Constraints for the design of variability-intensive service-oriented reference architectures – An industrial case study

ContextService-oriented architecture has become a widely used concept in software industry. However, we currently lack support for designing variability-intensive service-oriented systems. Such systems could be used in different environments, without the need to design them from scratch. To support the design of variability-intensive service-oriented systems, reference architectures that facilitate variability in instantiated service-oriented architectures can help.ObjectiveThe design of variability-intensive service-oriented reference architectures is subject to specific constraints. Architects need to know these constraints when designing such reference architectures. Our objective is to identify these constraints.MethodAn exploratory case study was performed in the context of local e-government in the Netherlands to study constraints from the perspective of (a) the users of a variability-intensive service-oriented system (municipalities that implement national laws), and (b) the implementing organizations (software vendors). We collected data through interviews with representatives from five organizations, document analyses and expert meetings.ResultsWe identified ten constraints (e.g., organizational constraints, integration-related constraints) which affect the process of designing reference architectures for variability-intensive service-oriented systems. Also, we identified how stakeholders are affected by these constraints, and how constraints are specific to the case study domain.ConclusionsOur results help design variability-intensive service-oriented reference architectures. Furthermore, our results can be used to define processes to design such reference architectures.     

As I Sit Studying: WWW-Based Reference Services

Abstract

This article reports on the current state of reference services on the World Wide Web (WWW). It explains what a WWW-based reference service is, describes several models of handling requests, and explores the impact of these services on traditional reference services. Based upon anecdotal information the author concludes that, to date, Web-based reference services have had little impact upon traditional reference services.     

It Wasn't Raining When Noah Built the Ark

SUMMARY

In 2004, ten libraries in the Texas A&;M University System began AskNow, a collaborative pilot project offering a chat-based virtual reference service to patrons. This article attempts to describe one of these libraries' experience with implementing virtual reference service.     

Automatically propagating changes from reference implementations to code generation templates

ContextCode generators can automatically perform some tedious and error-prone implementation tasks, increasing productivity and quality in the software development process. Most code generators are based on templates, which are fundamentally composed of text expansion statements. To build templates, the code of an existing, tested and validated implementation may serve as reference, in a process known as templatization. With the dynamics of software evolution/maintenance and the need for performing changes in the code generation templates, there is a loss of synchronism between the templates and this reference code. Additional effort is required to keep them synchronized.ObjectiveThis paper proposes automation as a way to reduce the extra effort needed to keep templates and reference code synchronized.MethodA mechanism was developed to semi-automatically detect and propagate changes from reference code to templates, keeping them synchronized with less effort. The mechanism was also submitted to an empirical evaluation to analyze its effects in terms of effort reduction during maintenance/evolution templatization.ResultsIt was observed that the developed mechanism can lead to a 50% reduction in the effort needed to perform maintenance/evolution templatization, when compared to a manual approach. It was also observed that this effect depends on the nature of the evolution/maintenance task, since for one of the tasks there was no observable advantage in using the mechanism. However, further studies are needed to better characterize these tasks.ConclusionAlthough there is still room for improvement, the results indicate that automation can be used to reduce effort and cost in the maintenance and evolution of a template-based code generation infrastructure.     

Ask a UT System Librarian

SUMMARY

University of Texas System libraries initiated a chat reference program to support distance learners enrolled at University of Texas component institutions, including the UT Telecampus Digital Library. Librarians at several geographically distant campuses staffed the collaborative chat reference service.

Librarians assisted students at other UT System campuses, in effect becoming “distance librarians” who must have thorough knowledge of both their own library resources and the resources available at other campus libraries.

Librarians at The University of Texas at San Antonio share their experiences with this collaborative chat reference service.     

Page Us

ABSTRACT

When patron workstations are located far from the reference desk, service suffers because patrons can't easily contact staff. While in-house chat services offer a partial solution to this problem, these services fail to provide the face-to-face element that the literature shows is critical for effective reference service. This study analyzes NCSU Libraries' method for solving this problem, a hybrid service that combines features of in-person and virtual reference service.     

