up249 Advanced GIS

ArcView File Structure

Project files (.apr) are created when you Save a project in ArcView. They manage the "look" of your project and keep track of where your windows are placed, what your GUI looks like, what tables have been added, what themes are in your view and how those themes look, and what layouts you have created.

Dbase files (.dbf) are entirely separate files which contain data in table format. These files include the attribute files you downloaded from MGI containing race, income, and other demographic data.

Shapefiles (.shp) are also entirely separate files which contain data in table format. However, the difference between a .shp and a .dbf is that the .shp has the "shape" field. This allows you to view boundaries in ArcView, such as census tract or state boundaries. All .shp files have a "twin" .dbf file. So if I have a theme of census tract boundaries called tracts.shp, I must also have a file called tracts.dbf. [Side note: When ArcView works with tables, it may create an "index" which allows it to analyze and manipulate the table more efficiently and quickly. These index files have the extension .shx or .aix. Just be aware that these files also exist.]

Therefore, when you save a project, you are simply saving information on how your project looks. The other files (.dbf, .shp, .shx) are not saved IN the project, they are simply REFERENCED by it. This is a critical point and please make sure you understand what it means. Please ask us to clarify it if you don't understand.

Side note: scripts are saved along with the .apr file. If you want to save a text copy of your script, you can. The function is called Write Script (there is a button for it on the Script GUI) and it will allow you to save a textfile (.ave) containing your script. It is only a textfile and can be opened in any word processing application (Word, Notepad). You can import .ave files into a script window (called a Script Editor) using the Load Script function (there is also a button for it on the Script GUI). In this way you can transfer scripts you have written to your friends or to other projects. [Note: when developing your custom application you can even embed your script into the project such that other users can not alter your script.]