Software Maintenance Essay -- essays research papers

SOFTWARE MAINTENANCE Abstract A consequence of the widespread utilisation of computer based technology over the past few decades has been the emergence of vast, highly complex computer systems whose content and structure are increasingly resistant to modification and change.   However fallible such legacy systems remain, many are â€Å"mission-critical† whereby their failure may lead to the collapse of the business or industry in which they serve.   In such cases, it is ultimately not possible to decommission the system in question.   The present report investigates the nature of such systems and examines why legacy systems cause problems to Software Maintenance Managers?   This report also provides a brief overview as to how such problems can be minimised and controlled. Keywords: Legacy systems, legacy system migration, mission critical systems, re-engineering, software wrapping, software evolution. 1. Introduction   Ã‚  Ã‚   The literature describes legacy systems in terms of being an existing software application that is predominately within the maintenance phase of its lifecycle.   Such systems are typically old and heavily modified from their original designs by years of maintenance, usually by many different people [Moor00].   Although legacy systems are technically obsolete, having been written in assembly or early third generation languages such as COBAL Fortran and Coral, they generally represent considerable investment, and maintain significant value to their users [Benn95] [Brod95].   Ã‚  Ã‚   Legacy systems typically form the backbone of information flow within an organisation, and as such, are essential for the function of its business. Failure in these systems is likely to have serious consequences hence why legacy software is often considered of a â€Å"mission critical nature† [Benn95] [Bisb99]. As can be expected, systems of this nature pose a number of problems to the users, and to the Software Maintenance Manager responsible for the upkeep of the system.   Such problems range from the cost of maintenance to the utilisation of obsolete skills and technologies.   However, several solutions have been proposed and documented in the literature in response to, and to minimise, these problems.   Generally, they are classified under four categories: maintenance, re-development, wrapping and migration [Bisb99] [Lee97].   Ã‚  Ã‚   Therefore, the remainder of this report is ... ...[Lien80] B.P. Lientz & B.E. Swanson, "Software Maintenance Management", Addison - Wesley, 1980 [Merl95] E. Merlo, P-Y. Gagne, J.K. Girard, K Kontagiannis & P. Panangaden, "Re-Engineering User Interfaces" IEEE Software Jan 1995, Vol 12 No 1 [Moor00] M.M. Moore, "Using MORPH", http://www.cis.gsu.edu/~mmoore/MORPH/dissertation/approach.html, 2000 [Nose90] J.T. Nosek, & P. Prashant "Software Maintenance Management: The Change in the Last 10 Years", Journal of Software Maintenance, 1999, Vol 2 No 3 [Press01] R.S. Pressnam, "Software Engineering: A Practitioner's Approach" McGraw Hill, 2001 [Somm01] Sommerville, "Software Engineering", Addison - Wesley, 2001. [Weid97] N. Weiderman, L. Northrop, D.Smith, S.Tilley & K. Wallnau, "Implications of Distributed Object Technology for Re-engineering", Technical Report CMU/SEI-97-TR-005, Carnegie Mellon University, June 1997