By closely observing complex business environments, one can identify business processes as its core elements. A business process can be defined as a sequential flow of business activities over a certain period. The performance of an organization depends upon business processes which provide the means for achieving the organization’s fundamental objectives. In a volatile modern economy, organizations must understand and constantly improve their business processes to make successful and competitive business decisions. The relevance of information technology and different business process management (BPM) methodologies are becoming key factors in controlling vast business environments. The process-oriented view of business environment provides a better understanding of the organization and helps in comprehending the needs of the information systems that support the business process. BPM provides support for the efficient management of a business environment with the purpose of increasing its flexibility and productivity. BPM implementation is a process of building a BPM solution in an existing business environment. BPM solution consists of multiple BPM applications (BPMA) which support different business processes in the organization. A set of modern BPM tools (suites, systems, or environments) offer the ability to model and analyze business process flows, detect defects and irregularities in processes and provide a wide range of advanced capabilities for business process optimization. BPM tools are mainly used to develop, maintain and optimize a composite process application. The key problem with the implementation of BPM in existing environments is the complexity and lack of standardized methods for the integration of the BPM solution with the existing business processes, legacy applications and systems. A series of theoretical discussions, found in scientific literature and practical studies from the industry, put the focus of the integration on the redesign of legacy systems, with little exploitation of existing functionalities and minimal reliance on existing structures. Existing applications are restructured and written as service modules, which are then used to build BPM solutions. The redesign of complex legacy environments requires large amounts of resources and time, and therefore, is a luxury that many organizations can not afford. Also, the organization’s ability to grow, respond to market demands and cope with ongoing challenges would be limited during the redesign period. Consequently, business owners rarely approve such a task. Apart from the complexity of the integration, an additional problem is the fact that presentation and interaction with business data is closely related to BPM suite and largely depends on the capabilities of that suite. E.g., the BPM implementation effort could encounter problems if the used tool does not support the implementation of complex business rules or the construction of interactive user interfaces. As the primary task of BPM suite is to manage business process flows, they often need to be used in combination with additional tools and frameworks to achieve more advanced business needs. In addition, the implemented BPM tool must be able to handle large volumes of business data and massive objects, which complicate the implementation process. Complete business logic required for the effective presentation of data must be included when creating complex forms. Such a cumbersome architecture can create quite a vulnerable application, which is difficult to maintain or upgrade efficiently. Furthermore, a business arranged in that manner is closely dependent on the BPM tool itself. There is still a lack of detailed models that describe the integration of a BPM system with existing legacy environments, and there are only few studies dealing with the analysis of the appropriate tools and implementation methodologies that would enable the described integration. As a result, the introduction of BPM systems in the organization is often done in a way that further complicates the existing environment and creates additional difficulties for the organization's business. In light of the above difficulties, this doctoral work aims to explore the interest areas in detail and develop a flexible model for integrating a BPM solution into an existing legacy environment by utilizing existing structures and exploiting existing functionalities. The usage of existing business activities, supported by the functionalities of the legacy applications, removes the need for extensive redesigns of the existing environment. By applying minimal changes to the existing legacy environment, organizations can, to the satisfaction of the business owners, minimize the time and resources needed for BPM implementation while enjoying the benefits provided by BPM. The focus of the work are legacy environments based on service-oriented architecture (SOA), i.e. environments comprising legacy applications based on an SOA architectural style, where a solid service background is present. Solid service backgrounds enable the flexibility of legacy applications and constitute a good foundation for the endeavor of BPM integration. The work also describes the evolution and gives an overview of BPM domain. The relationship between business processes and the functionality of a system that supports the actions of a business process is explored in detail. Legacy systems based on service-oriented architecture are analyzed with the focus on inherited functionalities, and the usage of those functionalities in conjunction with a BPM system. Challenges and difficulties, involved in the implementation and the integration of a BPM system in a legacy environment, are analyzed on a real-life example. BPM suites are discussed, their importance is outlined, and guidelines for choosing the most appropriate suite are given. Further on, the work analyses existing models for integrating BPM systems with legacy environments, and presents a study of used architectures, tools and technologies. An overview of the existing