When creating an entity class, you must specify several entity class properties that define its structure.
In most scenarios, it's best to accept the default values for these properties. However, this section describes each feature class property to help you understand when and why you need to use non-default values, and how changing those values affects your data.
Creating an appropriate entity class for your data model depends on the entity class properties described below.
names and pseudonyms
When creating an entity class, provide a name that identifies the data that the entity class will store.
Resource class names must be unique within a database or geodatabase; You cannot have more than one entity class with the same name. It is not allowed to have two feature classes with the same name in the same geodatabase, even if they are in different feature datasets.
To ensure that a feature class name is unique, ArcGIS uses fully qualified feature class names to avoid possible duplicate names. A fully qualified entity class name can precede the name of the schema in which the entity class is stored, and it can also precede the name of the database in which the entity class is stored in the entity class name. If any of the Distinguished Name components is unique, the entity class name is considered unique.
The following image shows examples of the same entity class:hurricane_paths– built on different types of geodatabases. In all cases, the geodatabase is namedFlorida. For the enterprise geodatabase samples, the owner of the feature class is calledSAY.
The following table maps the numbers in the figure above to the appropriate data store type, description, and fully qualified resource class naming structure when stored in a database or geodatabase.
|Image number||type of data storage||Description|
Only the specified resource class or table name is used.
The structure for a fully qualified entity class name would be as follows[resource class name].
Mobile geodatabases are based on aSQLiteDatabase and contains a logical and physical database name. The physical database name consists of the file path, the user-supplied database name, and the file extension. Regardless of the physical database name specified when creating a mobile geodatabase,SQLitealways uses the name of the called reserved primary databaseDirectoras a logical name.
The structure for a fully qualified entity class name would be as follows[main].[resource class name].
Enterprise geodatabase in PostgreSQL
In some of the databases supported by ArcGIS, such aspostgresql, the database name or data source name is also part of the fully qualified name of the entity class.
The structure for a fully qualified entity class name would be as follows[database name].[schema name].[resource class name].
Enterprise geodatabase in SQL Server
In company databases and geodatabases such as e.goraclejServer-SQL, ArcGIS appends only the schema name in which the feature class is stored to the feature class name.
The structure for a fully qualified entity class name would be as follows[schema name].[resource class name].
Rules and restrictions for resource classes and table names
The following table lists the supported character rules for table names and resource classes:
|Character||beginning of the name||another place||with pseudonyms|
Underscore ( _ )
Symbols (except underscore)
Superscript letters and numbers
Letters and digits subscript
Additional rules and restrictions for resource classes and table names are as follows:
- Table and entity class names cannot contain reserved words such as select or add. Consult your database management system (DBMS) documentation for other reserved words.
- Entity classes or table names with the following prefixes are not supported:
- The length of the entity class and table names depends on the underlying database. To seeFile geodatabase name and size limits,Name and size limits for mobile geodatabases, ÖDatabase data and ArcGISfor more information on database-specific limitations.
verfield nameslearn more about itRename fieldsjRules and restrictions for field names.
When creating a table or resource class in a geodatabase, you can give it an alias. An alias is an alternative name. When you assign an alias to a feature class or table, this is the name users will see when they add it to the map. Users can search by resource class or table name by accessing theThoseinstructions continueCharacteristicsdialog box.
When you create a feature class or table in a geodatabase using geoprocessing tools, there are no parameters to specify the alias. However, you can define an alias for the resource table or class in theThoseleader ofCharacteristicsdialog box.
- Right-click the entity class or table in theCatalogCrystal.
- give clickCharacteristics.
- click noThoseEyelash.
- click noPseudonymproperty to enable name editing.
- Enter an alias and clickACCORDINGLYto define the alias for that resource class or table.
Types of Entity Classes
Vector features (spatial objects with vector geometry) are versatile and widely used geographic datasets that are useful for representing features with discrete boundaries, such as B. roads, states and parcels. A feature is an object that stores its geographic representation, which is usually a point, line, or polygon, as one of its properties (or fields) on the line. In ArcGIS, feature classes are homogeneous collections of features with a common spatial representation and set of attributes stored in a database table, such as For example, a line feature class to represent freeway centerlines.
When creating a feature class, you are prompted to set the feature type to specify the feature class type (point, multipoint, polyline, or multipatch).
Feature classes are typically thematic collections of points, lines, or polygons, but there are several types of feature classes. The first three support databases and geodatabases. The last four are only supported in geodatabases.
- Points: Features that are too small to be drawn as lines or polygons, and point locations (such as GPS observations).
