Versioning

This thesis discusses how folk music changes as it is passed down over time and transmitted through different cultures. These changes, wherein older cultural material is re-worked into a new artefact is sometimes referred to as the ‘Folk Process’. This project explores how existing digital tools can be used to both identify and map these changes in such a way that is demonstrative of how folk songs that might sound musically different can be linked through their narrative or origin. This research seeks to identify cultural motifs and tropes within an existing cycle of folk songs that are essentially versions or descendants of an older cycle of songs. In charting the genesis and evolution of this case study, it is hoped that this research will be indicative of how the folk process is instrumental in the shaping of cultural identity. Through encoding, analysing, and mapping this information, this thesis seeks to create a pedagogical tool that, it is hoped, may lead to new discussions on how musicological and folkloristic research can be enhanced through Digital Humanities methodologies.

With data volumes increasing at a high rate and the emergence of highly scalable infrastructures (cloud computing, petascale computing), distributed management of data becomes a crucial issue that faces many challenges. This thesis brings several contributions in order to address such challenges. First, it proposes a set of principles for designing highly scalable distributed storage systems that are optimized for heavy data access concurrency. In particular, it highlights the potentially large benefits of using versioning in this context. Second, based on these principles, it introduces a series of distributed data and metadata management algorithms that enable a high throughput under concurrency. Third, it shows how to efficiently implement these algorithms in practice, dealing with key issues such as high-performance parallel transfers, efficient maintainance of distributed data structures, fault tolerance, etc. These results are used to build BlobSeer, an experimental prototype that is used to demonstrate both the theoretical benefits of the approach in synthetic benchmarks, as well as the practical benefits in real-life, applicative scenarios: as a storage backend for MapReduce applications, as a storage backend for deployment and snapshotting of virtual machine images in clouds, as a quality-of-service enabled data storage service for cloud applications. Extensive experimentations on the Grid'5000 testbed show that BlobSeer remains scalable and sustains a high throughput even under heavy access concurrency, outperforming by a large margin several state-of-art approaches.

As Internet-based commerce becomes increasingly widespread, large data sets about the demand for and pricing of a wide variety of products become available. These present exciting new opportunities for empirical economic and business research, but also raise new statistical issues and challenges. In this article, we summarize research that aims to assess the optimality of price discrimination in the software industry using a large e-commerce panel data set gathered from Amazon.com. We describe the key parameters that relate to demand and cost that must be reliably estimated to accomplish this research successfully, and we outline our approach to estimating these parameters. This includes a method for "reverse engineering" actual demand levels from the sales ranks reported by Amazon, and approaches to estimating demand elasticity, variable costs and the optimality of pricing choices directly from publicly available e-commerce data. Our analysis raises many new challenges to the reliable statistical analysis of e-commerce data and we conclude with a brief summary of some salient ones.

The data warehouse (DW) technology was developed to integrate heterogeneous information sources for analysis purposes. Information sources are more and more autonomous and they often change their content due to perpetual transactions (data changes) and may change their structure due to continual users' requirements evolving (schema changes). Handling properly all type of changes is a must. In fact, the DW which is considered as the core component of the modern decision support systems has to be update according to different type of evolution of information sources to reflect the real world subject to analysis. The goal of this paper is to propose an overview and a comparative study between different works related to the DW evolution problem.

Versioning is predicated on the fact that an archival legacy of iterative data exists from which subsequent creations can source material as they make adjustments to what has already been created, and music cultures provide some of the best examples of this through the constant processes of sampling, mashing up, and recreating found within them. Such archival legacies signal the ways in which remix practices are intimately connected to memorizing and memorializing – in the necessity of the former to retain elements of a given tradition, in the particular ways the latter captures and presents moments of the past, and in their reciprocity when they become more noticeably conflated. There is perhaps no other musical group as culturally pervasive as The Beatles, and this paper specifically considers how processes of memorizing and memorializing manifest in the film Yesterday (2019). The film revolves around an alternative reality wherein The Beatles suddenly never existed, and the main character, a struggling musician named Jack, is somehow able to remember them when no one else can. Jack spends a brief, wildly successful musical career reproducing (for him) their songs for the very first time (for everyone else), but one of his main struggles is the difficulty he finds in remembering the exact lyrics and arrangements. Since he cannot consult any “texts” and is forced to only draw on what he remembers, the film also uniquely engages with critical discussions surrounding orality and writing across cultural traditions. Thus, this paper draws on the plot of Yesterday in order to demonstrate how iterative processes of remembrance and preservation intersect with questions and concerns over authenticity that emerge amid versioned media.

