This paper focuses on the version models underlying both commercial systems and research prototypes. It provides an overview and classification of different versioning paradigms. Furthermore, it defines and relates fundamental concepts such as revisions, variants, configurations, and changes. In particular, we focus on intensional versioning, i.e., construction of versions based on configuration rules. Finally,we provide an overview of systems whichhave had significant impact on the development of the SCM discipline, and classify them according to a detailed taxonomy

Abstract. This paper studies the RDF model from a database perspective. From this point of view it is compared with other database models, particularly with graph database models, which are very close in motivations and use cases to RDF. We concentrate on query languages, analyze current RDF trends, and propose the incorporation to RDF query languages of primitives which are not present today, based on the experience and techniques of graph database research. 1

Graph database models can be characterized as those where data structures for the schema and instances are modeled as graphs or generalizations of them, and data manipulation is expressed by graph-oriented operations and type constructors. These models flourished in the eighties and early nineties in parallel to object oriented models and their influence gradually faded with the emergence of other database models, particularly the geographical, spatial, semistructured and XML. Recently, the need to manage information with inherent graph-like nature has brought back the relevance of the area. In fact, a whole new wave of applications for graph databases emerged with the development of huge networks (e.g. Web, geographical systems, transportation, telephones), and families of networks generated due to the automation of the process of data gathering (e.g. social and biological networks). The main objective of this survey is to present in a single place the work that has been done in the area of graph database modeling, concentrating in data structures, query languages and integrity constraints.

. This paper gives a cohesive approach to modeling and implementation with graphs. This approach uses extended entity relationship #EER# diagrams supplemented with the Z-like constraint language GRAL. Due to the foundation of EER#GRAL on Z a common formal basis exists. EER#GRAL descriptions give conceptual models which can be implemented in a seamless manner by e#cient data structures using the GraLab graph library. Descriptions of four medium size EER#GRAL-applications conclude the paper to demonstrate the usefulness of the approach in practice. 1 Introduction Using graphs as a means for discussing problems, as a medium for formal reasoning, or as a paradigm for data structures in software is folklore in today's computer science literature. But most of the di#erent approaches that use graphs are not used in a coherentway. There are di#erent models in use based on undirected or directed graphs, with or without multiple edges or loops. Sometimes graph elements are typed or at...

A framework using so called second-order signature for the specification of database models has been presented in earlier work. The goal of this approach is to provide generic tools for the implementation of database systems, in particular for parsing and rule-based optimization and for execution of query plans, that can be used with widely varying data models and query languages. In this paper we apply this specification technique to the graph based data model GraphDB. We develop an algebraic description for the querying facilities of GraphDB and use second-order signature to specify the GraphDB data model and its algebra.

We describe how reachability-based orthogonal persistence can be supported even in uncooperative implementations of languages such as C++ and Modula-3, and without modification to the compiler. Our scheme extends Bartlett's mostly-copying garbage collector to manage both transient objects and resident persistent objects, and to compute the reachability closure necessary for stabilization of the persistent heap. It has been implemented in our prototype of reachability-based persistence for Modula-3, yielding performance competitive with that of comparable, but non-orthogonal, persistent variants of C++. Experimental results, using the OO7 object database benchmarks, reveal that the mostly-copying approach offers a straightforward path to efficient orthogonal persistence in these uncooperative environments. The results also characterize the performance of persistence implementations based on virtual memory protection primitives. 1 Introduction Incorporating orthogonal persistence [11] ...

PM3 is an orthogonally persistent extension of the Modula-3 systems programming language, supporting persistence by reachability from named persistent roots. We describe the design and implementation of the PM3 prototype, and show that its performance is competitive with its nonorthogonal counterparts by direct comparison with the SHORE/C++ language binding to the SHORE object store. Experimental results, using the traversal portions of the OO7 benchmark, reveal that the overheads of orthogonal persistence are not inherently more expensive than for nonorthogonal persistence, and justify our claim that orthogonal persistence deserves a level of acceptance similar to that now emerging for automatic memory management (i.e., "garbage collection"), even in performance-conscious settings. The consequence will be safer and more flexible persistent systems that do not compromise performance.

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We argue the significance of a fundamental shift in bioinformatics, from in-the-small to in-the-large. Adopting a largescale perspective is a way to manage the problems endemic to the world of the small — constellations of incompatible tools for which the effort required to assemble an integrated system exceeds the perceived benefit of the integration. Where bioinformatics in-the-small is about data and tools, bioinformatics in-the-large is about metadata and dependencies. Dependencies represent the complexities of large-scale integration, including the requirements and assumptions governing the composition of tools. The popularmake utility is a very effective system for defining and maintaining simple dependencies, and it offers a number of insights about the essence of bioinformatics in-the-large. Keeping an in-the-large perspective has been very useful to us in large bioinformatics projects. We give two fairly different examples, and extract lessons from them showing how it has helped. These examples both suggest the benefit of explicitly defining and managing knowledge flows and knowledge maps (which represent metadata regarding types, flows, and dependencies), and also suggest approaches for developing bioinformatics database systems. Generally, we argue that large-scale engineering principles can be successfully adapted from disciplines such as software engineering and data management, and that having an in-the-large perspective will be a key advantage in the next phase of bioinformatics development.

We present a management system whose functionality goes beyond commercial systems for project management, workflow management, and engineering data management in particular with respect to the dynamics of development processes. AHEAD (Adaptable and Human-Centered Environment for the MAnagement of Development Processes) supports the coordination of engineers through integrated management of products, activities, and resources. For activity management, dynamic task nets are provided which are characterized by seamless interleaving of planning, execution, analysis, and monitoring. All management data (e.g., task nets, version histories, and product configurations) are internally represented by graphs in a uniform manner. Management tools are generated from a formal specification which is based on programmed graph rewriting.