Domain Constraints from CAD Data
Today’s obvious topic is domain CONSTRAINTS! My daughter’s domain constraints have to be a safe area in her home free from the perils of automobile traffic, harmful chemicals and other normally harmless everyday objects that when placed in the hands of a two year old become life threatening.
In ArcGIS attribute domain constraints limit the valid values in a column to a discrete set or a range of values. One can use a table to help set the domain constraints in ArcGIS for the valid values in a column.
Today’s suggestion is to use the ArcView FREQENCY geoprocessing tool on CAD properties to get a table that I can use as the basis for my ArcGIS domain constraints. This is common when loading new CAD data into an ArcGIS feature class. If I have lots of AutoCAD blocks with ATTRIBUTES or Microstation TAGS and want to find all the values used in the drawing for a particular attribute TAG I can use the FREQUENCY tool to build a table of all the unique occurrences of a particular value. The resulting table will be the unique occurrences and their frequency (c0unt). Even if the values are coded as symbolic variances like COLOR or LINESTYLE at least I will know how many different kinds of features or values I am dealing with in any given CAD dataset.
As a secondary benefit to running the FREQENCY tool I may find values that I consider to be invalid for that attribute domain. In this way the FREQUENCY tool is useful for many types of quality control tasks.