Back to Table of Contents

5. Access System Implementation by Functional Areas

This chapter discusses implementation of the GCDIS access services, including an overview of the GCDIS access system, a discussion of how GCDIS access function implementation will be coordinated, a summary of the GCDIS access services, and discussions of each GCDIS access system functional area. This will be followed by discussions of the relation between GCDIS access functions and State, local, and international programs with which GCDIS must work.

For the GCDIS, the definition of system embraces the full range of people, procedures, hardware, software, and infrastructure (e.g., networks, telephones, mail) that together constitute a system providing users with access to data and information services (a mix of online and offline).

Access System Overview

The GCDIS is the set of individual agency data and information systems: a mix of manual and automated, online and offline functions, supplemented by a minimum amount of new crosscutting infrastructure, and made interoperable by use of standards, common approaches, sharing of technology, and coordination of data policies. Thus, each agency's own data and information system will be that agency's component of the GCDIS.

The GCDIS comprises individual agency systems that must evolve to meet changing agency user needs and agency missions, and to take advantage of emerging information system technology. Such evolution will pose a major challenge to the agencies to ensure that it does not disrupt the interoperability that allows the GCDIS to exist. Also, changing needs of global change users and technology will create an evolutionary pressure to which agencies must respond while protecting agency missions and users. The coordinating mechanisms and the agency implementation approaches, including the standards used, must allow flexibility and change.

Conceptual View of the GCDIS Access System

The conceptual view of the GCDIS access system is in marked contrast to the present system where, for the most part, individual agencies service only their own user communities. Although with the GCDIS each agency will continue to serve its own user community, agency data and information systems will be interconnected.

Users accessing any of the agency data and information systems making up the GCDIS access system will be able to obtain a comprehensive view of common GCDIS access system services (common across the GCDIS agencies), while also continuing to have access to the specific services of that agency (which are tailored for the user community specific to that agency according to the agency's own individual mission requirements). The actual physical configuration within this conceptual framework will evolve dramatically as user needs and technology change and as the different agencies attain increasing degrees of GCDIS interoperability. The system will also evolve in terms of the number of participating agencies. The IWGDMGC will actively work to broaden GCDIS participation to include the other agencies with data and information needed for the USGCRP. To encourage their participation, the GCDIS is planned as a system that an agency can join with only a modest commitment and then work toward a fuller implementation of the information service objectives of GCDIS. Although the desirable level of enhanced participation will involve provision by the agency of the full suite of metadata appropriate for their data and information, the minimal requirement for agency participation will be

There is now and always will be significant diversity among and within agencies regarding their data and information systems, ranging from highly automated systems to largely manual systems. The evolution of systems within agencies will proceed at different rates, given agency user requirements, mission needs, and budget constraints (this plan assumes that the GCDIS access system implementation must be accomplished within currently projected agency budgets). The GCDIS access system approach must be sufficiently flexible and adaptable to function in such a highly heterogeneous and changing environment.

Interoperability of Services

From the users' point of view, the interoperability required for the GCDIS access system implementation to be successful must result from a sufficient degree of commonality among agency data and information systems and services. Commonality does not imply major changes to the data and information systems. Locator technology freely available on the international Internet will be used to provide a common look and feel at a general level for systems that differ radically from each other, although the underlying systems may be quite different in supporting more specific functions. This enables users to view the overall aggregate global change data base and supporting services as a coordinated whole and yet still have the potion of accessing agencies' data and information services by the methods defined by each agency. Sufficient commonality in this context can not be defined a priori - continuing involvement of global change users in advising, testing, and evaluating the evolving implementation of the GCDIS access system will be essential to ensure that the degree of interoperability attained by the GCDIS access system meets their needs. The agency elements that will become agency components of the GCDIS access system are and will be a heterogeneous collection, ranging from almost entirely manual systems to highly but never completely automated systems. Interoperability must be addressed in terms of common standards and guidelines for manual procedures as well as information system functions.

There must be interagency coordination on the common standards and approaches required to meet the needs of the global change user community, while also meeting the needs of agency- specific user communities. Sufficiency will be measured by users evaluating the usefulness of the GCDIS access system.

Underlying the interoperability seen by the user will be a variety of implementation approaches, such as use of a client-server architecture that will evolve with advances in information systems technology. The pace and extent to which individual agencies are able to implement interoperability will vary with the agency's own mission, schedule, and cost constraints. Attainment of the goal of making disparate services and systems look like a common logical system to the user will, therefore, not be achieved uniformly across all agencies. Thus interoperability and the GCDIS access system gradually will evolve.

Standards and Procedures Approach

The GCDIS will adopt recommended common standards and procedures in areas critical to the consistency and coherence of the global change data and information holdings and supporting access services. The purpose of reliance on standards is not only to facilitate use of the system and its products by users but also to facilitate evolution of elements of the system by building in technology independence through adoption of such standards as the Portable Operating System Interface (POSIX), the Spatial Data Transfer Standard (SDTS), and related approaches.

The Standards Subgroup will provide support to all the IWGDMGC subgroups. Examples of support will be to provide information on training, documentation, and contacts; to be the focal point for the coordination of recommendations on standards for agency implementation plans; and to promote the development of new standards where needed. The Standards Subgroup will submit these recommended standards to the IWGDMGC for adoption.


In the functional areas described in this plan, the objective will be to identify and use existing standards, whenever possible, rather than to develop new standards. Where FIPS either do not exist or are not applicable, preference will be given to adopting international and national standards developed by recognized voluntary standards bodies such as the International Standards Organization (ISO) and the American National Standards Institute. If no FIPS or voluntary standards exist for an important area of need, and if timely development by existing standards bodies seems unlikely, then consideration will be given to establishing an interagency standard to meet the need.

International Standards

Implementation of the GCDIS access system by U.S. agencies will facilitate international cooperation by making use of international standards and protocols (e.g., the Unicode and the ISO standards, the CEOS standards) wherever practical. The U.S. GCDIS access system will be a node on an international global change data and information system.


