Architecture and System Design Issues of Contemporary Web-based Information Systems

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Architecture and System Design Issues of Contemporary Web-based Information Systems
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  > 1 Architecture and System Design Issues of Contemporary Web-based Information Systems B.Molnár  1 , Á. Tarcsi 21 Corvinus University of Budapest, 1093, Budapest Fővám tér 13 -15., Sóház II/225, Hungary 2 Eötvös Loránd University, Faculty of Informatics, Department of Information Systems, 1117, Budapest, Pázmány Péter sétány 1/c. Hungary, The rapid changes of information technology led to the proliferation of Web-based Information Systems (WIS). Therehas been already some research on thegeneral model for analysis and design of WIS. This paper attempts to define a comprehensive framework for integrating the various viewpoints of model for WIS. Several components that compose of aWIS as analyzing and designing element are investigated and described as modeling element and enabling tool for creating consistent and integrated system. Themajor modeling componentsare: the Web site, semi structured document, business processes, element of knowledgemanagement, theenterprise and information architecture, and autonomous software components providing functional services. These elements are integratedinto a unified framework exploiting partly the object-oriented paradigm and partly other approaches for information system modeling. The outlined WIS model incorporates the most recent approaches for various paradigms of traditional information systems analysis and the most modern different approaches of WIS. The research result would be useful both theoretically and practically as it could presenta comprehensive model for WIS assisting our understanding of properties of WIS and supporting, at the same time, a framework for being able to formulate a practical development method for achievementof WIS by organizationsmaking the most of Web.  Index Terms —Object oriented modeling, Object oriented methods, Software architecture, Web services. I.INTRODUCTION HE PAST DECADES has presented a dramatic change of the use of information technology within organizations and enterprises. To control the inherent complexity of structure of large-scale information systems and information resources, various IS architectures have been elaborated to describe and to keep in hand the several layers, tiers and components of architecture.Architecture provides a kind of synthesis through providingviews and viewpoints that can be realized by various models  proposed in different methodologies for architecture and information systems analysis and design. A web information system ( WIS  ) is database-intensive and/or transaction intensive information system that is implementedandmade accessibleover the web byuser access via web browsers.In web informationsystem, data is obtainablethrough web interfaces that are manifested in semi-structured document formatincluding a navigation structure among the documents and pages organized into some kind of networks or hierarchy;moreover there are links to sites outside the systemas well. Furthermore,there should also be servicesforretrievingand modifyingdata out ofthe system or from the underlyingdatabase. Service-Oriented Architectures ( SOA ) have appeared after the WIS being in existence for a while; they achieved large success within the Web communities, especially at WIS. Rather than pure technology improvements SOA intends to increase manageability and sustainability of information systems and to better align business requirements and technology implementations. Therefore it is reasonable to link SOA to the concept of enterprise architecture (  EA ). As the enterprise architecture  provides a global framework to deal with the inherent problem of WIS modeling, design and operation. In addition, the change processes occurring during the life of a WIS dedicated to an organization are typically concurrent and interact with one another. To handle the complexity of changes and change management some concepts are required namely the concept of the life history, the life cycle of systems, and the life history of entities or  classes (of objects) . We should use these concepts to distinguish between two  behavioral aspects of WIS. The terms of life history of systems means “the actual sequence of steps a system has gone or will go through during its lifetime”, and life cycle seen as ‘‘the finite set of generic phases and steps a system may go through over its entire life history’’ [1]. Thus, life history and life cycle are in fact orthogonal, as shown in a typical life history example is provided in [2]. A WIS fitting into the Enterprise Architecture of an organization has a static perspective representing the structural aspects at a specified point in time and a dynamic perspective capturing the various stages of architecturedevelopment that happens to a WIS as an application system [2]. These two perspectives may reflect the changes that take place at component level of architecture of a WIS –both statically and dynamically -, however there is a need to represent the time dimension at components of development, implementation and operation level, i.e. the life history of components or entities . Although the development of the logic of a Web Application is similar to the conventional software development the process of implementing the web-based T Manuscript received April 18, 2011. The Project is supported by the European Union and co-financed by the European Social Fund (grant agreement no. TAMOP 4.2.1./B-09/1/KMR-2010-0003).Bálint Molnár is with Corvinus University of Budapest, 1093, Budapest Fővám tér 13 -15., Sóház II/225, Hungary (corresponding author e-mail: (molnar@infomatika.uni-corvinus.hu ).   > 2information systems behind these applications has, however, shown the deficiencies of the existing methodologies for modeling, analysis and design and the need for the specification, design and implementation of new mechanisms.The WIS contains traditional information systems element and semi-structured XML documents which behaves actively  beside other important partsof the system. The XML documents make use of active hyperlinks and other featuresof Web and Web services.This paper wants to elaborate a modeling framework for WIS taking into account of the development of past decades considering the various architectural and technological component and solution. We discuss the proposed model and show how the earlier created methodologies and methods for analysis, design, implementation and management can be used to construct web-based applications in a framework to combineaspects of data, behavior, state and presentation and exploit the various perspectives and aspects of approaches to make consistent information systems. An attempt is made in this research to create a (1) firstly a comprehensive model including the relevant aspects of WIS, (2) based on the model a methodology and related methods to support the design process.II.R  ELATED W ORKS There were already attempts to put into a unified framework the modeling of WIS at a given point in time taking into account of the existing technology and approaches. A general model for WIS using an object-oriented approach is described in [3]. The use of semi-structured, active XML documents and a disciplined design approach are discussed in [5] to construct web-based applications. Another paper [6] presents a design methodology for a systematic design process to organize and maintain large amounts of data in a Web site, in the form of a hypermedia design methodologies. For large-scale WIS design [10] contains a method.Beside the different analysis and design model for WISs, the concept of architectural approach is that can be used in model creation, the various IS architectures have been used to assist in understanding the relationship between the various  perspectives, aspects, components and single models [7], [1], [2]. Zachmanarchitectures developed for information systems. TOGAF is developed by Open Group on Architecture Framework. It contains two main parts: The Architecture Development Method (ADM) and the Foundation Architecture with generic functions/services on which specific architectures and building blocks can be built [8].The service orientation is emerging at multiple organizational levels in business, and it leverages technology. The service-oriented architecture (SOA) can be considered as a technical architecture, a business modeling concept, a piece of infrastructure, an integration source, and thereby an architecture for contemporary WIS [9]. While each of the above approaches overlaps with some of the features of our work, the contribution we make is to address at problems that concludes the dynamical behavioral of WIS-s in several aspects and how to handle at modeling level the issues of consistency, integration, confidentiality, accuracy and timelines.III.I  NFORMATION S YSTEM A RCHITECTURE   The  Information System Architecture represents the structure of certain componentsof information processing systems, their relationshipsamong components, those technological principles and directivesof organizationof whichthe main purposeis to support business. The description of how a system was internally builtdepicted primarily the technological components, especially the software building blocks. The  Zachman Framework  ([7])can be considered as the first important phenomenonthat  pinpointed to the fact that software architectures were not enough. While software architectures represent internal system details (using, for example, E-R and DFD diagrams)  Information System Architecture focus on the high-level  business and information system processes. We perceive  Enterprise IT Architecture as the suite of strategic and architectural disciplines that includes the Information, Business System, and Technical Architectures.An  Enterprise Architecture can be divided into severallevels:  Business (systems) architecture -Defines the structure and content (information and function) of all business systems in the organization.  Information (or Data) Architecture  –represents main data types that support business; furthermore the structure (including interdependencies and relationships) of information required and in use by the organization;  Application Architecture  –defines applications needed for data management and business support;the collection of relevant decisions about the organization (structure) of a software system, and the architectural style that guides this organization. Technical Architecture  –represents the main technologies used in application implementation and the infrastructures that  provide an environment for information systemdeployment.Technical architecture describes and maintains the integrity of the hardware, software, and infrastructure environment required to support the  BusinessSystems Architecture and  Information Systems Architecture. A.Controlarchitecture:Theproductofdynamic modeling Control architecture  providesatemporal viewonthedynamicsofdata,application,and technology.The temporal dimension and behavior of data and/or information reflected in the form of entity life history, life cycle, state chart or state transition diagram. However, there are no established and widely accepted formalism and approaches at developmental control, operational control, and maintenance controlto keep in hand the ever changing environment and provide a descriptive method to support handling the related issues.  > 3  Developmental control handlesallthechanges occurringintheprocessofnewapplicationdevelopmentovertime.Alsocalledversioncontrolor software configuration management  , developmentalcontrolrecordsvariousaspects(who,what, andwhen)ofeachchangemade. Operational control concernstheperformance andintegrityofcurrentdata,applications,and technologyconfiguration.In WIS, the changes may happen at both documen t (XML / HTML) leveland data level, sometimes parallel; both changes indicates alteration on the application (logic) level as well. Thisiswhen maintenance control  becomesa criticalissue.Howcanwemanagethesechanges withoutseverelydisruptingtheexistingoperationsofthebusiness?Whatwillbetheimpactof acertainchangetospecificpartsoftheorganization?Whoareinchargeofwhat?Someoftheseareincludedinthe “impactanalysis”portionsofmoderndatadictionarysystems.The business processes within information function of organization should provide adequate answers within the ITIL (Information Technology Infrastructure Library, [17]). TABLE 1 HERE  B.Service-Oriented Architectures (SOA) and the WIS Service-oriented computing (SOC) is considered as a newinformation technology paradigm after the object-oriented  paradigm. Itutilizes services as fundamental, reusableelements for developingapplications/solutions. One of the  basic components of SOA approach is the concept of services that maps the business services to information services in the form of Web-services .The SOC paradigm and Web-services together provide an appropriate approach for building Web based information systems (WIS) that a definite feature of the collaboration i.e. the comprising element work together in an interactive manner within a dynamically changing environment.The WIS-s making use of SOC have -as an advantage -the direct connection to the organization business processes, workflows, activities and tasks. The  Business Process  Modeling (BPM) realizes this direct mapping between the organizational level services and the information system level services. The Business Process Execution Language for Web Services (BPEL) is an example for an executable language that implements the results of BPM.As the size of Web applications grows, it becomes clear that  better models, methods, methodologies and tools are required to deal with their increasingcomplexity. A model and a design methodology of WIS promotes the idea that the large and complex Information Systems made available by the Web technology should be modeled and designed as large scale Information Systems embedded into  business and organizational environment. The model and design methodology should take into account both the socio-technological environment and the Web and / or software engineering approaches.WIS analysis, modeling and design methodologyshould include 1.aspects of computing on theInternet, 2.distributed transaction processing,3.knowledge management, 4.hypermedia-the Web site,5.intranets, 6.and extranets7.XML / HTML documents either as Web pages or information resources,8.database management systems and data warehouses,9.document management systems,10.Enterprise Architecture, Service Oriented Architecture, Web services.a.Mediator; b.wrapper architecture for Web applications;c.Web servies -software agents.11.Business processes analysis and managementthe Web site-online business processing.12.Information Security: integrity, confidentiality, accuracy, availability, timeliness-information infrastructure.13.Performance and scalability issues.The core of WIS is an information system in the traditional sense. Models, analysis and design approaches of conventional information system are evolved trough decades, the most important modeling approaches applied nowadays include:1.Data- flow diagram method ( [20],[21],[222.entity-relationship method ([23]);3.Relational analysis;4.Functional analysis, hierarchy and decomposition;5.Business and information event analysis and mapping to state transition of the conceptual information and/or datamodel. The WIS’s goals can be formulated as to support networked organizations in the integration of specializedWeb sites into acommon set of tasks for them and providing organizational computing network properties. The overlapping of WIS and conventional business ISappears in the form of data  processing systems, data base management, report systems, and decision support systems. The differencebetween a set of Webpages, typical Web Applicationsand a WIS can be described as follows: WIS supports business process(Business Process Modeling, BPM) and is usually tightly integrated with other IS.WIS can also be viewed as database applications for structured as well as semi-structured data(XML / HTML). There is a comprehensive meta-model for WIS ([3]) that overarching all views, aspects and perspectives from semi-structured documents to knowledge management. There are models in object-oriented style for all element of Wang’s meta-model and the components of meta-model can perceived as artifacts of Zachman architecture and put into the proper cells (Table 2). The semi-structured documents embodying hypermedia or hypertext document plays a crucial role in the most modern IS as WIS ([24],[25], [26]). Historically documents have been used in displaying, interchanging, and retaining information. The so-called form documentshave been used in traditional IS  > 4as well, srcinally for presenting user