Sub-Lists Keyword

Sub-lists= sublist1,sublist2...sublistn

This keyword is not available in LISTSERV Lite.

This keyword makes it possible to define a "super-list" (the opposite of sub-list), that is, a "container" list that includes all the subscribers of a predefined set of sub-lists. This can be done recursively to any depth. For security reasons, only the administrator can create a super-list. Concretely, the "Sub-lists=" keyword is protected from owner tampering in the same fashion as "Notebook=". The value is a comma-separated list of all the sub-lists, which must all be on the same (local) machine. For instance:

• Sub-lists= MYLIST-L,MYOTHERLIST-L

The default value for this keyword is null, which is to have no sub-lists.

The only difference between a normal list and a super-list is what happens when you post to it. With the super-list, the membership of all the sub-lists is added (recursively), and duplicates are suppressed. Other than that, the super-list is a normal list with its own archives, access control, etc. You can even subscribe to it, and this is actually an important aspect of the operation of super-lists. If you are subscribed to the super-list itself, the subscription options used to deliver super-messages to you are taken from your subscription to the super-list, just like with any other list. All combinations are allowed, and in particular NOMAIL is allowed, meaning you don't want to get messages that are posted to the super-list. When you are subscribed to multiple sub-lists, on the other hand, things work differently:

• NOMAIL subscriptions are ignored. You will get the super-message if you have an active (not NOMAIL) subscription to at least one sub-list. The idea is that the super-message must be equivalent to posting to all the sub-lists, without the duplicates. Since all it takes to get a message posted to all the sub-lists is a single non-NOMAIL subscription, this is how the super-list works. The only way not to get the super-messages is to subscribe to the super-list directly and set yourself to NOMAIL.


• The DIGEST and INDEX options are ignored and internally converted to MAIL. The first reason is that, since in most cases the user will be on multiple sub-lists (otherwise you don't need a super-list in the first place), the only safe method to set subscription options for super-messages is by subscribing to the super-list so that there is no ambiguity. The second reason is that, in most cases, super-lists will be used for administrative messages rather than for large-volume discussions, so it is actually preferable to have the message sent directly. The third reason is that the super-list and sub-lists may not necessarily offer the same options (DIGEST and INDEX). In particular, it is expected that many super-lists will not have archives. If you want a DIGEST or INDEX for the super-messages, you must subscribe to the super-list directly.

Topics, if defined, are evaluated on a per-list basis. That is, for every sub-list (and for the super-list), LISTSERV determines whether the topic of the message is one that you want to see. If not, it acts as if you were not subscribed to this particular list. Roughly speaking, this works very well if all the sub-lists have the same set of topics (or a well-defined set of common topics), and doesn't work well at all if every list has its own set of topics.