This information is for a release that is no longer supported by the Globus Toolkit. The currently supported versions of the Globus Toolkit are 4.2 (recommended) and 4.0.

Information Services in the Globus Toolkit® 3.0 Release

Note:  This page contains information and document links for MDS3, the latest version of MDS.  MDS2 information is now available at http://www.globus.org/toolkit/docs/2.4/mds/.

The Information Services component framework of the Globus Toolkit Version 3.0 (GT3) provides information about Grid resources for use in resource discovery, selection, and optimization.  This information is critical to the operation of the Grid and construction of applications.

In the Open Grid Service Architecture (OGSA) on which GT3.0 is based, everything is represented as a Grid service.  These Grid services can be a static set of persistent services as well as transient services.  There may be one or more instances of a particular Grid service.  Each Grid service expresses its state in a standardized way as Service Data Elements (SDEs).

Information Services provides the functionality within which Service Data can be collected, aggregated, and queried; data feeds can be monitored; and Service Data can be created dynamically on demand.

The Information Services component is therefore a broad framework that includes any part of GT3.0 that generates, registers, indexes, aggregates, subscribes, monitors, queries, or displays Service Data in some way.

The Monitoring and Discovery Service

The features provided in GT2 by the Monitoring and Discovery Service (MDS2) are now provided by the GT3.0 Information Services component, which is now also known as MDS3.  When used in conjunction with standard Open Grid Services Infrastructure (OGSI) mechanisms that provide a consistent way of querying any Grid service about its configuration and status information, these services provide all of the capabilities of MDS2 and more, all within a OGSA-compliant environment.

The GT3.0 Index Service provides an information aggregation service that is more extensible than the GT2 GIIS.  In GT3, the need for a separate GRIS goes away as OGSA-standard Service Data Elements and Service Data interfaces enable any GT3.0 OGSA service to act as its own GRIS.  OGSI itself provides an important addition to these services: a consistent mechanism for notifying services of changes in Service Data Elements, allowing data to be pushed or pulled into indexes.

To simplify the development of Service Data Providers, GT3.0 provides a pluggable information provider architecture similar to the one used in GT2.   Standard GT3.0 components such as GRAM have been designed to provide Service Data Elements whose information is similar to the existing GT2 MDS data.

Note that GT2 MDS clients will not be able to communicate with GT3.0 Index Services or use GT3.0 Service Data features without modification.  GT3.0 Index Service data is available only in XML form, whereas a GT2 GIIS expects LDIF.  However, existing GT2 information providers can be ported into GT3.0 as described in the Porting Guide linked below.

Information Services Documentation

The documents linked from this page describe GT3.0 Information Services overall, the Index Service and its related components, the creation and porting of service data providers, and tools for browsing and querying service data.  These tools can be used with any Grid service.  As development of GT3.0 continues past this release, these documents will expand to include more information and this page will link to additional documents that will describe other aspects of GT3.0 Information Services.

Note that documentation for MDS2 is available at http://www.globus.org/toolkit/docs/2.4/mds/.

Getting Started with GT3.0 Information Services

GT3.0 Index Service

Extending GT3.0 Information Services

Service Data Tools

Additional Information