research papers from the area of interest is presented, with a conclusion that they were written quite general and lack detailed elaboration of the integration process. Existing papers mainly emphasize the importance of controlling business processes, analyze the success factors of the BPM initiatives and try to determine the role of the BPM in the overall business of the organization. The discussed BPM implementation models are mainly focused on building a BPM solutions from scratch, or overwriting existing functionalities and redesigning existing legacy application environments. Reuse is limited to existing SOA services, while the concept of using parts of existing applications, user interfaces and complete functionalities incorporated in existing business processes, is not thoroughly studied. In the literature authors often discus the question: When, how, and to what extent can one use existing systems as part of a BPM solution? The lack of guidelines and models that would describe the structure and the implementation of such a BPM solution is also underlined. Disadvantages of the existing models were also noted on a study of a real-life candidate for a BPM implementation, a complex banking application. Based on the discussion, the idea for a new, improved, integration model is presented in detail. It includes the use of rudimentary business process management functionalities, provided by the BPM tool, with a combination of a specific solutions and interfaces implemented in existing applications. On a process level, all activities of the business process are executed trough the legacy applications, while the created BPM application holds the basic business process data and provides a central point of interaction with the activities of the process. Basic characteristics of the new, flexible, model for the integration of BPM systems with existing service-oriented legacy applications are also defined. The main characteristic of the new model prevents the extensive redesign and complete re-writing of existing functionalities and business processes. Therefore, the new model maximizes the utilization of existing functionalities, existing applications and architecture while requiring as little adaptation and change as possible. Consequently, it reduces the cost of BPM implementation, use of resources and the amount of work needed. Adaptability of the new model provides a loose coupling between a BPMA and the existing systems which enables the operation of legacy applications without the BPM solution. In that manner, the business of the organization is not dependent on the BPM solution and one can still execute existing business processes through legacy applications. The central point of interaction with the activities of the process is achieved which sets the foundation for easier tracking, measurement and optimization of individual parts of the process. Every business process flow on the BPM environment reflects the state of the underlying data in the background systems in real-time. Changes in business processes must be visible in the underlying applications automatically, and the state of the data in those applications needs to be promptly displayed in the process application. A procedure for a simple integration and use of various legacy applications in the BPM solution was proposed. Due to simplicity, a BPMA manipulates with only a reduced set of business data required to achieve the desired functionality. The new model allows changes in business process flow by changing the process model in BPMA with minimal, or no, changes to existing applications. Model is also independent of different hardware, operating systems, or technologies used in the organization. The advantages of a new model over the existing integration attempts are discussed in detail. A more detailed theoretical elaboration and formal definition of the integration model is also given. The importance and the role of the models’ layers is explained, communication between the layers is elaborated. The integration model is based on three key layers: the legacy application layer, BPM communication layer (BPMCL) and a BPMA built in the BPM tool. Legacy applications contain parts of the functionalities of existing business processes and execute the actions of the existing business processes. To enable their communication with the BPMA, a Legacy Application Adapter (LAA) component is created. Integrated into the legacy application, the LAA has the task of sending instructions to the BPMA and responding to the requests of the BPMA with the help of the BPMCL. BPMCL is a component, a middleware layer, which enables the communications between the legacy systems that perform specific business actions and the BPMA. It contains the methods for manipulating process data by calling process application programming interfaces (APIs) exposed in the BPM environment. BPMCL gives flexibility to the integration model by providing means for the orchestration of business processes built in a legacy environment using a generic BPM suite. BPMA describes the existing business process with a BPD modeled in congruence with the Process Model and Notation (BPMN) standard. A BPMA is built in a BPM environment with the use of BPM tools. The process of BPMA creation requires that flow charts of business processes and sub-processes be defined. A BPMA created in this manner contains a process model of an existing business process that is executed in a legacy environment with the help of several existing legacy applications. Further on, the role, functionality and capabilities of each layer are shown and explained in detail. In addition, the question of user roles, security and access control mechanisms is also considered. To clarify the communication between the components in the new model the terms "process points" and "interaction points" were defined. Process points mark the locations where the LAA and the BPMA exchange information, while interaction points identify parts of the process where the user begins/ends the interaction with the process in