The World Wide Web has succeeded in large part because its software architecture has been designed to meet the needs of an Internet-scale distributed hypermedia system. The Web has been iteratively developed over the past ten years through a series of modifications to the standards that define its architecture. In order to identify those aspects of the Web that needed improvement and avoid undesirable modifications, a model for the modern Web architecture was needed to guide its design, definition, and deployment. Software architecture research investigates methods for determining how best to partition a system, how components identify and communicate with each other, how information is communicated, how elements of a system can evolve independently, and how all of the above can be described using formal and informal notations. My work is motivated by the desire to understand and evaluate the architectural design of network-based application software through principled use of architectural constraints, thereby obtaining the functional, performance, and social properties desired of an architecture. An architectural style is a named, coordinated set of architectural constraints. This dissertation defines a framework for understanding software architecture via architectural styles and demonstrates how styles can be used to guide the architectural design of network-based application software. A survey of architectural styles for network-based applications is used to classify styles according to the architectural properties they induce on an architecture for distributed hypermedia. I then introduce the Representational State Transfer (REST) architectural style and describe how REST has been used to guide the design and development of the architecture for the modern Web. REST emphasizes scalability of component interactions, generality of interfaces, independent deployment of components, and intermediary components to reduce interaction latency, enforce security, and encapsulate legacy systems. I describe the software engineering principles guiding REST and the interaction constraints chosen to retain those principles, contrasting them to the constraints of other architectural styles. Finally, I describe the lessons learned from applying REST to the design of the Hypertext Transfer Protocol and Uniform Resource Identifier standards, and from their subsequent deployment in Web client and server software.

The World Wide Web has succeeded in large part because its software architecture has been designed to meet the needs of an Internet-scale distributed hypermedia application. The modern Web architecture emphasizes scalability of component interactions, generality of interfaces, independent deployment of components, and intermediary components to reduce interaction latency, enforce security, and encapsulate legacy systems. In this article we introduce the Representational State Transfer (REST) architectural style, developed as an abstract model of the Web architecture and used to guide our redesign and definition of the Hypertext Transfer Protocol and Uniform Resource Identifiers. We describe the software engineering principles guiding REST and the interaction constraints chosen to retain those principles, contrasting them to the constraints of other architectural styles. We then compare the abstract model to the currently deployed Web architecture in order to elicit mismatches between the existing protocols and the applications they are intended to support.

Presentation Diagram" section). 7. Other implementations: Adapt the observer pattern 11 to hypermedia environments. Navigational access diagram For a more general perspective of the approach, we'll use a discussion list management system as an example. As a basic explanation (for reasons of brevity), we assume the list manager system contains several discussion lists dealing with different Web technology topics, and the system forms each list by a set of hierarchically ordered messages relating to each other through a parent--child unary relationship. The discussion list user can read all the messages included inside any lists and reply to any of them. We previously noted that one or more NADs capture the navigation model. Designers should construct as many NADs as different views of the system are required, and they should provide at least one different NAD for each user type (agent type) allowed to navigate through the system. A NAD is based on four types of constructs: navigational classes, navigational targets, navigational links, and collections. Also, when defining the navigation structure, designers must consider some orthogonal aspects, such as the desired navigation behavior, the object population selection, the order in which objects should be navigated, or the cardinality of the access. We capture these features by different kinds of navigation patterns and filters associated with links and collections. We further develop these concepts below. Navigational classes. Enriched domain classes whose attributes and method visibility have been restricted according to the user access permissions and navigation requirements. A sample enrichment is the differentiation among three types of attributes: V-attributes (visible attributes), R-attributes (referenced attr...

The web is more and more used as a platform for fullfledged, increasingly complex information systems, where a huge amount of change-intensive data is managed by underlying database systems. From a software engineering point of view, the development of such so called DataWeb applications requires proper modeling methods in order to ensure architectural soundness and maintainability. The goal of this paper is twofold. First, a framework of requirements, covering the design space of DataWeb modeling methods in terms of three orthogonal dimensions is suggested. Second, on the basis of this framework, eight representative modeling methods for DataWeb applications are surveyed and general shortcomings are identified pointing the way to nextgeneration modeling methods.

The web is more and more used as a platform for full-fledged, increasingly complex applications, where a huge amount of change-intensive data is managed by underlying database systems. From a software engineering point of view, the development of web applications requires proper modeling methods in order to ensure architectural soundness and maintainability. Existing modeling methods for web applications, however, fall short on considering a major requirement posed on today's web applications, namely customization. Web applications should be customizable with respect to various context factors comprising different user preferences, device capabilities and locations in mobile scenarios, to mention just a few. The goal of this paper is twofold. First, a framework of requirements, covering the design space of customizable web applications is suggested. Second, on the basis of this framework, existing approaches for developing customizable web applications are surveyed and general shortcomings are identified pointing the way to next-generation modeling methods.

Modern distributed web applications should oer high customizability, various communication resources, exible data and document representations, persistence, metadata, mechanisms for interaction and coordination, etc. Often these requirements are either badly supported by the development tools or a diverse set of technologies has to be used which is orthogonal to web technology and is based on overlapping concepts, abstractions, and paradigms. In this paper we present ActiWeb as a single framework centers around the notion of active web objects. Those integrate web documents with objects of an objectoriented scripting language. The scripting language enables rapid application development and component gluing. Moreover, several basic services, such support for XML, RDF, remote procedure calls, code mobility, object persistence, and object registration are provided.

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Web-based application developers face a dizzying array of platforms, languages, frameworks and technical artifacts to choose from. We survey, classify, and compare technologies supporting Web application development. The classification is based on (1) foundational technologies; (2) integration with other information sources; and (3) dynamic content generation. We further survey and classify software engineering techniques and tools that have been adopted from traditional programming into Web programming. We conclude that, although the infrastructure problems of the Web have largely been solved, the cacophony of technologies for Web-based applications reflects the lack of a solid model tailored for this domain.

thesis of CHRISTOPHER JERRY MALLERY find it satisfactory and recommend that it be accepted. ii Chair ACKNOWLEDGEMENT I would like to thank my entire committee for their infinite amount of support throughout my research. I would also like to thank Jeff Offutt, Roger Alexander and Kshamta Jerath for their extremely helpful feedback and for providing much of the groundwork on which this thesis is based. iii Chair: Anneliese A. Andrews

In the enterprise information systems environment, web based systems in general, and e-commerce applications in particular, are required to face a very high pace of change. The evolution of such systems is caused both by adaptation to the customer needs and enterprise continuous improvement strategies. Such rapid change can be achieved adopting a model-based approach in which the application is customized according to a model. The concept of model proposed in this paper is more wide that the one adopted in most modeling languages such as UML. We propose an object model that allows an application access the model according to different perspectives and abstraction levels.