A Decision Making Tool for the Selection of Service Oriented-Based Legacy Systems Modernization Strategies

Transcription

1 A Decision Making Tool for the Selection of Service Oriented-Based Legacy Systems Modernization Strategies Rafik A. Salama, Sherif G. Aly The American University in Cairo Abstract In this article, we present a process and tool that facilitates the decision making process of selecting an appropriate migration strategy for legacy software systems using the Service Oriented Architecture. Issues related to legacy system migration were initially discussed, followed by two famous techniques namely the Service-Oriented Migration and Reuse Technique of the Department of Defense, as well as that of Erradi. A hybrid process was then introduced, and a tool following the process was illustrated. The tool takes into consideration choosing key migrating evaluation factors, rating the relative importance of such factors, inputting the organizational significance of each factor, as well as operating on individual system components. Keywords: Legacy Software, Modernization, Service Oriented Architecture, Decision Making, Tool 1. Introduction Legacy Information Systems are termed as such since they mainly use old technologies and architectures that became obsolete relative to the current state of art in technology. They are mainly mission critical systems, and their failure can have a serious impact on business. In fact, a Legacy Information System can be defined as Any information system that significantly resists modification and evolution [1]. They can cause host organizations several problems: Legacy Information Systems usually run on obsolete hardware that is slow and expensive to maintain. Software maintenance can also be expensive, due to the lack of documentation, understanding of system details, and time consumption for tracing faults. The lack of proper and current interfaces makes the task of integrating Legacy Information Systems with other systems a difficult task. Legacy Information Systems are also difficult, if not impossible, to extend. A legacy information system represents a massive, long-term business investment. Unfortunately, such systems are mostly brittle in the sense of being resistant to change, are slow, and non extensible when faced with new technologies [2]. Although the above problems with the current legacy systems exist, such systems represent organizational assets that are virtually important for business continuation, so they need to be evolved to either match the continuously evolving business or to cope with continuous evolution of the other systems around them. Much research has been done in the domain of legacy system analysis and modernization. Reverse engineering research of legacy systems has been discussed in [10-14]. Design discovery of legacy systems was also tackled in [15-17]. The work in [18] also tackled the issue of design metrics in legacy systems. The continuous emergence of new technologies that are proven to be more robust, scalable, and maintainable, such as those using the Service Oriented Architectures (SOA), is currently attracting numerous legacy systems modernization stakeholders. The selection process of the SOA modernization strategy that best fits a given legacy system has been proposed previously in multiple researches. The most comprehensive process is the process of the Department of Defense (DoD) termed the Service-Oriented Migration and Reuse Technique (SMART) [3]. Another work is that of Erradi [4]. Erradi s contribution mainly presents an assessment process followed by a decision framework for strategy selection. The Erradi and SMART processes agree in the main steps, except for the fact that SMART ends by designing the strategy that best fits the application being modernized while the Erradi process ends by decision making for selecting the best strategy out of the existing migration strategies.

2 Modernizing a legacy system to the Service Oriented Architecture, as for example to Web Services, is somehow a straightforward process since the SOA offers a promise to enable and expose the existing legacy functionality in the form of services presumably without making any changes in the legacy system using the wrapper design pattern [5,6]. Although migration to the Service Oriented Architecture is mostly a straight forward process, it is sometimes not particularly as such. In some extreme cases, the SOA modernization of legacy systems involve total reengineering of the system [8] or even migration to new platforms [9]. The Service Oriented Architecture however still shapes the hope for the modernization of legacy systems in the form of web services with minimum change involved as in the case of componentization [7]. In all cases, the SOA has attracted the focus of major organizations to modernize their legacy systems using a variety of modernization techniques that fit their current architecture and the desired architecture. In this article, we focus on providing a tool that assists the selection of a suitable hybrid modernization strategy from the current catalog of modernization techniques while taking into consideration the modernization business drivers, the quo state, the post modernization state of the system, and finally the boundaries of the organizations in terms of cost and duration (effort and resources). 2. The SMART and Erradi Strategies One of the most comprehensive processes of legacy systems modernization is the Service- Oriented Migration and Reuse Technique (SMART) [3]. The word migration is used here to express the idea of modernization in the Department of Defense (DOD). This technique, in summary, involves: 1. Understanding the target SOA requirements. 2. Analyzing the current system, and performing a gap analysis between the target system and the current one. 3. Developing a migration strategy. The Erradi technique on the other hand explores the organizational factors that influence the decision of strategy selection, but they assess the system using a simple paper and pencil matrix as follows: 1. Legacy modernization business context: Identify the key business goals and the key pains in the current system and requirement from the future system in terms of performance and reliability. 2. Legacy portfolio assessment: Assess the current system portfolio in terms of size, interfaces with other systems and technologies used. Manual and automated techniques should be used to handle such step. 3. Choosing of legacy modernization options using scoring and pair-wise comparison models: Using the below matrix as in Figure 1, the legacy system strategy is chosen according the best matching between the factors given through the assessment phase and the context of the modernization. Figure 1: Matrix of SOA Modernization Strategy Evaluations [4]. The Erradi model however lacks considering the organizational factor weights in the decision, as well as lacking considering the legacy system as a set of components rather than one big system that should be modernized using the one strategy fits all approach. 3. A Hybrid Decision Framework We enhanced the decision making process of the selection of appropriate modernization strategies starting from the work of Erradi and guided by the work of SMART. Hence, we started from the decision framework proposed by Erradi and

