Extended Exception Mechanisms for Contingencies

van Ellen, Thorsten and Hasselbring, Wilhelm (2008) Extended Exception Mechanisms for Contingencies [Paper] In: Proceedings of the Software EngineeRing for rEsilieNt systEms 2008 workshop (SERENE 08) .


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We observed a general problem of sequential programs, which often results in design and programming errors in in- dustrial software engineering projects, and propose a solu- tion approach. Telephone lines may be busy, banking ac- counts may be overdrawn and disks may be full. These things happen in the real world, causing the disruption and non-fulllment of an expected service. Ignoring these prob- lems leads to violations of the postconditions of the caller that depends on the service. The conditions are exactly known and cannot always be avoided, but measures could be taken afterwards. A good program should handle them as part of the specication. As such they are not specication violations and should not be regarded as errors. Unfortu- nately, they usually can or shall not be handled immediately within the direct caller, e.g., for information hiding reasons. The problem is similar to the problem of error code han- dling and handling them with exception mechanisms seems reasonable, but the problem is even more complex. These situations must not terminate the system suddenly, because that also violates postconditions. Consequently, exceptions for these situations must be distinguished from exceptions for errors and are worth handling separately. Therefore, we introduce the new concept contingency for such situations. Since the conditions are dened, they are candidates for for- ward recovery, but conventional exception mechanisms are not appropriate for that purpose. Appropriate mechanisms are presented in this paper. A systematic inspection and handling of contingencies with these mechanisms before run- time can diagnose and avoid subsets of specication viola- tions eectively. An evaluation approach will be presented.

Document Type: Conference or Workshop Item (Paper)
Keywords: contingency, exception, forward recovery, reliability, resumption
Research affiliation: Kiel University > Software Engineering
Date Deposited: 18 Feb 2012 06:05
Last Modified: 20 Sep 2012 08:50
URI: http://eprints.uni-kiel.de/id/eprint/14480

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