B. Code snippets information
Apart from the hardware information, the knowledge
database needs to store code snippets that will describe the
behavior of each part found in the input data set. The code
snippets must be written in a language that is supported by
all manufacturers, and can be simply copied in a logic editing
program like Siemens STEP 7. The programming language
that’s most suited for the task is Structured Text. A key fact
that needs to be taken into account is that the syntax for ST
used by different manufacturers is not the same, so a
different snippet needs to be written for each PLC family.
The code snippet provides information for Step1, Step2,
Step4 and Step5 of the SCADA generation algorithm. Taking
into account the information needed in the steps mentioned
before we can deduce that we need to extract from the code
snippet information about the tags used within, and
considering that these tags need to be consistent throughout
all the snippets written for various PLC families it would be
easier to define them when creating the first code snippet. All
the tags have generic names, which are used in the code
snippet itself, in the final program these names are replaced
with generated ones to avoid naming conflicts that can occur
if multiple instances of the same part are used