path: root/doc/rfc/rfc2259.txt

Network Working Group                                         J. Elliott
Request for Comments: 2259                      Epic Systems Corporation
Category: Informational                                       J. Ordille
                                          Bell Labs, Lucent Technologies
                                                            January 1998


                Simple Nomenclator Query Protocol (SNQP)


Status 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 Simple Nomenclator Query Protocol (SNQP) allows a client to
   communicate with a descriptive name service or other relational-style
   query service.  The protocol is useful to services that search many
   data repositories for query responses.  Clients can pose queries on
   relations, list descriptions of relations, and obtain advice on
   reducing the search time and cost of their queries.  Clients are
   informed of the age of information in caches, and may request more
   recent information.  SNQP provides support for graphical user
   interfaces.  It also supports different types of comparison
   operators, so services can use SNQP with a variety of back-end
   servers, e.g. relational database servers, CCSO servers, and servers
   providing relational views of X.500.

   SNQP is an ASCII protocol in the request-reply style of SMTP.  It was
   specifically designed for use with the Nomenclator name and
   information service, and has been useful elsewhere.

1. Introduction

   The Simple Nomenclator Query Protocol (SNQP) is a protocol for
   querying servers that search collections of data repositories.  Users
   retrieve information from an SNQP server by describing attributes of
   the information.  SNQP servers contact one or many data repositories
   to retrieve the response to a user query.  If the data repositories





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   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.






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   ---------------------------------------------------------------------
      Command       Description
   ---------------------------------------------------------------------
      advice        Provide advice on query costs without executing
                    query.
      attributes    List the attributes for a relation.
      compare       Set type of comparison operation.
      help          Explain the SNQP commands.
      imagui        Format replies for a graphical user interface.
      next          Stop processing current query, continue with next
                    query in block.
      noadvice      Provide responses to queries.  Do not advise
                    on costs.
      noimagui      Format replies for people.
      query         Submit a block of one or more SQL query statements.
      relations     List the relations available through the SNQP
                    server.
      stop          End processing of current query, and cancel any
                    queries remaining in block.
      quit          Terminate the query session.


                         Table 1: SNQP Commands

   ---------------------------------------------------------------------

   SNQP queries are posed in SQL, a standard relational database query
   language [4,12].  Information that is obtained through SNQP servers
   is organized by type into database relations.  SQL queries may often
   have more functionality then a server supports or an application
   demands.  Moreover, advice on query costs, some types of comparison
   operations or t-bounds may not be supported by a particular server.
   SNQP defines a minimal subset of functionality for a working SNQP
   protocol.  Functionality beyond this subset is optional.  Servers
   that do not support optional functionality must return replies that
   indicate this to the user.  The required and optional features of
   SNQP are summarized in Section 5.

   SNQP was specifically designed for use with the Nomenclator name and
   information service [8,7,5].  Nomenclator produces query responses by
   integrating information from data repositories with different
   protocols and data formats.  It constrains the searches for query
   responses through a variety of distributed indexing techniques.  SNQP
   has also been found useful elsewhere, even as a query language for a
   single data repository.

   SNQP is defined for US-ASCII only, and use with other character sets
   will require further work.



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   Section 6 concludes this document with a description of security
   considerations.

2. Scenarios

   This section illustrates the basic SNQP commands by presenting
   several client scenarios.  The scenarios include a new user, a user
   who prefers CCSO style comparisons and more current responses, a
   graphical user interface program, a user with a change of mind, and a
   user worried about costs.  Although SNQP will work for a human client
   on a bare connection (like one provided by telnet), it also works for
   client programs.  Several of these programs have been written and
   provide enhanced interfaces.

2.1 New User

   A new SNQP user will first make a tcp connection to an SNQP server.
   For purposes of illustration, we will assume that the user makes the
   connection with the Unix telnet command, and that the server is
   located at nomen.research.bell-labs.com on port 4224. The user enters
   a relation command to discover what relations are available, and an
   attributes command to discover the attributes for a particular
   relation.  The user eventually asks for people with a given name of
   "J*" and a surname of "Ordille" who work for "Lucent Tech*". The
   response is current through June 11, 1996 at 11 p.m. EDT.  Figure 1a
   and Figure 1b provide this scenario.

























