In this paper, we define and explore proofs of retrievability (PORs). A POR scheme enables an archive or back-up service (prover) to produce a concise proof that a user (verifier) can retrieve a target file F, that is, that the archive retains and reliably transmits file data sufficient for the user to recover F in its entirety.A POR may be viewed as a kind of cryptographic proof of knowledge (POK), but one specially designed to handle a large file (or bitstring) F. We explore POR protocols here in which the communication costs, number of memory accesses for the prover, and storage requirements of the user (verifier) are small parameters essentially independent of the length of F. In addition to proposing new, practical POR constructions, we explore implementation considerations and optimizations that bear on previously explored, related schemes.In a POR, unlike a POK, neither the prover nor the verifier need actually have knowledge of F. PORs give rise to a new and unusual security definition whose formulation is another contribution of our work.We view PORs as an important tool for semi-trusted online archives. Existing cryptographic techniques help users ensure the privacy and integrity of files they retrieve. It is also natural, however, for users to want to verify that archives do not delete or modify files prior to retrieval. The goal of a POR is to accomplish these checks without users having to download the files themselves. A POR can also provide quality-of-service guarantees, i.e., show that a file is retrievable within a certain time bound.

PORs: Proofs of Retrievability for Large Files

2005년 대한 생화학·분자생물학회 하계학술대회를 다녀와서

A super-peer is a node in a peer-to-peer network that operates both as a server to a set of clients, and as an equal in a network of super-peers. Super-peer networks strike a balance between the efficiency of centralized search, and the autonomy, load balancing and robustness to attacks provided by distributed search. Furthermore, they take advantage of the heterogeneity of capabilities (e.g., bandwidth, processing power) across peers, which recent studies have shown to be enormous. Hence, new and old P2P systems like KaZaA and Gnutella are adopting super-peers in their design. Despite their growing popularity, the behavior of super-peer networks is not well understood. For example, what are the potential drawbacks of super-peer networks? How can super-peers be made more reliable? How many clients should a super-peer take on to maximize efficiency? we examine super-peer networks in detail, gaming an understanding of their fundamental characteristics and performance tradeoffs. We also present practical guidelines and a general procedure for the design of an efficient super-peer network.

Designing an Super-Peer Network

Thematic analysis is an approach that is often used for identifying, analyzing, and reporting patterns (themes) within data in primary qualitative research. 'Thematic synthesis' draws on the principles of thematic analysis and identifies the recurring themes or issues from multiple studies, interprets and explains these themes, and draws conclusions in systematic reviews. This paper conceptualizes the thematic synthesis approach in software engineering as a scientific inquiry involving five steps that parallel those of primary research. The process and outcome associated with each step are described and illustrated with examples from systematic reviews in software engineering.

/pdf/recommended-steps-for-thematic-synthesis-in-software-2d7hm9adkh.pdf

Recommended Steps for Thematic Synthesis in Software Engineering

Let X(t) be the number of tumor cells at time t, and Pr{X(t) = n} = pn(t) is the density of X. A “birth”, i.e., an increase of one of the total population of cancer cells, can occur either by mutation of a normal cell caused by the action of the carcinogen, consisting of randomly (Poisson) distributed hits, or by reproduction of existing cancer cells. A death of a tumor cell occurs as an additive combination of non-immunological and immunological elements. Once a tumor is initiated by carcinogenic action, it undergoes a birth and death process with infinitesimal birth rate linear and infinitesimal death rate composed of a linear and a nonlinear term, the former due to non-immunological deaths, the latter to immunological feedback. The death rate per tumor cell due to immunological response is proportional to the total number of antigen-producing (tumor) cells; thus, the total death rate is quadratic. Although this assumes a very simple mechanism for the action of immunological feedback, it is nevertheless a first step.

The Mathematical Model

There is a growing interest in applying agile practices in Global Software Development (GSD) projects. The literature on using Scrum, one of the most popular agile approaches, in distributed development projects has steadily been growing. However, there has not been any effort to systematically select, review, and synthesize the literature on this topic. We have conducted a systematic literature review of the primary studies that report using Scrum practices in GSD projects. Our search strategy identified 366 papers, of which 20 were identified as primary papers relevant to our research. We extracted data from these papers to identify various challenges of using Scrum in GSD. Current strategies to deal with the identified challenges have also been extracted. This paper presents the review’s findings that are expected to help researchers and practitioners to understand the challenges involved in using Scrum for GSD projects and the strategies available to deal with them.

