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Overview
of CORBA Services
Query
Service
• The
purpose of the Query Service is to allow users and objects to invoke queries on
collections of other objects. The queries are declarative statements with
predicates and include the ability to specify values of attributes; to invoke
arbitrary operations; and to invoke other Object Services.
• The
Query Service allows indexing; maps well to the query mechanisms used in
database systems and other systems that store and access large collections of
objects; and is based on existing standards for query, including SQL-92, OQL-93,
and OQL-93 Basic.
• The
Query Service provides an architecture for a nested and federated service that
can coordinate multiple,
nested query evaluators.
Licensing
Service
• The
Licensing Service provides a mechanism for producers to control the use of their
intellectual property. Producers can implement the Licensing Service according
to their own needs, and the needs of their customers, because the Licensing
Service does not impose it own business policies or practices.
• A
license in the Licensing Service has three types of attributes that allow
producers to apply controls flexibly: time; value mapping, and consumer. Time
allows licenses to have start/duration and expiration dates. Value mapping
allows producers to implement a licensing scheme according to units, allocation
(through concurrent use licensing), or consumption (for example, metering or
allowance of grace periods through "overflow
licenses.") Consumer attributes allow a license to be reserved or assigned
for specific entities; for example, a license could be assigned to a particular
machine. The Licensing Service allows producers to combine and derive from
license attributes.
• The
Licensing Service consists of a LicenseServiceManager interface and a
ProducerSpecificLicenseService interface: these interfaces do not impose
business policies upon implementors.
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