- Lines: Represent the shape and location of geographic features, such as B. the center lines of streets and streams that are too narrow to be represented as areas. Lines are also used to represent features that have length but no area, such as B. Contour lines and borders.
- Polygons—A set of multifaceted area features that represent the shape and location of homogeneous feature types, e.g. B. States, counties, parcels, terrain types and land use zones.
- Annotation - Text on the map, including the properties of how the text is rendered. For example, in addition to the text string for each annotation, other properties are included, such as: B. the shape points for placing the text, its font and point size, and other display properties. The annotation can also be associated with entities and contain subclasses.
- Dimensions - A special type of annotation that displays specific lengths or distances, for example to indicate the length of a side of a building or the boundary of a lot or the distance between two features. Dimensions are commonly used in GIS design, engineering, and furnishing applications.
- Multipoint: Entities composed of more than one point. Multipoints are often used to manage very large sets of point collections, e.g. B. Lidar point clusters that can contain literally billions of points. Using a single line for such point geometry is impractical. Grouping into multipoint lines allows the geodatabase to handle large sets of points.
- Multipatch - A 3D geometry used to represent the outer surface or shell of features that occupy a discrete area or volume in three-dimensional space. Multipatches consist of flat 3D triangles and donuts used in combination to model a three-dimensional layer. You can use multipatches to render anything from simple objects like spheres and cubes to complex objects like isosurfaces and buildings.
- 3D Object: A 3D geometry specialized to represent additional shape supports, such as materials along the outer surface or coverage of features, occupying a discrete area or volume in three-dimensional space. You can use 3D objects to render materials with a high level of detail to support aesthetic aspects such as shine or roughness. You can use them for simple or advanced objects like spheres and cubes, and complex structures like isometric surfaces and building materials. 3D objects use advanced linked tables to store different components for materials. These tables are used in combination with 3D planar donuts and triangles to model a three-dimensional layer.
When creating a feature class, you can allow coordinates to contain measure (m) or z-values for three-dimensional data.
Whether you need m or z values depends on the type of data you are using.
Including m-values in your data allows attribute values to be stored in the vertex coordinates of the point. In linear referencing, m-values store measurements at vertices along a linear feature. This allows you to find a position along the line. If you use linear referencing or dynamic slicer applications with your data, your coordinates must contain m-values.
Z-values are used to represent elevation or some other attribute for a specific surface location. In a terrain or elevation model, the Z value represents elevation; In other types of surface models, it represents the density or quantity of a specific attribute, e.g. B. annual precipitation, population and other surface measurements. When modeling elevations, creating terrain, or working with 3D surfaces, your coordinates must include z-values.
When creating a feature class, you must choose, or possibly create, a coordinate system. The coordinate system forms together with the tolerance and resolution values aspatial referencean entity class. A spatial reference describes where resources are located in the real world.
You can define a coordinate system for your new feature class in a number of ways:
- Choose one of the predefined coordinate systems provided with ArcGIS. Find a geographic or projected coordinate system that adequately represents the area in your data model.
- Import coordinate system parameters used by another feature class. If you want to use another feature class's coordinate system as a template, you can browse and import it.
- Define a new custom coordinate system. You can enter values to create a coordinate system tailored to your needs.
If you specify z-values with your coordinates, you must also specify a vertical coordinate system. A vertical coordinate system georeferences z-values, which are most commonly used to indicate elevation. A vertical coordinate system includes a geodetic or vertical datum, a linear unit of measurement, an axis direction, and a vertical offset.
Measured values have no coordinate system.
If you don't have the coordinate system information for your data or you don't know which coordinate system to use, you can select an unknown coordinate system.
You can also edit the properties of an existing coordinate system by copying and modifying it.
Learn more about coordinate systems and projections
A spatial reference in the geodatabase also includes tolerance values, XY coordinates, Z coordinates, and M coordinates that are associated with tolerance values that reflect the accuracy of the coordinate data. The tolerance value is the minimum distance between the coordinates. If one coordinate is within the tolerance of another, they are interpreted as being in the same place. This value is used in relational and topological operations to determine whether two points are close enough to have the same coordinate value or far enough apart that each has its own coordinate value.
The default tolerance is set to 0.001 meters or the equivalent in map units. This is 10x the standard resolution value and is recommended in most cases. The minimum allowable tolerance value is twice the resolution value. Setting a higher tolerance value results in less accuracy of coordinate data, while setting a lower value results in higher accuracy.
Different tolerance values can produce different responses for relational and topological operations. For example, two geometries with the smallest tolerance can be classified as disjoint (no points in common), but a larger tolerance can cause them to be classified as in contact.
