After years of research on ontology matching, it is reasonable to consider several questions: is the field of ontology matching still making progress? Is this progress significant enough to pursue further research? If so, what are the particularly promising directions? To answer these questions, we review the state of the art of ontology matching and analyze the results of recent ontology matching evaluations. These results show a measurable improvement in the field, the speed of which is albeit slowing down. We conjecture that significant improvements can be obtained only by addressing important challenges for ontology matching. We present such challenges with insights on how to approach them, thereby aiming to direct research into the most promising tracks and to facilitate the progress of the field.

/pdf/ontology-matching-state-of-the-art-and-future-challenges-486jer3je8.pdf

Ontology Matching: State of the Art and Future Challenges

Ontologies play a key role in the advent of the Semantic Web. An important problem when dealing with ontologies is the modification of an existing ontology in response to a certain need for change. This problem is a complex and multifaceted one, because it can take several different forms and includes several related subproblems, like heterogeneity resolution or keeping track of ontology versions. As a result, it is being addressed by several different, but closely related and often overlapping research disciplines. Unfortunately, the boundaries of each such discipline are not clear, as the same term is often used with different meanings in the relevant literature, creating a certain amount of confusion. The purpose of this paper is to identify the exact relationships between these research areas and to determine the boundaries of each field, by performing a broad review of the relevant literature.

/pdf/ontology-change-classification-and-survey-4n37nzlmdf.pdf

Ontology change: Classification and survey

In this paper, we present WebProtege---a lightweight ontology editor and knowledge acquisition tool for the Web. With the wide adoption of Web 2.0 platforms and the gradual adoption of ontologies and Semantic Web technologies in the real world, we need ontology-development tools that are better suited for the novel ways of interacting, constructing and consuming knowledge. Users today take Web-based content creation and online collaboration for granted. WebProtege integrates these features as part of the ontology development process itself. We tried to lower the entry barrier to ontology development by providing a tool that is accessible from any Web browser, has extensive support for collaboration, and a highly customizable and pluggable user interface that can be adapted to any level of user expertise. The declarative user interface enabled us to create custom knowledge-acquisition forms tailored for domain experts. We built WebProtege using the existing Protege infrastructure, which supports collaboration on the back end side, and the Google Web Toolkit for the front end. The generic and extensible infrastructure allowed us to easily deploy WebProtege in production settings for several projects. We present the main features of WebProtege and its architecture and describe briefly some of its uses for real-world projects. WebProtege is free and open source. An online demo is available at http://webprotege.stanford.edu.

WebProtégé: A collaborative ontology editor and knowledge acquisition tool for the Web

Ontologies are becoming so large in their coverage that no single person or a small group of people can develop them effectively and ontology development becomes a community-based enterprise. In this paper, we discuss requirements for supporting collaborative ontology development and present Collaborative Protege--a tool that supports many of these requirements, such as discussions integrated with ontology-editing process, chats, and annotations of changes and ontology components. We have evaluated Collaborative Protege in the context of ontology development in an ongoing large-scale biomedical project that actively uses ontologies at the VA Palo Alto Healthcare System. Users have found the new tool effective as an environment for carrying out discussions and for recording references for the information sources and design rationale.

https://link.springer.com/content/pdf/10.1007%2F978-3-540-88564-1_2.pdf

Supporting Collaborative Ontology Development in Protégé

In this paper, we present WebProtege—a lightweight ontology editor and knowledge acquisition tool for the Web. With the wide adoption of Web 2.0 platforms and the gradual adoption of ontologies and Semantic Web technologies in the real world, we need ontology-development tools that are better suited for the novel ways of interacting, constructing and consuming knowledge. Users today take Web-based content creation and online collaboration for granted. WebProtege integrates these features as part of the ontology development process itself. We tried to lower the entry barrier to ontology development by providing a tool that is accessible from any Web browser, has extensive support for collaboration, and a highly customizable and pluggable user interface that can be adapted to any level of user expertise. The declarative user interface enabled us to create custom knowledge-acquisition forms tailored for domain experts. We built WebProtege using the existing Protege infrastructure, which supports collaboration on the back end side, and the Google Web Toolkit for the front end. The generic and extensible infrastructure allowed us to easily deploy WebProtege in production settings for several projects. We present the main features of WebProtege and its architecture and describe briefly some of its uses for real-world projects. WebProtege is free and open source. An online demo is available at http://webprotege.stanford.edu.