To accommodate the needs of large-scale distributed P2P systems, scalable data management strategies are required, allowing applications to efficiently cope with continuously growing, highly distributed data. This paper addresses the problem of efficiently storing and accessing very large binary data objects (blobs). It proposes an efficient versioning scheme allowing a large number of clients to concurrently read, write and append data to huge blobs that are fragmented and distributed at a very large scale. Scalability under heavy concurrency is achieved thanks to an original metadata scheme, based on a distributed segment tree built on top of a Distributed Hash Table (DHT). Our approach has been implemented and experimented within our BlobSeer prototype on the Grid'5000 testbed, using up to 175 nodes.

As data volumes increase at a high speed in more and more application fields of science, engineering, information services, etc., the challenges posed by data-intensive computing gain an increasing importance. The emergence of highly scalable infrastructures, e.g. for cloud computing and for petascale computing and beyond introduces additional issues for which scalable data management becomes an immediate need. This paper brings several contributions. First, it proposes a set of principles for designing highly scalable distributed storage systems that are optimized for heavy data access concurrency. In particular, we highlight the potentially large benefits of using versioning in this context. Second, based on these principles, we propose a set of versioning algorithms, both for data and metadata, that enable a high throughput under concurrency. Finally, we implement and evaluate these algorithms in the BlobSeer prototype, that we integrate as a storage backend in the Hadoop MapReduce framework. We perform extensive microbenchmarks as well as experiments with real MapReduce applications: they demonstrate that applying the principles defended in our approach brings substantial benefits to data intensive applications.

________________________________________________________________________ Software Configuration Management (SCM) is an important discipline in professional software development and maintenance. The importance of SCM has increased as programs have become larger, more long-lasting, and more mission and life critical. This paper discusses the evolution of SCM technology from the early days of software development to present, with a particular emphasis on the impact that university and industrial research has had along the way. Based on an analysis of the publication history and evolution in functionality of the available SCM systems, we trace the critical ideas in the field from their early inception to their eventual maturation in commercially and freely available SCM systems. In doing so, this paper creates a detailed record of the critical value of SCM research and illustrates how research results have shaped the functionality of today's SCM systems.

Infrastructure-as-a-Service (IaaS) cloud computing has revolutionized the way we think of acquiring resources by in- troducing a simple change: allowing users to lease computational resources from the cloud provider's datacenter for a short time by deploying virtual machines (VMs) on those resources. This new model raises new challenges in the de- sign and development of IaaS middleware. One of those challenges is the need to deploy a large number (hundreds or even thousands) of VM instances simultaneously. Once the VM instances are deployed, another challenge is to simultaneously take a snapshot of many images and transfer them to persistent storage to support management tasks, such as suspend-resume and migration. With datacenters growing at a fast rate and configurations becoming heterogeneous, it is important to enable efficient concurrent deployment and snapshotting that is at the same time hypervisor- independent and ensures a maximum of compatibility with different configurations. This paper addresses these challenges by proposing a virtual file system specifically optimized for virtual machine image storage. It is based on a lazy transfer scheme coupled with object-versioning that demonstrates excellent performance in terms of consumed resources: execution time, network traffic and storage space. Experiments on hundreds of nodes demonstrate performance improvements in concurrent VM deployments ranging from a factor of 2 up to 25 over state-of-art, with storage and bandwidth utilization reduction of as much as 90%, while at the same time keeping comparable snapshotting performance, which comes with the added benefit of high portability.

In an essay for Keywords in Remix Studies (2017), Richard Rinehart notes that archives function as instruments of social and collective memory, and as the “primary sources” around which histories are based and selectively constructed. The archive exists, then, as a remixed collection of our history and cultural heritage. What this paper considers, however, is the metaphorical application of such framing in the context of religious traditions and their developments. General assumptions cast “religions” as referring to very specific cultural creations: their variations, denominations, sects, and the like pull acceptable elements from certain conceptual databases to be considered as such (i.e., “new” while still maintaining a tie to the “old”). Whether these “new” manifestations point to something static and “original” or not, an archive of source material does exist that determines what can be utilized in subsequent iterations of a “religion.”

