The Sub-collections feature allows you to group together all documents in a collection for which a specified metadata value matches a given pattern. Within this section are two related views, chosen by clicking the appropriate tab on the tabbed pane. The Sub-collection Controls are discussed here, while the Sub-index Controls are relegated to the 'advanced topics' below.

To add a new sub-collection, first give it a name by typing into the name field. Next, choose what part of the documents must match in order to belong to this sub-collection. You can choose any metadata, or the name of the file in question. Next, enter a regular expression that will be used in the match. You can toggle between [I]ncluding documents that match the filter, or e[X]cluding them. Finally, you can specify flags to be set while matching. These may be any of the standard PERL regular expression flags, such as 'i' for case-insensitive matching; alternatively just leave this field blank. Once you have filled out these fields, click on the [A]dd New Sub-collection button to add the sub-collection to the list. This list contains the sub-collection commands exactly as they appear in the collection configuration file.

To remove a sub-collection, select it from the list of assigned sub-collections and click [R]emove Selected Sub-collection.

Once you have a sub-collection you can instruct Greenstone to build indexes specifically for that sub-collection, or for a group of sub-collections. To do this, click on the Sub-index Controls tab. The centre of the pane changes to show two lists, a field and four buttons. The upper list shows all currently assigned Sub-collections. Below it is a list of groupings for which you can build indexes. The field shows the current default sub-collection sub-index. Note that sub-indexes are not the same as indexes.

To assign a sub-index, select the desired sub-collection or sub-collections from the upper list, using multiple selection methods as necessary. Now click [A]dd Selected As New Sub-index, and a new grouping for the selected sub-collections will appear in the assigned sub-indexes.

Remove an existing sub-index group be first selecting it from the sub-index list, then clicking the [R]emove Selected Sub-index.

You can make a particular sub-index the default by selecting it from the list of sub-indexes, then click [S]et Default Sub-index. The grouping of the selected sub-index will appear in the default sub-index field.

To clear the default sub-index, click [C]lear Default Sub-index.