Procedural guidelines in areas such as user services and billing and other related administrative functions will be adopted and implemented to improve services important to the global change researcher.

Technology Sharing among Agencies

Technology sharing initially will focus on software needed to provide commonality required to reduce differences among agency data and information systems. The exchange of software will simplify interagency mediation needed to bring about the interoperability needed for the GCDIS access system. Technology sharing also may offer cost savings for agencies and facilitate more rapid implementation of needed capabilities. Bilateral or multilateral technology sharing will expedite implementation of the GCDIS access system.

Software will be shared among agencies participating in the GCDIS access system. The software will be fully documented and will embody architecture and design approaches, such as layering and use of standard interfaces to avoid hardware dependence or vendor dependence, and to allow modification or addition of modules without redoing architecture. The agency accepting software will be responsible for implementing the software in its own environment, establishing the capability to support it, and adapting or extending the software as needed to meet the agency's own needs while maintaining the agreed degree of commonality needed to support the GCDIS access system. The agency providing the software will provide full documentation, technical assistance, and support to the extent possible within its program constraints, but the receiving agencies will need to have or develop their own capabilities.

Coordinating Access Implementation

Access Subgroup

Data access issues will be coordinated by the combined efforts of the Catalog, Networks, Standards, and Libraries Subgroups. The Catalog Subgroup will act as the IWGDMGC overseer of the GCMD. The Network Subgroup will analyze requirements for internal and external networking required for the success of the GCDIS access system.

The Standards Subgroup will develop recommendations for FIPS and voluntary standards to be adopted in the functional areas described in this plan. These recommendations will be submitted to the IWGDMGC for adoption. Agencies will decide whether to adopt the recommendations and the appropriate time frame for their implementation. An overall decision to accept a recommended standard will be by agreement of the agencies involved in the GCDIS access system implementation.

The IWGDMGC Library Information Subgroup will coordinate the identification, organization, creation, and distribution of library and information products and documents related to global change research, referral, and educational activities, and serve as a clearinghouse that coordinates library and information center collection efforts among organizations involved in global change research.

Other GCDIS access system functions will be implemented entirely within the participating agency elements, with specific coordination of existing implementation efforts to be accomplished through the mechanisms discussed in the next section. In addition, the Access Subgroup will include a catalog and distribution services team, which will include representatives from agency implementation efforts, to ensure that these efforts are coordinated across the agencies.

Agency Implementation Coordination

Agencies in the process of upgrading or developing their agency data and information systems as their components of the GCDIS access system will coordinate the technical details of the design and implementation of their systems within the framework provided by this implementation plan. Agency representatives participating at this level will be directly involved in each agency's data system implementation effort; these people are in the best position to arrive at a consensus on specific technical recommendations to the GCDIS access system agencies. They also can help establish appropriate links to other interagency data and information access programs.

Each agency will establish its own mechanism within its own implementation effort, inviting participation of agencies engaged in parallel efforts, to make recommendations concerning specific design choices or implementation decisions to allow the interoperability required for the GCDIS access system. Each agency should then incorporate the GCDIS access system recommendations into its own systems to the extent possible, given cost and schedule constraints.

Access Services

This section defines the system functionality required for GCDIS access services. Access services include a complete range of data and information services to users - catalog, order, browse, distribution, and user support - and underlying archive and network services. Electronic access to these services will be provided to users via the Internet. For the GCDIS access system to succeed, participating agencies must cooperate to achieve interoperability among their various methods of providing these services. That interoperability will allow users to see a consistent set of services spanning the agencies; users will be able to identify, order, and receive ensembles of data and information products held by some or all of the agencies. Their use of these products will be facilitated by common media and formats and consistent documentation.

Some agencies' participation in the GCDIS access functions will be limited. In particular, DOD participation in the GCDIS is limited to making unclassified and unrestricted data and information available to appropriate civil agencies; GCDIS access functions for DOD data and information will be assumed by those other agencies.

Although it is a driving assumption that development and extension of electronic, online capabilities is needed for GCDIS access services, GCDIS access services always will be provided by a mix of manual and automated, online, and offline functions. Whereas that mix might include more electronic services in the future, the need for manual services in such key areas as user support will remain. Thus, the broad definition of system in the GCDIS is a combination of hardware, software, people, and procedures.

A user view of the functional areas and an overall schedule establishing goals for progressively achieving interoperability in these areas will be presented. This will be followed by a discussion of each functional area in detail, including definitions of levels of implementation of the functionality within each functional area, and milestones for progressive, phased implementation by the agencies.

Therefore, the overall plan for the GCDIS access system implementation will be presented as a combination of efforts for the individual functional areas, and within each area implementation will be addressed on an agency-by-agency basis, with individual agency implementation plans set in the context of the overall schedule and priority.

User View of the Functional Areas

The following is a presentation of the GCDIS access system functional areas from a user point of view. This is not intended to suggest a strictly sequential approach to implementing the GCDIS, but to provide guidance based on user needs for phased and overlapping progressive implementation of the GCDIS access system. There is a fundamental requirement for user support services, provided by expert personnel, accompanying any and all access functions, regardless of the degree of automation of the functions.

Networking is an underlying requirement for all these functions, except offline access. Each functional area requires network support, therefore network requirements will be addressed for each functional area.

International access is the extension of these services to provide access to global change data sets held internationally and, in turn, to allow international access to GCDIS functionality. The program plan calls for implementation of international access during the period 2001-2010. Some GCDIS access system agencies are now actively involved in international efforts that will be broadened in the future.

Access Function Implementation Link to Data Set Priorities

Resources for implementing GCDIS access functions will be limited. It is essential that data sets of greatest importance to the USGCRP receive the highest levels of support. Table 4 maps the level of implementation for each access functional area against the categories of data set priority, and is a companion to the similar table in Chapter 4 that maps content areas against data set priority. The table should be interpreted as establishing a goal for a floor level of implementation in each case. For example, an inventory implementation level of 2 for a high-priority data set would be the minimal goal for the GCDIS access system. The access functional areas and the levels of implementation for each will be discussed in detail in later sections.

