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File systems (FS) are an essential part of operating systems in that they are responsible for storing and organising files and then retrieving those when needed. Because of the high capacity of modern storage devices and the growing... more
File systems (FS) are an essential part of operating systems in that they are responsible for storing and organising files and then retrieving those when needed. Because of the high capacity of modern storage devices and the growing number of files stored, the traditional FS model is no longer able to meet modern users’ needs in terms of storing and retrieving files. So using metadata emerges as an efficacy solution for the limitations of file systems. In this paper we propose a new model dubbed VennTags to solve the FS problems. We do this by utilising the idea of overlapping the sets as in Venn diagram, and adopting DAG structure (instead of tree) to achieve that we have used tagging capability and exposed a query language at the level of the API. We evaluate the expressive power of VennTags model that shows its ability to resolve the FS limitations compared to other solutions
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Recently proposed form-based web information systems liberate the capture and reuse of data in organizations by substituting the development of technical implementations of electronic forms for the conceptual modelling of forms’... more
Recently proposed form-based web information systems liberate the capture and reuse of data in organizations by substituting the development of technical implementations of electronic forms for the conceptual modelling of forms’ tree-structured schemas and their data access rules. Significantly, these instance-dependent rules also imply a workflow process associated to a form, eliminating the need for a costly workflow design phase. Instead, the workflows thus created in an ad hoc manner by unsophisticated end-users can be automatically analyzed, and incorrect forms rejected. This paper examines fundamental correctness properties of workflows that are implied by instance-dependent access rules. Specifically, we study the decidability of the form completability property and the semi-soundness of a form’s workflow. These problems are affected by a choice of constraints on the path language used to express access rules and completion formulas, and on the depth of the form’s schema tree...
Embarking on a large-scale research project to investigate aspects of academic workload management, it was first necessary to gain some understanding of current practice in that context within Australia. With that aim a pilot survey was... more
Embarking on a large-scale research project to investigate aspects of academic workload management, it was first necessary to gain some understanding of current practice in that context within Australia. With that aim a pilot survey was conducted in 2013 that targeted Deans of Science on the one hand, and workload managers on the other. Survey questions covered three key areas related to workload management: models and rules; process and policy; and systems and software. Comparisons between different types of university, different allocation models for teaching, research and service components of academic workload, and different sizes of academic unit were explored. While the number of responses in absolute terms was relatively limited, and hence the outcomes were not always statistically testable or generalisable, broad trends were readily identifiable. This paper reports on the method and outcomes of the survey, and describes how the information that was obtained has informed the ...
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The Australian higher education sector has undergone significant changes over the last two decades, and is set to be challenged by various pressures well into the future as debate on public funding and productivity continues. A recent... more
The Australian higher education sector has undergone significant changes over the last two decades, and is set to be challenged by various pressures well into the future as debate on public funding and productivity continues. A recent report on the higher education workforce of the future identified agility of its workforce as the foremost attribute that a university must possess to be successful going forward. Furthermore, the report singled out more flexible academic workload models as a critical factor. The choice of model used at an institution has both significant and diverse impacts, including those on casualisation levels, financial viability, and productivity. In this paper, we report on our preliminary findings from a research project that aims to compare diverse academic workload models being used in a number of Australian universities. We show where models offer broad agreement throughout the sector, but also where there are significant differences. The observed variation...
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Aim: To propose a relatively preliminary yet sufficiently general GUI-based technique to collect rich metadata for documents, to be used in a file system wrapper such as Microsoft's forthcoming WinFS. Methods: With the recent beta... more
Aim: To propose a relatively preliminary yet sufficiently general GUI-based technique to collect rich metadata for documents, to be used in a file system wrapper such as Microsoft's forthcoming WinFS. Methods: With the recent beta release of Microsoft's WinFS file system wrapper, the traditionally disjunct research areas of databases, document computing, and file systems are merging. In such environments, it is relatively clear how to query the file system for metadata about documents. However, it is not yet clear how rich metadata can be collected for documents in an intuitive manner suitable for novice users. We present a GUI-based technique for capturing both formative and contextual metadata. The former relates to metadata that can be set automatically when a document is created (such as the shutter-speed setting for a digital camera image), while the latter represents the much richer metadata that can only be determined through user interaction (e.g. the persons appea...
