Development of an Open Source Software Framework as a Basis for Implementing Plugin-Based Environmental Management Information Systems (EMIS)

EnviroInfo 2008 (Lüneburg) Environmental Informatics and Industrial Ecology Development of an Open Source Software Framework as a Basis for Implementing Plugin-Based Environmental Management Information Systems (EMIS) Volker Wohlgemuth 1, Tobias Schnackenbeck, Dominik Panic and Robert-Lee Barling Abstract The software-sided support of state of the art problems in the area of environmental management information systems (EMIS) generally leads to redevelopment of often used basic functionalities before implementation of the intended functions, which focus on the problem under investigation. This affects components regarding a certain aspect (e.g. material flow analysis or simulation runs) as well as software-related infrastructure components e.g. GUI, logging or persistence. Within the EMPORER project, supported by the German Federal Ministry of Research and Technology (BMBF), an extendible and component based software platform is developed. Based on this software platform there will be some components and applications developed for the fields of material flow management and simulation as a proof of concept. Thus, the objective of this development is to offer an easy to use tool kit and framework which can seamlessly be extended by components with a close-to-the-problem functionality. To bring forward further development and distribution, the platform will be made available as an open source software framework enabling further methods and components to be complemented by third parties. This paper describes the basic architecture and the fundamental extension possibilities of the software platform which is based on Microsoft s.net. 1. Introduction Environmental Management information systems (EMIS) are often complex systems which have high requirements concerning their integration possibilities with other business systems like Enterprise Resource Planning Systems (ERP-Systems), Production Planning Systems (PPS) etc. To gather environmental data and to support planning and controlling of environmental protection actions, diverse techniques and methods from computer science are applied (Rautenstrauch 1999). The used methods, the data to be connected and the information to be generated are always in change. For research in the area of EMIS there is the challenge to implement new or modified methods by software while either integrating into already existing systems or creating new applications. Due to missing customizability, functional changes in existing systems oftentimes have to be integrated with big effort without decreasing usability. In many cases it is even likely that integration plans are condemned to fail due to system seclusiveness. Additionally it can be worried that the extension of the host EMIS with new functionalities that are only used in a certain context or for a special problem, might lead to an overloading, which can result in frustrated users that feel confused by the plenty of new but not essential features. Another possibility of a software-based implementation of problem-specific methods is the approach of self-development. It requires big effort since the software infrastructure and other base functionalities have to be created before development of the desired problem-specific methods and components can begin. Furthermore, this infrastructure is often already available in many EMIS. Providing an expandable soft- 1 FHTW Berlin, University of Applied Sciences, Department of Engineering II, Blankenburger Pflasterweg 102, D-13129 Berlin, volker.wohlgemuth@fhtw-berlin.de, tobias.schnackenbeck@fhtw-berlin.de, panic@fhtw-berlin.de, robert.barling@fhtw-berlin.de 584

ware platform containing a basic infrastructure with typical reusable methods and components for the field of environmental protection (like visualization methods, modeling and simulation capabilities, material flow management features and so on) can reduce effort. Thus, an application developer can concentrate on solving his actual problems because he does not have to implement basic functionality before. Based on a basis infrastructure platform it should also be possible to provide components (especially in the field of EMIS) which can be configurated to build a software solution suited to the special needs of a certain application field. The objective of the here presented research project EMPORER is to concept and develop such a platform. Network partners are besides the FHTW Berlin, the Leuphana University Lüneburg, a small or medium sized enterprise (SME) as beta tester and application user and a software development company, all located in Germany. Target of the plan is the development of a component based software system, providing typical basic functions of an EMIS. The project is supported by the German Federal Ministry of Research and Technology (BMBF). The software shall serve as starting point of a method kit for EMIS, while having the focus on the software based assistance of material flow analysis and simulation methods. Computer simulation is an important tool for analyzing and modeling complex systems (Košturiak and Gregor 1995, Liebl 1995, Page and Kreuzer 2005). Concerning environmental management information systems, a simulation can be specified as a method which must be offered by a EMIS (Rautenstrauch 1999, page 15). For material flow analysis and simulation a concept has been created (Wohlgemuth 2005) where an discrete event simulation was linked to the material flow based view of industrial environmental protection. A realization of this concept with software has already been developed by the University Hamburg with the project Milan (Wohlgemuth 2005), but it used Microsoft COM-Technology which is outdated in the meantime (Microsoft COM 2008). For both methods of material flow analysis and simulation exemplary components are provided which are combined to one prototype software system, so a SME can test the software. The following paragraphs will describe the motivation for providing the software framework as open source. The system architecture and planed resp. already developed plug-in components for the framework will also be introduced. 2. Open-Source Open source normally means to give free access to the software source code, allowing a community of interested developers and users to review, reuse and further develop the code and to increase the reputation of the application (Wikipedia, Open Source 2008). A very successful example for a plug-in based architecture is given with the java-based open source platform Eclipse. Originally created as an integrated development environment (IDE) for the development of java software, Eclipse actually serves as a base for any kind of application. One possibility of using Eclipse is the use as a so called rich client platform (RCP, Eclipse 2008). RCP provides an application framework for plug-in based development of software demanding a rich graphical user interface. The technical realization of the RCP in Eclipse adds important ideas to the architecture into the EMPORER project. But also the providing and successful further evolution of Eclipse as an open source development shall be exemplary for the transfer to the requirements and application within the field of EMIS. In 2001 Eclipse released the source code for its platform and created the fundament for the successful Eclipse community (Eclipse Foundation 2008). Today Eclipse is one of the most often used IDEs for javasoftware. Additionally several projects are processed with Eclipse, using the built-in components of the platform to develop different types of software. An example like this for a community-driven development is rarely known for the field of EMIS. Especially in the scientific community and in teaching great synergies could be made when basic EMIS functionalities are supplied and furthermore a constant transfer between developed methods and instruments in form of plug-ins can be established. 585

