Abstract
This chapter presents the development and design of an industrial application based on new technologies and explores the technological dimension of data acquisition, storing, access, and use; the data structure and integration and aggregating values from data necessary for the control of production processes. The demo application presented here was designed according to the Enterprise-Control System Integration Standard (ISA-95) with the goal of maintaining a standard that defines the interface between control functions and other enterprise management and business functions. The component-based object-oriented development concept was implemented in order to utilize advantages provided by creating a complete plant equipment model. The value of semantics was rediscovered in applications, which communicate among their system modules on Simple Object Access Protocol (SOAP), the standard defined by W3C, whose initiative has provided standard semantics markup languages based on XML as well. The data format and the format of standard XML messages that are used in industrial applications are defined by Business To Manufacturing Markup Language (B2MML) as W3C XML Schema for implementation of ISA-95, while offering the framework for project integration, the separation of business processes from manufacturing processes and focusing on functions instead of systems, organizations or individuals themselves.
TopBackground: The Technology Which Is Here For Us To Be Used
XML Documents and Their Components
XML is the technology available here for us for sharing information easily based on a format of documents designed for reading over the Internet. XML is made for everybody and to be used by everybody and for almost anything by being easy to understand, easy to use, and easy to implement (Ortiz, 2002). This is one of the many reasons why it has become the universal standard and has faced and met the challenges of convincing us - the development and user community.
When the creators of XML were working out their design, their goals set for an XML document, among others factors, were defined by directions as to how XML is to be used:
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XML documents shall be easy to create, legible to read and reasonably clear, it should be easy to write programs that process XML documents,
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XML design should be prepared quickly, it should also be formal and concise,
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XML shall be straightforwardly usable over the Internet,
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XML shall support a variety of applications.
As referred to sources (Ortiz, 2002), XML offers a simple solution to a complex problem, a standard format for structuring data or information in a self-defined document format. This way, the data can be independent of the processes that will consume the data. But this concept behind XML is not new. It is a subset of a huge amount of specifications and conditions declared and developed by the World Wide Web Consortium (W3C) in 1986. The W3C began to develop the standard for XML in 1996. Since then, many software vendors have implemented various features of XML technologies.
An XML document contains a variety of constructs, also referred to as elements. Some of the frequently used ones include:
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Declaration:Each XML document can have the optional entry <?xml version=“1.0”?>. This standard entry is used to identify the document as an XML document conforming to the W3C recommendation for version 1.0.
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Comment: An XML document can contain HTML-style comments such as <!--Equipment data -->.
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Schema or Document Type Definition (DTD): In certain situations, a schema or DTD might precede the XML document. A schema or DTD contains the rules about the elements of the document. For example, we can specify a rule like “An equipment element must have EquipmentName, but AliasName is optional.” .NET uses these schemas exclusively.
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Elements: An XML document is mostly comprised of elements. An element has a start-tag and an end-tag, for example Equipment Requirement. In between the start-tag and end-tag, we include the content of the element. An element might contain a piece of data, or it might contain other elements, such as EQUIPMENT. For example:
<Equipment Requirement>
<Property List/>
<Segment Requirement>
<EQUIPMENT>
<Property List/>
</EQUIPMENT>
</Segment Requirement>
</Equipment Requirement>
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Root element: In an XML document, one single main element must contain all other elements inside it. This specific element is often called the root element.
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Attributes: Since an element can contain other elements or data or both, an element can also contain zero or more so-called attributes. An attribute is just an additional way to attach a piece of data to an element. An attribute is always placed inside the start-tag of an element, and we specify its value using the “name=value” pair protocol. For example: <RollMill_Diameter ID=”3501” EquipmentName=”RM_Diameter” Alias=”RM_Diameter” Description=”Roll Diameter” />
There is a more complete list of XML’s constructs at www.w3c.org/xml.
In an XML document, the data are stored in a hierarchical structure. This hierarchy is also referred to as a data structures tree. That suits very well to the purpose of using it by system clients in our system architectures (Babiuch, 2007).
Key Terms in this Chapter
XML Document: A textual representation of hierarchical data structures. XML documents are case sensitive. XML schema specifies the XML structure of the document made up of XML elements.
Supervisory Control (SC): Control where one or more human operators are continually programming and receiving information from a computer that interconnects through sensors to the controlled process or task environment.
Xpath: A query language for XML documents. Search results in these documents are returned as a list of items.
Manufacturing Execution System (MES): A system that companies use to measure and control critical performance and production activities.
Application Server (AS): Executes applications for end users and controls networking, is usually between a database and a client application presenting data, application logics, controls data saving into a database and provides data to client applications.
Data Acquisition (DA): The detection and collection of data from processes and systems external to the computer system.
Graphical User Interface (GUI): The display presentation of some GUI controls based on runtime information, for example, to change the style of data presented when entered into a software and data format changes independent from the required database data type.
Application Programming Interface (API): A set of declarations of the functions (or procedures) that an operating system, library or service provides to support requests made by computer programs.
Business Logic (BL): A term generally used to describe the functional algorithms, which handle information exchange between a database and a user interface. It is distinguished from input/output data validation and product logic.
Component: In object-oriented programming and distributed-object technology, a component is a re-usable program building block that can be combined with other components in the same or other computers in a distributed network to form an application. Components can be deployed on different servers within a network and can communicate with each other to perform services. Examples include a single button in a graphical user interface, a small interest calculator and an interface to a database. [Garbrecht, S. D., 2006]
Service Oriented Architecture (SOA): The software architecture for production control and information management systems that uses software services independent of the underlying platform and programming language.