Drawing on various thinkers within remix studies and particular concepts like “bricolage” and “restrictive remix,” this paper engages “archive” in a way that uniquely intersects with our digital age, its conceptual metaphors, and developments in cultural traditions. Demonstrating Lev Manovich’s assertion that culture’s “computerization” has affected our “reservoirs” of metaphors, this paper takes Stephen Batchelor’s work on Buddhism as its main example in considering the utility of rethinking religious traditions in terms of cultural archives: Buddhism 1.0 (the normative “operating system” and database of Buddhism, with various schools as “programs” on top of it) is placed in contrast to Batchelor’s proposed Buddhism 2.0 (a newly conceived “operating system” and database aiming to provide a more original form of Buddhism for use in newer “programs”).

This paper describes a conceptual framework and methodology for managing scheme versioning for the Semantic Web. The first part of the paper introduces the concept of vocabulary encoding schemes, distinguished from metadata schemas, and discusses the characteristics of changes in schemes. The paper then presents a proposal to use a value record–similar to a term record in thesaurus management techniques–to manage scheme versioning challenges for the Semantic Web. The conclusion identifies future research directions.

Versioning helps users to keep track of different sets of edits on a document. Version merging methods enable users to determine which parts of which version they wish to include in the next or final version. We explored several existing and two new methods (highlighting and overlay) in single and multiple window settings. We present the results of our quantitative user studies, which show that the new highlighting and overlay techniques are preferred for version merging tasks. The results suggest that the most useful methods are those which clearly and easily present information that is likely important to the user, while simultaneously hiding less important information. Also, multi window version merging is preferred over single window merging.

Scientists working in eScience environments often use workflows to carry out their computations. Since the workflows evolve as the research itself evolves, these workflows can be a tool for tracking the evolution of the research. Scientists can trace their research and associated results through time or even go back in time to a previous stage and fork to a new branch of research. In this paper we introduce the workflow evolution framework (EVF), which is demonstrated through implementation in the Trident workflow workbench. The primary contribution of the EVF is efficient management of knowledge associated with workflow evolution. Since we believe evolution can be used for workflow attribution, our framework will motivate researchers to share their workflows and get the credit for their contributions.

We investigate profit-maximizing versioning plans for an information goods monopolist. The analysis employs data obtained from a web-based field experiment in which potential buyers were offered information goods in varied price-quality configurations. Maximum simulated likelihood (MSL) methods are used to estimate parameters describing the distribution of utility function parameters across potential buyers of the good. The resulting estimates are used to examine the impact of versioning on seller profits and market efficiency.

The recent explosion in data sizes manipulated by distributed
scientific applications has prompted the need to develop specialized storage systems capable to deal with specific access patterns in a scalable fashion. In this context, a large class of applications focuses on parallel array processing: small parts of huge multi-dimensional arrays are concurrently accessed
by a large number of clients, both for reading and writing.
A specialized storage system that deals with such an access
pattern faces several challenges at the level of data/metadata management. We introduce Pyramid, an active array-oriented storage system that addresses these challenges. Experimental evaluation demonstrates substantial scalability improvements brought by Pyramid with respect to state-of-art approaches both in weak and strong scaling scenarios, with gains of 100% to 150%.

Large-scale data-intensive applications are a class of applications that acquire and maintain massive datasets, while performing distributed computations on these datasets. In this context, a a key factor is the storage service responsible for the data management, as it has to efficiently deal with massively parallel data access in order to ensure scalability and performance for the whole system itself. This PhD thesis proposes BlobSeer, a data management service specifically designed to address the needs of large-scale data-intensive applications. Three key design factors: data striping, distributed metadata management and versioning-based concurrency control enable BlobSeer not only to provide efficient support for features commonly used to exploit data-level parallelism, but also enable exploring a set of new features that can be leveraged to further improve parallel data access. Extensive experimentations, both in scale and scope, on the Grid5000 testbed demonstrate clear benefits of using BlobSeer as the underlying storage for a variety of scenarios: data-intensive grid applications, grid file systems, MapReduce datacenters, desktop grids. Further work targets providing efficient storage solutions for cloud computing as well.

