A logical collection is used when a set of data items form a composite data structure. An example of this is the association between a data buffer and a byte count of the data. The collection establishes the link between the count and the buffer
A named array is a logical collection contains an array of selector usages. For a given function the set of selectors used by similar devices may vary. The naming of fields is common practice when documenting hardware registers. To determine whether a device supports a particular function like Status, an application might have to query for several known Status selector usages before it could determine whether the device supported Status. The Named Array usages allows the Array field that contains the selectors to be named, thus the application only needs to query for the Status usage to determine that a device supports status information.
A physical collection is used for a set of data items that represent data points collected at one geometric point. This is useful for sensing devices which may need to associate sets of measured or sensed data with a single point. It does not indicate that a set of data values comes from one device, such as a keyboard. In the case of device which reports the position of multiple sensors, physical collections are used to show which data comes from each separate sensor.
Defines a logical collection that wraps all the fields in a report. A unique report ID will be contained in this collection. An application can easily determine whether a device supports a certain function. Note that any valid Report ID value can be declared for a Report collection.
Modifies the meaning of the usage attached to the encompassing collection. A usage typically defines a single operating mode for a control. The usage modifier allows the operating mode of a control to be extended. For instance, an LED is typically on or off. For particular states a device may want a generic method of blinking or choosing the color of a standard LED. Attaching the LED usage to a Usage Modifier collection will indicate to an application that the usage supports a new operating mode.
A Usage Switch is a logical collection that modifies the meaning of the usages that it contains. This collection type indicates to an application that the usages found in this collection must be special cased. For instance, rather than declaring a usage on the LED page for every possible function, an Indicator usage can be applied to a Usage Switch collection and the standard usages defined in that collection can now be identified as indicators for a function rather than the function itself. Note that this collection type is not used for the labeling Ordinal collections, a Logical collection type is used for that.
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A group of Main items that might be familiar to applications. It could also be used to identify item groups serving different purposes in a single device. Common examples are a keyboard or mouse. A keyboard with an integrated pointing device could be defined as two different application collections. Data reports are usually (but not necessarily) associated with application collections (at least one report ID per application).