the legacy applications. Additionally, discussion regarding similarities and differences of the integration model with Enterprise Service Bus (ESB) architectures, Enterprise Application Integration (EAI) principles and the role of SOA is undertaken. The work presents a detailed elaboration of the proposed integration model from the technical side, with the goal of identifying technologies, tools and frameworks that will be used in the design of the proposed model. Ideas on different technical realizations of individual layers are presented. According to the defined requirements, ease of implementation and overall efficiency, appropriate tools, technologies and implementation methods are proposed. Detailed technical description of the framework that enables the implementation of the described model and its integration with the existing legacy environment is presented. Guidelines for modeling process flows, connecting the processes with service modules and legacy applications and creating user interfaces are given. An original, iterative, approach for the development of a BPM application and the integration of the BPM application with the existing systems, according to the proposed model, is defined and elaborated. Also, some experience based conclusions and guidelines regarding the implementation of the model and its components are given. The application of the proposed integration model in a real-life use case scenario is also shown. The process of selecting most favorable tools, frameworks and methods for the implementation effort of the integration model is outlined. A specific business use case scenario (the business process of issuing and processing loan utilization requests) is chosen to illustrate the feasibility of the integration and demonstrate the structural innovations introduced into the mentioned process. The results of the development, and the integration of the BPM application with existing systems, are presented based on the original iterative approach that was defined previously. Additionally, the introduced structural innovations and process improvements are elaborated. A brief discussion regarding the definition of the visual identity of BPM application was also undertaken. Further on the principles of business process monitoring, analysis and the techniques for determining process measures, in the environment with the proposed integration model, are briefly described. An original model for measuring and mapping the metrics of the lower level (simple services and human actions in the legacy applications) to the metrics of activities, business processes and business goals is proposed. A direct connection between the low-level metrics and the strategic business goals of the organization is shown. Optimization recommendations are given based on detected shortcomings in the process flows. This sets the foundations for the performance optimization of business processes supported by the proposed integration model and opens a wide area for a future research. A detailed evaluation of the proposed integration model, along with the validation of the idea on which the model is based is also provided. The evaluation was done in two separate studies. The first study involved a broader set of respondents and was aimed at the validation of the idea behind the proposed integration model. Views about the importance of BPM are collected, along with the opinions on the methods for integrating a BPM system in a legacy environment. The main goal of the first study is to answer whether, and to which dosage, one should rely on existing legacy systems during the implementation of a BPM solution. In the second study, the proposed integration model was presented to a narrower set of relevant experts from the BPM area, and they were asked to give their opinions, criticisms, suggestions and identify possible use cases for the integration model. All interviewed experts were familiar with the BPM but differed in the amount of experience with different BPM initiatives. A Delphi method based detailed evaluation of the usefulness of the proposed integration model was undertaken. Further on, comments on potential disadvantages of the proposed integration model, as concluded in the analysis with experts, were discussed. Additionally, a review of the state and the needs of business environments in which the interviewed experts operate are given. At the end, a summary of the conducted research, critical review of the research results, guidelines and suggestions for further development are provided. This doctoral work gives a review of the BPM research areas with an emphasis on the integration of the BPM solution with legacy environments. Special attention is given to modern BPM suites used to model business process flows and their ability to integrate with existing applications and reuse existing functionalities. A model which allows the integration of a BPM suite with the legacy environment was developed, and framework for the implementation of the described model and its integration with the existing systems is proposed. This research explores how important it is for organizations to control their business processes. Furthermore, it shows how control of business processes can be achieved by integrating BPM into existing SOA based legacy environments. The original contribution of this work can be seen in the definition of the BPMCL layer and the principles of integrating the BPMA with different legacy applications via the BPMCL in a way that exploits the existing functionalities and user interfaces while avoiding extensive redesigns of existing environments. Additional contributions lie in the conclusions of the presented case study, proof-of-concept implementation study and the extensive evaluation of the model by relevant experts from the BPM area. The presented research may provide organizations with the opportunity to use the proposed integration model as a platform for achieving greater business value and thereby help them to become more flexible and more focused on their core business objectives.