interfaces, displaying the underlying data structures, and demonstrating the related transactions; later on, the form documents have become the typicallayout for the WIS user interfaces using the HTML standard. Within the context of an organization, the activities of creation, exchange and modification of documents comprise a series of tasks within business processesthat all together makes workflows. Each relevant workflow can be represented as directed acyclic graph having tasks or information processes in its nodes. The document flow within business can be mapped to the information flow of a single workflow that isimplemented by information technology; previously the base of realization was the traditional IS, nowadays the business  processes are carried out by WIS. This phenomenon can be summarized as evolution of the information processing  paradigm, shifting from the process-oriented, data intensive application typically represented and designed in object-oriented style to document-oriented  computing. The development of information technology has led to the active semi-structured documents. The documents –e.g. theform documents intended to collect data –, contain procedures for information processing as it is required at a given time at a certain position within the workflow, thereby the documents demonstrate active behavior. FIG. 1 HERE C.Architectural viewpoint  Anoverall architecture approach assists in creating and conceptualizing a comprehensive model for WIS. As WIS not only a variant of information systems but it is a new technological approach for realizing information system.The most modern architectural approach is SOA that slowly  becomes the typical basic architecture for a large number of WIS. The mapping the elements, models are outlined in Table 1, Table 2.  D.WIS Functional Viewpoint  The business processes carried out by WIS can be described  by object-oriented analysis and design methods. The business  processes realized by WIS demonstrate the functional side or functional services of IS.A business process can be modeled by using three fundamental types of object classes:  Conceptual mapping of entities or concepts , -objects represent the structured data inWIS;  event  , -represent events of routine operations (e.g., order processing), decisionactivities;  document  -information entities that enter the system (e.g.,electronic order applications), or that are  produced by the system (e.g., online business reportsand client side scripting XML/HTML documents), or stored the system as semi-structured data (XML documents).Beside the above mentioned parts the WIS generally contains knowledge management components as well, namely, organizational learning, mapping some cognitive activities onto a structures representing cognitive properties (“cognizant” element [3]):production rules,semantic networks, cognitive maps, or other formsof knowledgeand knowledge representation.All of the models covering each single part of WIS use the object-oriented paradigm making comparable, verifiable, through cross-checking pair of models. The object-oriented framework provides an explicit logical schema of WIS, and can be tailored and actualized based on the requirements of a specific WIS.  E.Integration within the tier of control architecture T We have now at least five separate dimension or aspect of IS (Fig. 1). An optional T synthesis of the five aspects can be formalized into a dynamic depiction as it follows: A business process starts with Web pagedescriptions,  presentation or design. Each of the operators of the Web pageinitiates messages to other types of objects. The four possible outcomes in response to aninitial message:a)The message from the Web site object invokesanother Web siteobject. b)The message triggers a knowledge object, which might be an element for representation of knowledge.c)The message evokes a software agent  or Web service (e.g., a search engine), which might in turn trigger a business process. d)The message passes through a network or Enterprise Bus Service, and then starts a Service realizing a  business process, usually, bytriggering an event  of the business process.e)After a business process starts, its entity (conceptual mapping of physical real-world objects), document  , and event  objects are triggeredsubsequently.f)Each of the objects of the business process activates the corresponding architecture elements (network service, other service component, logical, physical application or information component, etc).g)The objects of the architecture elements send messages to other information architecture objects to verify thecomponentsof the information infrastructurewhether there are or were any breach of consistency or security. TABLE 2 HERE F.WIS Semi-Structured Document Viewpoint  T The Web is playing a critical role as a source of information. Most of Web-based applications are document centric. Most of business processes in an organization are carried out through workflows making use of documents as information source and transmitter. Moreover, the Internet technology accelerates business processes to be implemented  by Web-based applications. T From theviewpoint of human-computer interaction, Web-based document actualize the structured and semi-structured data through the computer-user interface of theWIS, and specify the dialogue between users  > 5(clients) and the WIS. A central part of WIS isthe Web pages and Web semi-structured data in the form of XML/HTML documentsfor the users on the network (Intranet, Extranet, Internet). Presentations of informationto the users and requests for input from the users are the two facetsof Websites from the viewpoint of the WIS. With the documents implemented in extensible markuplanguage (XML), the relationshipand information exchange between the Web pages and the associatedbusiness processes and knowledge representationis realized. G.WIS Dynamic Behavior Viewpoint  The intrinsic nature of WIS is the dynamic behavior in every component, the user interface and its semi-structured document and the underlying IS, but not only in respect the data content however the data an processing structure as well.  