The paper presents an application of the FRBR OO document model for defining an information ontology of legal resources that takes into account the dimension of time. FRBR-based paradigms are used within several existing projects in computer support of activities in the legal domain, but they are mostly oriented to bibliographic organization of documents without a real modeling of the peculiar characteristics of the legal domain. Also, all of them refer to the current version of the FRBR model, called FRBR ER. Yet, in these years the FRBR model is undergoing a major revision and a new version using an object-oriented approach is being developed. Thus we first have updated the model of legal resources to rely on the new object-oriented model, called FRBR OO. More importantly, consistency problems were corrected and the time dimension was introduced, which came very useful when considering the legal domain and dealing with legal resources. Therefore, while it is not in the scope of this paper to define an abstract model of the norms (e.g. obligations, permissions, etc.) or the representation of the norms (e.g. rules model), we rather focus our attention on the abstract description of the normative acts lifecycle and how it is possible to fill the gap between the rule modeling and the structure of the legal resources.

Elsa Pereira (2021) The concept of version in genetically oriented scholarly editing, Studia Neophilologica, 93:1, 107-119, DOI: 10.1080/00393274.2021.1885306
The idea of textual variation was notably rejected in the early days of critique génétique, but versions have been playing a prominent role in most editorial schools of genetic orientation. This article presents a systematic review of the literature to distinguish the main working definitions and editorial approaches to the notion of version, both in genetic analogue editions and digital archives based on text encoding and computer-assisted collation.

Full article: https://www.tandfonline.com/doi/full/10.1080/00393274.2021.1885306

RESUMO
Este artigo debruça-se sobre alguns poemas de Pedro Homem de Mello (1904-1984) que foram sujeitos a processos de reescrita profunda. Segundo a argumentação aqui exposta, por mais divergentes que possam ser, essas versões, resultantes de revisão vertical, não podem ser separadas e devem editar-se em simultâneo. Neste sentido, as abordagens digitais surgem como as mais adequadas, para cotejar, editar e reorganizar automaticamente os testemunhos, explorando a natureza dinâmica da condição textual.

ABSTRACT
This article deals with a few poems by Pedro Homem de Mello (1904-1984), which were subject to rewriting through vertical revision. It argues that, no matter how different they may seem to be, versions cannot be unlinked from one another and should be brought together in a genetic-critical edition. In order to explore diachronic revision, electronic strategies must be devised, so that new patterns and relationships may be rearranged through automatic processing, thus exploring the dynamic textual condition.

http://revistas.ufpr.br/abralin/article/view/51933

As data volumes increase at a high speed in more and more application fields of science, engineering, information services, etc., the challenges posed by data-intensive computing gain an increasing importance. The emergence of highly scalable infrastructures, e.g. for cloud computing and for petascale computing and beyond introduces additional issues for which scalable data management becomes an immediate need. This paper brings several contributions. First, it proposes a set of principles for designing highly scalable distributed storage systems that are optimized for heavy data access concurrency. In particular, we highlight the potentially large benefits of using versioning in this context. Second, based on these principles, we propose a set of versioning algorithms, both for data and metadata, that enable a high throughput under concurrency. Finally, we implement and evaluate these algorithms in the BlobSeer prototype, that we integrate as a storage backend in the Hadoop MapReduce framework. We perform extensive microbenchmarks as well as experiments with real MapReduce applications: they demonstrate that applying the principles defended in our approach brings substantial benefits to data intensive applications.

