or linking fields in both tables
       May have different names
       Must be of same data type
   Origin Primary Key
       Key field in origin class
   Destination Foreign Key
       Key field in destination class
Relationship Class Properties
   Name
   Labels
   Type
   Cardinality
   Notification
   Origin/Destination Classes
   Key Fields
Names & Labels
   Relationship Class names must be
    unique in the GDB
   Relationships may be navigated either
       Each end need a label for navigation
       Labels must be unique only for
        relationship, not GDB
       Visible in ArcMap
       Should describe the nature of the
   Determines how referential integrity is enforced
   Simple
       “Peer-to-Peer”
       Related objects exist independently
   Composite
       “Parent-child”
       Existence of destination objects controlled by origin
            Delete origin (parent) and destination (child) ceases to exist
       Spatial effect
            Moving or rotating origin moves or rotates destination
            Feature linked annotation is an example
   Number of objects in origin that are related to a
    number of objects in destination
   One-to-one
       One origin object to one destination object
            A parcel can have only one legal description
       Also covers many-to-one
            One origin object still only matches one destination
   One-to-many
       One origin object can relate to many destination objects
            A parcel can have many buildings
   Many-to-many
       One origin object can relate to multiple destination objects
       One destination object can relate to many origin objects
       A property can have many owners and an owner can have
        many properties
   Requires an intermediate “key” table
       Associate key values between classes
       ArcGIS generates the fields
       User populates records
   May choose to store attributes about
    the relationship
       i.e. percentage of ownership
Relationship Messages
   Primarily used by programmers
   AKA “Notification”
   Related objects notify each other when they are
   Can control behavior of composite relationships
   Have no effect on simple relationships
   Choices:
       None: Cascade delete, no feature following
       Forward: Cascade delete, feature following, and annotation
       Backward: Cascade delete, no feature following
       Both: Cascade delete, feature following, and annotation
Relationship Rules
   Rules make cardinality more specific
       Set between subtypes
       Can make some relationships illegal
       Help maintain integrity in the geodatabase
Setting Rules
   In the properties of an existing
    relationship class
   Set between subtypes
   If one rule is set, then others must also
    be set
   No set rule = invalid relationship
Referential Integrity
   RI manages values of keys fields
   Choice of origin and destination is
       When you delete a record in origin, the RC
        finds related records in destination and
        sets value of key field to Null
       Incorrect choice may damage database
RI Examples
   Case 1: WRONG
       Parcel (origin) to Zoning (destination)
       Delete a parcel and the corresponding zone key
        field is set to Null
       Other parcels that have that zoning code no
        longer have a match
   Case 2: RIGHT
       Zoning (origin) to Parcel (destination)
       Delete a parcel and there is no effect on the
       Deleting a zoning code sets parcel key field to
        Null, which is how it should be
            It needs to be re-zoned
Creating Relationship Classes
   ArcCatalog context menu
       Specify name, participating classes, type,a
        nd other properties
   Geoprocessing framework
       ArcToolbox>Data Management Tools
        toolbox>Relationship Classes toolset
Relationship Classes in ArcMap
   Use them to:
       Query
       Analyze
       Edit
       Make Reports
   Can view properties of all related objects
   To label or symbolize using related records, a
    join is required
   Join based on relationship class

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