The shapefile format is a digital vector storage format for storing geometric location and associated attribute information. The shapefile format was introduced with Arc View GIS version 2 in the early 1990s. The shapefile format is supported by a wide range of software systems.
The term shapefile is quite common, but is misleading since the format consists of a collection of files with a common file name prefix, stored in the same directory. The three mandatory files have filename extensions .shp, .shx, and .dbf. The actual shapefile relates specifically to the .shp file, but alone is incomplete for distribution as the other supporting files are required.
When validating if a set of given files represent a shapefile the Application Server checks following rules
•The file stem (the name of the file without the extension) must be the same for all files.
•All mandatory files must be present
o.shp — shape format; the feature geometry itself
o.shx — shape index format; a positional index of the feature geometry to allow seeking forwards and backwards quickly
o.dbf — attribute format; columnar attributes for each shape, in dBase IV format
•Additionally to the mandatory files only files with following extensions are allowed (optional files). Note that the Application Server does not make use of the information stored in these files.
o.prj — projection format; the coordinate system and projection information, a plain text file describing the projection using well-known text format
o.sbn and .sbx — a spatial index of the features
o.fbn and .fbx — a spatial index of the features that are read-only
o.ain and .aih — an attribute index of the active fields in a table
o.ixs — a geocoding index for read-write datasets
o.mxs — a geocoding index for read-write datasets (ODB format)
o.atx — an attribute index for the .dbf file in the form of shapefile.columnname.atx (ArcGIS 8 and later)
o.shp.xml — geospatial metadata in XML format, such as ISO 19115 or other XML schema
o.cpg — used to specify the code page (only for .dbf) for identifying the character encoding to be used
o.qix — an alternative quadtree spatial index used by MapServer and GDAL/OGR software
