Programming Internet Email

ACAP Datasets

Information in an ACAP server is held in a slash (/) separated hierarchical structure of entries. Each entry has attributes. Each attribute consists of some metadata that describes what it holds and who may modify it.

Each level of the hierarchy is called a dataset. Datasets are used to hold information that should be interpreted together, such as an address book or the configuration information for a particular application. Figure 12-2 shows the relationship between entries, attributes, and datasets. A dataset is just a special type of entry: an analogy that won’t hold up as we progress is that a dataset is like a directory on a filesystem and an entry is like a file.

A new dataset can be created by making an entry and placing a period (.) into its “subdataset” attribute. This is another way of saying that an entry is just an entry (with attributes), but if its “subdataset” attribute contains a period (.), then it becomes a dataset in its own right and can then hold other entries.

Each entry must have an attribute called (confusingly) entry. This attribute’s metadata names the entry and holds its access control list and other information. Each attribute has metadata (which are just name-value pairs) like this.

Figure 12-2. ACAP data hierarchy

Datasets are named in an interesting way. They have a long, hierarchical name but may also be accessed by “nicknames” to make searches ...