In this paper we present a theoretical model to study the characteristics and the commercial sustainability of dual licensing, an open source (OS) business strategy that has gained popularity among software vendors. With dual licensing, a firm releases the same software product under both a traditional proprietary license and an open source one. We show that the decision to employ a dual licensing strategy occurs whenever the feedbacks of the open source community are valuable enough compared to the quality of the software that the firm is able to develop in-house. Our analysis points to the central role of an appropriate managing of OS licenses in order to balance the pros and cons of "going open source" and to make this versioning strategy viable for software vendors; our analysis also suggests a possible explanation for the observed proliferation of open source licenses. J.E.L. codes: L11, L17, L86, D45. Keywords: open source software, open source business models, embedded software, dual licensing, versioning, license proliferation. * Much of this work has been conducted while the authors were visiting the School of Information of the University of California at Berkeley. We are extremely grateful to Hal Varian for his hospitality. Financial support from "Progetto di Ateneo" -Padova, 2005-07. Paper presented at the 2 nd FLOSS international workshop on Free/Libre open source software -Rennes 2008, at the 3 rd annual conference of the EPIP association -Bern, 2008, and at the 36 th annual conference of the EARIE -Ljubjana, 2009. The authors are grateful to Mark Schankerman, Laura Vici and Marcus Wagner for helpful suggestions and comments on earlier versions of the paper.

The current Web is a dynamic collection where little effort is made to version pages or to enable users to access historical data. As a consequence, they generally do not have sufficient temporal support when browsing the Web. However, we think that there are many benefits to be obtained from integrating documents with their histories. For example, a document's history can enable us to travel back through time to establish its trustworthiness. This paper discusses the possible types of interactions that users could have with document histories and it presents several examples of systems that we have implemented for utilizing this historical data. To support our view, we present the results of an online survey conducted with the objective of investigating user needs for temporal support on the Web. Although the results indicated quite low use of Web archives by users, they simultaneously emphasized their considerable interest in page histories.

Whereas traditional Desktop Grids rely on centralized servers for data management, some recent progress has been made to enable distributed, large in- put data, using to peer-to-peer (P2P) protocols and Content Distribution Networks (CDN). We make a step further and propose a generic, yet efficient data storage which enables the use of Desktop Grids for applications with high output data re- quirements, where the access grain and the access patterns may be random. Our solution builds on a blob management service enabling a large number of con- current clients to efficiently read/write and append huge data that are fragmented and distributed at a large scale. Scalability under heavy concurrency is achieved thanks to an original metadata scheme using a distributed segment tree built on top of a Distributed Hash Table (DHT). The proposed approach has been imple- mented and its benefits have successfully been demonstrated within our BlobSeer prototype on the Grid'5000 testbed.

In the past, shareware has been mainly used to market small and simple software, the developers of which could not afford to distribute their products through a physical retail channel. Shareware was often distributed through complimentary floppy or CD disks attached to PC or games magazines. However, with increased network speed, it has become viable for digital files, even large ones, to be distributed over the Internet. The Internet channel has opened up new opportunities for developers, small or large, to distribute their products as shareware to reach consumers directly. Indeed, in recent years, we begin to see big firms, including Microsoft, Adobe, and Google, distributing their products as shareware. We find that shareware is an increasingly widespread marketing strategy for selling software products via the Web. Because the emergence of shareware has not been driven by economic concerns, there is limited analytical research on shareware. However, as shareware gains in popularity as a strategy to reduce consumers' uncertainty about new software products, there is a need for deeper understanding of the economic implications of its use. This paper analyzes the interrelationships among key issues that are central to the software industry, including uncertainty, piracy, shareware quality, and full version price. We show that customers' aversion to the uncertainty of software quality tends to increase shareware quality while piracy tends to decrease it. Counter intuitively, the perceived quality of the full version software or the trust toward the software developer does not affect the full version price and the profit of the firm when piracy is prevalent.

Ontologies are built on systems that conceptually evolve over time. In addition, techniques and languages for building ontologies evolve too. This has led to numerous studies in the field of ontology versioning and ontology evolution. This paper presents a new way to manage the lifecycle of an ontology incorporating both versioning tools and evolution process. This solution, called VersionGraph, is integrated in the source ontology since its creation in order to make it possible to evolve and to be versioned. Change management is strongly related to the model in which the ontology is represented. Therefore, we focus on the OWL language in order to take into account the impact of the changes on the logical consistency of the ontology like specified in OWL DL.

