Platform Independent Functional Specifications

Platform Independent Functional Specifications Francis Lovering, ControlDraw Ltd This presentation was first written in 1998 Little has changed since then! Topics: Real Batch Projects, real problems A Brief History of Specifications and System Life Cycles Contents of a Functional Requirements Spec ControlDraw Software

Real Automation Software Projects The Plant is nearing completion, the IO Cabinets are being cabled in and back at the software supplier's works someone suddenly realises that the project is late. (Worse still it happens on site) As testing begins, or a short time before, it becomes clear that there is no way they are going to finish on time. There are thousands of errors and things missing. The project goes into panic mode. At the suppliers People are working endless hours. They are battling against time, trying to obtain detailed information, testing software and finding faults, working their way through a huge list of comments and deviations. Eventually the software gets delivered, typically with some functionality removed, in to order accelerate completion.

What is the problem? It is not the Control Systems Modern Control Systems are wonderful , DCS or PLC/SCADA, they can all do everything that a Control engineer could hope, If they are programmed right! It need not take long to program them If you know what needs programming

Ask the Programmers Why are there so many errors? they only programmed what the spec said the spec was wrong. most ‘faults’ were ‘improvements’ or ‘changes’ Why it is taking so long? they spend most of their time looking for missing information Things got added Time is spent changing what they had already programmed

A Brief Instrument Engineers History We did not used to have ‘Life Cycles’ - We Wrote Specifications and drew schematics Panel Instruments Back of Panel Instruments Panels Logic Diagrams Loop diagrams Our Objects were Physical

We wrote Product Independent Specs Vendors sold 6*3 panel mounted instruments - all made similar functions PID, Indicate, Ratio etc We specified them , Got Quotes, Chose a Vendor We drew Loop diagrams Finally we put the model numbers on the Specs Along came DCS’s and PLCs. Technology ran ahead of our ability to specify, most especially in Batch.

Life Cycle Concepts Introduced to cater for complexity Borrowed from the IT industry In General, URS became high level without detail, produced by the ‘User’ FDS became the container for the Detail FDS became a supplier document and Product Specific - why?

GAMP Life Cycle Does this includes Phase Logic, Loops, Basic Control? Rarely includes the detail Not a strong dependency Not a strong dependency

Requirement or Functional ? Examples “The Reactor uses Cascaded temperature control” Is a Requirement - and does not depend on system! “On Step 3 open valve XV1245” As above

Functional Requirements Specification Term used by the FDA, Microsoft et al Includes full detail of all required functions Can still be system independent but might presume certain capabilities Need to be highly detailed Develop over the life of a project

Functional Requirements Content Words Modules Graphics Phase Logic Recipe Procedures Database Underpinned by Standards Control Modules Phase Logic Procedures Graphics System Database Words

Where does FRS fit in the Life Cycle Outline Function Requirements Detailed Functional Requirements Control Modules Phase Logic Procedures Graphics System Database

Requirements Analysis Identify Main Procedures Define Procedures Identify Operations Define Operations Identify Phases Define Phases Identify essential H&S Requirements Design appropriate Safety Systems Design Equipment Interlocks Implement Independent Safety Systems Piping & Instrument Diagrams Control & Operability Philosophy Process Description + Recipe Data Health & Safety Requirements Equipment Protection Requirements Identify Process Cells Define Process Cells Identify Units Define Units Identify Equipment Modules Define Equipt. Modules Identify Control Modules Identify Resources Define Resources Identify Control Modules Define Control Modules Order Here? Or Here?

Vendor Independent Graphics Look at a Graphic DeltaV, Wonderware, Fix - Can you tell? Some details may be different but the Functionality should be the same Graphics

Vendor Independent Control Loops Look at Control Loops Same functionality in any system Have hardly changed in decades Used to be SAMA, now IEC1131 Function charts Control Modules System Database

Vendor Independent Interlock Logic ISA Logic , IEC1131 Ladder Diagram etc Same functionality Control Modules

Vendor Independent Batch Procedures Different styles, same meaning S88 PFC represenation Fill with 1000 kg Water Manually add 50 kg Salt Heat with steam to 50  C Manually add 30 kg sugar Phase Logic Procedures

Advantages of Product Independence Competitiveness Can keep vendors competing longer Can get a more fixed price Avoids a scope battle with vendor Can get the Functional Details approved much earlier Can order the actual system later The Programmers like it too

Tools for Specifiers Standards - S88, S5.1, IEC61131 MS Office for Words, Spreadsheets, Databases Visio or alike for Diagrams Maybe CASE Tools - Doors, UML etc? Demo versions of HMI’s for Graphics ControlDraw The only one designed for the purpose

Platform Independent Functional Specifications

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Platform Independent Functional Specifications