Sustainability of Digital Formats: Planning for Library of Congress Collections
Sustainability of Digital Formats: Planning for Library of Congress Collections |
|
|
|
| Introduction | Sustainability Factors | Content Categories | Format Descriptions | Contact | |
| Full name | dBASE Table for ESRI Shapefile (DBF) |
|---|---|
| Description | The dBASE table (.dbf) file is one of the three files required for a valid ESRI Shapefile. In addition to a file containing the dBASE table, instances of the ESRI Shapefile format must include a main file and an index file, and may include several others. The dBASE table file contains feature attributes with one record per feature. The one-to-one relationship between geometry and attributes is based on record number. Attribute records in the dBASE file must be in the same order as records in the main (.shp) file. The dBASE table (.dbf) file cannot exceed 2 GB, thus allowing approximately 70 million point features at most. |
| Relationship to other formats | |
| Component of | ESRI_shape, ESRI Shapefile |
| Subtype of | DBF, dBASE Table File (DBF). ESRI Shapefile (DBF) .dbf files are in dBase format |
| LC experience or existing holdings | See ESRI_shape. |
|---|---|
| LC preference | See ESRI_shape. |
| Disclosure | The Shapefile dataset format was developed by ESRI as an open GIS format, and uses as its table format for structured data a dBASE Table File (DBF) that is based on versions of dBASE format in use when the Shapefile was introduced. dBASE is a well-documented format. |
|---|---|
| Documentation | See DBF for general documentation for the dBase Table format. The Shapefile format, including the constraints on the dBASE Table File for use in a Shapefile, is defined in ESRI Shapefile Technical Description, July 1998. The description of the .dbf file is on page 25. |
| Adoption | See ESRI_shape. |
| Licensing and patents | See DBF. |
| Transparency | See DBF. |
| Self-documentation | See DBF. |
| External dependencies | |
| Technical protection considerations |
| GIS images and datasets | |
|---|---|
| Normal functionality | The functionality of the dBASE file format versions used for the ESRI Shapefile format is limited in terms of describing or performing calculations upon attributes. These limits include the format's inability to store null values, the maximum length of field names set at 10 characters, the maximum number of fields set to 255 (thus limiting support for Unicode), and the storage of floating point numbers as text (thus introducing possible rounding errors). There are other limits in play regarding the types and character widths of the data-field types that are supported. ESRI provided a complete and candid overview in its online help document titled "Geoprocessing Considerations for Shapefile Output." in 2009 (for ArcGIS Desktop 9.3). |
| Tag | Value | Note |
|---|---|---|
| Filename extension | dbf |
Database formatting for feature attributes based on earlier versions of dBASE (IV, V) |
| Internet Media Type | application/dbf application/dbase |
| General | |
|---|---|
| History |
|
|