Geospatial information changes continually, and geospatial datasets become outdated and unsuitable for decision support due to inadequate data quality. They are also costly to maintain. There is a growing demand for accurate and consistent geospatial information in critical sectors such as emergency response. Within the land fabric geospatial vector data context, the ownership of data is distributed vertically among many

Scientists working in eScience environments often use workflows to carry out their computations. Since the workflows evolve as the research itself evolves, these workflows can be a tool for tracking the evolution of the research. Scientists can trace their research and associated results through time or even go back in time to a previous stage and fork to a new branch of research. In this paper we introduce the workflow evolution framework (EVF), which is demonstrated through implementation in the Trident workflow workbench. The primary contribution of the EVF is efficient management of knowledge associated with workflow evolution. Since we believe evolution can be used for workflow attribution, our framework will motivate researchers to share their workflows and get the credit for their contributions.

This paper discusses the design challenges encountered when building an ontology repository for an application framework devoted to assistive technologies that can be browsed and queried in a highly heterogeneous and expressive way. As a main vehicle to achieve this goal we propose to use metadata and meta-reasoning. We analyze how metadata can be used in the context of open repositories of ontologies, and how it can and needs to be extended in various ways. In particular, we study a redesign of the Ontology Metadata Vocabulary OMV by restructuring and enriching it with the ABC ontology and domain-specific categories for assistive technologies. Examples of an elderly assistance system illustrate how this extended OMV can support more sophisticated reasoning and querying over repositories of ontologies for assistive applications.

Geospatial information changes continually, and geospatial datasets become outdated and unsuitable for decision support due to inadequate data quality. They are also costly to maintain. There is a growing demand for accurate and consistent geospatial information in critical sectors such as emergency response. Within the land fabric geospatial vector data context, the ownership of data is distributed vertically among many

In most business software systems the time dimension of business objects plays a significant role. Time is a crosscutting concern that is hard to separate from other business logic. We have developed a toolkit that allows existing business application systems to be extended with "time-conscious" behavior in a nonintrusive way by factoring out all aspects of time-related behavior into a framework and a set of classes that is distinct from the existing code base. The Time Conscious Objects TM (TCO TM ) toolkit is currently implemented in Java TM , but through the use of generation technology the toolkit can easily be made available in any language that supports polymorphism.

In this paper we present a theoretical model to study the characteristics and the commercial sustainability of dual licensing, an open source (OS) business strategy that has gained popularity among software vendors. With dual licensing, a firm releases the same software product under both a traditional proprietary license and an open source one. We show that the decision to employ a dual licensing strategy occurs whenever the feedbacks of the open source community are valuable enough compared to the quality of the software that the firm is able to develop in-house. Our analysis points to the central role of an appropriate managing of OS licenses in order to balance the pros and cons of "going open source" and to make this versioning strategy viable for software vendors; our analysis also suggests a possible explanation for the observed proliferation of open source licenses. J.E.L. codes: L11, L17, L86, D45. Keywords: open source software, open source business models, embedded software, dual licensing, versioning, license proliferation. * Much of this work has been conducted while the authors were visiting the School of Information of the University of California at Berkeley. We are extremely grateful to Hal Varian for his hospitality. Financial support from "Progetto di Ateneo" -Padova, 2005-07. Paper presented at the 2 nd FLOSS international workshop on Free/Libre open source software -Rennes 2008, at the 3 rd annual conference of the EPIP association -Bern, 2008, and at the 36 th annual conference of the EARIE -Ljubjana, 2009. The authors are grateful to Mark Schankerman, Laura Vici and Marcus Wagner for helpful suggestions and comments on earlier versions of the paper.

In this paper we present a theoretical model to study the characteristics and the commercial sustainability of dual licensing, an open source (OS) business strategy that has gained popularity among software vendors. With dual licensing, a firm releases the same software product under both a traditional proprietary license and an open source one. We show that the decision to employ a dual licensing strategy occurs whenever the feedbacks of the open source community are valuable enough compared to the quality of the software that the firm is able to develop in-house. Our analysis points to the central role of an appropriate managing of OS licenses in order to balance the pros and cons of "going open source" and to make this versioning strategy viable for software vendors; our analysis also suggests a possible explanation for the observed proliferation of open source licenses. J.E.L. codes: L11, L17, L86, D45. Keywords: open source software, open source business models, embedded software, dual licensing, versioning, license proliferation. * Much of this work has been conducted while the authors were visiting the School of Information of the University of California at Berkeley. We are extremely grateful to Hal Varian for his hospitality. Financial support from "Progetto di Ateneo" -Padova, 2005-07. Paper presented at the 2 nd FLOSS international workshop on Free/Libre open source software -Rennes 2008, at the 3 rd annual conference of the EPIP association -Bern, 2008, and at the 36 th annual conference of the EARIE -Ljubjana, 2009. The authors are grateful to Mark Schankerman, Laura Vici and Marcus Wagner for helpful suggestions and comments on earlier versions of the paper.

