To make your CEC useful in the Virtual Observatory, you must register, in an IVOA-compliant resource registry, the CEC as a service.
The service registration states the service endpoint (the URL for access) and lists the applications that the CEC can run. For each registration, you submit a resource document (an XML file) stating the necessary metadata in a machine-readable format.
The CEC presents the possible registration documents at the "Manage Registration" side bar menu. The resource documents have to be registered manually with a registry, the method of doing this with an Astrogrid registry below.
It is not always possible or necessary to register all of the applications that your CEC is capable of running. If the CEC is mirroring an application that was originally published by another CEC (and consequently already registered), then it is not necessary to try to reregister that application. The "manage registrations" page indicates when a particular application is already present in the registry.
Most registries have a web-browser interface whereby you can submit resource documents manually. Typically, and especially in the AstroGrid implementation of the registry, you can upload the registration documents from files on disc or better in this instance via a URL (see below).
You can get a registration document using the "show registration document" link in the sidebar. Save this to disc and edit it as necessary. You need to be very careful not to "break" the structure of the document. Refer to the registration template in your configuration directory for advice on what to write.
The Astrogrid registry is capable of loading a registration document directly from a URL. This is probably the easiest way to register from the CEC as it is possible to use a web browsers "copy link" operation on one of the application registrations and then paste that URL to the registry upload page on the registry application.
If you want to cease service of an application, then you should update the list of managed applications in the service registration of your CEC. Do this by changing the configuration - see the manual-registration section, above - and repeating the registration of the CEC as described above. This states to the IVO that your own CEC no longer provides the application. It doesn't eliminate the registered description of the application; thus you can do this whether or not you originally registered the application and whether or not other services are offering the same application.
Unregistering an application removes it from the IVO resource-register causing the IVO to forget its details. You must do this if you control the application implementation - i.e. the HTTP service that the CECs call - and you are taking it out of service permanently.
To deregister an application, use the controls for the registry; you can't do this from the CEC's local controls. The exact technique varies between registry implementations, but typically you set the status attribute of the registration to "deleted".
If you want to withdraw your CEC from service permanently or for a lengthy period (but not just for short down-time), then you should deregister it. You do this by editing the service resource-document, changing the value of the status attribute on the Resource element to "deleted" and re-registering it, as described above, under the same identifier.