In the case of the directory function, the levels of implementation are not readily correlated with data set priority. Rather, it is most urgent that the directory information be assembled and made available for the most important data sets; priorities for these efforts will be consistent with data set priorities.

Access Function Implementation Link to Type of User

The wide spectrum of the user community includes users with

The GCDIS will recognize and meet these disparate user access requirements. The technical capability for meeting such a spectrum of needs in the first two areas is well developed and available. To meet the needs in the last area, it will be necessary to build special directory capabilities to help guide specific classes of users to the data and information products that they require.

For example, educators in the K-12 levels will need to be directed to those products suitable for their use without being immediately confronted upon entry into the GCDIS with the total contents of the GCDIS. Similarly, many of the users interested in policy aspects will need to have identified data and information products that can either meet their needs or help guide them to more detailed information.

A final example of the need for these special directory capabilities is that of researchers in one discipline wanting to work on interdisciplinary problems. Many such users will need special help in finding summary-level information in disciplines outside their own to guide them in their more detailed use of the GCDIS.

User Support and Outreach


User support services include providing expert staff personnel to assist users with any of the GCDIS access system functions. Regardless of the degree to which the GCDIS access system functions become automated or accessible online, a requirement will exist for user support personnel to interact directly with users, answering questions, and providing advice and guidance. This function also includes preparation and distribution of user aids of various types.

The data or information center should reach out to the researchers, policy makers, educators, and the general interested public that make up the user community. Data and information product announcements in scientific journals, flyers to discipline departments at universities, and maintenance of mailing lists that include attendance lists from major workshops or meetings are effective ways of informing the user community of a center's holdings and services. A periodical center newsletter is one means to establish a stable audience for center communication.

Just as it is important to reach out to users to inform them of the system capabilities, user feedback is critical to the growth of the global change data and information program. The components of the system of user services, directory or catalog offerings, networks, and procedures must be capable of responding to such changes as increased user sophistication, priorities' changes, and technology advances. The direction of these changes often come from the users. Information about problems experienced by users can provide valuable guidance on system technical shortcomings. Feedback through user forums and questions that come into information centers offer indicators about needed data and information lacking in the system. These and other techniques, such as automatic collection of access system search statistics, will be implemented to guide enhancements to the overall system.

Needed Interoperability

The user support staffs of the various agency GCDIS access system elements will exchange information about their organization's data and services so that a user contacting the user support staff of any GCDIS element can obtain information about all other GCDIS elements, and obtain referrals to GCDIS access system elements offering data and services of interest to the user.

Agency Applicability

This function applies to all agencies (or their designees) participating in the GCDIS access system at any level.

Agency Implementation Overview

Continual coordination of agency user support functions will be provided through the standing User Support Team, composed of agency user support staff with active participation of members of the User Advisory Group and other user representatives.



Each GCDIS agency will establish a suitable level of connectivity to the Internet, a global network of networks connecting the research and education communities throughout the United States and to nearly 60 (as of March 1993) other countries. In the United States, the Internet consists of NSFNET, regional and State networks, agency networks, and local networks such as campus networks. The future development of the U.S. infrastructure will be strongly influenced by the NREN program, the networking component of the HPCC program, and the NII program. Connections to this networking infrastructure are required to support external user access to GCDIS access system services and internal operations between the GCDIS access system components needed to support user services.

This set of connections is referred to as the GCDIS access system virtual network. Connections on the GCDIS access system virtual network will be set up to handle the types of operations that may take place to support GCDIS functions accessed by a user at one GCDIS access system node. For example, if a user connects to agency A's system and performs an inventory search spanning the inventories of agencies B and C as well as A, some communication between agencies A, B, and C will be necessary to relay the search request to the inventories and then transfer the search results back to agency A for assembly and presentation to the user. The nature of the communications between the agency systems will be a high frequency of small transactions that require very rapid response in order that the end-to-end or net response time to the user be rapid enough to meet user needs. Also, in some cases, the connections will be needed to support other global-change-related functions, such as supercomputer access.

In the case of both external and internal network requirements, an analysis of the frequency and size of the transactions that the network must support will be made. Response times will be established that meet user needs. Attention will be paid to peak as well as average capacity requirements (e.g., in terms of concurrent user support).

Needed Interoperability

In order to support open electronic access by users or electronic exchanges with other GCDIS access system elements (in the same or other agencies), agency GCDIS access system elements must have the appropriate network connections, including Internet access. The capacity of the agency elements network interface must be sized to support the GCDIS access system functions requiring network support.

Agency Applicability

The need for networking support as an integral part of the GCDIS access system applies to all agencies (or their designees).

Agency Implementation Overview

Agency plans for implementing online GCDIS access system functions will include implementation of required network support. For example, agency plans for implementing online GCDIS access system inventory services will include identifying agency elements involved and establishing network connectivity for those agency elements, and sizing the networking capacity to meet the needs of the inventory function.

Three levels of network user performance requirements have been identified that are needed to provide access to GCDIS user services:

  • Network user performance level 1: Online data services. Network user performance level 1 supports online dynamic science, which means transfer of data in real time, access to supercomputer computational models, and scientific conferences. This level of network performance requires sustained transfers of up to 1 megabit per second (Mbps) or more. This network performance level is provided with either dedicated Ethernet and T1 services (1.544 Mbps and higher), or shared fiber- optic networks (e.g., a fiber-optic digital data interface local area network [FDDI LAN] with T3 or switched multimegabit data service access, or asynchronous transfer mode).

