【正文】 nd so on. And with a click of a button, to draganddrop the sensor that appears on screen to the database icon to start logging historical values. All without needing to manually configure a fieldbus port on the puter, a fieldbus address for the sensor, a conversion formula to scale raw values to real temperature values, alarm settings, scan rates, creating a file for calibration history, and repeating all these configuration steps for each system that will connect to the sensor (think HMI, SCADA, maintenance server, operator PDA, assetmanagement system, etc). Moreover, multiply by 10,000 sensors found in a factory and the magnitude of the configuration effort bees overwhelming. And the same applies to any motor, actuator, or controller that is connected to the factory network.III. TECHNOLOGICAL TRENDSA. XMLIn this information age, we take it for granted that Unix servers, Windows PCs and Laptops, PDAs, mobile phones, vending machines, electronic door locks, and even street lights can interact in the blink of an eye. Much of this has to do with the Internet and a vast number of wireless networks available anywhere and everywhere. However, much of the success in being able to connect such different devices depends on how information is formulated. Enter XML.XML, which stands for eXtensible Markup Language, has in the last ten years bee the lingua franca of municating devices [1]. Combine XMLspeaking puters with the Internet and you get Web Services, a group of technologies that allow devices to speak to other devices much in the same way that people find friends online and start chatting instantaneously.B. Web ServicesWeb Services is a software paradigm that allows organizing functional units (a sensor, a motor, a controller) as independent software entities that:l Can be easily invoked using XML messages (. send a “Turn On” XML message to a motor over the network).l Can be discovered and monitored online (. find all connected sensors of type ViscositySensor and check their status)l Automatically describe themselves (. service Sensor3295 describes itself as a pressure sensor with specific max/min limits, an alarm limit for excessive pressure detected, units of measurement, last calibration date, and location in the factory)l Provide notifications to other Web Services on noteworthy conditions (. alarm, maintenance needed, process pleted)l Can be accessed over any IPbased network (. Ethernet LAN, WiFi WLAN, Bluetooth, GPRS, modem, etc.)Thus, each sensor, motor, actuator, controller will be seen as a Web Service by the rest of the factory as soon as they are connected. Each Web Service can be easily filtered by type and scope (location) and readily used and integrated into a larger system.Web Services technology is defined by a large set of posable standards. Each standard contemplates a single functional aspect, and can be bined with others toenable a plex Web Services application. For example, the SOAP standard defines the main syntax and structure of Web Services messages in XML. The WSAddressing standard defines header elements to describe the content of messages. The WSDiscovery standard defines particular messages, using SOAP and WSAddressing, for discovering Web Services that are online.The core set of standards which can be used in factory automation applications is defined by the Devices Profile for Web Services [2]. This profile defines a set ofspecifications which can provide the core functionality of any automation device. The standards are listed in Table 1.TABLE ISPECIFICATIONS IN THE DEVICES PROFILE FOR WEB SERVICESSpecificationPurposeSOAPCore XML message structure: Envelope, Header and Body.WSDLUsed to define applicationspecific message structures and request/response interactions.WSAddressingProvides unique identification for each message and for each Web Service.WSDiscoverySearches and discovers Web Services existing in the factory network.WSEventingGenerates and distributes event messages (alarms, changes in values, process pletion, etc).WSMetadataExchange service descriptions (. parameters for aExchangesensor such as max/min values, units, alarm limits, etc).WSPolicyDescription of service requirements and capabilities.WSSecurityEnhancements for protecting message integrity and confidentiality.C. Semantic Web ServicesCurrent Web Services implementations still present some manual (re)configuration challenges to overe. Service advertisements, which are used to publish, discover and select services, contain semantic content that can only be interpreted by human programmers. As a consequence, humans are still needed to integrate and write the glue code for every application. If the system ponents are to be reused in a new configuration, then the integration logic must be rewritten.A potential solution to this challenge is to enrich the service descriptions with machineinterpretable semantics using Semantic Web Services. Semanticallyrichdescriptions allow using machine reasoning to perform automatic matchmaking of required and offered services using logical inference, rather than performing hardcoded onetoone mappings. This type of matchmaking enables utilizing services that did not exist or were not known when the requestor side was programmed. Automatic matchmaking enables reconfiguring the system by dynamically selecting services without reprogramming the integration logic. The Description Logics (DL) formalism has been developed in order to represent knowledge as ontologies by describing concepts and their semantic relationships. Thefundamental premise in DL is “to represent the knowledge of an application domain (the “world”) by first defining the relevant concepts of the domain (its terminology), and then using these concepts to specify properties of objects and individuals occurring in the domain (the world description)” [3]. DL has a strong foundation on formal