Behavior  : A behavior means a method of processing a document implied in abusiness document. Behaviors include (1) general computation logics, (2) rules of defining and controlling business processes such as business rules, (3) data integrity constraints necessary for validation of data, and (4) workflow execution.  Behavioral correctness : The correctness of behavioral composition is concerned with the security, safety, faithfulness and fairness of behavioral properties. The composition of two components should behave properly. The composition may mean the creating or modifying a semi-structured document then storing , or linking to the data structure and content of underlying IS. The composition may mean the orchestration and / or choreography of service component. The composition could mean storing of the semi-structured document in native format, independently from the data content and structure of underlying IS and then later-on could be reconciled and integrated to eliminate the inconsistencies between the documents and WIS. To resolve the inconsistencies a name mapping associates the classes and objects declared in a component with the classes and objects declared in the composition of this component and other components.  H.Consistency and Reconciliation of Model Element  Having seen previously the heterogeneous approaches and models that reflect important aspects of WIS, we encounter the question what general modeling framework can be employed to describe a comprehensive methodology for modeling and design that provides the option for further development in the sense of refinement and towards a semi-formal and later-on a formal description. To put the disparate and different models into a unified framework, the first attempt is to map the WIS and its possible models into the Zachman architecture that contains the important aspects and views of an IS within an organization context. To make the various models comparable, verifiable in the sense of correctness, the object-oriented modeling approach can be used for each modeling artifact as all the views of Zachman can be modeled byobject-oriented  paradigm from the classical IS and database technology to the document-oriented WIS.  Axiomatic Design Theory ([27], [28]) is a systematic methodology that assists designers to structure design  problems. Originally, AD identifies four concepts, namely: domains, hierarchy of design artifacts, zigzagging between domains and element of hierarchy, two axioms.  Independence  Axiom : Maintain the independence of the functional requirements;  Information Axiom : Minimize the information content of the design. The axiomatic design can be applied to modeling and design of systems that consist of components that present comprehensible complexity, the components are independent from each other and the requirements can be unambiguously distinguished from each other.There are four domains: the customer domain, the functional domain, the  physical domain, and the process domain.Instead of the srcinally defined domains of axiomatic design, we will use the perspectives of Zachman architecture as “domains” as all domains of axiomatic design theory is contained within the set of Zachman’s perspectives and represents the life cycle of system development and operation.The artifacts that describe what  , how , where and why the features and systems of features operate in the logical and  physical domains can be defined in an explicit, well thought-out manner using of object-oriented paradigm. The framework matrix consists of a vertical axis that provides multiple  perspectives of the overall architecture and a horizontal axis, which provides a classification of the various artifacts within the architecture. The applicable perspectives and classifications within the framework are illustrated inTable 2.The advantage of object-oriented approach is that it operates as a lingua franca at syntactical level of modeling and there are modeling approach in object-oriented paradigm for each artifacts of Zachman architecture. As to axiomatic design theory, the elements within each domain are Customer Needs (CNs), Functional Requirements (FRs), Design Parameters (DPs), and Process Variables (PVs). The axiomatic design methods provide a powerful design documentation tool that can be easily understood by people uninvolved in the process. Not only is it clear which DPs satisfy which FRs, but it is easily understood how the system has been decomposed, and the level of coupling within the design.The mapping process between the domains can be expressed mathematically in terms of the characteristic vectors that define the design goals and design solutions. At a given level of design hierarchy, the set functional requirements that define the specific design goals constitutes a vector {FRs} in the functional aspects . Similarly, the set of design parameters in one of the perspectives for the FRs also constitutes a vector {DPs}. The relationship between these two vectors can be written as:   DPsAFRs   (1)The matrix  A type represents the actual “method”, the transformation and mapping between the functional
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