Extreme Programming (XP) is a new and controversial sojiware process for small teams. A practical training course at the university of Karlsruhe led to the following observations about the key practices of Xl? First, it is unclear how to reap the potential benejits of pair programming, although pair programming produces high quality code. Second, designing in small increments appears problematic but ensures rapid feedback about the code. Third, while automated testing is helpful, writing test cases before coding is a challenge. And last, it is dificult to implement XP without coaching. This paper also provides some guidelines for those starting out with XR

The Hydra project offers version control for distributed case files in α-Flow. Available version control systems lack support for independent versioning of multiple logical units within a single repository each with its own version history and head. Our use case also requires mechanisms for labeling versions by their validity and for validity-based navigational access. Hydra is a multi-module and validity-aware version control system.

This paper offers an analysis of the evolution of e-commerce markets. We develop a model in which an initial group of small, no-name click firms create such markets by offering horizontally differentiated customized or versioned products and competing in prices. Subsequently, a traditional brick firm enters by stretching its brand name into the digital marketplace. Such entry causes many initial entrants to exit. Contrary to much popular and formal literature, we show that the volume of initial entry may well be inefficiently low despite the anticipated later exit. In addition, the conventional relationship between sunk cost and market structure is substantially weakened.

The research area of ontology engineering seems to have reached a certain level of maturity, considering the vast amount of contemporary methods and tools for formalising and applying knowledge representation models. However, there is still little understanding of, and support for, the evolutionary aspects of ontologies. This is particularly crucial in distributed and collaborative settings such as the Semantic Web, where ontologies naturally co-evolve with their communities of use. For managing the evolution of single ontologies, established techniques from data schema evolution have been successfully adopted, and consensus on a general ontology evolution process model seems to emerge. Much less explored, however, is the problem of evolution of interorganisational ontologies. In this “complex” and dynamic setting, a collaborative change process model requires more powerful engineering, argumentation and negotiation methodologies, complemented by support for context dependency management.. It turns out that much can be learned from other domains where formal artefacts are being collaboratively engineered. In particular, the field of system engineering offers a wealth of techniques and tools for versioning, merging and evolving software artefacts, and many of these techniques can be reused in an ontology engineering setting. Based on this insight, this chapter gives a unified overview of the wide variety of models and mechanisms that can be used to support all of the above aspects of ontology evolution. The key remaining challenge is to construct a single framework, based on these mechanisms, which can be tailored for the needs of a particular environment.

This paper addresses the problem of efficiently storing and accessing massive data blocks in a large-scale distributed environment, while providing efficient fine-grain access to data subsets. This issue is crucial in the context of applications in the field of databases, data mining and multimedia. We propose a data sharing service based on distributed, RAM-based storage of data, while leveraging a DHT-based, natively parallel metadata management scheme. As opposed to the most commonly used grid storage infrastructures that provide mechanisms for explicit data localization and transfer, we provide a transparent access model, where data are accessed through global identifiers. Our proposal has been validated through a prototype implementation whose preliminary evaluation provides promising results.

We consider the challenge of building data management systems that meet an important requirement of today's data-intensive HPC applications: to provide a high I/O throughput while supporting highly concurrent data accesses. In this context, many applications rely on MPI-IO and require atomic, non-contiguous I/O operations that concurrently access shared data. In most existing implementations the atomicity requirement is often implemented through locking-based schemes, which have proven inefficient, especially for non-contiguous I/O. We claim that using a versioning-enabled storage backend has the potential to avoid expensive synchronization as exhibited by locking-based schemes, which is much more efficient. We describe a prototype implementation on top of ROMIO along this idea, and report on promising experimental results with standard MPI-IO benchmarks specifically designed to evaluate the performance of non-contiguous, overlapped I/O accesses under MPI atomicity guarantees.