3 designed a new selection process that uses Erradi s work and complemented it using the SMART process. We called this process the Modernization Strategy Selection Framework (MSSF). The final evaluation of the strategies is typically achieved given the following parameters (which flows directly from the assessment process): Factors contributing to the decision and their rates versus each strategy. User input to give the key important characteristics of the decision and their relative importance. User input to rate the importance of each characteristic contributing to the decision, which basically flows from the gap analysis. Legacy system/component source code which is used to measure code quality. These characteristics affect all the relevant characteristics of the decision as defined by the organization. The estimated cost of each strategy to give a rough cost benefit analysis. Using the above parameters, we designed a process that automatically uses this information to give a general guidance for the strategies that should be followed to modernize the legacy system. The decision making process mainly relies on decision theory specifically the Multi Criteria Decision Making (MCDM) tools to calculate the value of each strategy. It mainly aims on using all the available information to automatically order the strategies using decision theory. The aim of these ordered strategies is to give the organization a guidance of the best strategies to follow in their modernization process. Guides the SOA modernization strategy selection framework through the mapping between the needed artifacts by the tool and output artifacts from the process. Automates the source code analysis for code quality metrics while forming a questionnaire for the rest of legacy system characteristics. The current version allows only for C++ code, although the code quality characteristics could be fed into the tool manually. The source code analysis is currently been done using the CCCC API [12]. Automates the decision making process of the framework over a component-service scope through an easy to follow wizard. The tool is a wizard application walking the organization through our combined migration selection strategy using the artifacts and executing the decision making process at the end. The wizard mainly ends by a report explaining the output of each step in the decision making process. The wizard screens is a one to one mapping to the decision making process. The screen flow is shown in Figure 2. Welcome Screen (Load Artifcats) Choose Key Evaluation Factors Rate Relative Importance of Key Evaluation Factors Input The Significance Of Each Factor 4. The Decision Making Tool The decision making tool is mainly based on the enhanced decision framework based on the work of Erradi and SMART. The tool helps the organization through the whole process either using the artifacts created or by helping them input the values of some artifacts on the tool itself. The real contributions of the tool are: View Evaluation Report Choose another module Input The Legacy System Characteristics Values Figure 2: Screen Flow of the Tool Choose Source Code (C++) for analysis

4 The decision making process only involves the user in only two input steps, while the rest of the evaluation is done automatically by the tool. 5. Screen Descriptions The following subsections explain in more detail the various steps in the strategy selection process inherent in the tool. Significance: By default all the key characteristics gets a double significance to favor the strategy that has higher rate for these characteristics. The screen is shown in Figure Welcome Screen This the first screen of the application as shown in Figure 3 mainly aims at introducing the wizard to the user to expect what is next and explain the requirements of each screen. This screen also is the point where the application loads the artifact files and validates them. Figure 3: The Informational Welcome Screen 5.2. Choosing the Key Evaluation Factors This is the screen corresponding to the decision making process mainly concerned with selecting key evaluation characteristics, which will affect two steps of the decision making process, namely: Filtration: The filtration step is an important step where the user gets the opportunity to filter the modernization strategies based on important key characteristics. For example, the organization can choose a certain modernization driver to be used as a filtering criteria where all the strategies that fall in this criterion are ignored. Figure 4: Choosing Key Evaluation Characteristics Screen 5.3 Rating Relative Importance This screen as shown in Figure 5 is intended to mainly rate the selected key characteristics relative to each other. The idea is to simply say which one of the key evaluation characteristics is more important than the other. The reason behind this is to give the organization a control over ordering the priority of these keys or to even give them equal priority. This will allow the focus to be more on the higher priority characteristics rather than the lower ones during the filtration step.