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   ---------------------------------------------------------------------

      > telnet nomen.research.bell-labs.com 4224
      Trying 135.104.70.9...
      Connected to nomen.research.bell-labs.com.
      Escape character is '^]'.
      220 nomen.research.bell-labs.com Nomenclator Query Service ready

      relations
      211-There is 1 relation defined:
      211 People

      attributes People
      212-There are 20 attributes in relation "People":
      212-Given_Name
      212-Middle_Name
      212-Surname
      212-Name_Suffix
      212-Title
      212-Organization
      212-Division
      212-Department
      212-Building
      212-Street
      212-City
      212-State_or_Province
      212-Postal_Code
      212-Country
      212-Phone
      212-Fax
      212-Email
      212-MHSmail
      212-Last_Modified
      212 Source


                       Figure 1a: New User Queries Server

   ---------------------------------------------------------------------












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   ---------------------------------------------------------------------

      query
      350 Send the query text, end with .

      select * from People where
             given_name = "J*" and surname = "Ordille" and
             organization = "Lucent Tech*";
      .
      351 Partial response follows, ended with .

      Given_Name: Joann
      Middle_Name: J.
      Surname: Ordille
      Title: MTS
      Organization: Lucent Technologies
      Division: Bell Laboratories
      Department: Computing Sciences Research Center
      Building: 2C-301
      Street: 700 Mountain Avenue
      City: Murray Hill
      State_or_Province: New Jersey
      Postal_Code: 07974
      Country: United States
      Phone: +1 908 582 7114
      Email: joann@bell-labs.com
      Source: nomen://bell-labs.com:17036/email=joann@bell-labs.com

      .
      250 All queries processed.  Current through 11-Jun-1996 23:00 EDT.

      quit
      221 nomen.research.bell-labs.com closing transmission channel

      Connection closed by foreign host.


                      Figure 1b: New User Queries Server
                                 (continued)

   ---------------------------------------------------------------------

2.2 User with CCSO and Currentness Preferences

   A user who is accustomed to CCSO name servers prefers CCSO word-based
   matching within attribute strings.  Each word in the query string for
   an attribute must appear in some order in the response string.  The
   wildcard "*" matches any substring within a word.  The default



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   matching, illustrated in Figure 1b, is exact matching of a query
   string.  The query string may include "*" wildcards which match any
   substring within the response string.  Both types of matching are
   case insensitive.

   In Figure 2, the CCSO-style user connects to the SNQP server, enables
   csso matching, and requests some information about Ordille who works
   in research at a lab division of some company.  The request asks for
   information that is more current than June 11, 1996 at 11 p.m. if it
   is available.

   ---------------------------------------------------------------------

      compare ccso
      213 Performing ccso equality comparisons

      query 11-Jun-1996 23:00
      350 Send the query text, end with .

      select given_name, surname, organization, division, department,
             email from People
             where surname = "Ordille" and department = "research"
             and division = "lab*";
      .

      351 Partial response follows, ended with .

      Given_Name: Joann
      Surname: Ordille
      Organization: Lucent Technologies
      Division: Bell Laboratories
      Department: Computing Sciences Research Center
      Email: joann@bell-labs.com

      .
      250 All queries processed.  Current through 12-Jun-1996 22:35 EDT.

             Figure 2: User with CCSO Preferences Queries Server

   ---------------------------------------------------------------------

2.3 Graphical User Interface Program

   A user designs a Windows program as a front end to the SNQP server.
   In Figure 3, the program requests replies formatted for a graphical
   user interface program.  The program submits two SQL queries, and





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   receives detailed responses that indicate the type and position of
   errors.  The error messages are discussed in more detail in Section
   3.

   ---------------------------------------------------------------------

      imagui
      214 GUI responses enabled

      query
      350 Send the query text, end with .

      select * from Peple where name = "Elliott";
      .
      735 00000001a000015 e Unknown relation, "Peple"

      735 00000001a000027 e Attribute "name" not found in any relation used.


      250 All queries processed.  Current through 12-Jun-1996 22:35 EDT.

      query
      350 Send the query text, end with .

      select * from People wher surname = "Elliott";
      .
      730 00000001a000022 e syntax error

      730 00000001a000027 e syntax error

      730 00000001a000037 e syntax error

      730 00000001a000039 e syntax error


      250 All queries processed

       Figure 3: Graphical User Interface Program Queries Server

   ---------------------------------------------------------------------

2.4 User Changes Mind

   An exuberant user decides to search everywhere for family members,
   then look up a friend who works at Epic Systems, and finally search
   everywhere for an old school friend.  Once the query set starts, the
   user realizes the folly of searching everywhere, stops the first




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   query, executes the second query and then stops executing the query
   block.  This scenario is illustrated in Figure 4.  The t-bound is
   represented by <time> in this scenario due to space restrictions.

