Structuring integrated Web applications for fault tolerance

This paper shows how modern structuring techniques can be employed in integrating complex web applications such as travel agency systems. The main challenges the developers of such systems face are dealing with legacy web services and incorporating means for tolerating errors. Because of the very nature of such systems, exception handling is the main recovery technique to be applied in their development. We employ coordinated atomic actions to allow disciplined handling of such abnormal situations by recursively structuring the integrated system and by associating handlers with such actions. We use protective wrappers in such a way that each operation on legacy components is transformed into an atomic action with a well-defined interface. To accommodate a combined use of several ready-made environments (such as communication packages, services and run-time supports), we employ a multilevel exception handling. We believe that these techniques are generally applicable for both: structuring integrated web applications and providing their fault tolerance.