You will generally add a Log Source in the course of creating a Profile. A Log Source is Urchin's way of identifying the characteristics of an access log (sometimes called a transfer log), for one of your websites. Access logs contain all the Hits, or requests for web documents, that are made to your website. Some of the log file characteristics that are associated with a Log Source are the path to the log file, what type of log file it is (e.g. W3C or NCSA), and whether a filter should be applied to the log file when processing.
An important concept to understand is that Log Sources exist independently of Profiles. Every Profile must have at least one Log Source associated with it to obtain reporting. However, several Profiles could conceivably use the same Log Source. For example, you may want to create multiple Profiles using the same Log Source, but give each Profile a different filter to produce varying report results. So there is not necessarily a 1:1 ratio between Log Sources and Profiles.
How to Use Log Sources
To get started adding a Log Source to the system, log-in to the Urchin administrative system as an administrator and click on the Configuration button at left. Next, click the Log Manager button. To create a new Log Source, click the Add button at top-right. You will be taken to the Add Log Source Wizard. This is a simple series of steps designed to help you get the Log Source set up quickly and easily. Each screen in the Wizard has explicit help information.
When configuring a Log Source, be careful to specify the correct type, either W3C or NCSA. If you select the wrong type, Urchin will not be able to produce report data for any Profiles that use that Log Source. Generally speaking, logs produced on Windows computers will be in W3C format, whereas those produced on a UNIX machine will most often be in NCSA format, which is the type of log that the Apache webserver typically produces.