A visual token-based formalization of BPMN 2.0 based on in-place transformations

ContextThe Business Process Model and Notation (BPMN) standard informally defines a precise execution semantics. It defines how process instances should be updated in a model during execution. Existing formalizations of the standard are incomplete and rely on mappings to other languages.ObjectiveThis paper provides a BPMN 2.0 semantics formalization that is more complete and intuitive than existing formalizations.MethodThe formalization consists of in-place graph transformation rules that are documented visually using BPMN syntax. In-place transformations update models directly and do not require mappings to other languages. We have used a mature tool and test-suite to develop a reference implementation of all rules.ResultsOur formalization is a promising complement to the standard, in particular because all rules have been extensively verified and because conceptual validation is facilitated (the informal semantics also describes in-place updates).ConclusionSince our formalization has already revealed problems with the standard and since the BPMN is still evolving, the maintainers of the standard can benefit from our results. Moreover, tool vendors can use our formalization and reference implementation for verifying conformance to the standard.     

R U There? How to Reach a Virtual Audience Through Affordable Marketing Strategies

ABSTRACT

Virtual reference is a vital service component of many libraries. Whether serving college students or the general public, a real-time reference service demands highly trained staff and quality resources. What can administrators do to make sure their users make the most of this cutting-edge service? The University at Buffalo (UB) was one of the first universities to establish a virtual reference service. Known as Instant Librarian, the chat room thrives as a major public service without placing a drain on staff or budget. This article discusses the marketing strategies UB applies to chat reference, including advertising, use of icons, and user surveys for assessment.     

Keep IT Simple

SUMMARY

Distance education students are often goal-oriented and task-driven. They do not appreciate roadblocks that prevent them from gaining access to the information or services they need to complete their course objectives. However, Web-based reference support sites are sometimes more frustrating than helpful. This article discusses some of the difficulties of accessing reference services faced by distance education students and examines ways in which librarians should “keep IT simple” when designing the tools and methods to access reference support.     

Internet Reference Services for Distance Education

SUMMARY

Published guidelines for distance learning library services provide a framework for distance education librarians to use in planning services for off-campus students. Other literature in the arena of distance education librarianship provides concrete examples of how reference services have been offered in real settings. This paper attempts to synthesize these two types of literature in order to offer models of reference service for distance learners.     

The Virtual Librarian and the Electronic Reference Interview

ABSTRACT

For many students, the World Wide Web is their main access point for library research and, therefore, libraries need to find a venue for the virtual reference interview. This paper discusses the use of the library home page as a reference tool and its importance in the online reference interview process. This article also discusses some of the research that went into the creation of a home page for a large, urban, academic institution, how this research was utilized, and how the resulting page serves as an online surrogate for the in-person reference interview.     

Chat Reference

ABSTRACT

Internet Reference Services Quarterly is introducing a new column that will focus on current developments and practice concerns in chat reference. This first entry gives some background on the column's origins, and details the directions it will take.     

The Information Navigation System

Abstract

Today's instruction and reference librarians face new challenges as the gatekeepers to information. The information explosion requires that we create strategies for our customers to navigate through a maze of material. This paper describes a reference tool developed at The Johns Hopkins University Applied Physics Laboratory to meet the information needs of our researchers and offers practical advice to other librarians interested in providing a similar service.     

Developing a Chat Reference Training Program

ABSTRACT

In the last few years, chat reference services have been implemented by public, college and university libraries. One important aspect of the chat reference service is library staff training. Literature shows that this is a vital step in offering a chat reference service. Library staff need to be well-trained in areas of chatting, reference interviewing in a digital environment and using electronic resources, such as the Internet and databases. This article discusses the chat reference training program at the University of Nevada, Las Vegas. The following text provides an outline for establishing a chat training program including planning, organization, implementation and assessment. Areas of discussion include the chat reference interview, chatting and patron management techniques.     

