I worked on technical Web applications for two different research groups for my master’s project. The first application was Adventure Learning Water Expeditions, an online learning environment for K-12 students in Idaho. The second was Project Engage, a computer science principles course for high school students. In this paper, I describe each Web application by going over the technical details of the application, describing the challenges I faced, and connecting my work with relevant research in the field of Learning Technologies. / text

The web of data has continued to expand thanks to the principles of Linked Data outlined by Tim Berners-Lee, increasing its impact on the semantic web both in its depth and range of data sources. Meanwhile traditional web applications and technologies, with a strong focus on user interaction, such as blogs, wikis, folksonomies-based systems, and content management systems have become an integral part of the World Wide Web. However the semantic web has not yet managed to fully harness these technologies, resulting in a lack of linked data coming from user-generated content. The high level aim of this thesis is to answer the question of whether semantic web applications can be configured to use existing technologies that encourage usergenerated content on the Web. This thesis proposes an approach to reusing user-generated content from folksonomybased systems in semantic web applications, allowing these applications to be configured to make use of the structure and associated reasoning power of the semantic web, but while being able to reuse the vast amount of data already existing in these folksonomy-based systems. It proposes two new methods of semantic web application development: (i) a reusable infrastructure for building semantic mashup applications that can be configured to make use of the proposed approach; and (ii) a approach to configuring traditional web content management systems (CMS) to maintain repositories of Linked Data. The proposed approach allows semantic web applications to make use of tagged resources, while also addressing some limitations of the folksonomy approach by using ontology reasoning to exploit the structured information held in domain ontologies. The reusable infrastructure provides a set of components to allow semantic web applications to be configured to reuse content from folksonomy-based systems, while also allowing the users of these systems to contribute to the semantic web indirectly via the proposed approach. The proposed Linked Data CMS approach provides a configurable tools for semantic web application developers to develop an entire website based on linked data, while allowing ordinary web users to contribute directly to the semantic web using familiar CMS tools. The approaches proposed in this thesis make use of lightweight ontology reasoning, which is both efficient and scalable, to provide a basis for the development of practical semantic web applications. The research presented in this thesis shows how the semantic web can reuse both folksonomies and content management systems from Web 2.0 to help narrow the gap between these two key areas of the web.

Web applications are widely used for email, online sales, auctions, collaboration, etc. Most of today’s highly-available web applications implement fault tolerant protocols in order to tolerate crash faults. However, recent system-wide failures have been caused by arbitrary or Byzantine faults which these applications are not capable of handling. Despite the abundance of research on adding Byzantine fault tolerance (BFT) to a system, BFT systems have found little use outside the research community. Reasons typically cited for this are the difficulty in implementing such systems and the performance overhead associated with them. While most research focuses on improving the performance or lowering the replication cost of BFT protocols, little has been done on making them easy to implement. The goal of this thesis is to evaluate the viability of BFT web applications and show that, given the right abstraction, it is viable to build a Byzantine fault tolerant web application without extensive reimplementation of the web application. In order to achieve this goal, it demonstrates a BFT implementation of the Apache Tomcat servlet container and the VQWiki web application by using the UpRight BFT library. The UpRight library provides abstractions that make it easy to develop BFT applications and we leverage this abstraction to reduce the implementation cost of our system. Our results are encouraging — less than 2% of the original system needs to be modified while still retaining all the functionality of the original system. Given the design trade-offs that we make in implementing the system, we also get comparable performance, indicating that implementing BFT is a viable option to explore for highly-available web applications. / text

Two important trends in computer systems are that applications are moved to the Internet as web applications, and that computer systems are getting an increasing number of cores to increase the performance. It has been shown that JavaScript in web applications has a large potential for parallel execution despite the fact that JavaScript is a sequential language. In this thesis, we show that JavaScript execution in web applications and in benchmarks are fundamentally different and that an effect of this is that Just-in-time compilation does often not improve the execution time, but rather increases the execution time for JavaScript in web applications. Since there is a significant potential for parallel computation in JavaScript for web applications, we show that Thread-Level Speculation can be used to take advantage of this in a manner completely transparent to the programmer. The Thread-Level Speculation technique is very suitable for improving the performance of JavaScript execution in web applications; however we observe that the memory overhead can be substantial. Therefore, we propose several techniques for adaptive speculation as well as for memory reduction. In the last part of this thesis we show that Just-in-time compilation and Thread-Level Speculation are complementary techniques. The execution characteristics of JavaScript in web applications are very suitable for combining Just-in-time compilation and Thread-Level Speculation. Finally, we show that Thread-Level Speculation and Just-in-time compilation can be combined to reduce power usage on embedded devices.