5 Figure 5: Relative Importance of Key Evaluation Characteristics 5.4 Input Significance of Each Factor This is the step added to the process of Erradi which gives the organization more control over the organizational variables using the result of the gap analysis. The gap analysis will indicate how far the current system is from achieving such characteristics. The significance of the variable doesn t necessarily indicate how large the gap is, but the organization may choose to neglect its effect when modernizing this component to the service. We also we added the value highly significant that is basically used to double the effect of a certain characteristic, which will give it more emphasis over the other characteristics. The screen is shown in Figure Choosing the Source Code This is the step where the tool allows for the selection of the source code of the component in the legacy system that is currently being evaluated. The source code selected is measured using the CCCC API. This is a recurrent screen in the sense that this screen is being used each time a component for evaluation is considered. The organization may want to consider a hybrid modernization approach, so it should evaluate each component vs. service in a separate thread to focus on its criteria s values alone. 5.6 Inputting Legacy System Characteristics This is the screen where the organization gets to input the result of their legacy system assessment. These are the values that are not involved in the code quality metrics or that are involved but the tool does not provide them. The screen is shown in Figure 7. Figure 7: Rating Other Factors 5.7 Viewing the Evaluation Report This is the final screen of the tool, as shown in Figure 8, where the organization gets to see a report of the process steps output as follows: Figure 6: Significance of the Characteristics First, the organization sees the output of the filtration process indicating the rates of the strategies before the filtration and the resulting filtered strategies.

6 Second, the organization sees the output of the assessment process in the form of an ordered list of the strategies giving the organization more benefits based on the following: o o o Rates of the characteristics Code Quality Metrics Significance of the characteristics Finally, the cost benefit analysis shows the result of the automatic cost benefit analysis using the benefits computed and the cost provided. The output is also an ordered list of the strategies based on the cost benefit analysis. Figure 8 : Final Report and Decision made by the Tool 6. Conclusion In this article, we presented a process and tool for assisting the decision making process of selecting appropriate migration strategies of legacy software systems using the Service Oriented Architecture. We discussed two key approaches for legacy software systems migration, presented a hybrid approach, and subsequently illustrated the tool that facilitates this decision making process. The tool takes into consideration key organizational factors deemed important to the migration process, as well as each factor s significance. 7. References [1] J. Bisbal, D. Lawless, B. Wu, J. Grimson, V. Wade, An Overview of Legacy Information System Migration, X/ IEEE [2] J. Bisbal, D. Lawless, B. Wu, and J. Grimson, Legacy Information Systems: Issues and Directions, IEEE Software September/October 1999 [3] G. Lewis, E. Morris, D. Smith, Service-Oriented Migration and Reuse Technique (SMART) in Proc. of the 13th IEEE International Workshop on Software Technology and Engineering Practice, 2005 [4] A. Erradi, S. Anand, N. Kulkarni, Evaluation of Strategies for Integrating Legacy Applications as Services in a Service Oriented Architecture in Proc of IEEE International Conference on Services Computing (SCC'06). [5] G. Canfora, A. R. Fasolino, G. Frattolillo, P. Tramontana, "A Flexible Wrapper For The Migration Of Interactive Legacy System To Web Services" in Proc. of the Conference on Software Maintenance and Reengineering, 2006 [6] M. Li, O. F. Rana, M. S. Shields, D. W. Walker "A Wrapper Generator for Wrapping High Performance Legacy Codes as Java/CORBA Components" in Proc. of the 2000 ACM/IEEE conference on Supercomputing, 2000 [7] H. Guo, C. Guo, Wrapping Client-Server Application to Web Services for Internet Computing In Proc. Of IEEE 6th Intl. Conf. of Parallel and Distributed Computing, Applications and Technologies (PDCAT 05), [8] U. Zdun, Reengineering to the Web: A Reference Architecture, in Proc. of sixth European Conference on Software Maintenance and Reengineering, 2002 [9] L. Aversano, G. Canfora, A. Cimitile, A. De Lucia, Migrating Legacy Systems to the Web: an Experience Report in Proc. of Proceedings of the Fifth European Conference on Software Maintenance and Reengineering, 2001 [10] G. A. Di Lucca, A. R. Fasolino, U. De Carlini, Recovering Class Diagrams from Data-Intensive Legacy Systems, Proceedings of the International Conference on Software Maintenance (ICSM'00), 2000 [11] E. Stroulia, M. El-Ramly, L. Kong, P. Sorenson, B. Matichuk, Reverse Engineering Legacy Interfaces: An Interaction-Driven Approach, in the Proceedings of the 6th Working Conference on Reverse Engineering, (WCRE 99), 1999

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