  • Network user performance level 2: Online browse. Network user performance level 2 supports user access to precomputed browse products that are stored online or near line. Near-line data are staged dynamically into the online hierarchy at the time of an initial preview request, so that whereas the initial browse product may not be transmitted back to the user for as long as a minute, subsequent products in the same data set may be sent within a few seconds. This level of network performance requires sufficient bandwidth to support burst transfers of up to 100 kilobytes per second (Kbps) for up to 1 or 2 seconds. This network performance level is typically provided with shared Ethernet connections using T1 access lines.

  • Network user performance level 3: Metadata access. Network user performance level 3 supports user access for directory, guide, and inventory searches of metadata. The metadata typically are text records accessed with brief text queries. This level of network performance requires sufficient bandwidth to support a number of short interactive messages with rapid response times. This network performance level typically is provided with voice-grade telephone line access (i.e., direct modem connection at 2.4 to 14.4 Kbps, or shared Ethernet connection via 56-Kbps access line).

    In addition, networking between GCDIS access system elements is also required to support GCDIS user services. Within a given agency, its GCDIS element might be a collection of agency elements linked together as a single but distributed agency GCDIS element, or a set of agency elements, each functioning as separate GCDIS access system nodes. Internal GCDIS access system networking refers to networking between the GCDIS access system nodes required to support GCDIS access system user services. These internal GCDIS access system network services are required to support the rapid searching and relaying of metadata and data in support of services provided at each agency's GCDIS access system node user interface. The nature of network communications within agencies and among agencies in support of each of the network user performance levels is similar to the levels seen by the users, except that in some cases there may be more system-to-system interaction than seen by the user, and that the internal GCDIS access system networking must be able to support a higher level of concurrent use than individual GCDIS access system node concurrent user support (i.e., concurrent users at a number of GCDIS access system nodes might invoke GCDIS access such system services as inventory searches that each spread out across all GCDIS nodes).



    The GCDIS directory will provide information to its users on all priority, global-change-related data and information that are available and that have sources identified for user help with both acquisition and use. This applies whether the source of the data and information is international, National (agency), State, local, or from an individual.

    The GCDIS directory consists of several elements. At the core is the GCMD and associated Directory Interchange Format (DIF)-based directories, such as the Consortium for International Earth Science Information Network (CIESIN) directory, which contain descriptions of data sets relevant to global change. The descriptions are provided by the agencies in a standard DIF which is automatically loadable into the DIF-based directory data bases. Conformance to DIF allows this core information to be searched by standard methods and to return data descriptions that are consistent in the type of information content. The DIF-based GCDIS directory function makes possible coherent searches across agencies by providing functional consistency in terms of space and time references and terminology used to name and describe data.

    The DIF is one of many formats that are used to convey locator information, and DIF can be converted to and from the Government Information Locator Service (GILS) core elements format without loss of information. This allows DIF-based directories to be easily incorporated into many other directory services, and also allows DIF- based directories to bring in entities from other directories throughout the world. To accommodate existing library information systems, the DIF also supports a representation in the U.S. Machine Readable Cataloging (USMARC) format. Transformation from the DIF format to the USMARC format, however, is not easily reversible because the DIF format has more specificity than is currently defined for the USMARC format.

    A number of data set directories for agency data and information existed before the creation of the DIF-based directories. These are the second element of the overall GCDIS directory. None of these directories are specifically oriented to the topic of global change, but many have relevant data descriptions. The information content varies in format, so it is not always easy to obtain comparative information. Nonetheless, the directories do represent a valuable resource and need to be made searchable through the GCDIS. These directories are searchable by the standard methods used in the past, but it is important also to be able to search multiple directories simultaneously for relevant data and information. The present way to do this is to use network tools such as Gopher and Wide-Area Information Server (WAIS) to allow access to these directories and make their information content searchable by standard text retrieval and field-searching methods. The DIF-based directories can also be made searchable by these methods, but these methods do not presently allow the user to know valid values that can be entered in some of the controlled fields. Consequently, it is important to continue the work of describing high-priority global change data sets in the DIF-based directories.

    Information other than data set descriptions, such as reference documents, regulations, study papers, and so forth, also needs to be locatable through the GCDIS directory. This could include, as well, pictorial materials such as maps and sample images. For this much broader amount of information, the GCDIS needs to function like a digital library and use the techniques that have been and are being developed for this purpose. Abstracts or summary descriptions for these materials (or even the documents themselves) can be retrieved through the GCDIS directory using the network tools mentioned earlier. The GCDIS directory will also lead the user to the standard online library search capabilities wherever available to the user community. The data set directories can be considered as one small part of this very large body of information.

    Finally, the GCDIS directory must provide pointers at the guide and inventory level to other data and information systems and allow the user to gain more detailed information about global change data or even the data themselves. In many cases the GCDIS directory provides automated connections to these other systems. The user must know or be told, however, that these systems can be accessed directly and that it is not always necessary to go through the GCDIS directory to use them. In the same way, the other systems can make known to their users that the GCDIS directory exists and, perhaps, offer an automated connection to it to get directory-level information about data being pursued.

    The GCDIS directory will be accessible by networks and dial-in lines from around the world. The directory will contain information from around the world and will not be limited to just U.S. entries. There will be at least one distributable version of the DIF-based directories available for stand-alone use on personal computers that retains as much of the functionality of the online versions as possible.

    The DIF-based directories are part of the CEOS International Directory Network (IDN), which is a federation of directory systems from around the world bound by sharing information about data in the Earth and space sciences through the exchange of DIF files. The GCMD is the U.S. coordinating node of the CEOS IDN. There are two other coordinating nodes in Italy and Japan that are the European and Asian coordinating nodes, respectively. These coordinating nodes are gathering points for information exchange within the CEOS IDN, and each of them have complete and identical data bases and software that are kept consistent with each other through biweekly automated information exchanges. Thus, the GCMD receives global change data information from international sources as well.

