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Updated 30 Aug 1998 Security and Privacy Notice | URL:/about/terms.html

Concepts and Terms

ASF concepts and base principles

Searchers employ a range of techniques to find many kinds of information.
In the ASF, search is directly supported through Internet access to search services at ASF Information Community nodes operated by ASF participants. Searchers using Internet client software typically access these services through Web browsers and Hypertext Transfer Protocol (HTTP) gateways or directly using GILS-aware client software. Although the search itself occurs on the Internet, referenced content is not so constrained and may include people, artifacts, events, maps, images, organizations, software--anything that can be documented in a Locator Record. It is also understood that participants and other intermediaries may exploit the ASF to support voice telephone information services, kiosks, printed catalogs, etc.
Information providers may support search access to primary information content and also provide referral to sets of information elsewhere.
In the ASF, primary information content is called a document set. Information that characterizes document sets is represented in ASF Summary Locator Records. An ASF Information Community consists of ASF Nodes and is delineated by the sharing of ASF Summary Locator Records among ASF participants.
Searches for information involve query/response interactions between searchers and information providers.
In the ASF, query/response interactions are standardized using the GILS Profile. This standard search interface applies to all document sets, including sets of Locator Records.
Each information provider may characterize its own and other document sets and may be subject to characterization by others.
ASF Summary Locator Records can be created through a machine-aided process that includes automated word indexing for some types of documents (e.g., HTML, ASCII text, and other types with proprietary add-on filters). ASF Summary Locator Records may also be created for document sets held at sources not actively participating in the ASF. Locator records within the ASF are always individually editable by people and searchable via a GILS-compliant server.
Each information provider focuses on the information needs of particular clientele and this focus influences the selection of document sets, referrals, and aspects of the search support provided.
In the ASF, each participant may support distributed or centralized search of document sets through the immediate ASF Node as well as throughout an ASF Information Community. Searchers may begin at any server and exploit other servers through ASF Summary Locator Records. Each ASF Node provides at least a GILS-compliant search service but may also offer additional search capabilities, such as advanced geospatial search or multi-lingual support.
Each information provider may characterize document sets in different ways to diverse clientele.
In the ASF, a document set is part of an ASF Information Community as long as the ASF participant provides an ASF Summary Locator Record for the document set. Each ASF Information Community has a Fallback Node with ASF Summary Locator Records that characterize each document set in the ASF Information Community. A document set may be referenced in multiple ASF information communities, and may be represented by different ASF Summary Locator Records in each.
Each information provider supports search of contents by characteristics, which may be unstructured (e.g., "full-text", "pattern-matching"), or structured (e.g., Title, Author, Subject).
Each ASF Node supports GILS-compliant search of Locator Record sets as well as document sets. Structured searches in the GILS Profile are defined for Boolean operations on about 100 common bibliographic and metadata elements and for temporal and spatial constraints. Unstructured search is supported only through full-text search at this time.
Information providers employ a complex range of server platforms, services, and search engines.
In the ASF, the design platform is a Unix environment with the Apache HTTP server. However, essential software components are freely distributed in source code to support porting to additional platforms. Also, the ASF uses open systems design principles where feasible to allow for maximum interoperability and component substitution. For example: the network interface supports OSI as well as TCP/IP transports; the network search interface is ISO 23950; the search engine is accessed through a generic Application Programming Interface, the ASF characterization of document sets is adapted from the IETF FIND protocol; and the network exchange of Locator Records is encoded in Extensible Markup Language (XML).
Information providers must be able to control access and support authentication.
In the ASF, access to documents and Locator Records is controllable through standard network and ISO 23950 mechanisms. A mechanism is also provided for searchers to authenticate the content served.
Reliability of Internet information access is a major concern.
In the ASF, the persistence of referenced information sources is somewhat improved through the use of Uniform Resource Names (URNs).

