TRANSFER Programming Manual

Items
TRANSFER Objects
40970 Tandem Computers Incorporated 3–3
Items and Packages A package is a collection of data that one correspondent sends to another
correspondent. A person-to-person package can be interoffice mail. A process-to-
process package can be data and transaction codes needed to update a database.
Packages are made up of discrete collections of data known as items.
Items Each item includes an item descriptor, which is composed of one or more records that
describe the attributes and composition of the item. In addition, the item can include
one or more data records. Examples of items are shown in Figure 3-2.
Figure 3-2. Items
Item
0100101110100
0101101000101
Item
Memo to John
From Jim
In response to
your letter of
July 19, 1992...
Data
Text
005
Item Descriptor Item Descriptor
Each item contains data in the form of text, ASCII data, digital facsimile data, or some
other type of data defined by your application. Each item is identified by its own
unique item ID. Items can range in size from a few to many thousands of bytes and
can also contain other (component) items. External objects can be attached as part of an
item.
Any process representing the correspondent who created an item can add, delete,
examine, or change the contents of the item—until the item becomes part of a
submitted package. For example, a process can retrieve a data record from an item,
insert records into the item, and change the order of the records within the item.
Similarly, a process can modify components in any list of component items that is part
of the item. A process cannot, however, delete or change an item if the item is part of a
package that has already been sent.