Manufacturing
Execution System (MES) applications provide real-time visibility
and control of plant floor operations.
MESs occupy a special niche between those applications traditionally associated with
the factory floor:
 plant-floor automation
supervisory control and data acquisition systems (SCADA)
and those applications associated with the front office:
enterprise resource planning (ERP)
supply chain management (SCM).
customer relationship management (CRM).
MESs excel at batch-oriented manufacturing
operations (e.g. build-to-order, box-build assembly, printed
circuit board assembly, automotive assembly lines). They are not
well suited to continuous process environments (e.g.
petrochemical refineries).
MESs are used to tighten the integration of
factory-oriented shop-floor operations with customer-oriented
front-office applications. The intention is to automate the data
interchange between the two systems. It makes that interchange
more efficient and less error-prone. It can allow customers
direct access to shop-floor operations.
Traditional MESs have been relatively
unsophisticated client/server applications targeted at medium-
to large-sized manufacturers with mid- to high-volume
operations. The client application is typically MS/Windows
based. The MES server application usually requires a medium- to
large-scale Unix computing platform (Solaris, HPux).
Additionally, an MES installation requires an RDBMS (e.g.
Oracle, Informix, Sybase) system, also usually running on a
medium- to large-scale Unix system.
Obviously there is a significant amount of
infrastructure, both human and hardware, required to support
such applications. Obviously there is an associated cost. In
addition, the MES application itself isn't cheap: the customer
is billed for delivering, installing and configuring the MES
product itself, plus an additional per-seat charge
(meaning, the fee for a single client workstation for one
operator). There may be an additional charge to install a new
RDBMS, or at least to configure a new instance in an existing
one. The total cost is hefty enough that there can be a tiered
pricing structure with stepped discounts for large numbers of
clients. And there may be additional charges for customer
service, long-term maintenance and access to future upgrades and
patches. Not that this is unfair: MES suppliers are certainly
entitled to make a profit for their work, as long as there is
sufficient competition between suppliers to keep prices
"reasonable" in a particular market segment.
Recent wrinkles in MES technology are driven by
the ongoing shift of customer computing environments from
specialized MS/Windows client applications directly connected
with large database server applications, to simpler web-based
clients and a distributed server architecture. This trend
follows the general shift of customer applications from simple
client/server applications to the vastly more flexible
multi-tier Java Two / Enterprise Java Beans (J2EE/EJB) web-based
architectures with light browser-based clients.
This new architecture has several big advantages
over earlier client/server technologies. First, it scales nicely
for larger transaction loads and bigger page hit rates. Second,
it is more secure since it isolates the sensitive, big-ticket
database installations behind a controlled firewall. All
database activity is buffered from direct contact by
potentially-nasty client applications.
This new architecture also allows the
client-side use of a variety of new thin-client technologies to
interconnect with multiple database services via a set of
specialized mid-tier application services. There is new
opportunity to monitor or inject data in the specialized data
interchanges between the mid-tier servers. It opens new
possibilities to combine and manipulate data sources and
redirect data flows.
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