   ---------------------------------------------------------------------

      query
      350 Send the query text, end with .

      select * from people where surname = "Smith";
      select given_name, surname, email from people
             where surname = "Elliott"
             and organization = "Epic Systems*";
      select * from people where surname = "Brown";
      .
      next

      352 Starting next query.  Any pending responses discarded.

      351 Partial response follows, ended with .

      Given_Name: Jim
      Surname: Elliott
      Email: jim@apocalypse.com

      .
      352 Beginning next query.  Previous current through <time>.

      stop

      251 All pending queries and responses discarded


          Figure 4: User Changes Mind About Submitted Queries

   ---------------------------------------------------------------------

2.5 User Worries About Costs

   In Figure 5a, the exuberant user decides to apply more caution, and
   asks for advice on searching for a friend named "Susan Brown".  The
   user can not recall the name of the organization where Susan works,
   but remembers that the state name begins with "I".  The advice
   response lists the locations of the data repositories that will be
   contacted. These locations can be supplied to the SNQP server using
   the "source" attribute.  Each location is followed by a blank and a
   descriptive phrase for the data repository. Continuing in Figure 5b,
   the SNQP server also supplies a list of attributes that may constrain



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   the query further.  The user recognizes the name Northeastern, and
   submits the query directly to that location.  The user could also
   have added "organization = "Northeastern*"" to the original query.
   Other advice options are described in Section 3.

   ---------------------------------------------------------------------

      advice
      214 Basic advice enabled.  Query responses disabled.

      query
      350 Send the query text, end with .

      select * from people where surname = "Brown" and
                                 given_name = "Susan" and
                                 state_or_province = "I*";
      .

      354 The query will contact 8 data repositories, ended with .
      ccso://ns.dacc.cc.il.us:105/* Danville Area Community College
      ccso://ns.eiu.bgu.edu:105/* Eastern Illinois University
      ccso://ns.ilstu.edu:105/* Illinois State University
      ccso://ns.imsa.edu:105/* Illinois Math and Science Academy
      ccso://ns.ne.edu:105/* Northeastern Illinois University
      ccso://ns.uiuc.edu:105/* University of Illinois at Urbana-Champaign
      ccso://ns.iup.edu:105/* Indiana University of Pennsylvania
      ccso://ph.indstate.edu:105/* Indiana State University
      .


          Figure 5a: User Asks About Costs Before Executing Query

   ---------------------------------------------------------------------


















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   ---------------------------------------------------------------------

      355 There are 8 attributes that may constrain the query, ended with .
      Organization
      Department
      Email
      State_or_Province
      Country
      Postal_Code
      Phone
      Source
      .

      250 All queries processed.  Current through 12-Jun-1996 22:35 EDT.

      noadvice
      214 Query responses returned.  Advice disabled.

      query
      350 Send the query text, end with .

      select * from people where surname = "Brown" and
                              given_name = "Susan" and
                                 state_or_province = "I*" and
                                 source ="ccso://ns.neiu.bgu.edu:105/*";
      .

      351 Partial response follows, ended with .

      Given_Name: Susan
      Middle_Name: W.
      Surname: Brown
      Organization: Northeastern Illinois University
      Email: sw-brown@ne.edu
      Source: ccso://ne.edu:105/alias=SW-Brown

      .
      250 All queries processed.  Current through 12-Jun-1996 22:35 EDT.

          Figure 5b: User Asks About Costs Before Executing Query

   ---------------------------------------------------------------------









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3. Commands

   SNQP commands are case insensitive and terminated with a newline <LF>
   or carriage return <CR>.  In the following descriptions, SNQP
   commands are in upper case and SNQP replies are in mixed case.  Items
   in a command list are separated by blanks.

   Most SNQP replies are short.  They have a rely code (see Section 4),
   followed by a continuation character and reply text.  If the
   continuation character is blank, the reply is complete.  If the
   continuation character is a dash ("-"), the reply continues on the
   next line.  Text within the reply can vary, but the reply code
   remains the same.  A two line reply example is given below:

   ---------------------------------------------------------------------

      nnn-Message1
      nnn Message2

   ---------------------------------------------------------------------

   In some cases commands or replies may be long, so these
   commands/replies use the '.'-terminated block structure that is used
   for message bodies in SMTP. Blocks are comprised of lines of text
   that constitute the command/reply.  Blocks are terminated with a
   period on a line by itself.

