PhD Thesis - staffweb - University of Greenwich

PhD Thesis by John Ewer.before the re-engineering commenced.Consistency with numerical CFD developers experience necessarily put limits on theimplementation language choice and limited the features that were used. The new system wasdesigned to be largely self descriptive and consistent with the known algorithms from the legacysystem. It was also a design requirement that data access was self-consistent for all softwaredevelopers and researchers.The coding interface between the GUI and numerical CFD code crosses the boundary betweenan event driven architecture and purely procedural code. The danger with integration of differentprogramming methodologies was that one or other component can tend to dominate with theeffect that the GUI could seem unresponsive while the CFD code was always processing or,alternately, the CFD code was never processing or behaving sluggishly as the GUI was alwayswaiting for input. Part of the design strategy that has been demonstrated in prior research is theuse of Blackboard objects for inter-component communications and for maintaining GUIdefaults.Since the target system was ultimately intended to have KBS support, there were considerationsthat had to made during the system design. The first choice was for the implementation languagesuch that data transfer between the CFD code and the KBS component was possible, portablebetween systems and efficient. If, as seemed likely at that stage, the KBS system was constrainedto be a separate process then the overheads and complexity of data transfer by file would haveto be assessed. In practice the KBS, GUI and CFD engine are coupled by a global "blackboard"data structure but are, for efficiency reasons, implemented within the same executable. Thisimplementation strategy was deemed to be both appropriate and necessary because of the hugeamounts of data required by a CFD simulation. A coupled system gives instant and unrestrictedaccess to all of the simulation data with no communications overheads. A mechanism ofrestricting control access was considered in order to prevent meaningless or potentiallyproblematic control modifications. There is a distinct possibility that pattern recognition codewould be required to summarise status information prior to reasoning although creation ofpattern recognition routines is outside of the scope of this research.3-40