    The GCMD and the CIESIN directory employ client-server architecture, with multiple clients accessing distributed servers. The DIF-based directories may evolve to become a single virtual GCMD directory composed of a federation of DIF-based servers, perhaps one for each participating agency, which can all be accessed through queries initiated by client software. These would support standard national and international protocols for information search and retrieval, such as ANSI Z39.50 and ISO 10163. This possible evolution of the DIF-based GCDIS directory function is now being tested with the GCMD and CIESIN servers.

    Needed Interoperability

    Agencies describe their priority global change data and information holdings according to GCDIS directory standards for scope, content, space-time references, and terminology used in names and descriptions or abstracts. The directory function should be interoperable with guide and inventory functions as described previously.

    Four levels of contribution by agencies to the GCDIS directory are defined as follows:

    Level 1.Agencies will operate a directory node containing information prepared to GCDIS directory standards describing agency global change data and information. This will include the resources necessary to keep the server's information up to date about the data and information resources to which it points. If a distributed server approach is adopted for the GCDIS directory, each agency directory would be one of the servers in the distributed GCDIS access system directory. If a centralized approach is continued, each agency node will contribute information to the central, coordinating node. This node will hold all information contributed by all of the agencies. This also will include the connection of underlying information systems to the distributed GCDIS directory using interoperable techniques to the extent possible.
    Level 2.Agencies contribute directory information for all global change data and information, prepared to GCDIS directory standards, to be added to the GCDIS directory data base.
    Level 3.Agencies contribute directory information for priority global change data and information, prepared to GCDIS directory standards, to be added to the GCDIS directory data base.
    Level 4.Agencies provide existing documentation of priority global change data and information to the GCDIS directory staff personnel, who in turn prepare directory entries and add these to the GCDIS directory data base.

    Agency Applicability

    The GCDIS directory applies to all U.S. agencies holding global change data and related information or supporting global change research and related data generation in outside agencies. The U.S. agencies work with their international counterparts to ensure that relevant international information is included in the directory function as well.

    Agency Implementation Overview

    The present directory implementation activities for the GCDIS access system are as follows:

    Agencies will continue to provide global change data set information descriptions to the GCMD by adding to and updating their data set descriptions in the present GCMD server. Useful and usable data sets will be described in DIF files and the DIF files loaded into the GCMD (in either the NASA or the CIESIN server). Adjunct products to the online GCMD, such as printed versions of selected information and CD-ROMs with information, data, and incorporated browse capability, will continue to be developed and distributed as resources permit. If the GCMD evolves to include multiple servers, agencies also may contribute information conforming to GCMD standards for new servers or provide access to servers containing agency directory information conforming to GCMD standards. All agencies will identify any data and information systems that can usefully be accessed through the automated connections (links) from the GCDIS directory level. Developments necessary to make these systems more interoperable will be carried out as resources permit.



    The guide function of the GCDIS access system provides detailed information about all agency global change data sets, to allow users to assess suitability of data sets for their research or application or to aid users in the use of the data set. This information includes bibliographic references to publications relevant to the data set and, in some cases, the abstracts or actual publications.

    The guide function of the GCDIS access system will make possible coherent searches across agencies by providing functional consistency through including a standard set of topics (as they apply to each data set) and consistent terminology (e.g., data set references). There will be agency interfaces to agency-based guide systems that may include other agency guide information, or access or point to other agency guide systems or information.

    Guides accomplish several functions within the GCDIS access system. Guides augment the general information in the directories with specific information about the data, such as detailed descriptions of the instruments and platforms used to acquire the data. This information permits the user to determine the availability and appropriateness of the data. Any information critical to the use and understanding of the data is collected in the guide. Explanations of projects under which the data were gathered also should be included. Short-term instrument outages, specifics about the recording instruments, and other factors that determine the suitability of the data are included.

    The guide also fulfills the need to document carefully information about how the data set was derived. Detailed instrument logs, including instrument location, response, calibration and external factors affecting the instrument, may be included. Information regarding the platform, such as description of satellites, stations, and observatories, also may be documented. Discussion of algorithms used to process the data must be detailed. Any information essential to the complete understanding of the data must be documented in the guide. This type of information is used to validate the data, and thereby the quality of research results. Without this information the data are useless.

    In the case of data sets consisting of multiple granules (see the inventory functionality - page 66), the guide will include a generic description of a granule for that data set (i.e., the content and documentation included with each granule). The guide will describe any subset creation or other options available to a user for the given data set.

    Needed Interoperability

    Functional consistency for the GCDIS access system guide requires a degree of consistency in the guide information across all data sets. This is limited to a standard set of topics, which will be addressed for each data set where they apply, and to standard terminology for terms such as data set names and parameter names.

    The guide function will be interoperable with directory and inventory functions: that is, to allow a user to access guide information corresponding to a given directory entry, or to allow a user to access guide information concerning a data set that contains granules meeting the user's inventory search criteria.

    Four levels of agency contribution to the GCDIS access system guide function are defined as follows:

    Level 1.Agencies provide access to their online guide information for guide searches originating from other agencies' online guide systems, and support online access to other agencies' guide systems for their own guide users. This requires network connectivity for guide sites and network performance level 1 for user access and internal GCDIS access system communications supporting the guide function.
    Level 2.Agencies make available online GCDIS access system standard guide information. This requires network connectivity for guide sites and network performance level 3.
    Level 3.Agencies make available in hard-copy form standard guide information about the GCDIS access system (i.e., addressing GCDIS access system guide topics as they apply, and using GCDIS access system standard terminology).
    Level 4.Agencies make available in hard-copy form (e.g., user guides or handbooks) existing detailed documentation of global change data sets.

    Agency Applicability

    The guide function applies to all agencies that hold global change data sets, unless for a given data set the directory level description constitutes a full description meeting the intent of the GCDIS access system guide functionality.

    Agency Implementation Overview

    Each agency will independently implement its GCDIS access system guide functionality according to its own approaches and methods, including establishing network connectivity at guide sites where needed. This implementation overview will indicate when the various levels of GCDIS access system guide functionality will be available at a user or interagency interface for each agency element separately implementing that functionality.



