Path expression of hierarchical addressing for PLC program

Since other tool or software than compilers can be consumers of information described in PLC programs, it is important to provide proper method for accessing desired information in PLC programs. I have investigated an abstract data model with tree structure applicable to PLC programs compliant to IEC 61131-3. Functions to access desired information in them are also investigated. I have proposed a path expression ‘S-Path’ for hierarchical addressing and developed an implementation of it. It is found that the present S-Path is superior in simplicity and flexibility. It also means that S-Path is suitable for applying to PLC programs.