Several of the windows in TOPCAT allow you to interface with so-called Data Access Layer services provided within the Virtual Observatory (VO). The buzzwords are not important, but the basic idea is that this allows you to locate a service providing data which may be of interest to you, and then query that service to obtain the data. The VO is not a single monolithic entity, but a set of protocols which allow a general purpose tool such as TOPCAT to talk to services made available by many different participating data providers in a uniform way, without having to have prior knowledge of what services are out there or the details of how their data is arranged.
The basic operation is similar for all of TOPCAT's access to these services:
These ideas are explained in more detail in the following subsections. The windows from which this is done are documented in Appendix A.9.
Note: For information on SAMP or PLASTIC, which are protocols developed within the Virtual Observatory context, but are not necessarily concerned with remote data access, see Section 9.