RFC 2259 (rfc2259) - Page 2 of 30
Simple Nomenclator Query Protocol (SNQP)
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RFC 2259 SNQP January 1998 differ in protocol or data format, it is responsibility of the SNQP server to translate protocols and data formats to provide one, integrated answer to the user's query. SNQP servers share the protocol needs of centralized data repositories that answer queries with locally stored data. SNQP servers also require specialized protocol features due to their distributed search characteristics. In highly distributed environments, it is unreasonable to expect all data repositories that need to be searched to be available when queries are posed. SNQP servers require facilities for returning partial results in the presence of communications errors with data repositories. The partial results must indicate how to resubmit the query only to those data repositories that are unavailable. In addition, users may pose queries without realizing the cost of the search for query responses. SNQP provides facilities for informing users of query costs and advising them on limiting that cost. Costs and advice are returned before queries are executed. Finally, SNQP servers may cache data and meta-data to speed query responses. Servers can inform users of the t-bound for their query response. A t-bound is the time after which changes may have occurred to the data that are not reflected in the query response [6,2]. A t-bound is the time of the oldest cache entry used to calculate the response. Users can request that query responses are more current then a particular t-bound. Making such a request flushes older items from the cache. SNQP provides support for graphical user interfaces. It also supports different types of comparison operators, so SNQP servers can query a variety of back-end data repositories, e.g. relational databases, CCSO servers [3], and servers providing relational views of X.500 [10]. SNQP is a connection-oriented protocol. A client initiates a query session with an SNQP server by making a TCP connection to a well- known port. The client then executes a series of SNQP commands. These commands are listed briefly in Table 1. Section 2 provides some typical scenarios for using these commands, and Section 3 describes the commands fully. The server replies to each command using the theory of reply codes described for the Simple Mail Transfer Protocol (SMTP) [9]. The theory of reply codes and the defined reply codes are described in Section 4. Elliott & Ordille Informational