Tolerance properties can be defined inenvironmentsleader ofCreate resource classTool.
Domain Resolution and Extension
All coordinates in your feature class or feature dataset are georeferenced according to the selected coordinate system and snapped to a grid. This grid is defined by the resolution, which determines the precision (i.e. the number of significant digits) of its coordinate values. Resolution defines the fineness of a grid that covers the extent of its feature class or feature dataset. All coordinates fit into this grid, and the resolution defines the distance between individual grid lines.
Resolution values have the same units as the associated coordinate system. For example, if a spatial datum uses a projected coordinate system with units of meters, the resolution value is set to meters. Use a resolution value that is at least 10 times smaller than the tolerance value.
The default (and recommended) resolution value is 0.0001 meters (1/10 mm) or the equivalent in map units.
For example, if a feature class is stored in State Plane Feet, the default precision is 0.0003281 feet (0.003937 inches). When the coordinates are in latitude and longitude, the default resolution is 0.000000001 degrees.
In the case of unknown coordinate systems or m-values, set the appropriate resolution values for the data type without explicitly setting the unit of measurement.
Domain extension and resolution properties can be set inenvironmentsleader ofCreate resource classTool.
You can specify configuration keywords when creating a feature or table class to customize how data is stored. Configuration parameters are grouped under one or more configuration keywords, one of which is the default configuration keyword, which specifies the default storage parameters.
In most cases theBY DEFAULTKeyword must be used. In some cases, however, you may want to specify alternate configuration keywords when creating specific data sets or data types to maximize their performance or to tune some aspect of their storage in the database.
The following are examples of configuration keywords and their usage:
- BY DEFAULT– This keyword uses reasonable defaults and storage settings for most geodatabase applications.
- MAX_FILE_SIZE_256 TB: If you are importing a very large image into a geodatabase file, you can specify theMAX_FILE_SIZE_256 TBThe config keyword and the geodatabase allows the raster dataset to be up to 256 terabytes in size.
- TEXT_UTF16: If you copy a resource class that contains Chinese characters into a geodatabase file, you can specify itTEXT_UTF16Configuration keyword so that text characters in attribute columns are stored in UTF-16, which stores Chinese characters more efficiently.
Learn about geodatabase file configuration keywords
Learn more about enterprise geodatabase configuration keywords
Fields and field properties
When you create a feature class using the Create Feature Class Wizard orCreate resource classonly fields maintained by the geodatabase are added to the resource class. You can add your own fields to the resource class inFields visualization. In the field view, you can set certain properties for each field, e.g. B. the field type and the maximum data size that can be stored in the field.
All fields have properties like the following:
- Pseudonym: This is an alternate name for the feature class field. Unlike a field's actual name, an alias doesn't have to respect database restrictions and can contain spaces and special characters and start with a number. You can only specify field aliases for feature classes in geodatabases.
- allow zeros: This controls whether the field has a NOT NULL constraint when the field is created. If allow nulls is set to No, the field definition in the database contains the NOT NULL constraint. If you keep the default value of Yes, the field is NULLABLE.
The geodatabase template inserts an empty value (numeric =0, Text =" ") instead of a databaseNULLif and only if the field in the database has aNOT ZERORestriction.
- default value: You can enter a default value to autocomplete a new resource or object when it is created withArcGIS ProEditing tools Default field values can only be specified for feature classes in geodatabases.
- Long: This is a property of text fields that determines the maximum number of characters that can be entered.
All entity classes have a set of mandatory fields that are required to record the status of a specific object in the entity class. These mandatory fields are automatically created when creating a resource class and cannot be deleted. Required fields can also have required properties, e.g. B. Domain Ownership. You cannot change the required property of a required field.
Example: In a polygon feature classIDOBJETOjFORMare mandatory fields. They have properties that you can change, e.g. B. the geometry type, but these fields cannot be deleted.
When you create a line feature class in a geodatabase, an additional field is automatically added to the feature class to record the length of the line. When you create a polygon feature class, two additional fields are automatically added to record the length (perimeter) and area of each polygon feature. The units of measurement for these values depend on the spatial reference defined for the feature class. The names of these fields vary depending on the database and spatial type used. These are mandatory fields and cannot be changed.
Certain field names appear in ArcGIS with their full names for feature classes stored in a corporate geodatabase. For example, if you create or import a polygon feature class that contains a field namedAREA, the database, schema, and entity class name are appended. This is the name you see in the resource class attribute table. This means that for a polygon feature class namedARCHITECTSstored in itLEHRERscheme ofMUSEOdatabase, theAREAfield looks like this:
The following list contains all fully qualified field names in an enterprise geodatabase:
- LEGAL ENTITY
In such cases, consider using a different field name or field alias.
