rfc2258.txt
来自「著名的RFC文档,其中有一些文档是已经翻译成中文的的.」· 文本 代码 · 共 844 行 · 第 1/3 页
TXT
844 行
Network Working Group J. OrdilleRequest for Comments: 2258 Bell Labs, Lucent TechnologiesCategory: Informational January 1998 Internet Nomenclator ProjectStatus of this Memo This memo provides information for the Internet community. It does not specify an Internet standard of any kind. Distribution of this memo is unlimited.Copyright Notice Copyright (C) The Internet Society (1998). All Rights Reserved.Abstract The goal of the Internet Nomenclator Project is to integrate the hundreds of publicly available CCSO servers from around the world. Each CCSO server has a database schema that is tailored to the needs of the organization that owns it. The project is integrating the different database schema into one query service. The Internet Nomenclator Project will provide fast cross-server searches for locating people on the Internet. It augments existing CCSO services by supplying schema integration, more extensive indexing, and two kinds of caching -- all this in a system that scales as the number of CCSO servers grows. One of the best things about the system is that administrators can incorporate their CCSO servers into Nomenclator without changing the servers. All Nomenclator needs is basic information about the server. This document provides an overview of the Nomenclator system, describes how to register a CCSO server in the Internet Nomenclator Project, and how to use the Nomenclator search engine to find people on the Internet.Ordille Informational [Page 1] RFC 2258 Internet Nomenclator Project January 19981. Introduction Hundreds of organizations provide directory information through the CCSO name service protocol [3]. Although the organizations provide a wealth of information about people, finding any one person can be difficult because each organization's server is independent. The different servers have different database schemas (attribute names and data formats). The 300+ CCSO servers have more than 900 different attributes to describe information about people. Very few common attributes exist. Only name and email occur in more than 90% of the servers [4]. No special support exists for cross-server searches, so searching can be slow and expensive. The goal of the Internet Nomenclator Project is to provide fast, integrated access to the information in the CCSO servers. The project is the first large-scale use of the Nomenclator system. Nomenclator is a more general system than a white pages directory service. It is a scalable, extensible information system for the Internet. Nomenclator answers descriptive (i.e. relational) queries. Users can locate information about people, organizations, hosts, services, publications, and other objects by describing their attributes. Nomenclator achieves fast descriptive query processing through an active catalog, and extensive meta-data and data caching. The active catalog constrains the search space for a query by returning a list of data repositories where the answer to the query is likely to be found. Meta-data and data caching keep frequently used query processing resources close to the user, thus reducing communication and processing costs. Through the Internet Nomenclator Project, users can query any CCSO server, regardless of its attribute names or data formats, by specifying the query to Nomenclator (see Figure 1). Nomenclator provides a world view of the data in the different servers. Users express their queries in this world view. Nomenclator returns the answer immediately if it has been cached by a previous query. If not, Nomenclator uses its active catalog to constrain the query to the subset of relevant CCSO servers. The speed of the query is increased, because only relevant servers are contacted. Nomenclator translates the global query into local queries for each relevant CCSO server. It then translates the responses into the format of the world view.Ordille Informational [Page 2] RFC 2258 Internet Nomenclator Project January 1998 -------------------------------------------------------------------- +-------------+ +-------------+ | | | | World View | | Local View | | Query | | Query | Relevant | ----------->| |------------>| | | Nomenclator | | CCSO | | | | | <-----------| |<------------| Server | World View | | Local View | | Response | | Response | | +-------------+ +-------------+ Figure 1: A Nomenclator Query Nomenclator translates queries to and from the language of the relevant CCSO servers. -------------------------------------------------------------------- The Internet Nomenclator Project makes it easier for users to find a particular CCSO server, but it does not send all queries to that server. When Nomenclator constrains the search for a query answer, it screens out irrelevant queries from ever reaching the server. When Nomenclator finds an answer in its cache, it screens out redundant queries from reaching the server. The server becomes easier to find and use without experiencing the high loads caused by exhaustive and redundant searches. The Internet Nomenclator Project creates the foundation for a much broader heterogeneous directory service for the Internet. The current version