The open source platform created in the EMPORER project shall enable possibilities for EMIS functions by further development from developers and the user community and promote use in productive business. The open approach along with the plug-in concept shall lead to the further development of the hereby created and developed system (like Eclipse), which hopefully can be used as a basis for the creation of EMIS-plug-ins and applications. On this fundament the framework may be used in research and teaching, so scientists and students do not have to concentrate on developing base-functionalities but can focus on special challenges of their work. In addition, by providing domain-specific components for material flow analysis the weak reusability of computer-supported material flow analysis and simulation components can be improved. 3. Concept and Implementation 3.1 Overview Aim of the project is as described in the introduction the development of a component oriented, flexible expandable software platform. Due to language independency and the broad support, the chosen technical base is Microsoft s.net technology (Microsoft.NET 2008). The main development language chosen for implementing the software framework is the.net language C#. The platform shall greatly support application developers in developing custom components (Griffel 1998, page 31) to extend the platform. Even so extensions may be developed for the underlying infrastructure (e.g. a new kind of persistence or a new logging mechanism) as well as for some methods of special interest (e.g. offering the execution of continuous simulation runs). An application developer shall find a broad coverage of basic functionalities and infrastructure provided by the platform. This way an application developer can focus on developing problem-specific functions for certain application fields. The components extending the platform, which are commonly activated or deactivated, using platform specific methods, are so called plug-ins. Through the composition and configuration of different plug-ins interacting with the platform it is possible to develop full EMIS applications with relatively low effort. Software developers and end-users can easily configure the complexity of an application based on the platform by selection appropriate plug-ins with functions for certain questions. Thus, an application may be suited best for its context and thus only providing the needed functionality, which is best for the usage scenario of the user. 3.2 Architecture From a software-technical point of view the platform creates a collaboration frame for components and a technical application framework (Griffel 1998, page 115). Using this framework a developer can create an application with a graphical user interface which focuses on EMIS features. On a low level of architecture the technical application framework provides an infrastructure for using plug-ins, offering the needed services to manage and use plug-ins. On a higher level specific plug-ins are integrated to realize special EMIS methods, functions and procedures. Finally an application is created by configuration and composition of infrastructure components in combination with domain-specific components (see figure 1). 586

Reference- Application SME-EMIS- Application... Simulation- Application Application Layer (Independent Applications) Simulation - Infrastructure - Simulation - Production System - - Components - Material Management... Analysis Domain Layer (Domain Specific Components) Main Window (Windows Forms) Model Editor Search...... Navigator Platform Workbench (User Interface) Configuration Persistence Component-Bus Domain Rules Platform Domain Model (Support for Domain Specific Languages) Platform Runtime (Plugin-Management, Core Services, Extension Registry) Platform Layer (Infrastructure) Fig. 1: System Architecture (Schnackenbeck et al. 2007) Besides the separation in technical infrastructure layer, domain layer and application layer, a further layer model is used to uncouple different components from each other independently (Züllighoren 1998, page 705). The separation in presentation layer, functional layer (application logic) and data view (persistence) (Züllighofen, 1998, page 172) e.g. allows to provide an additional web-interface besides the standard graphical user interface, without having to modify the components of the remaining layers. This enables the use of special components of the application layer in totally different usage contexts, detached from the GUI. To realize the plug-in architecture it is necessary to detach the single plug-ins resp. their components and to provide a mechanism to allow access to activated plug-ins resp. components with domain-specific functionalities. The implementation of this mechanism on the platform orientates on the Eclipse OSGI implementation concepts (Eclipse OSGI 2008). Components, which shall be extendible, provide one or more extension points each with contracts defining extension possibilities. A contract normally is formed as an interface (Wikipedia Interface 2008) or as a XSD (W3C Scheme 2008). A component wanting to provide an extension for an extension point is responsible to fulfill the contract it must implement the interface into a class or offer a XML document satisfying the XSD rules (see figure 2). With the extension registry (part of plug-in management) components can access the extensions registered at the extension point. Since every component basically can be an extension for more than one extension point and automatically can provide own extension points, a more or less hierarchic network of linked components is created. 587

