Paul Janecek

Adaptive resource provisioning for read intensive multi-tier applications in the cloud

A Service-Level Agreement (SLA) provides surety for specific quality attributes to the consumers of services. However, current SLAs offered by cloud infrastructure providers do not address response time, which, from the users point of view, is the most important quality attribute for Web applications. Satisfying a maximum average response time guarantee for Web applications is difficult for two main reasons: first, traffic patterns are highly dynamic and difficult to predict accurately; second, the complex nature of multi-tier Web applications increases the difficulty of identifying bottlenecks and resolving them automatically. This paper proposes a methodology and presents a working prototype system for automatic detection and resolution of bottlenecks in a multi-tier Web application hosted on a cloud in order to satisfy specific maximum response time requirements. It also proposes a method for identifying and retracting over-provisioned resources in multi-tier cloud-hosted Web applications. We demonstrate the feasibility of the approach in an experimental evaluation with a testbed EUCALYPTUS-based cloud and a synthetic workload. Automatic bottleneck detection and resolution under dynamic resource management has the potential to enable cloud infrastructure providers to provide SLAs for Web applications that guarantee specific response time requirements while minimizing resource utilization.

A comparative analysis of techniques for predicting academic performance

This paper compares the accuracy of decision tree and Bayesian network algorithms for predicting the academic performance of undergraduate and postgraduate students at two very different academic institutes: Can Tho University (CTU), a large national university in Viet Nam; and the Asian Institute of Technology (AIT), a small international postgraduate institute in Thailand that draws students from 86 different countries. Although the diversity of these two student populations is very different, the data-mining tools were able to achieve similar levels of accuracy for predicting student performance: 73/71% for {fail, fair, good, very good} and 94/93% for {fail, pass} at the CTU/AIT respectively. These predictions are most useful for identifying and assisting failing students at CTU (64% accurate), and for selecting very good students for scholarships at the AIT (82% accurate). In this analysis, the decision tree was consistently 3-12% more accurate than the Bayesian network. The results of these case studies give insight into techniques for accurately predicting student performance, compare the accuracy of data mining algorithms, and demonstrate the maturity of open source tools.

Video artifacts for design: bridging the Gap between abstraction and detail

Video artifacts help bridge the gap between abstraction and detail in the design process. This paper describes how our use and re-use of video artifacts affected the re-design of a graphical editor for building, simulating, and analyzing Coloured Petri Nets. The two primary goals of the project were to create design abstractions that integrate recent advances in graphical interaction techniques and to explicitly support specific patterns of use of Petri nets in real-world settings. Using a participatory design process, we organized a series of video-based design activities that helped us manage the tension between finding useful design abstractions and specifying the details of the user interface. Video artifacts resulting from one activity became the basis for the next, facilitating communication among members of the multi-disciplinary design team. The video artifacts provided an efficient way of capturing and incorporating subtle aspects of Petri Nets In Use into our design and ensured that the implementation of our design principles was grounded in real-world work practices.

CPN/Tools: A Post-WIMP Interface for Editing and Simulating Coloured Petri Nets

CPN/Tools is a major redesign of the popular Design/CPN tool from the University of Aarhus CPN group. The new interface is based on advanced, post-WIMP interaction techniques, including bi-manual interaction, toolglasses and marking menus and a new metaphor for managing the workspace. It challenges traditional ideas about user interfaces, getting rid of pull-down menus, scrollbars, and even selection, while providing the same or greater functionality. It also uses the new and much faster CPN simulator and features incremental syntax checking of the nets. CPN/Tools requires an OpenGL graphics accelerator and will run on all major platforms.

An evaluation of semantic fisheye views for opportunistic search in an annotated image collection

Visual interfaces are potentially powerful tools for users to explore a representation of a collection and opportunistically discover information that will guide them toward relevant documents. Semantic fisheye views (SFEVs) are focus + context visualization techniques that manage visual complexity by selectively emphasizing and increasing the detail of information related to the user’s focus and deemphasizing or filtering less important information.In this paper we describe a prototype for visualizing an annotated image collection and an experiment to compare the effectiveness of two distinctly different SFEVs for a complex opportunistic search task. The first SFEV calculates relevance based on keyword-content similarity and the second based on conceptual relationships between images derived using WordNet. The results of the experiment suggest that semantic-guided search is significantly more effective than similarity-guided search for discovering and using domain knowledge in a collection.