of Nomenclator provides integrated access to CCSO and relational database services. The Nomenclator System Architecture supports fast, integrated searches of any collection of heterogeneous directories. The Internet Nomenclator Project can be enhanced to support additional name services, or provide intergated query services for other application domains. The project is starting with CCSO services, because the CCSO services are widely available and successful. Section 2 describes the Nomenclator system in more detail. Section 3 explains how to register a CCSO server as part of the project. Section 4 briefly describes how to use Nomenclator. Section 5 provides a summary.Ordille Informational [Page 3] RFC 2258 Internet Nomenclator Project January 19982. Nomenclator System Nomenclator is a scalable, extensible information system for the Internet. It supports descriptive (i.e. relational) queries. Users locate information about people, organizations, hosts, services, publications, and other objects by describing their attributes. Nomenclator achieves fast descriptive query processing through an active catalog, and extensive meta-data and data caching. The active catalog constrains the search space for a query by returning a list of data repositories where the answer to the query is likely to be found. Components of the catalog are distributed indices that isolate queries to parts of the network, and smart algorithms for limiting the search space by using semantic, syntactic, or structural constraints. Meta-data caching improves performance by keeping frequently used characterizations of the search space close to the user, thus reducing active catalog communication and processing costs. When searching for query responses, these techniques improve query performance by contacting only the data repositories likely to have actual responses, resulting in acceptable search times. Administrators make their data available in Nomenclator by supplying information about the location, format, contents, and protocols of their data repositories. Experience with Nomenclator shows that gathering a small amount of information from data owners can have a substantial positive impact on the ability of users to retrieve information. For example, each CCSO administrator provides a mapping from the local view of data (i.e. the local schema) at the CCSO server to Nomenclator's world view. The administrator also supplies possible values for any attributes with small domains at the data repository (such as the "city" or "state_or_province" attributes). With this information, Nomenclator can isolate queries to a small percentage of the CCSO data repositories, and provide an integrated view of their data. Nomenclator provides tools that minimize the effort that administrators expend in characterizing their data repositories. Nomenclator does not require administrators to change the format of their data or the access protocol for their database.2.1 Components of a Nomenclator System A Nomenclator system is comprised of a distributed catalog service and a query resolver (see Figure 2). The distributed catalog service gathers meta-data about data repositories and makes it available to the query resolver. Meta-data includes constraints on attributeOrdille Informational [Page 4] RFC 2258 Internet Nomenclator Project January 1998 values at a data repository, known patterns of data distribution across several data repositories, search and navigation techniques, schema and protocol translation techniques, and the differing schema at data repositories. -------------------------------------------------------------------- +-------------+ +-------------+ | | | | World View | | Meta Data | | Query | | Request | Distributed | ----------->| Query | ----------->| | | Resolver | | Catalog | | | | | <-----------| (caches) | <-----------| Service | World View | | Meta Data | | Response | | Response | | +-------------+ +-------------+ Figure 2: Components of a Nomenclator System -------------------------------------------------------------------- Query resolvers at the user sites retrieve, use, cache, and re-use this meta-data in answering user queries. The catalog is "active" in two ways. First, some meta-data moves from the distributed catalog service to each query resolver during query processing. Second, the query resolver uses the initial meta-data, in particular the search and navigation techniques, to generate additional meta-data that guides query processing. Typically, one resolver process serves a few hundred users in an organization, so users can benefit from larger resolver caches. Query resolvers cache techniques for constraining the search space and the results of previously constrained searches (meta-data), and past query answers (data) to speed future query processing. Meta- data and data caching tailor the query resolver to the specific needs of the users at the query site. They also increase the scale of a Nomenclator system by reducing the load from repeated searches or queries on the distributed catalog service, data repositories, and communications network.Ordille Informational [Page 5]⌨️ 快捷键说明
复制代码Ctrl + C
搜索代码Ctrl + F
全屏模式F11
增大字号Ctrl + =
减小字号Ctrl + -
显示快捷键?