A Collaborative Ontology Editor and Knowledge Acquisition Tool for the Web

With the wider use of ontologies in the Semantic Web and as part of production systems, multiple scenarios for ontology maintenance and evolution are emerging. For example, successive ontology versions can be posted on the (Semantic) Web, with users discovering the new versions serendipitously; ontology-development in a collaborative environment can be synchronous or asynchronous; managers of projects may exercise quality control, examining changes from previous baseline versions and accepting or rejecting them before a new baseline is published, and so on. In this paper, we present different scenarios for ontology maintenance and evolution that we have encountered in our own projects and in those of our collaborators. We define several features that categorize these scenarios. For each scenario, we discuss the high-level tasks that an editing environment must support. We then present a unified comprehensive set of tools to support different scenarios in a single framework, allowing users to switch between different modes easily.

/pdf/a-framework-for-ontology-evolution-in-collaborative-3ewmuvderr.pdf

A framework for ontology evolution in collaborative environments

The authors describe a novel, direct technique for determining the small-signal equivalent circuit of a heterojunction bipolar transistor (HBT). The parasitic elements are largely determined from measurements of test structures, reducing the number of elements determined from measurements of the transistor. The intrinsic circuit elements are evaluated from y-parameter data, which are DC-embedded from the known parasitics. The equivalent-circuit elements are uniquely determined at any frequency. The validity of this technique is confirmed by showing the frequency independence of the extracted circuit elements. The equivalent circuit models the HBT s-parameters over a wide range of collector currents. Throughout the entire 1-18-GHz frequency range, the computed s-parameters agree very well with the experimental data. >

Direct extraction of the AlGaAs/GaAs heterojunction bipolar transistor small-signal equivalent circuit

A technique for determining the small-signal equivalent-circuit model of an AIGaAs/GaAs heterojunction bipolar transistor (HBT) is presented. Most of the parasitic ele- ments are independently extracted from measurements of test structures. The intrinsic elements are calculated from y-parameter data, which are de-embedded from the previously determined parasitics. The agreement between the measured and model-produced data is excellent over the frequency range of 1 to 18 GHz. I. INTRODUCTION CCURATE, physically based equivalent circuits are A very useful for designing devices with reduced par- asitics and optimized performance. Although numerical optimization is often used to fit the model-generated s-parameters to the measured s-parameters, the resulting element values depend on the starting values and may be nonphysical. This uncertainty in the element values has been addressed by several authors. A new de-embedding method for determining the FET model was proposed by Dambrine et al. ( 11. Trew et al. (2) described a parameter extraction technique for an HBT that makes use of the emitter-to-collector time delay to constrain the element values used in optimization. We propose a new technique for determining the small-signal equivalent circuit of an HBT. With this technique, most of the parasitics are first obtained from measurements of test structures and those remaining are determined from measurements of the tran-

http://ieeexplore.ieee.org/iel1/16/2732/00083724.pdf

Direct Extraction of the AlGaAs/GaAs Heterojunction Bipolar Transis tor Small- S ig nal Equivalent Circuit

An analytical solution for the minority carrier concentration to the 2-D diffusion equation in the base of a mesa-structure bipolar transistor is derived. The solution is especially applicable for AlGaAs/GaAs heterojunction bipolar transistors for which the extrinsic base surface has a high surface recombination velocity if the surface is not passivated. The different components of the base current are determined from the derived 2-D minority carrier concentration in the base. The major components to the base current include: surface recombination at the extrinsic base surface, at the base ohmic contact and bulk recombination in the base. The relative importance of each component is discussed as a function of the extrinsic base length, emitter length and base doping. The effects of quasielectric field in the base and the passivation on the extrinsic base region are also evaluated. The results indicate that as base doping is increased, the current gain is limited by bulk recombination, independent of the details of the device geometry.

Theoretical comparison of base bulk recombination current and surface recombination current of a mesa AlGaAs/GaAs heterojunction bipolar transistor

The relative importance of the base bulk recombination current and the base-emitter junction space charge recombination current is examined for AlGaAs/GaAs HBTs with different grading schemes in the base-emitter junction. Experimental results demonstrate that, in abrupt HBTs, the base bulk recombination current is larger, and the base current increases with the base-emitter bias with an ideality factor of ∼1. In contrast, in graded HBTs, the space charge recombination current dominates and the base current ideality factor is ∼2. These experimental results agree well with a published theoretical calculation.

William Liu

Papers

A framework for ontology evolution in collaborative environments

Direct extraction of the AlGaAs/GaAs heterojunction bipolar transistor small-signal equivalent circuit

Direct Extraction of the AlGaAs/GaAs Heterojunction Bipolar Transis tor Small- S ig nal Equivalent Circuit

Theoretical comparison of base bulk recombination current and surface recombination current of a mesa AlGaAs/GaAs heterojunction bipolar transistor

Experimental comparison of base recombination currents in abrupt and graded AlGaAs/GaAs heterojunction bipolar transistors