Metadata catalogs store descriptive information (metadata attributes) about logical data items. These catalogs can then be queried to retrieve the particular logical data item that matches the criteria. However, the query has to be formulated in terms of the metadata attributes defined for the catalog. Our work explores the concept of virtual metadata, where catalogs can be queried using metada...

We present a catalog of 36 120 QSO candidates from the GALaxy Evolution EXplorer (GALEX) GALEX Release Two (GR2) UV catalog and the USNO-A2.0 optical catalog. The selection criteria are established using known quasars from the Sloan Digital Sky Survey (SDSS). The SDSS sample is then used to assign individual probabilities to our GALEX-USNO candidates. The mean probability is ∼ 50%, and would ri...

Catalog Services play a vital role on Data Grids by allowing users and applications to discover and locate the data needed. On large Data Grids, with hundreds of geographically distributed sites, centralized Catalog Services do not provide the required scalability, performance or fault-tolerance. In this article, we start by presenting and discussing the general requirements on Grid Catalogs of...

The CORDS Multidatabase System (MDBS) provides applications with an integrated view of a collection of distributed heterogeneous data sources. Applications are presented with a relational view of the available data and are able to access the data using standard SQL operations. The information needed by the MDBS to provide its services is kept in an internal database called the MDBS Catalog. Thi...

The Globus Replica Catalog is a fundamental Data Grid service. It is important to evaluate the performance of this complex system, currently based on LDAP servers. The paper presents the results obtained during performance tests, which were done with three popular LDAP implementations (OpenLDAP, Oracle Internet Directory (OID), Netscape Directory) available today. Oracle9i is a new product and ...

Faceted based search is an increasingly common part of search interfaces. This study examines the use of a library catalog search interface which supports but text searching and faceted based searching. Log analysis is performed of library catalog search records to analyze how and when faceted based searching is used in conjunction with text based searching. The logs are from the Triangle Resea...

In order to facilitate the availability of and access to spatial data, Spatial Data Infrastructures must set up a series of services to be reused by their community of users in the construction of different applications and value-added services. One of the key elements to exploit the resources provided by these infrastructures is to facilitate a catalog of services describing the features of th...

–Based on the epicyclic approximation, we have simulated the motion of the young open star clusters IC 4665 and Collinder 359. The separation between the cluster centers is shown to have been minimal 7 Myr ago, 36 pc. We have established a close evolutionary connection between IC 4665 and the Scorpius-Centaurus association — the separation between the centers of these structures was ≈ 200 pc 15...

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