Explaining the Business-Technological Age of Legacy Information Systems

Aged information systems are commonly referred to as legacy information systems or just merely as legacy systems. Typically, these are mission-critical systems developed years ago that significantly resist evolution. Many organizations have lived with these systems for a long time and consider them a burden because they hold back their businesses and cause unreasonably high evolution and operating costs. However, they also cannot easily be discarded and replaced by modern solutions. Despite their relevance, no universally accepted concept exists that explains these systems or the mechanisms behind them. Accordingly, the properties and challenges associated with legacy systems vary significantly depending on their respective author and intentions. This needs to be improved, and this is also where our research comes in. To this end, we first describe the causes of information systems’ aging, typical symptoms by which legacy systems are often recognized, and the consequences of using outdated solutions. Based on this empirical point of view, we introduce a holistic model to explain legacy systems objectively as well as the concept of business-technological age to distinguish between chronological age and actual obsolescence of a deployed system. This approach provides practitioners and researchers with a foundation for stringently explaining the hitherto fuzzy legacy phenomenon, promoting a common understanding of legacy systems, and simplifying communication by employing specific concepts. Practitioners can use this approach to better understand their stock application systems in terms of aging and improve their decision-making regarding evolution.