As with any endeavor, the more time you spend planning, the less trouble you will have creating a good product. There are three stages in planning a VTS application:
1. Review and understand the physical system for which you will be developing your application;
2. Design the software version of the physical system
3. Plan the operator interface.
Each stage has its own list of tasks. For example:
Review the physical system
The first step in planning any application is to review and understand the physical system for which you will be developing the monitoring and control application. This involves meeting with the client to review the system requirements, reviewing existing process and instrumentation diagrams for the system, familiarizing yourself with the equipment, and examining the how the equipment and processes interact.
Design the software version of the system
Once you have a clear understanding of the client's requirements, the equipment that makes up the system, and its operation, you can begin to list processes and gather data. This will include such things as:
• The communications chain (communications port and drivers)
• The types of process data being read or written (analog and digital)
• I/O address tables
• Scaling information for each device
• Alarm conditions
• Data logging
• Data storage
Plan the operator interface
The last stage in planning is to consider the layout of the operator interface, and develop some rules to assist you in maintaining a consistent layout between pages.
A useful tool to consider is the storyboard.
Web developers often use storyboards in the planning stages of web site development. You may find it useful to adopt this practice to help you in your application development. When we talk about a storyboard in VTS terms, it is an outline of the pages that will be included in your application, including a summary of the equipment or processes that will be displayed on each page.
When developing rules to assist you in keeping the elements of your application consistent, it is important to keep in mind the needs of the operators, as they will ultimately be the ones to use your application. It may help to switch your thought process from that of a developer to that of an operator. Remember that system operators are less likely to make mistakes if the finished application is easy to understand and efficient to use.
Working through these 3 stages will be an iterative process; you will work through a stage several times before moving on to the next stage. You will likely find that you need to go back to review earlier stages as you work through later ones.
The tutorial, starting on page X, provides an example of how to work through all three stages of application design.