The web is evolving: what was once primarily used for sharing static content has now evolved into a platform for rich client-side applications. These applications do not run exclusively on the client; while the client is responsible for presentation and some processing, there is a significant amount of processing and persistence that happens server-side. This has advantages and disadvantages. The biggest advantage is that the user’s data is accessible from anywhere. It doesn’t matter which device you sign into a web application from, everything you’ve been working on is instantly accessible. The largest disadvantage is that large numbers of servers are required to support a growing user base; unlike traditional client applications, an organization making a web application needs to provision compute and storage resources for each expected user. This infrastructure is designed in tiers that are responsible for different aspects of the application, and these tiers may not even be run by the same organization. As these systems grow in complexity, it becomes progressively more challenging to identify and solve performance problems. While there are many measures of software system performance, web application users only care about response latency. This “fingertip-to-eyeball performance” is the only metric that users directly perceive: when a button is clicked in a web application, how long does it take for the desired action to complete? MT-WAVE is a system for solving fingertip-to-eyeball performance problems in web applications. The system is designed for doing multi-tier tracing: each piece of the application is instrumented, execution traces are collected, and the system merges these traces into a single coherent snapshot of system latency at every tier. To ensure that user-perceived latency is accurately captured, the tracing begins in the web browser. The application developer then uses the MT-WAVE Visualization System to explore the execution traces to first identify which system is causing the largest amount of latency, and then zooms in on the specific function calls in that tier to find optimization candidates. After fixing an identified problem, the system is used to verify that the changes had the intended effect. This optimization methodology and toolset is explained through a series of case studies that identify and solve performance problems in open-source and commercial applications. These case studies demonstrate both the utility of the MT-WAVE system and the unintuitive nature of system optimization.

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With the recent growth of the mobile market, companies want to target mobile devices while at the same time keeping product development costs low. One way to do this is to develop web applications, which are accessed from a mobile de- vice’s web browser, instead of native applications. The same web application can then be used on different platforms such as Android and iOS. However, devices such as smart phones and tablets often include cameras and sensors that a web ap- plication may want to access, but which are only accessible from native applica- tions. A framework was developed that enables web applications to communicate with native Android applications. Native applications are launched by clicking a link in the browser, and the result produced is made available to the web applica- tion through a HTTP POST request or a local web server running on the device. Key characteristics of the framework include ease of extension and the ability to enable secure (SSL) communication if desired. The ZXing Barcode Scanner ap- plication was integrated with the framework so that a scanned barcode can be dis- played in the browser. Performance measurements were conducted measuring the time taken from clicking a link to start a test application to the result being avail- able in the browser. The mean times measured were between 323 and 394 mil- liseconds. This indicates that the method used is sufficiently fast to not detract from the user experience. Future work could expand on the measurements or per- form a feature and performance comparison with PhoneGap.

Yes / The web environment has been developing remarkably, and much work has been done towards improving web based notification systems, where servers act smartly by notifying and feeding clients with subscribed data. In this paper we have reviewed some of the problems with current solutions to real-time updates of multi user web applications; we introduce a new concept “adaptive polling” based on one AJAX technique “Polling” to reduce the high volume of redundant server connections with reasonable latency, we demonstrated a prototype implementation of the new concept which is then evaluated against the existing one; the positive results clearly indicated more efficiency in terms of client-server bandwidth.

Portability of web applications between web servers of different organizations can be challenging and can complicate sharing and collaborative use of such tools. Given the distributed nature of the web, this lack of portability is usually not a concern because a user in one organization can link to and use a web application hosted by another organization. However, access control or differentiation may be needed by an organization in terms of area of interest, input data, analytical techniques, access control, presentation, branding, and language. This is true for many government organizations, and their associated web sites, and servers. In such cases, there are compelling political, branding, security, and privacy motivations that require each organization or agency to host and manage web applications on their own servers rather than using third party web sites over which they have little or no control. Also, web applications are classically developed by setting up a local software development and testing environment which can be challenging for new developers, be restricted by the software and hardware availability, cost significantly to obtain software development licenses and compatible hardware and is prone to code and data loss due to hardware damage or software corruptions. To simplify the discovery, deployment of web-based applications, I present the design, development, and testing of a system for discovering, installing, and configuring environmental analysis web applications on localized web servers. The system works with applications developed using Tethys Platform, which is an open-source software stack for creating geospatially enabled web-based applications. The developed Tethys App Store includes a Tethys application user interface that allows a server manager to retrieve applications from the central repository and install them on a local server with relatively simplicity, similar to the installation of a mobile application to a mobile device from a mobile application store. Next, I present the design concept of a cloud-based web application development platform, Tethys App Nursery, that attempts to overcome the above hurdles associated with localized development environments. A prototype of this system is developed and presented which is tightly integrated with Tethys platform and various cloud technologies provided by Amazon Web Services. The developed app nursery allows users to register for new Tethys portal instances in the cloud, develop new applications and test existing applications, without installing any local dependencies or development tools. Various cloud components used in this service's development as well as their associated costs are described. These systems were developed to support development of water and environmental analysis web apps for the international Group on Earth Observations (GEO) Global Water Sustainability (GEOGloWS) initiative of the National Aeronautics and Space Administration (NASA) and several partner organizations.