   SNQP generally ignores blank lines in both directions, except that
   blanks lines separate tuples within query response blocks.

   Whenever a time is listed in a command or response, it has the
   format:

   ---------------------------------------------------------------------

   DD-MMM-YYYY HH:MM ZZZ

   ---------------------------------------------------------------------

   where DD is the day, MMM are the first three characters of the month,
   YYYY is the year, HH the hours on a 24 hour clock, MM the minutes,
   and ZZZ the commonly used US timezone abbreviations.  If time zone is
   unspecified in a command, the timezone of the SNQP server is assumed.

   SNQP servers support a source attribute in every relation.  In
   queries, the source attribute directs the SNQP server to a particular
   data repository.  In query responses, the source attribute indicates
   the origin of the information in a tuple.  In advice and error



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   messages, the source attribute is provided so the client can contact
   the source in later queries.  The source attribute has two possible
   forms:

   ---------------------------------------------------------------------

   <protocol>://<domain-name>:<port>

   <protocol>://<domain-name>:<port>/<tuple-id>

   ---------------------------------------------------------------------

   <protocol> identifies the protocol used to contact the data
   repository. The data repository can be (was) contacted at <domain-
   name> and <port>.  When present, <tuple-id> identifies a specific
   entry in the data repository.  It is missing when the data repository
   does not have an attribute that uniquely identifies its entries.
   Although the source string is similar to a URL, the protocols listed
   may or may not be supported by World-Wide Web browsers.  An effort
   should be made to keep the protocol identifiers consistent with
   accepted standards, but in the end they are specific to SNQP servers.

   When a connection is established with an SNQP server, the server
   returns the following greeting where <domain-name> is the domain name
   of the server host, e.g.  nomen.research.bell-labs.com,  and
   <service-name> is the name of the service, e.g. Nomenclator:

   ---------------------------------------------------------------------

      220 <domain-name> <snqp-service-name> Query Service ready

   ---------------------------------------------------------------------

   The following sections describe each command in detail.  The commands
   are ordered alphabetically.  Typical reply messages are explained
   with each command.  Exceptional error conditions, for example system
   errors or rejection of connections due to load, may sometimes occur.
   These error replies are documented in Section 4.













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3.1 Advice

   ---------------------------------------------------------------------

      ADVICE
      214 Basic advice enabled. Query responses disabled.
      514 Advice not available

      ADVICE <RELATION> <ATTRIBUTE>
      214 Advice enabled for "<attribute>" in "<relation>"
      553 Unknown relation
      554 Unknown attribute
      514 Advice not available for "<attribute>"

   ---------------------------------------------------------------------

   In all cases, advice disables query searches. When queries are
   submitted, advice is returned about the cost of the query or ways of
   constraining the query further.  There are two forms of the advice
   command.

   The first form of command does not include an attribute name.  When
   an SQL query is processed, the SNQP server returns a list of data
   repositories that it will contact.  It also returns a list of
   attributes that may constrain the query further.  The specific values
   of the attributes will determine whether the query is constrained
   further.  If advice is not available from the server, an error is
   returned.

   The second form of advice includes the name of a relation and the
   name of an attribute in that relation.  SQL queries return a list of
   possible values for the attribute.  The list may be complete, or may
   only include values that are known to constrain the search.  This
   distinction is described further in the query command.  If advice is
   not available on the attribute or the relation or attribute is
   unknown, an error is returned.  When advice is not available on an
   attribute, basic advice and advice on other attributes may be
   available.

   Basic advice and advice for one or more attributes can be enabled
   simultaneously. They are not mutually exclusive.

   The advice command is useful to application programs which present
   lists of alternatives to the user.  A query-form program can enable
   advice for an attribute, submit an empty query, and obtain the list
   of options for the attribute.  The list will indicate whether it is a
   full list of all values for the attribute, or a constraint list of




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   only those values known to constrain queries.  The program can use
   full lists to create a selection menu on its query form.  A program
   can also enable basic advice, submit the query, and then ask the user
   to select the data repositories to search from the resulting list.