    The GCDIS access system inventory function provides the user with the ability to identify particular combinations of parts of data sets (or whole data sets if the data set is most useful as a whole), ranging from one to all agencies, that meet user-provided search criteria (e.g., common space-time reference, or selected descriptors - information internal to the content of a data set that either distinguishes between parts of a data set or otherwise is important to the use of a data set).

    Where a directory entry provides a summary description of an entire data set, and a data set guide provides detailed descriptive information about an entire data set, a data set inventory provides detailed information about individual parts of a data set in those cases where single or multiple parts of a data set are of greatest use to users rather than the entire data set. The individual parts of a data set are called granules. The decision about what constitutes a granule for a given data set is based upon patterns of use of the data set. The goal is to provide a user with the most meaningful way to identify and ascertain the availability of specific data to work with. A granule is a logical subset of a data set (or a whole data set if the data set is most often used as a whole) that may correspond to a physical subset of a data set. The information describing each granule (the descriptors) would distinguish one granule from another in ways important to the use of the data, such as space-time reference, presence or absence of a given condition or feature, or the value of a parameter.

    As examples, an inventory of in situ data might contain information about an individual ship track's sequence of measurements or time sequence of observations taken at a particular site; an inventory of AVHRR satellite data would contain information about individual data acquisitions or passes; and an aircraft data set inventory would contain information about individual scenes or frames within a flight line.

    Needed Interoperability

    Inventory information held by individual agencies must employ a consistent approach to space and time references to allow cross- inventory searches, given user space-time criteria. In all cases where an internal attribute of a given data set granule is to be available to GCDIS users as a cross-inventory search parameter, it must be consistently named and defined in all applicable cases, using content standards enforced as the metadata are entered. The inventory function should be interoperable with the directory and guide functions; that is, it should allow a user to refer to summary (directory) or detailed (guide) information about a data set or data set's granules from which were identified by an inventory query as meeting the user's inventory search criteria.

    Four levels of agency contribution to GCDIS access system inventory functionality are defined as follows:

    Level 1.Agencies provide access to their online inventory information for inventory searches originating from other agencies' online inventory systems, and support online access to other agencies' inventory systems for their own inventory users. This requires network connectivity for guide sites and network performance level 1 for user access and internal GCDIS access system communications supporting the guide function.
    Level 2.Agencies make available online, searchable inventory information using GCDIS access system standard space- time references as applicable and, optionally, GCDIS access system standard descriptors as applicable. This requires network connectivity for guide sites and network performance level 3.
    Level 3.Agencies make available in hard-copy form or via a manual service inventory information for priority global change data sets, using GCDIS access system standard space-time references where applicable and, optionally, standard GCDIS access system descriptors.
    Level 4.Agencies make available in hard-copy form or via a manual service (e.g., user service personnel) existing inventories of priority global change data sets, using existing space- time references and/or internal descriptors.

    Agency Applicability

    The GCDIS access system inventory function applies to all agencies that make global change data and information available to users.

    Agency Implementation Overview

    Each agency will independently implement its GCDIS access system inventory functionality according to its own approaches and methods. The overviews in Appendix B summarize agency plans. To establish a framework for individual agency efforts, a cooperative study will be conducted to develop an initial description of the inventory interoperability functional model and system architecture (including functional interface definitions) that will be used by GCDIS access system. This is critical since the scope and complexity of implementation issues and tasks will be greatly influenced by the chosen architecture. The study will address an inventory content guideline that describes the GCDIS access system standard approach to space-time reference and definition of GCDIS access system standard descriptors (possibly including an initial set, but developing a process for defining them in the future). This study will define GCDIS access system user inventory search capabilities. The initial search capabilities will evolve as users and agencies gain experience). This study will be completed in September 1994. An assessment of other interagency access systems will be included to maximize connectivity and to benefit from the lessons learned by others.



    The browse function will allow GCDIS access system users to screen data for usefulness by examining samples of data or summary or reduced resolution versions of large data sets or large data set granules. Examples might include a sample surface meteorological observation, a sample publication of climatological information, a sample ship track of oceanographic observations, or a reduced resolution AVHRR scene (e.g., to check for cloud cover). Browse products can be available online or offline (e.g., printed hard copy or on CD-ROMs). Browse products may be precomputed and available for static browse, access, or may be computed on demand to a users specification dynamic browse.

    Needed Interoperability

    The browse function will be data set dependent, but approaches to browsing should be consistent within data types to allow users to compare different data sets. Graphical and image browse products should be designed to facilitate their combined use. Agencies should coordinate in planning browse products for like data held across agencies so that a GCDIS access system user may be able to make meaningful comparisons when browsing similar data available from multiple agencies or agency elements.

    The browse function should be accessible from the GCDIS inventory function to allow users to browse granules that otherwise meet users' inventory search criteria or the directory or guide functions (if a data set is most often used as a whole and not described as containing multiple granules).

    Four levels of contribution of agency implementation of the browse function are defined as follows:

    Level 1.Online, on-demand generation of browse products accessible from GCDIS catalog functions. This requires network performance level 2.
    Level 2. Online static browse products accessible from GCDIS catalog functions. This requires network performance level 2.
    Level 3. Offline digital browse products (e.g., on CD- ROMs).
    Level 4. Offline hard-copy browse products.

    Agency Applicability

    The browse function applies to all agencies providing global change data sets of substantial size.

    Agency Implementation Overview

    Agencies will implement browse functionality individually, but will coordinate to ensure that browse products for similar data sets are similar and support intercomparison between data sets.

    Order Placement


    The order placement function of the GCDIS access system allows a user, having selected specific global change data or information of interest through use of the GCDIS directory, guide, or inventory functionality, or by being able to specify completely the desired items without the need for use of those services or as a result of previous use of one or more of those services, to place an order for those data and information. The single order may be for a variety of items available from a variety of GCDIS agencies or agency elements. The order must be accessible either independently or from any of the GCDIS access system catalog system functions (directory, guide, or inventory).

