Functional Analysis

What is a Functional Analysis?

A functional analysis is a document that specifies, in some detail, WHAT an automation system is required to do (and not, in general, how it is to do it).  A perfect functional analysis would contain all the information necessary for a team of Engineering (or PLC logic) designers and programmers to produce an automation system which functioned as required.  Although that is rarely practical, a typical functional analysis should go a long way toward that goal.

There are many synonyms for "functional analysis" such as:  specification, functional specification, structured analysis, and functional description.

 

What are the benefits of doing a Functional Analysis?

The information specifying what the automation system is required to do must get to the Engineering (or PLC logic) designers and programmers somehow.  If a Functional Analysis is not produced, then they must get the information in a less structured, more informal fashion.  This carries with it the risk of problems such as:
 

• Slower than expected progress as designers/programmers wait for additional  information or change already completed designs and programs when the informal specification changes.
   
• The re-opening of a "firm" bid when the customer makes changes or additions to what the vendor thought was required.
   
• Difficult system startups involving many last-minute changes when the system does not function as desired. The expense of such a startup can be enormous, as the process being controlled can be crippled or down for extended periods of time.
   
• Long term problems for the customer with the system as new "bugs" are uncovered, and old ones are tolerated rather than suffering the the required downtime and expense to fix them.
   
• Poorly designed and documented systems that are difficult to troubleshoot and modify, because requirements (often verbal) from the customer got translated directly into code (or logic) with no intervening analysis or design steps.

IPACT firmly believes that the extra time, effort, and expense of producing a good Functional Analysis "up front" more than pays for itself by avoiding the problems listed above.  Good communication between customer and vendor, and between specifier and designer is critical to project success.  A good Functional Analysis provides the most solid, most explicit, and most detailed basis for that communication.

 Where does a Functional Analysis fit into a typical IPACT project bid cycle?
 

If the customer's Request for Quote (RFQ) contains sufficient information to support a fixed-price bid, IPACT will submit a bid, and production of the Functional Analysis will typically be included in IPACT's scope of supply.

Where less information is available up front, IPACT has for some customers done the project in two phases - a Functional Analysis first, to be followed by a fixed-price phase for the design and implementation of the project. The price of the second phase is determined by requirements documented in the Analysis.

IPACT has also produced Functional Analysis to support a customer's RFQ process, i.e. the completed Functional Analysis was used as part of the customer's subsequent RFQ.

 

What methods does IPACT use to produce a Functional Analysis?

Typically, IPACT uses what are termed structured methodologies for producing Functional Analyses.  These methodologies are used because they are more rigorous, less ambiguous, and easier to grasp than an English narrative description of system requirements.  Among the structured methodologies used by IPACT are:
 

• Yourdon Methodology.  This methodology is based on data flow diagrams (which depict data moving between processes and data stores in a hierarchical fashion), mini specs (which describe what each process does,) and a data dictionary (which describes the content of all the data flows and data stores.)  It is best applied to data intensive systems.

• Sequential Function Charts (SFCs - sometimes referred to as "Grafcet.")  This methodology is based on steps (which depict control actions) and transitions (which depict sequencing between steps.)  It is best applied to control or sequencing systems.

Systems which have both data intensive and control/sequencing intensive functions will use both of these methodologies in the Functional Analysis, or a hybrid method which is a combination of the two.

 

A Functional Analysis specifies "what" the system is to do, not "how" it is to do it.  Isn't the "how" important too?

Yes.  "How" the automation system accomplishes a given function is part of the System Design.  IPACT is also very competent at System Design, and uses another set of structured methodologies to produce them.  However, specifying "what" naturally needs to precede the specification of "how," so analysis comes before design.

This does not mean that our customers cannot specify some aspects of the System Design.  IPACT works with customers to produce systems that exceed their requirements not only in functionality, but also in design and implementation.

Integrated Process Automation & Control Technologies