They originate from the integrated components with their extension points supplied by the platform infrastructure. When two components offer the same interface it is possible to swap both of them allowing the replacement of the GUI with a web-based interface e.g. Fig. 2: Interface-based Communication between Components (Schnackenbeck et al. 2007) Based on the extension point mechanism the platform infrastructure can be extended with functionalities flexibly, e.g. plug-ins for EMIS methods and procedures, analysis components and more. The following paragraphs will take a closer look at platform integration possibilities of methods and procedures on some of the planned resp. already developed plug-ins and will focus on the infrastructure. 3.3 Infrastructure 3.3.1 Runtime Environment The centre of the platform infrastructure is the platform runtime, which manages plug-ins and their components. Their main responsibilities are the activation and deactivation of plug-ins, the provision of directory services for plug-ins and components, the creation of component instances and the resolving of component dependencies among each other. Communication options are further provided, so plug-ins can communicate with each other and with the platform services. The runtime environment does not depend on the GUI and all other plug-ins. Furthermore the platform runtime component represents a minimal runtime environment for all other plug-ins, such as GUI elements or domain-specific EMIS plug-ins. Further important parts of the platform, which are currently under construction, are persistence, management, support of background operations, capsulated access to the file system, update and error handling and logging. 3.3.2 Infrastructure for Domain-specific Plug-ins Different components also belong to the infrastructure for including EMIS-methods and procedures in a consistent way (platform domain model) into the platform. For domain-specific plug-ins which are com- 588

bined to assemble a specific application (e.g. a material flow simulator) it is of importance that these plugins communicate in a well-defined manner, following domain-specific rules. There must be possibilities for these special plug-in components to find already existing (installed) components, to react on the events of these components (e.g. creation, modification, deletion) and to enforce certain constraints e.g. When component X is deleted from a model, component Y, which depends on component X, also must be deleted. Specific directory services allow access to the different registered domain-specific methods, their components and models. With the help of a communication service (component-bus, see figure 1) components can react on events inside of methods and models, e.g. when certain data are changed. The domainspecific components must not just react passively on specific events; they are also able to send new events, to register event types and to define rules and constraints. These application rules are managed from a further service, which also monitors the established rules inside of the particular method by using the events of the communication service. These explicit rule and event definition allows the implementation of generic mechanisms for checking user action or displaying error messages within the GUI. 3.3.3 User Interface Based on the services of the runtime environment and partially on the just described infrastructure components for plug-ins, further technical components offer a platform workbench for end-users. Application developers should be brought in the situation to create plug-in based applications with similar look and feel with low effort. The platform workbench shows a main window as default, where other plug-ins can display views. Also it is possible for toolbars, menus, context menus and elements for the status bar to be provided and extended by plug-ins. Several generic user interface components are also provided and can be used from other plug-ins. To be specific, a tree view for displaying any hierarchical structure (navigator view), a table view (grid view) and a property editor for editing of any kind of object, e.g. model elements, are available today. A graphical model editor enables end-users to link models and model components with each other in a graphical manner. To use these user interface components in their most simple form, not even code has to be implemented by a plug-in developer, because.net metadata (Microsoft.NET Metadata 2008) is used to generate the content of a view. Further technical components regarding the user interface are the search function, help, progress bar, support for graphical model editors, configurable start-views, docking and generation of reports. At the moment the user interface relies on Microsoft s Windows Forms components from.net 2.0. On the long run other graphical interfaces shall also be supported, e.g. for web browsers. Summarizing this means that providing this technical infrastructure will allow easy development of domain-specific plug-ins, which are where possible detached from reoccurring technical aspects. Within this concept the platform itself is an independent part of a concrete EMIS application. In all consequence this leads to less development effort for the developer of plug-ins and end-applications. 3.4 Methods: Domain-specific Plug-ins for Applications Within the EMPORER project exemplary plug-ins with the main focus on material flow analysis and simulation in combination with the mentioned platform runtime are developed resp. implemented to a build a domain-specific application prototype for a SME. For this each domain-specific entity (e.g. work station, buffer and material flows for the material oriented simulation of the production systems domain) within a domain-specific plug-in is linked together with help of the basic infrastructure. The plug-ins are 589

