  The advent of large instantaneous bandwidth receivers and high spectral
resolution spectrometers on (sub-)millimeter telescopes has opened up the
possibilities for unbiased spectral surveys. Because of the large amount of
data they contain, any analysis of these surveys requires dedicated software
tools. Here we present an extension of the widely used CLASS software that we
developed to that purpose. This extension, named Weeds, allows for searches in
atomic and molecular lines databases (e.g. JPL or CDMS) that may be accessed
over the internet using a virtual observatory (VO) compliant protocol. The
package permits a quick navigation across a spectral survey to search for lines
of a given species. Weeds is also capable of modeling a spectrum, as often
needed for line identification. We expect that Weeds will be useful for
analyzing and interpreting the spectral surveys that will be done with the HIFI
instrument on board Herschel, but also observations carried-out with ground
based millimeter and sub-millimeter telescopes and interferometers, such as
IRAM-30m and Plateau de Bure, CARMA, SMA, eVLA, and ALMA.
