【導讀】化方法，讓僵化的證明系統(tǒng)屬性被核查和驗證。不過，現(xiàn)有的軟件已被優(yōu)化，改變，或移植到。新系統(tǒng).有需要找到從某一PLC程序開始的方法。因此，規(guī)范PLC程序是一個現(xiàn)。該文章概述了基于形式化的PLC程序基礎(chǔ)上從新啟動的方法。這項措施的重要中間步驟。這表明如何XML和相應(yīng)的技術(shù)可用于形式化和可視化。應(yīng)用PLC的目的是控制某一特定的或可選擇的過程，它是通過產(chǎn)生。的電控制信號回應(yīng)電器中相關(guān)的輸出信號來實現(xiàn)的。PLC控制有著極大的不同，方，特別是對安全性要求特別嚴格的地方。而重用的PLC守則正在建立，作為一種打擊復雜PLC程序的。連線控制設(shè)備，PLC日益受到重視，。的編程語言之前，正在制定為了個別PLC實用的專有編程語言。委員會，以確定一個基于格式accordingto的IEC61131-3的XML項目。新格式將緩解形式化的工具，使之成為PLC項目的所有相關(guān)的信息。它是專門設(shè)計用于支持從根本上使用不同形式的數(shù)據(jù)的系統(tǒng)之

　　

【正文】 OOA :L KF+20 LAENGE DES DATENPAKETS oooc :T DLO OOOD :L KF+O ZIELNUMMER O=MASTER OOOF :T DRO 0010 0011 : FANGEN WIEDER ERLAUBEN 0012 :S 0013 MOOl :NOP 0 0014 0015 :BE BAUSTEIN ENDE Fig. 1 A PLC program written in Siemens S5 Instruction List B. Conversion of a PLC Program inio a wellformed XML Given a PLC program in ASCII format and in a tabular structure with separate columns for addresses, labels, instructions, operands and descriptions delimited by whitespaces, XSLT can convert it into a wellformed XML document. The XML document obtained through this transformation is a hierarchically structured document. The XML document is structured in a hierarchy in which the root element is the IL Code Block representing the whole PLC code. Each of the rows of the PLC code is contained within a corresponding ILRow element which is M e r smtctured into child elements. Note: The structure chosen for the XML representation of ILCode is oriented at the working proposal of the PLCopen. C. XML Validation against the XML Schema The XML obtained as a result of the previous processing can be validated using a validating parser that confirms that the XML document in addition to being wellformed conforms to the set of syntactic rules defined in context of the PLC programming language. D. rdenhpcation of instructions This step in the process of visualization of PLC programs using XML ensures that the XML document to be used for visualization contains only valid can be used to transform the wellformed and valid Xh4L to another XML which as a result of identification on instructions has an additional attribute appended to the instruction tags. This attribute notifies whether the instruction is a valid instruction of the concerned instruction set. This transformation procedure is also capable of attaching attributes to the instruction tags that declares a classification of the instructions into predefined classes. The instruction identification of the transformed XML proofs the semantic of the XML in accordance with the operation types of the PLC programming language. In the example of this section, (cf. Fig. 2), the new XML contains additional attributes which classify the instructions according to the type of operation it represents. The STEPS instructions are categorized into eleven different types of operations . logical, jump, load or transfer operation assignment, etc. ?xml version= encOding=ISO88591 ? ILCodeBlock ILRow (Instruction instructionId=39。Logical Operation) U/Instruction /ILROW . ILRow Instruction instructionId=Jump Operation SPB/Instruction Instruction instructionId= special Operation BE/Instruction /ILROW /ILRow Fig. 2 A new transformed XML showing only the inslructions and the corresponding instruction ID E. Visualization of XML Both of the XML documents generated above can be transformed into HTML or other readable documents with the help of XSL. An ingenious XSL can be designed so as to produce an HTML which can convey the logical and other features of the PLC program in an easily conceivable form. Moreover, the DOM structure embedded in the XML， also enables the user to navigate through the PLC programs in an easy way. For the example the visualization is done in HTML. This visualization is done for the transformed XML after the validation of it39。s syntax as a table where the child elements of the ILRow are the columns of this table. The XML after the instruction identification is transformed using the XSL, where the instruction and the instruction Id, obtained after extracting the XML according to the type of operations are visualized in a table containing two columns (Instruction, Instruction Id) in HTML. The HTML structures suggested here are not the only possibilities, with which the XML can be visualized, but they give a very easy practical option for the user39。s grasp of the PLC code. VI. CONCLUSIONS AND OUTLOOK Reengineering of PLC programs needs a formal approach to be developed. In this paper one way to solve this task is introduced. Based on a given PLC program written in Instruction List a stepwise transformation to a formal representation is proposed. Since this process will not be fully automatic, the need for flexible visualization of intermediate steps is derived. XML is presented as a flexible, standardized means to serve as data format for the description of the PLC code. The corresponding technology of XSL transformations and the Document Object Model are presented as tools for the variety of customized visualization tasks during the reengineering process. Based on the XML description of PLC programs further transformations will be applied to finally derive a pletely formalized description of the original PLC code. This will be in the form of a finite automaton. During this process it is planned to identify mon IL structures and formalize them via a library. Gaining the Benefit of the XML Metadata Interchange (XMI) as an open industry standard that applies XML to abstract systems such as UML and referring to the classification of the instructions of IL into the eleven categories mentioned above. We can extract UML classes from this classification, as it resembles the action semantics of UML. VII. AKNOWLDGMENT We would like to express gratitude to the “StiAung RheinlandPfalz fir Innovation” for sponsoring our work under project number 616.