An open system’s value is based upon its ability:
- to be created from a variety of products from a variety of vendors,
- to be installed by multiple integrators,
- to be maintained by competitive service providers, and
- to take advantage of the highest level of system integration.
Many people think interoperability pertains only to the installed devices; however, there's more to an open system than its devices. Open encompasses many layers of the system. The physical elements of an open system include:
- Users interfaces
- Enterprise connectivity
A bad open system forces users to install products from a single source. If they later want to change vendors, they'll need to replace some or all of the system with a new, competitive system. This adds significant cost to the facility and often reduces its efficiency and maintainability, thanks to the high cost of locked-in service contracts and the reluctance to replace older, proprietary systems.
How can each of these system elements be closed or locked in? If a vendor puts a barrier between something they offer and the ability of a competitor to interface to their offering, the system becomes locked-in or proprietary. An open system can be closed by any one of these offerings:
System devices such as controllers, sensors, and actuators should be able to interoperate and to be replaced by competitive products. If a product has a unique functionality, it should not force users to install another component that's not competitively available. Some vendors require their devices to be installed along with their proprietary gateway; this locks in the system.
Typical systems are based on networked devices that use a common protocol and common media type (such as twisted pair wire, power line, fiber optic cable, or radio frequency). To ensure an open system, each networked device should be able to be installed on a common specified media, and the protocol running on the devices should be fixed and standardized for the system. The infrastructure also includes the routers, network interfaces to computers, and bridges to other networks, like Ethernet. All of these should be specified based upon open standards—not based upon one vendor's specific product. Without careful specifying, any one of these can lock a system in to a single vendor.
Networks are installed, configured, and commissioned using software tools that typically run on a computer. Some vendors use these tools – some complex, others relatively simple – to configure their devices. If the tools used on the system cannot co-exist with anyone else’s tool, they’re likely locking-in the user to some degree. Device-configuration plug-ins were developed to solve this problem. These software-based configuration modules can be used by any standard, network management tool that follows the LonMark Interoperability Guidelines. This lets integrators configure vendors’ devices with an open tool; instead of forcing integrators to use only that vendor’s tool on the entire network.
Computer-based user interfaces come in two categories: Web-based tools and custom user interfaces. Web-based tools have become increasingly popular because they leverage the same level of openness that the Internet provides: Users launch a Web browser from any computer and, with password access, can interface with the system. User interfaces allow for control, monitoring, reporting, alarming, scheduling, and diagnostics. In some cases, vendors try to sell the extensive features of their user interface but allow only their user interface on the control network—thereby locking in the system. A good open system will let multiple tools from multiple manufacturers co-exist simultaneously on the same networked control system. The standards exist to ensure this.
Connecting a control system to an IT network provides visibility via a much wider audience. The LON-LAN-WAN concept ensures that the control system becomes an element of all of the data sources available to the enterprise. IT professionals are quickly learning that the control system offers access to information that executives need. To provide this connectivity, enterprise-level infrastructure devices are needed; and they must be specified as open. Open interfaces have been developed to ensure that data communications between the LON and LAN are accessible by any vendor. The LONMARK IP-852 standard was developed for this reason. By specifying IP-852 for LON-LAN routing, any user interface can access any device anywhere on the network—without custom gateways or drivers and without needing to be physically at the facility. Additionally, other standards have emerged to allow IT back-office computers to access information from the network to allow a control system to share information with typical enterprise systems that are Web Services-savvy.
To ensure an open system, be sure to specify that all five system elements are open. We highly recommend that each element is interoperable, and that training and servicing are also specified as open. This will help create as open a system as possible, yielding the best return on investment and the lowest lifecycle costs. Click here for more information on the LonMark Open Specification.