    Processing and filling an order by the agency or agencies involved will be accomplished agency by agency according to each agency's own procedures and policies. Orders spanning agencies will be filled in parallel by the agencies as if they were independent single orders rather than parts of an overall order for data and information that spans agencies. Standard GCDIS approaches regarding such things as data formats and distribution media are discussed on page 72.

    Needed Interoperability

    Agencies must provide an interface function for GCDIS access system user order placement at each agency participating in the GCDIS access system. This function must accept user orders, and be able to forward appropriate portions of the order to other agencies for processing.

    Three levels of agency contribution to GCDIS access system order placement functionality are defined as follows:

    Level 1.The agency provides an online order placement function that is fully integrated with the catalog system (directory, guide, or inventory) functionality of the GCDIS access system. This requires network connectivity for guide sites and network performance level 3 for user access and internal GCDIS access system communications supporting the guide function.
    Level 2.In addition to a manual interface, the agency provides an online order placement function allowing users to order data from the participating GCDIS access system agency elements.
    Level 3.The agency provides a manual interface through user support staff at agency elements offering global change data and information and agreed manual procedures for forwarding orders to other elements of the agency and other agencies elements as needed.

    Agency Applicability

    This applies to all agencies from which users may order global change data and information.

    Agency Implementation Overview

    A cooperative study will be done by December 1995 to develop interagency procedures for supporting this function, including determination of the information required from the user to accompany specification of the items ordered.

    Archive Function


    U.S. global change data policy states that preservation of all data needed for long-term global change research is required. For example, each regional or global observation of the Earth system represents a unique observation of the system, one that will never be repeated exactly; assessment of changes and the mechanisms responsible for them must rely on time series of such unique snapshots. The archives for global change data must be available for a long time, regardless of the changing interests of the researcher, group, or agency that collected and analyzed the observations. Each GCDIS access system agency has the responsibility to manage, store, and maintain data sets under its purview. A GCDIS access system agency may designate another GCDIS agency to archive some data and information.

    Data set stewardship is the safe storage and preservation of data sets that are clearly part of the normal operations of each archive site. Each participating GCDIS access system agency will follow government media, storage, and handling standards as prescribed by the National Archive and Records Administration (NARA), the National Institute of Standards and Technology (NIST), and, where appropriate, WDC-A requirements. GCDIS access system archives will be staffed by professionals who understand the data and their sources and processing. Ideally, GCDIS access system archives also will be associated with an agency or university group that undertakes research using the data, verifying quality assessment and documentation of the data. GCDIS access system centers with scientists on the staff or associated with scientist groups are better able to seek out actively and acquire data needed for global change research, but might not be supplied to the archive as a matter of course.

    Examples of archive storage and maintenance practices that GCDIS access system archive sites should employ include provision of a clean environment; use of tested and certified media designated for long-term storage; provisions for media backup and off-site storage; adequate security and internal controls to safeguard equipment, software, and media; fire and water protection; and a routine, scheduled media maintenance program, including detection of media deterioration and migration of the data to newer, more stable media when proven reliable.

    As part of the archive function, guidelines will be developed for preparing data sets and associated documentation and metadata for long-term permanent retention at GCDIS access system archive sites. Data-purging policies are the responsibility of the archiving agency. Nonetheless, the GCDIS access system will develop interagency coordination procedures to prevent the loss of important data sets. This will include notification of the IWGDMGC contacts concerning plans to purge a data set at least 1 year in advance of any action to do so, to allow other GCDIS access system agencies to state requirements for the data set or agree to assume responsibility for archiving the data set. NARA procedures will apply if no agreement can be reached on disposition of a data set identified for purging.

    Needed Interoperability

    All participating GCDIS access system data centers responsible for long-term archiving of global change data sets should adhere to accepted standards for their safe storage and preservation. All centers should follow a common set of cross-agency procedures and guidelines for interagency notification before purging data sets that may be of potential value to global change research.

    Four levels of agency contribution to GCDIS access system archive functionality are defined as follows:

    Level 1. As in level 2, with off-site copies (or equivalent).
    Level 2. As in levels 3 and 4 with on-site backup copies (or equivalent).
    Level 3. Full compliance with NARA-NIST guidelines for data storage and preservation.
    Level 4. Storage of data under controlled conditions.

    Agency Applicability

    GCDIS access system agencies holding global change data sets are responsible for archiving. Some agencies, however, may arrange to have their data sets archived and distributed by other GCDIS access system agencies, either when the data sets are generated or after the data sets have been generated and the originating agency's operational mission (or research program) for those data sets has been completed.

    Agency Implementation Overview

    An ad hoc archive coordination team will be formed as a near-term interagency implementation activity. The team will develop guidelines by December 1994 for preservation of global change data.

    Distribution Functions


    The GCDIS distribution function encompasses delivery of data to users on a variety of standard media, including (for moderately sized products) electronic delivery. Standard distribution media for digital data may include 6,250-bpi magnetic tapes, 3480 cartridges, 8-mm and 4-mm cartridges, floppy disks, CD-ROMs, and so forth. Digital data may be distributed electronically via a network, either by allowing online access to the data or by allowing users to request that data be temporarily staged for later access. Nondigital products include publications, charts, and photographic images.

    Needed Interoperability

    Agencies will agree on a set of standard distribution media for digital data, allowing users a choice, and also allowing users to request data on common media from the GCDIS agencies.

    Agencies will agree on a set of standard formats for digital data (whether for offline delivery or online access), including standard distribution formats (for similar data sets), when possible, in addition to native formats that agencies might employ. Standard formats should be chosen on the basis of acceptance and usefulness to users and availability of support, such as software tools for supporting the formats.

    Agencies will agree on distributing documentation (including metadata) with the data. The documentation may be either embedded in data products or distributed as separate hard-copy or electronically accessible text.

