Image Processing Reference
In-Depth Information
TABLE .
Field, Automation, and Management Level
Field
Interact with environment
Obtain and adapt measurements;
switching, setting, positioning
Automation
Autonomous processes
Open-loop (logical interconnections)
and closed-loop control
Management
Supervise, plan, adjust
(global preferences)
Presentation, notification, logging;
configuration
Owing to these many degrees of freedom, the relevant part of the BA world standard [] also
refrains from specifying a particular system architecture. However, the division into field, automa-
tion and management levels remains useful, provided that it is understood as a purely functional
classification (instead of classes of device hardware).
∗
For this reason, the generic system architec-
ture of [] also remains aligned with it. The three-level functional classification is summarized in
Table ..
29.5 Open Standards
The field of building automation has been dominated by a plethora of proprietary solutions for a long
time.hismaybeduetothefactthatcustomsolutionsarepossibleatrelativelylowcost,giventhe
moderate performance requirements involved.
Gateways can certainly be used to gain access to and integrate all kinds of systems, including pro-
prietary ones. But even when all requirements are met at the time of construction, the long life cycle of
a building and its services must be considered. BAS have high life expectancy and need to be capable
of continued evolution. A rigid system that solely satisfies the demands identified at design time often
makes future extensions or tighter integration impossible. Only an open system can guarantee that
one does not find oneself tied to the contractor that originally installed the system when extension or
alteration is required. Unlike gateways, which need only expose data points defined at contract time,
open systems are indeed future proof.
Customers are recognizing that escaping vendor lock-in can significantly lower the total cost of
ownership. Moreover, open systems allow integrators to mix and match devices from different man-
ufacturers for increased performance and cost eiciency. his would not be feasible using gateways.
Thus, pushed by market demand for open systems, even market leaders are abandoning proprietary
designs. Still, this does not mean that gateways will fall from use any time soon. hey may still connect
subsystems using different open protocol standards best suited to a particular task.
Very different notions exist concerning the meaning of the word “open” in this context. For the
purposes of this discussion, the main criterion is whether a system can be repaired, modified, and
extended by everyone with the necessary basic qualifications without having to rely on the original
manufacturer. his requires that access to the specifications and implementation of the relevant inter-
faces and protocols is possible at reasonable and nondiscriminatory (RAND) conditions. Certain fees
may be involved, however.
The effort required to engineer a system that uses open standards can easily be higher than for a
proprietary system. his can especially be the case when the system is built from a
heterogeneous
mix
of components from different manufacturers, since specifications typically leave a certain degree of
freedom—resulting in additional parameters that have to be aligned to achieve interoperability and
provide the end user with a
homogeneous
system. herefore, the benefits of open systems are not free.
The reduction in life-cycle cost thanks to the flexibility gained, however, is generally considered to
offset the initial additional engineering (and, possibly, hardware) cost.
∗
∗This nontrivial relationship between functional and operational architecture is known from the OSI layer model.