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Research Interests: Computer Science, Relational Database, Higher Education, Peer Review, Student Experience, and 11 moreComputer Assisted Learning, SQL, Student Learning, Computer-assisted assessment, Theory and Practice, Automatic Assessment, Structured Query Language, Software Tool, Learning Experience, Data Definition Language, and Query by Example
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Abstract: Semistructured databases require tailor-made concurrency control mechanisms since traditional solutions for the relational model have been shown to be inadequate. Such mechanisms need to take full advantage of the hierarchical... more
Abstract: Semistructured databases require tailor-made concurrency control mechanisms since traditional solutions for the relational model have been shown to be inadequate. Such mechanisms need to take full advantage of the hierarchical structure of semistructured data, for instance allowing concurrent updates of subtrees of, or even individual elements in, XML documents. We present an approach for concurrency control which is document-independent in the sense that two schedules of semistructured transactions are ...
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Abstract. Semistructured databases require tailor-made concurrency control mechanisms since traditional solutions for the relational model have been shown to be inadequate. Such mechanisms need to take full advantage of the hierarchical... more
Abstract. Semistructured databases require tailor-made concurrency control mechanisms since traditional solutions for the relational model have been shown to be inadequate. Such mechanisms need to take full advantage of the hierarchical structure of semistructured data, for instance allowing concurrent updates of subtrees of, or even individual elements in XML documents. In earlier work, we presented two equivalent path locking schemes and two schedulers which guarantee serializability of schedules on XML documents. However, ...
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In recent years a small number of web-based tools have been proposed to help students learn to write SQL query statements and also to assess students' SQL writing skills. SQLify is a new SQL teaching and assessment tool that... more
In recent years a small number of web-based tools have been proposed to help students learn to write SQL query statements and also to assess students' SQL writing skills. SQLify is a new SQL teaching and assessment tool that extends the current state-of-the-art by incorporating peer review and enhanced automatic assessment based on database theory to produce more comprehensive feedback to students. SQLify is intended to yield a richer learning experience for students and reduce marking load for instructors. In this paper SQLify is compared with existing tools and important new features are demonstrated.
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Abstract: Semistructured databases require tailor-made concurrency control mechanisms since traditional solutions for the relational model have been shown to be inadequate. Such mechanisms need to take full advantage of the hierarchical... more
Abstract: Semistructured databases require tailor-made concurrency control mechanisms since traditional solutions for the relational model have been shown to be inadequate. Such mechanisms need to take full advantage of the hierarchical structure of semistructured data, for instance allowing concurrent updates of subtrees of, or even individual elements in, XML documents. We present an approach for concurrency control which is document-independent in the sense that two schedules of semistructured transactions are ...
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Recently proposed form-based web information systems liberate the capture and reuse of data in organizations by substituting the development of technical implementations of electronic forms for the conceptual modelling of forms'... more
Recently proposed form-based web information systems liberate the capture and reuse of data in organizations by substituting the development of technical implementations of electronic forms for the conceptual modelling of forms' tree-structured schemas and their data access rules. Significantly, these instance-dependent rules also imply a workflow process associated to a form, eliminating the need for a costly workflow design phase. Instead, the workflows thus created in an ad hoc manner by unsophisticated end-users ...
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Research Interests:
Modern computer systems are based on the tradi- tional hierarchical file system model, but typically contain large numbers of files with complex interre- lationships. This traditional model is not capable of meeting the needs of current... more
Modern computer systems are based on the tradi- tional hierarchical file system model, but typically contain large numbers of files with complex interre- lationships. This traditional model is not capable of meeting the needs of current computer system users, who need to be able to store and retrieve files based on flexible criteria. A metadata file system can asso- ciate
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Role-based delegation model (RBDM) based on the role-based access control (RBAC) has proven to be a flexible and useful access control model for infor- mation sharing in a distributed collaborative environ- ment. In today's highly... more
Role-based delegation model (RBDM) based on the role-based access control (RBAC) has proven to be a flexible and useful access control model for infor- mation sharing in a distributed collaborative environ- ment. In today's highly dynamic distributed systems, a user often needs to ...