Faceted classification in web information architecture: A framework for using semantic web tools

– The purpose of this paper is to develop and implement a faceted classification structure to improve web information organization, access and navigability., – Some case studies of commercial web sites using faceted metadata were analyzed to develop the classification approach. The proposed framework adapts the facet analysis theory from Faceted Classification System (FCS) to use semantic web tools especially XML and RDF store, and ontology, and is designed to be integrated within a Content Management System (CMS). A detailed example of a faceted classification system for an academic information system is used to demonstrate the construction of an FCS from metadata., – Detailed examples show how classifying and organizing information in multidimensional hierarchies is more accessible than simple one‐dimensional taxonomic hierarchies., – A prototype, based on the proposed framework, is being developed using the web site of an academic institution as a case study., – Enhances the FCS research with a notion of integrating ontology driven faceted classification structures by XML/RDF language and content management tools. A dynamic approach to organizing and searching web information provides users with multiple ways of accessing information based on their knowledge and information needs.

Performance and usability testing of multidimensional taxonomy in web site search and navigation

Purpose – Development of an effective search system and interface largely depends on usability studies. The aim of this paper is to present the results of an empirical evaluation of a prototype web site search and browsing tool based on multidimensional taxonomies derived from the use of faceted classification.Design/methodology/approach – A prototype Faceted Classification System (FCS), which classifies and organizes web documents under different facets (orthogonal sets of categories), was implemented on the domain of an academic institute. Facet are created from content oriented metadata, and then assembled into multiple taxonomies that describe alternative classifications of the web site content, such as by subject and location. The search and browsing interfaces use these taxonomies to enable users to access information in multiple ways. The paper compares the FCS interfaces to the existing single‐classification system to evaluate the usability of the facets in typical navigation and searching tasks.F...

The implementation of faceted classification in web site searching and browsing

Purpose – The aim of this paper is to develop and implement a multidimensional classification system in the web that can provide an alternative but convenient structure for organising and finding information content.Design/methodology/approach – A prototype system is developed following the views of Ranganathans faceted classification, which is to provide multiple classifications of the web documents through content oriented metadata organised under different facets (orthogonal groups of categories).Findings – Based on an architectural framework this study demonstrates a prototype faceted classification system (FCS) that is integrated into a general open‐source content management system and populated with a sample collection of institutional web pages/documents.Originality/value – The study provides significant grounds for the IR community to improve interface structure for easy access, management, and retrieval of web information. In addition, the integration of content management tools with multidimens...

Searching with Semantics: An Interactive Visualization Technique for Exploring an Annotated Image Collection

Effective opportunistic search in visual interfaces for large information collections, such as documents, web pages, and annotated images, often requires domain knowledge that the information seeker does not have. Relevant semantic information, such as metadata and especially ontologies, are valuable resources for helping the user learn this domain knowledge. In this paper we describe an interactive “focus + context” visualization technique for integrating this semantic information into the representation of the information collection to support effective opportunistic search. We have implemented a prototype using these techniques that integrates WordNet, a general lexical ontology, and a large collection of professionally annotated images. As the user explores the collection, the prototype dynamically changes the visual emphasis and detail of the images and keywords to reflect the relevant semantic relationships. This interaction allows the user to rapidly learn and use the domain knowledge required for effective opportunistic search.

CPN/Tools: A Tool for Editing and Simulating Coloured Petri Nets ETAPS Tool Demonstration Related to TACAS

CPN/Tools is a major redesign of the popular Design/CPN tool for editing, simulation and state space analysis of Coloured Petri Nets. The new interface is based on advanced interaction techniques, including bi-manual interaction, toolglasses and marking menus and a new metaphor for managing the workspace. It challenges traditional ideas about user interfaces, getting rid of pull-down menus, scrollbars, and even selection, while providing the same or greater functionality. CPN/Tools requires an OpenGL graphics accelerator and will run on all major platforms (Windows, Unix/Linux, MacOS).