Digital Archive Directions (DADs) Workshop

(A part of the ISO Archiving Workshop Series)


Position Paper

Digital Archive Directions (DADs) Workshop

DATE: June 22-26, 1998

HOST: The National Archives and Records Administration
Archives II
8601 Adelphi Road
College Park, MD 20740-6001



1. Identification of Proposed Topic [Required]


Catalog Interoperability Procol (CIP)and the Interoperable Catalog (ICS): Standards for Access

1.2 Contributor(s)

George Percival / Raytheon
Louis Reich / CSC
Yonsook Enloe / NASA

1.3 Description of Proposed Project

Background and Introduction

The Committee on Earth Observation Satellites (CEOS) is an organization which aims to achieve international coordination in the planning of satellite missions for Earth observation and to maximize the utilization of data from these missions world wide.

CEOS promotes the interoperability of its member agency catalogues through the definition and development of interoperability concepts. By enhancing the standardization of EO data and information management services, CEOS enables the services to be more accessible and usable to data providers and data users worldwide. Catalogue Interoperability also extends beyond just the members of CEOS in promoting data access within a wider community of EO data providers and eventually to non EO data providers.

The CEOS Protocol Task Team is comprised of the following international agencies:

  • British National Space Center (BNSC)
  • Canadian Center for Remote Sensing (CCRS)
  • Center for Earth Observation (CEO)
  • Deutsche Forschungsanstalt fur Luft-und Raumfahrt (DLR)
  • European Space Agency (ESA)
  • National Aeronautics and Space Administration (NASA)
  • National Space and Development Agency of Japan (NASDA)

The Protocol Task Team (PTT) is the body that produces, ratifies, and publishes formal Interoperable Catalog System (ICS) user requirements, the Catalog Interoperability Protocol (CIP) specification, ICS system design document, and other associated documents. Based on the ICS user requirements as defined by the PTT, Z39.50 1995 Version 3 was selected as the base protocol for CIP. CIP is a profile of Z39.50, i.e. it uses a well-defined subset of the "out of the box" functionality defined by Z39.50. CIP has defined attributes and tag sets, and uses Explain and Extended Services, and several externally defined messages for search control, ordering, and authentication. Other Z39.50 profiles from which CIP derived some of its features include GILS, GEO, and the Digital Collections Profile.

The CIP is used to integrate into a single environment (as perceived by the user) federations of different Earth Observation catalogue services maintained by different organizations and also provides a standard framework for the design of Earth Observation user information systems.

The main objectives of CIP are to provide transparent distributed search, retrieval, browse, order and other services against Earth Observation catalogues, provide such access in a catalogue independent way, enable clients to dynamically learn about services and features, and allow creation of and access to collections of data organized thematically, independent of the physical location of the data.

In this way, a user of EO data can discover a collection of data with a common theme that is of interest, apply searches against collections to find the data of the user's choice and apply a retrieval or order of that refined data. Using the CIP, this discovery, searching, and retrieval can occur transparently and independently of the physical structures or locations of the catalogues containing that data.

Overview of CIP Architecture

Catalogue Interoperability Protocol (CIP) standardizes the services needed for interaction between users and catalogues. The Interoperable Catalogue System (ICS) is a reference design which uses CIP as the common protocol between data providers and users. To support transparent access to multiple catalogues, a three tier structure was used to design the CIP space. Clients exchange messages with a middleware layer which in turn interacts with multiple catalogue servers. The middleware provides the routing and translation services to allow client requests to be presented at the multiple heterogeneous catalogues. The middleware is of two types of elements: Retrieval Managers and Translators. Retrieval Managers provide an access point for clients and route the requests to the various servers. Translators, bound with the clients and servers, translate CIP to and from the native protocol of the client or server. Future client and server developments may use CIP directly and hence not require translators.

This approach supports a diversity of clients, Retrieval Managers, translators, and servers. Depending on the design of an existing catalogue system, services may be provided by different servers and translators. Because the routing service provided by a Retrieval Manager is independent of the type of service, separate translators may be provided for inventory, browse, ordering, and user profiles. This architecture is also applicable for small data providers, such as university reserach groups, who are unable to provide a Retrieval Manager at their site but still wish to join the CIP domain. Their local catalogue inventory can be made available to the CIP community by the inclusion within another agency's Retrieval Manager.

CIP Features

CEOS has established the following CIP and ICS standards:

  • Search standardization - how searches can be invoked and executed both by end user clients and Retrieval
  • Managers; the search language and its syntactical rules. Collection searches, product searches, guide searches, and browse requests can be serviced by the ICS and CIP systems.
  • Retrieval Standardization - the procedure for retrieval of query results and other objects which need to be presented to the client; an exact description of what is the retrieval content, its format and meaning
  • Attribute standardization - the list of fields or attributes which can be searched and the definition of their semantic meaning. The CIP attributes were taken from the International Directory Network (IDN) Directory Interchange Format (DIF) attributes, Federal Geographic Data Committee (FGDC) attributes, EOSDIS Core System (ECS) attributes, and attributes from various international systems. Dynamic Client Configuration Standardization - a mechanism which is used for dynamic client configuratoin , ie. to make a client understand which functionality can be invoked at the server side, which attributes are understood, and what are their meanings.
  • Order Procedures Standardization - a common way of defining product lists and associated order, packaging and online/offline delivery options; communication of price and accounting information; order and delivery addresses.
  • Security - a reliable and secure mechnism for user authentication and authorization

CIP Collections Data Model

In an interoperable catalog environment it is important that data providers organize the metadata which describes their data holdings to enable users to locate and identify data of interest quickly and easily. This may be achieved by establishing archive-oriented and theme-oriented structures that can be described in a hierarchical manner to facilitate efficient searching. The grouping of data holdings within the ICS data model is termed a collection. A collection may contain descriptions of data products, guide docuements, or other collections. In addition to the value of collections for presentation of data organization to users, collections provide the mechanism for routing distributed searches.

The collection structure has the benefit that catalogue information is presented to users according to "thematic" criteria or organised by clear topics.

CIP Prototypes and Implementations

The following is a list of CIP prototypes and implementations : (provide links to individual pages that describe these efforts - currently will have dummy pages linked in)

  • CIP-A Demonstrator Prototype
  • CEO Enabling Services
  • NASA CIP/ECS Translator
  • ESA CIP Prototype

Implementations of CIP components are expected to be available as freeware starting in summer 1998.

1.4 Justification

CIP and ICS were intended to provide a Common, minimal access mechanisms for all archives of data from Earth Observing Satellites.

1.5 Definitions of Concepts and Special Terms


1.6 Expected Relationship with OAIS Reference Model

Standards for Access
Adaptable Consumer Clients
Standards for Data Management



2. Scope of Proposed Standard [Desired]

2.1 Recommended Scope of Standard

2.2 Existing Practice in Area of Proposed Standard

2.3 Expected Stability of Proposed Standard with Respect to Current and Potential Technological Advances

Wider Views

Overview of the DADs Workshop
Overview of US Effort
Overview of International Effort


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Author: The Author (The Author@The Org) +1.The Phone
Curator: John Garrett ( +1.301.286.3575
Responsible Official: Code 633.2 / Don Sawyer ( +1.301.286.2748
Last Revised: (June 17, 1998, John Garrett)