HVAC Control in the New Millennium.pdf - HVAC.Amickracing

PC-based Control, Software and Bus Trendsimportance of software architecture and software reuse. Object-orientedmethods are used in day-to-day analysis, design, implementation, andmaintenance tasks.There is a major technology shift from waterfall-style developmentand structured methods to iterative development and object-orientedmethods. In waterfall-style development, the analysis, design, coding,unit-testing, software-integration, and delivery phases occur sequentiallyand the software is delivered at the end of the process.Iterative development is more economical and predictable sinceyou specify the objectives for the software system and then build anddeliver a series of partial but increasingly complete implementations.These implementations, or iterations, are working products en route tothe completion of the tuned project. Using iterative development, youintegrate the software at each iteration instead of at the end of theproject. This frequent integration reduces risk by exposing it early in theproject life cycle.This concept, which is used by most major vendors like Microsoft,allows feedback from users who exercise the software delivered at eachiteration. Users can actively participate in the refinement of the softwarethrough all phases of the acceptance process.Each iteration exposes problems and risk in the system includingfunctionality, performance and user interface. The remaining elements ofrisk become the focus of the next iteration.ActiveXActiveX is based on Microsoft’s COM. It can be used for connectingdifferent vendors’ applications and serves as the glue that connectsan application and makes it versatile. One example is USDATA’s systemswhere they are built upon a COM/ActiveX foundation. Each applicationis a collection of components that is part of the system. This technologyis used with an object model to allow a flexible and open environment.Northwest Analytical’s software also uses ActiveX objects. Datamay come from a variety of applications, but it can be presented in thesame standard way regardless of source application. The use of ActiveXprovides the necessary components for this capability.The use of ActiveX brings up the question of security, since an©2001 by The Fairmont Press, Inc. All rights reserved.