A Historical Overview of Internet Reference Services for Distance Learners

SUMMARY

The advent of library services and collections on the Internet revolutionized reference services to students enrolled in distance learning programs. Prior to the Internet, reference librarians who supported distance learning programs had few methods, and many of them costly, to provide the equivalent library services advocated by the ACRL Guidelines. Through the Internet, these librarians were able to approximate the services and resources that had always been available to students who came into the library. This article describes the development of reference services on the Internet in a variety of libraries that support distance learners.     

Heuristic improvement through triangulation

Abstract

This paper presents a method for improving heuristics using a triangulation technique. Instead of using a heuristic to directly estimate distance (X₁, X₂) between nodes X₁ and X₂, the proposed technique selects a reference node R_i applies the heuristic to (X₁,R_i) and (X₂,R_i), and uses the Euclidean distance formula to calculate a new heuristic value. If two nodes are close to each other, then they should also be approximately equidistant to a third reference node. Utilizing a set of many such reference nodes, node expansions can be reduced for a large class of heuristics. Very early results for this method, referred to as multi-dimensional heuristics, showed that fewer node expansions were needed when using the triangulation technique. New results in this paper include the development of a new learning procedure for selecting reference nodes, experimentation on reusing reference node sets for multiple goal instances, a comparison of multi-dimensional heuristics with weighting and how they dynamically weight states near the goal, and some observations which help explain how and why this technique improves heuristics.     

丢包环境中H.264视频编码的快速模式判决

目的 视频编码中传统的快速模式判决算法通常基于对视频源特性的分析,但如果考虑到信道传输中的差错,编码模式的率失真特性就会随之改变,快速模式判决算法的性能也会随之下降,需要考虑丢包环境对快速模式判决算法进行优化。方法 为了解决这一问题,首先分析了丢包环境下各种编码模式的端到端率失真特性,在此基础上提出了一个分层结构的快速模式判决算法。通过快速估计出丢包环境下skip和intra模式的编码率失真代价,进而将模式判决的路径划分为non-intra和non-skip。结果 将本文算法与基于遍历算法的容错视频编码算法进行对比实验,本文算法平均可以降低50%左右的编码时间,同时几乎不会降低率失真性能。结论 实验结果表明,在对丢包环境下端到端率失真代价进行估计的基础上,所提出的分层结构快速模式判决的算法,可以在保证解码端图像质量的同时,显著节省编码时间,满足实时视频通信中对低复杂度和鲁棒性的要求。     

Constrained dynamical systems,robust model reference adaptive control,and unreliable reference signals

ABSTRACT

In this paper, we address the robust control design problem for nonlinear dynamical systems tracking unreliable reference signals. Specifically, we present robust model reference adaptive control laws that guarantee uniform ultimate boundedness of the trajectory tracking error for nonlinear plants that are affected by matched, unmatched, and parametric uncertainties, and are subject to constraints on the state space and the measured output. These control laws guarantee satisfactory results even in case the reference trajectory or the reference output signal do not verify the given constraints and hence, may draw the plant's trajectory or measured output outside their constraint sets. A numerical example involving the attitude control of a spacecraft illustrates the feasibility of the theoretical results presented.     

Finding Acorns in the Technical Services Arboretum: A Reference Librarian's Guide to Vendor Home Pages

Abstract

Historically reference librarians have had limited contact with the book vendors and serials agents used by their colleagues in technical services. However, most vendors now support Web sites, including information on publishing trends, price studies of books and periodicals, and access to useful databases. The proliferation of such sites offers reference librarians additional resources, particularly for questions regarding the publishing industry. An overview of the nature and scope of these sites is offered, along witH some suggested reference uses. In addition, a brief survey of some vendor home pages is presented.