also linked to each other and to the persistence service building together a specific application with certain functionality. This is where the determined domain-specific rules (e.g. No material may have a quantity smaller than zero ) and logic are applied (e.g. calculations or rating). The entities and the domain-specific rules can be defined with XML resp. code (see the paper of Busse et al. in this conference volume). Connecting to the platform takes place in an almost automatic way thanks to defined metadata, partially with code generation. The following paragraphs shortly describe the mentioned domain-specific plug-ins for certain application fields, which will be implemented within this project (Schnackenbeck et al. 2007). 3.4.1 Simulation Infrastructure The plug-in for providing the simulation infrastructure contains components for executing discrete event simulations, e.g. event scheduler, simulation clock, environment for planning simulation runs and so on (Wohlgemuth 2005). The basic support for simulation models is given by random number generators, stochastic distributions, entities and events as well as wait queues (Law and Kelton 2000). During a simulation run, statistic data can be collected and together with the remaining results a reporting component will analyze the delivered information. Creation of a simulation model is supported by the graphical model editor which is implemented as a technical plug-in within the infrastructure. 3.4.2 Material Flow Analysis Because of the specific requirements within the EMPORER project the prior described simulation infrastructure has to be extended by components, which integrate the more job-based economic view of simulation with the more material-oriented ecologic perspective of material flow analysis on a combined methodical basis. Thus, an event oriented material and energy booking system is used (Wohlgemuth 2005, pages 222-224). For implementation of such an event oriented booking system for material and energy flows, it is required that every model component generates events according to the logic of the discrete event simulation engine. 3.4.3 Material Management The material information used when executing a material flow simulation will be provided by a plug-in for material management. The plug-in architecture will allow other material management systems to be connected with low effort e.g. from other EMIS so a redundant data storage and reimplementation can be avoided. For calculation of the material booking during a simulation run another plug-in will be involved, which communicates to the simulation engine and material management over a special interface (Wohlgemuth 2005, pages 218 ff). 3.4.4 Simulation Components for Production Systems For the application prototype, which will be used to simulate the SME s production processes, simulation components will be implemented as a domain-specific plug-in, which allows modeling of production systems in a generic way (Köpcke and Schnackenbeck 2001). These non-visual simulation components are connected to the simulation infrastructure with generic interfaces, which do not contain details of the production system s context. This connection to the user interface and to the model editor succeeds with a generic adaptor. In this way the development of further simulation model component extensions is possible 590

without having to make changes on the simulation engine or the user interface. It is also planned to implement further special model components for other industry branches to test the concept with regard to usability and portability (Wohlgemuth et al. 2004). 3.4.5 Result Analysis Different domain-specific plug-ins allow the material-orientated and economic evaluation and analysis of the modeled production processes, where especially results of the material flow simulation are interpreted. To create appropriate result reports, some technical plug-ins of the infrastructure platform will be used to create for instance pie-charts or tables. 3.5 Applications A selection of developed plug-ins shall finally be bundled up to build the SME application prototype. It will provide functions for modeling, simulating and reporting of the production processes of this enterprise. Like this integration of plug-ins shall be tested as a complete application. 4. Conclusions and outlook The planned and already developed software components within this research project have great potential to be used in different application contexts. On the one hand selection and configuration of existing plugins leads to new software tools which suit special application contexts due to their dedicated functionality. On the other hand the platform is a basis for custom developments of plug-in-based software tools, where the existing source code can be extended or customized. If necessary the GUI elements provided by the platform can be used to build a low effort user interface with basic core functionalities. Finally the prototype will be used as a prototype application for the involved SME which can be directly used without further development steps. The loose linkage of the plug-ins and the detachment of the user interface from the application logic ease the integration of nearly any part of an application based on this architecture, as long as the applications possess the according extension possibilities. The other way around, also existing applications and components can be used in the plug-in architecture by developing one or more plug-ins to integrate the existing software components. By providing the platform and additional plug-ins as open source, the fundament for community building should be given which is the first step for community improvement, spreading and expanding of the software. Using this platform in teaching allows collaboration on big software systems, allowing Bachelor- and Master-Thesis to be written. Even now the platform is used as a prototype in research projects to enable a quick realization to software. 5. Acknowledgement This research project is funded by the German Federal Ministry of Research and Technology (BMBF). The authors thank for the support. References Eclipse, Internet: http:www.eclipse.org, last access: 30.05.2008. 591

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