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@techreport{piecemeal-tr, author = {Jan Hidders and Stijn Dekeyser}, title = {A Notion of Serializability for Document Editing and Corresponding Optimal Locking Protocols}, institution = {Delft University of Technology}, year = {2010},... more
@techreport{piecemeal-tr, author = {Jan Hidders and Stijn Dekeyser}, title = {A Notion of Serializability for Document Editing and Corresponding Optimal Locking Protocols}, institution = {Delft University of Technology}, year = {2010}, month = {March}, url = {http://www.st.ewi ...
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The World Wide Web revolutionized the use of forms in everyday private and business life by allowing a move away from paper forms to easily accessible digital forms. Data captured using such HTML forms could be processed using relational... more
The World Wide Web revolutionized the use of forms in everyday private and business life by allowing a move away from paper forms to easily accessible digital forms. Data captured using such HTML forms could be processed using relational databases or other applications that enforce and apply business logic. Lately XForms has been introduced, offering a logical evolution of digital data capture and dissemination using Internet and document technology. This paper introduces two important new ideas. The ...
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Abstract. Semistructured databases require tailor-made concurrency control mechanisms since traditional solutions for the relational model have been shown to be inadequate. Such mechanisms need to take full advantage of the hierarchical... more
Abstract. Semistructured databases require tailor-made concurrency control mechanisms since traditional solutions for the relational model have been shown to be inadequate. Such mechanisms need to take full advantage of the hierarchical structure of semistructured data, for instance allowing concurrent updates of subtrees of, or even individual elements in XML documents. In earlier work, we presented two equivalent path locking schemes and two schedulers which guarantee serializability of schedules on XML documents. However, ...
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In the last few years an interest in native XML databases has surfaced. With other authors we argue that such databases need their own provisions for concurrency control since traditional methods are inadequate to capture the complicated... more
In the last few years an interest in native XML databases has surfaced. With other authors we argue that such databases need their own provisions for concurrency control since traditional methods are inadequate to capture the complicated update-behavior that is possible for XML documents. Ideally, updates should not be limited to entire document trees, but should involve subtrees and even individual elements. Providing a suitable scheduling algorithm for semistructured data can significantly improve collaborative systems that store ...
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The hierarchical and semistructured nature of XML data can cause complicated update-behavior. The updates are not limited to entire document trees, but can involve subtrees and even individual elements. These document parts correspond to,... more
The hierarchical and semistructured nature of XML data can cause complicated update-behavior. The updates are not limited to entire document trees, but can involve subtrees and even individual elements. These document parts correspond to, eg sections in text documents or sub-diagrams in vector graphics files. Providing suitable locking mechanisms for semi-structured data can significantly improve collaboration systems that store their data as XML documents. We show that concurrency control mechanisms in ...
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While collaboration on documents has been supported for several decades by a variety of systems and tools, in recent months a renewed interest is apparent through the appearance of new collaborative editors and applications. Some of these... more
While collaboration on documents has been supported for several decades by a variety of systems and tools, in recent months a renewed interest is apparent through the appearance of new collaborative editors and applications. Some of these distributed groupware systems are plug-ins for standalone word processors, while others have a purely web-based existence. Most exemplars of the new breed of systems are based on Operational Transformations, although some are using traditional version management tools and still ...
The hierarchical and semistructured nature of XML data may cause complicated update-behavior. Updates should not be limited to entire document trees, but should ideally involve subtrees and even individual elements. Providing a suitable... more
The hierarchical and semistructured nature of XML data may cause complicated update-behavior. Updates should not be limited to entire document trees, but should ideally involve subtrees and even individual elements. Providing a suitable scheduling algorithm for semistructured data can significantly improve collaboration systems that store their data — e.g. word processing documents or vector graphics — as XML documents. In this paper we improve upon earlier work (see [5]) which presented two equivalent concurrency control mechanisms based on Path Locks. In contrast to the earlier work, we now provide details regarding the workings of a commit scheduler for XML databases which uses the path lock conflict rules. We also give a comprehensive proof of serializability which enhances and clarifies the ideas in our previous work.