/pdf/using-scrum-in-global-software-development-a-systematic-57gry79i7m.pdf

Using Scrum in Global Software Development: A Systematic Literature Review

Mashup is a new application development approach that allows users to aggregate multiple services to create a service for a new purpose. Even if the Mashup approach opens new and broader opportunities for data/service consumers, the development process still requires the users to know not only how to write code using programming languages, but also how to use the different Web APIs from different services. In order to solve this problem, there is increasing effort put into developing tools which are designed to support users with little programming knowledge in Mashup applications development. The objective of this study is to analyze the richnesses and weaknesses of the Mashup tools with respect to the data integration aspect.

/pdf/data-integration-in-mashups-wk7lvypiq5.pdf

Data integration in mashups

The need for integration of all types of client and server applications that were not initially designed to interoperate is gaining popularity One of the reasons for this popularity is the capability to quickly reconfigure a composite application for a task at hand, both by changing the set of components and the way they are interconnected Service-Oriented Architecture (SOA) has recently become a popular platform in the IT industry for building such composite applications with the integrated components being provided as Web services A key limitation of solely Web-service-based integration is that it requires extra programming efforts when integrating non-Web service components, which is not cost-effective Moreover, with the emergence of new standards, such as Open Service Gateway Initiative (OSGi), the components used in composite applications have grown to include more than just Web services Our work enables progressive composition of non-Web-service-based components such as portlets, Web applications, native widgets, legacy systems, and Java Beans Further, we proposed a novel application of semantic annotation together with the standard semantic Web matching algorithm for finding sets of functionally equivalent components out of a large set of available non-Web-service-based components Once such a set is identified, the user can drag and drop the most suitable component into an Eclipse-based composition canvas After a set of components has been selected in such a way, they can be connected by data-flow arcs, thus forming an integrated, composite application without any low-level programming and integration efforts We implemented and conducted extensive experimental study on the above progressive composition framework on IBM's Lotus Expeditor, an extension of an SOA platform called the Eclipse Rich Client Platform (RCP) that complies with the OSGi standard

/pdf/semantic-based-mashup-of-composite-applications-51i2gp3ob8.pdf

Semantic-Based Mashup of Composite Applications

In a blockchain-based system, data and the consensus-based process of recording and updating them over distributed nodes are central to enabling the trustless multi-party transactions. Thus, properly understanding what and how the data are stored and manipulated ultimately determines the degree of utility, performance, and cost of a blockchain-based application. While blockchains enhance the quality of the data by providing a transparent, immutable, and consistent data store, the technology also brings new challenges from a data management perspective. In this paper, we analyse blockchains from the viewpoint of a developer to highlight important concepts and considerations when incorporating a blockchain into a larger software system as a data store. The work aims to increase the level of understanding of blockchain technology as a data store and to promote a methodical approach in applying it to large software systems. First, we identify the common architectural layers of a typical software system with data stores and conceptualise each layer in blockchain terms. Second, we examine the placement and flow of data in blockchain-based applications. Third, we explore data administration aspects for blockchains, especially as a distributed data store. Fourth, we discuss the analytics of blockchain data and trustable data analytics enabled by blockchain. Lastly, we examine the data governance issues in blockchains in terms of privacy and quality assurance.

/pdf/analysis-of-data-management-in-blockchain-based-systems-from-2fhqe3b37a.pdf

Analysis of Data Management in Blockchain-Based Systems: From Architecture to Governance

There is growing interest in applying agile practices in Global Software Development (GSD) projects. But project stakeholder distribution in GSD creates a number of challenges that make it difficult to use some agile practices. Moreover, little is known about what the key challenges or risks are, and how GSD project mangers deal with these risks while using agile practices. We conduct a Systematic Literature Review (SLR) following existing guidelines to identify primary papers that discuss the use of Scrum practices in GSD projects. We identify key challenges, due to global project distribution, that restrict the use of Scrum and explore the strategies used by project managers to deal with these challenges. Our findings are consolidated into a conceptual framework and we discuss various elements of this framework. This research is relevant to project managers who are seeking ways to use Scrum in their globally distributed projects.

https://ulir.ul.ie/bitstream/handle/10344/1851/2009_Hossain.pdf?sequence=2

Hye-Young Paik

Papers

Using Scrum in Global Software Development: A Systematic Literature Review

Data integration in mashups

Semantic-Based Mashup of Composite Applications

Analysis of Data Management in Blockchain-Based Systems: From Architecture to Governance

Risk Identification and Mitigation Processes for Using Scrum in Global Software Development: A Conceptual Framework