    Three levels of agency contribution to the GCDIS access system distribution function are defined as follows:

    Level 1.Agencies offer delivery of data (online or offline) in access system standard formats chosen by the user.
    Level 2.Agencies offer electronic delivery of data. This requires network performance level 3.
    Level 3.Agencies offer GCDIS access system standard media as a user option.

    Agency Applicability

    This applies to all GCDIS agencies (or their designees) that provide digital and nondigital data and information products to users.

    Agency Implementation Overview

    An ad hoc standard distribution format and media team will be formed as a near-term interagency implementation activity. The team will develop guidelines for standard distribution formats and media by December 1994.

    Billing and Related Administrative Functions

    GCDIS access system billing and administrative functions will be addressed in the future when the agencies agree on the underlying policies.

    Information Functions and Services


    Just as the management of data is handled by major data centers or other organizations in participating agencies, the management of information is handled through centralized scientific and technical programs in a number of GCDIS access system agencies. These programs enable a comprehensive collection of literature produced by the agencies and their contractors and allow aggressive acquisition of documented results of international research and development efforts. The results are compiled into bibliographic data bases for searching and retrieval by the global change community. In terms of U.S. federally funded documentation, the central STI programs maintain systems to provide full archiving and full text retrieval of this material for current and future research. The GCDIS will build upon these existing STI services in Federal agencies.

    The interfaces required to provide users with access to bibliographic and text information will be ubiquitous, easy to use, well publicized, and interoperable with the full GCDIS access system. Single-channel access should enable the user to step from data to information or to make decisions about the extent and depth of information desired. Libraries and information centers are experienced in providing access to a broad range of information through catalogs; networks; national and regional systems; and links among public, academic, Federal, nonprofit, and corporate institutions. Decisions concerning levels of access, user fees, summary or full-text information, and links to national and international data bases and networks will be embedded in the overall implementation of the GCDIS access system. These functions will be made as consistent as possible between the data and information providers and communities.

    Needed Interoperability

    Information interoperability is needed in terms of systems development, standards in data base definition, and format of data base content.

    A new information architecture, whereby a user of global change data and information can sit at a workstation and navigate freely between data files and documentation, is being considered by these STI programs. This work involves systems development, including gateways, navigational tools (e.g., directories), standards development for both information content and for systems, and postprocessing technology for further analysis of the results from the data and information.

    Specialized library and information center functions that require interoperability or commonality in the GCDIS include the following:

    Agency Implementation Overview

    The following initial steps will be taken through the Library Subgroup:

    State and Local Government Access

    State, regional, and local governments may require access to detailed global change information to support decisions at regional scales and to augment their own data collection efforts, especially when intergovernmental coordination is needed. For example, global change information may be used to manage fisheries or to control chlorofluorocarbon emissions.

    State, regional, and local governments will be able to access the GCDIS through the Internet and its successors. GCRP agencies will assist them in obtaining the necessary information to facilitate networking access and in obtaining the necessary software to use the GCDIS. Currently, States are able to use some Federal systems through special data-sharing arrangements. These arrangements will be extended to include the full array of GCDIS functionality. Outreach will be necessary through organizations, such as the National Governors Association, to assure that the States and local governments understand the range of services available and the extent and distribution of potentially useful data.

    State, regional, and local governments make extensive use of spatial data in their geographic information systems. It is expected that much of the data requested from the GCDIS access system will be spatial data at the highest resolution available. These requests could include the finest resolution available from predictive model runs, as well as remote sensing and in situ monitoring data. Links between the GCDIS and States' geographic data systems are expected. Historical data may be required to develop status and trends assessments for varying environmental applications. The GCDIS access system will make it easier to obtain this information.

    International Access

    In this section a discussion of international access will be followed by a discussion of several international efforts important to global change research in which GCDIS agencies are involved. Additional descriptions of international data and information systems are provided in Chapter 7.


    The agencies acting collectively under the GCDIS access system umbrella will provide international users with access to the same data and information quality and similar delivery services to those available to U.S. users. The agencies will act individually and collectively to secure for U.S. researchers access to internationally available global change data and information services.

    Access to global change research data and information anywhere in the world can be ensured more easily by an international extension of the GCDIS access system approach, with the GCDIS access system becoming the U.S. node of an international, distributed, global change data and information network system.

    Needed Interoperability

    GCDIS agencies will cooperate in establishing bilateral or multilateral links (including offline and online interoperability of services) with international global-change-related agency, multiagency, and multinational groups and systems. These will include the ICSU- sponsored WDC system (individual elements of GCDIS agencies are or may become ICSU WDCs), the ICSU International Geosphere- Biosphere Program Data and Information System (IGBP-DIS, in which some GCDIS agencies now participate), the Human Dimensions of Global Environmental Change Programme (HDP) being conducted under the auspices of the International Social Science Council (ISSC), and the International Earth Observing System (IEOS) effort being coordinated by the Earth Observation-International Coordination Working Group (EO-ICWG) and the CEOS (in which some GCDIS agencies are now participating). In general, if one or more GCDIS agencies establish links with or interfaces to such efforts or if agency elements become participating nodes in such efforts, then, through the GCDIS access system mechanisms, all GCDIS agencies should gain access and participate. As a result, all users of GCDIS access system services provided by the agencies should benefit from these efforts.

    Agency Applicability

    All agencies that participate in any way with international efforts, such as those mentioned previously, and that produce or hold unclassified or unrestricted global change data and information will ensure that those data and information are accessible through the GCDIS access system to scientists and researchers not only in the United States but also in other countries.

    Agency Implementation Overview

    Each agency will implement its international access functionality according to its own mission and methods. Some agencies with existing international disciplinary or technical relationships have already established extensive links for exchanging global change data and information across the U.S. national boundaries.

    Go back to Chapter 4. Content System Implementation

    Go to Chapter 6. Agency Implementation

    Return to the Table of Contents