When creating a feature class, you have the option of importing fields from another feature class or table. This option allows you to use another feature class or table as a template for the field definitions of the ones you create. After importing the fields, you can edit the field names, their data type, and their properties.
Importing fields during feature class creation does not affect required fields. For example, if you are defining the geometry type property for the new feature class to store points, import the field definitions from a feature class that contains theFORMIf the Geometry Type property of the field is set to store polygons, the feature class geometry type will not be overridden.
By default, when you create a line or polygon feature class, a split model is automatically defined in the feature class. The split model is used to determine how the feature geometry and its attributes are split on schedule when a feature is split during the editing process.
The split model has the following two behaviors that can be set:
- Update/Insert(By default)
The forward slashes in the split template name represent an ordered list of operations performed on the entity within the entity class being split.Update/InsertThis is the default behavior of the shared template and most users will never need to change it. HeDelete/Paste/PasteThe partitioning model is appropriate when you have specific modeling needs, e.g. B. Adapting a specific format for interoperability and data conversion that need to identify a split as a removal of the original feature.
In addition to defining the splitting model in an entity class, you can also define the splitting policy in a relationship class. The relationship class split policy is used to determine how related records are handled in the target table when a feature in the source feature class is split during the editing process. Depending on the type of relationship class, simple or compound, different split policy behaviors can be defined, includingdefault (simple),default (composite)jDuplicate linked objects.
verRelationship Class Separation Policyfor more details on setting and using this relationship class property.
The splitting model in an entity class can be specified using either of the following two methods:
- Resource class properties: doThoseinstructions continueResource class propertiesdialog box, scroll down toSplit-Modell. Click the cell next toSplit-Modellallows a drop down menu. Selecting a shared model from the list completes theDefine the partitioning model for resource classesgeoprocessing tool and runs it in the background.
- Define the partitioning model for resource classesTool - Use thisDefine the partitioning model for resource classesGeoprocessing tool to change the split model for a feature class.
If the input resource class is from an enterprise geodatabase, you must own the data to run this tool.
One by defaultUpdate/Insertthe line of business model is defined in entity classes when it is created. Therefore, if a feature within that feature class is split during editing, the original feature will be updated to become the larger feature and the smaller feature will be inserted as a new row in the table.
The image below shows the before and after of a single cable.IDOBJETO2 is split within the cable resource class and the split model is set to the default value,Update/Insert. Before splitting, the first row is selected,IDOBJETO2, and the split edit tool will be used to split this selected item. After the division, look at the first row,IDOBJETO2, residues and their geometry andIDOBJETOthe attribute value has been updated. This shows thatIDOBJETO2 contains the largest characteristic after splitting and the smallest characteristic was inserted as a new row in the table with aIDOBJETOfrom 5. After the division,IDOBJETO2 yearsIDOBJETO5 have the same overall length as the original lengthIDOBJETO2 before the breakup.
Once the split model is defined asDelete/Paste/PasteFor a feature class, if a feature within that feature class is split during editing, the split operation will result in the deletion of the originally split feature, followed by the insertion of both parts of the split feature as new entities with two new ones lines on the table.
Any resource class with a shared model defined asDelete/Paste/Pastewill not open in versions older thanArcGIS Pro2,6 oArcGIS Enterprise10.8.1.
The image below shows the before and after of a single cable.IDOBJETO2 is divided within the cable resource class and where the division model has been setUpdate/Insert. Before the breakupDefine the partitioning model for resource classesRun the geoprocessing tool to modify the split modelDelete/Paste/Paste. The first row is selectedIDOBJETO2, and the split edit tool will be used to split this selected item. After the division, look at the first row,IDOBJETO2, has been removed and two newlines,IDOBJETO6 yearsIDOBJETO7, inserted. After the split, the two newly entered functions have the same total length as the length of the original function before the split.
When split model is setDelete/Paste/PasteIn an entity class that has been registered as versioned and the same entity is split into two forms in two versions, e.g. B. the standard version and the minor version, you will not see a conflict because the original entity has been deleted and two new entities have been inserted. Therefore, the child version ends up containing all the variations of the splitting function in voting. If heUpdate/InsertUsing the default split model and splitting the same resource into two versions in two ways would generate an update conflict alerting the user that something is wrong with the changes made.
Resource class properties
The split model for the feature class can be viewed in theThoseinstructions continueResource class propertiesdialog box, and then scroll down toSplit-Modell.
Comments on this topic?