Term hierarchies in ASF Content, Participation, and Freeware

Alphabetic list of ASF Terms

Advanced Search Facility (ASF):
The ASF has three distinct aspects: content, participation, and software. ASF content consists of information in the form of Locator Records and documents, with special cases for ASF Participant Locator Records and ASF Summary Locator Records. ASF participation is organized into ASF Information Communities and there are particular operational responsibilities prescribed for ASF participants. ASF software is implemented at ASF Nodes, each of which includes a suite of software components to achieve the various requirements of the ASF.
ASF Node:
A single host machine, which runs the ASF software, is an ASF Node. ASF Nodes may participate in any number of ASF Information Communities.
Document:
An ASF document is any information that can be indexed by an ASF Indexer Service, including Locator Records as well as textual matter. (The ASF Indexer Service does not handle images, numeric tables, maps, or other abstract information sources at this time.)
Document Collection:
The set of document sets accessible at an ASF Node.
Document Set:
An ASF document set is made accessible through an ASF Search Service. ASF does not prescribe the rationale for grouping documents into sets, although common criteria include subject, format, ownership, etc. In addition to being directly searchable through the Search Service of an ASF Information Community node, a document set is referenced in an ASF Information Community through an ASF Summary Locator Record. An example of a document set is the set of HTML pages at the Internet location "http://www.usgs.gov/".
Gatherer Service:
An ASF Gatherer Service is a component of an ASF Search Subsystem. It compiles a list of documents to be indexed by extracting documents from other servers (one such technique is known as "Web crawling"). The compilation can be constrained by location, data type, and other parameters.
Indexer Service:
An ASF Indexer Service is a component of an ASF Search Subsystem. It provides for parsing documents and creating index files that allow fast search and retrieval on document sets. The ASF Indexer Service also has the capability to generate a locator record for each indexed document.
Information Centroid:
A summary of the information content contained in a document set. This might be as simple as a list of the indexed words in a document set.
Information Community:
An ASF Information Community is an organization of ASF participants. The sharing of ASF Participant Locator Records and ASF Summary Locator Records delineates its content. In software, an ASF Information Community is implemented at ASF Nodes. The full set of participants and summarized document sets within an ASF Information Community are described in a compilation of Locator Records at the ASF Information Community Fallback Node. An example of an ASF Information Community is the Clearinghouse of the U.S. National Spatial Data Infrastructure.
Information Community Fallback Node:
An ASF Information Community Fallback Node provides Search Service access to the full set of ASF Participant Locator Records and ASF Summary Locator Records within an ASF Information Community. For example, a likely host for an ASF Information Community fallback Server for the "U.S. Government Cabinet-level Agencies" information community would be the Executive Office of the President.
Information Community Node:
An ASF Information Community node is a software component of an ASF Information Community as operated by an ASF participant. It includes a Web browser user interface, an ASF Search Subsystem, and an ASF Web-Z39.50 gateway with embedded GILS-aware client. ASF provides freely distributable software for all node components, with enhanced capabilities possibly available on a component basis.
Information Community Node Administrator:
A person performing administrative functions in support of an ASF Information Community Node.
Information Provider:
In the ASF, an information provider is a person or organization providing access to information as owner or intermediary, whether publicly or restricted. Every ASF participant is an information provider. However, because Locator Records can reference outside information sources, not every information provider is an ASF participant. For example, the U.S. Geological Survey would be a participant in the "U.S. Government Earth Science" information community. Outside Earth Science sources (e.g., commercial, educational, foreign governments) could be summarized as information providers but would not be participants in this particular community.
Intermediary:
An intermediary is any information provider referencing content owned by another. ASF does not distinguish between intermediaries and other information providers, except that the provider role is evident by information in Locator Records. For example, the U.S. Government Printing Office acts as an intermediary for most U.S. Geological Survey publications.
Locator Record:
A Locator Record describes an information resource, the information available in the resource, and how to obtain the information. ASF introduces ASF Participant Locator Records and ASF Summary Locator Records for document sets. Except for how they are constructed and exchanged with an ASF Information Community, these and all other Locator Records are handled as any other document sets in the ASF. While Locator Records may originate in a range of formats, all are searchable and presentable through the model described in the GILS Profile.
Management Service:
The ASF Management service consists of a variety of software tools to simplify tasks performed by ASF Information Community node administrators. Among the functions addressed by these tools are management of document sets, URNs, and thesauri, and configuring information communities and Z39.50 subsystem components.
Participant:
An ASF participant is an information provider operating at least one ASF Information Community node. An ASF participant must be described in an ASF Participant Locator Record on the ASF Information Community Fallback Node.
Participant Locator Record:
An ASF Participant Locator Record describes an ASF participant in the context of an ASF Information Community. The initial building of an ASF Participant Locator Record is accomplished when the participant first joins the ASF Information Community. The content of an ASF Participant Locator Record is similar to a "GPO pathway record".
Resource:
Any information described in a Locator Record.
Search API (Applications Programming Interface):
The ASF search API is a software layer within an ASF Search Service. It provides communication to an ASF Z39.50 Subsystem, but is generalized to support other query mechanisms such as LDAP and SQL as well.
Search Engine:
This term is ambiguous in this document and in the industry itself. In its narrow usage, a search engine is software that responds to search requests, typically by indexing some set of information. A GILS-compliant search engine in this sense is embedded within an ASF Search Service. A broader usage of the term "search engine" includes the means by which information content supported by the search engine is acquired.
Search Service:
An ASF Search Service is a component of an ASF Search Subsystem. It provides search access to at least one set of Locator Records, and may offer search access to other sets of Locator Records or document sets. The ASF Search Service includes the ASF search API.
Search Subsystem:
An ASF Search Subsystem is a component of an ASF Node. The ASF Search Subsystem includes an ASF Gatherer Service, an ASF Indexer Service, and an ASF Search Service.
Summary Locator Record:
An ASF Summary Locator Record describes a document set made available by an ASF participant on an ASF Node. The content of an ASF Summary Locator Record is similar to other Locator Records except that the Subject Index element of the record references a summary object such as a centroid.
Uniform Resource Name (URN):
A persistent name applied to an online resource.
URN Resolver:
A URN resolver is a software utility function used throughout the ASF. The function can be achieved through a variety of software and administrative mechanisms.
Web Browser User Interface:
An ASF Web browser user interface is a component of an ASF Node. It communicates with the Web-Z39.50 gateway on the same ASF Node.
Web-Z39.50 Gateway:
An ASF Web-Z39.50 gateway is a component of an ASF Web browser interface and includes an embedded GILS-aware client. An ASF Web-Z39.50 gateway communicates with an ASF Search Subsystem.
Z39.50 Subsystem:
An ASF Z39.50 Subsystem is a component of an ASF Search Service. It includes the core ANSI Z39.50 (ISO 23950) capabilities required, including GILS-compliance.