Geodatabase Concepts Flashcards
3 Reasons to Group Features in A Geodatabase
- If a set of objects and features have relationships
- Features that have topological associations
- If you need to concurrently edit a set of features
3 Reasons to Separate Features into Different Geodatabases
- If different departments have responsibility over different datasets.
- Commercial relationship databases must be served through separate geodatabases.
- Personal geodatabases have size limits that may require partitioning data.
Attribute Tasks
Assign default attributes
Set up attribute domains
Declare attribute update policies for splitting & merging
Attribute Indexes
Indexes on one or several attributes in a table to make query performance faster.
Spatial Indexes
ArcInfo automatically creates on feature classes. It determines and applies an optimum grid size for you.
To optimize, you can define up to three grid sizes for best retrieval of data.
Polyline Feature Type
Has one or more paths. A path is a connected collection of segments, each of which can be a line, circular arc, elliptical arc, or Bezier curve.
Polylines can have an optional z (elevation) or m (measurement) value.
Null geometry
A specific feature in a feature class can have null geometry to represent objects that are sometimes represented as explicit features and sometimes as implicit features within composite objects.
Scale
Defines how many integers correspond to a map unit. If the scale is 1,000, then the maximum precision is 1/1,000 of a map unit.
Types of Attributes
Continuous Numeric (Floats & Doubles)
Discrete Numeric Values (Shorts & Integers)
Coded Values (Shorts, Integers, Text)
Description (Text)
Time Values (Dates)
Object Identifiers
Multimedia (BLOBs - Videos, Images, or Sound)
Subtype
A special attribute that lets you assign distinct simple behavior for different classifications of your objects or features. All subtypes share the same set of attributes.
Attribute Domains
Constraints on attributes including ranges, coded value domains, and default values
Validation Rules
Control feature and attribute integrity.Types include attribute rules, connectivity rules, relationship rules.
Connectivity Rules
Edge-Junction Rule
Edge-Edge Rule
Default Junction Type
Edge-Junction Cardinality
Attribute Relationship Rules
Constrains the cardinality between an origin class and a destination class.
One-to-one
One-to-many
Many-to-one
Many-to-many
You can create specialized cardinalities, like a state must have two senators.
Splitting Feature Rules
Default value applied to both.
Duplicate of the original feature.
Geometry ratio - the proportional value of the split areas or lengths.
Merging Feature Rules
Default value
Sum values - two numeric attributes are summed.
Weighted average of the original features’ attributes.
3 Relationship Rules
Topological, Spatial, General
Topological Relationships
Geometric Network or Planar Topology
Spatial Relationships
Determined by ArcInfo through common spatial operations.
General Relationships
Explicitly defined relationship cardinality controlled in a relationship class.
Simple relationship - peer-to-peer
Composite relationship - one-to-many
Notifications
A relationship class can be used to transmit notifications on edits & deletions to related objects.
Annotation Class
A feature class that contains annotation.
Feature-linked annotation: will add & remove annotation with editing based on values in attributes.
Simple annotation: not linked to feature.
Envelope
A geometry that describes the spatial range of feature geometries.