### Introduction

DVO (the Desktop Virtual Observatory) is system for manipulating collections of images and measurements related to astronomical objects. The DVO system consists of several programs which insert data in the database system, or manipulate data in the database. One of these is the `DVO shell`, which provides a command-line driven, programmable user interface to the objects and measurements in the database. The DVO shell is based on the Opihi shell, which provides the tools to manipulate and display data in various representations. The DVO shell adds to this basic command set a collection of functions which provide direct access to the contents of the DVO database tables.