3.2 Attributes

   ---------------------------------------------------------------------

      ATTRIBUTES <RELATION> <TIME>
      212-There are <n> attributes in relation "<RELATION>":
      212-<Attribute-name>
      212-<Attribute-name>
      212 Current through <TIME>

      553 Unknown relation.  Current through <TIME>.
      556 T-bounds not supported

   ---------------------------------------------------------------------

   The attributes command lists the attributes defined for the given
   relation.  Since characteristics of relations may be defined outside
   the SNQP server and cached there, the user may ask for an answer that
   is more recent than <TIME>.  The SNQP server will endeavor to provide
   this information.  The first line of the reply notes the number of
   attributes <n>.  Subsequent lines list the attribute names.  The
   information in the response is current through the time returned, but
   may have changed after that time.  Accepting requests to improve a
   t-bound and indicating the t-bound of the result are optional for
   SNQP servers.

   If the relation is unknown, an error is returned.  If <TIME> is
   submitted when t-bounds are not supported, an error is returned.

3.3 Compare

   ---------------------------------------------------------------------

      COMPARE <COMPARISON-TYPE>
      213 Performing <COMPARISON-TYPE> comparisons

      555 Unknown comparison type

   ---------------------------------------------------------------------

   The compare command lists the type of equality comparison performed
   for SQL queries.  The compare command can be followed by a comparison
   type to set the type.  Reply 555 is returned if the comparison type



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   is unknown or unsupported.  "Default" and "CCSO" are defined
   comparison types.  The default equality comparison is exact string
   matching.  The query string may include "*" wildcards which match any
   substring within the response string.  The CCSO equality comparison
   matches words within strings.  Each word in the query string for an
   attribute must appear in some order in the response string.  Words
   are delimited by blank, comma, colon, semi-colon, tab, and newline.
   The wildcard "*" matches any substring within a word.  Both string
   and word comparisons are case insensitive.

3.4 Help

   ---------------------------------------------------------------------

      HELP
      210-The following commands are available:
      210-<comma-separated-command-list>
      210 <comma-separated-command-list>

      HELP <COMMAND>
      210-<explanation of <COMMAND>>
      210 <explanation of <COMMAND>>

      500 Sorry, no help available for "<COMMAND>"

   ---------------------------------------------------------------------

   The help command returns the list of available commands. If some
   commands are not supported, for example advice, they should not be
   listed.  Use of unsupported commands should still return an
   informative error message.  Help can be followed by a command name
   for information on that command.  If no help is available for a
   command or the command does not exist, Reply 500 is returned.

3.5 Imagui

   ---------------------------------------------------------------------

      IMAGUI
      215 GUI responses enabled

   ---------------------------------------------------------------------

   The imagui command informs the server that the client is a graphical
   user interface (GUI).  The client requests more comprehensive,
   program-oriented errors and progress reports. It replies that GUI
   responses are enabled.  See Section 4 for more information on GUI
   responses.



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3.6 Next

   ---------------------------------------------------------------------

      NEXT
      353 Starting next query.  Any pending responses discarded.

      450 No query in progress

   ---------------------------------------------------------------------

   The next command stops processing of the current SQL query.  It
   starts the next SQL query in the block submitted with the last query
   command.  If none remain, the query command is completed.  An error
   is returned if no query is in progress.

3.7 Noadvice

   ---------------------------------------------------------------------

      NOADVICE
      216 Query responses enabled.  Advice disabled.

   ---------------------------------------------------------------------

   The noadvice command disables advice for query commands.  It
   activates query searches, so queries will return responses.  See the
   advice command for more information.

3.8 Noimagui

   ---------------------------------------------------------------------

      NOIMAGUI
      215 GUI responses disabled

   ---------------------------------------------------------------------

   The noimagui command disables detailed messages to a graphical user
   interface program. It replies that GUI responses are disabled.  See
   Section 4 for more information on GUI responses.

3.9 Query

   The query command behaves differently depending on whether responses
   or advice are enabled. We first describe the submission of a query
   and the possible immediate error responses.  We then describe the




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   possible replies to the query command when responses are enabled.  We
   finish by describing the possible replies to the query command when
   advice is enabled.

   ---------------------------------------------------------------------

      QUERY <TIME>
      350 Send query text, end with .

      450 Query already in progress
      552 Query blocks are limited to one SQL query
      556 T-bounds not supported

   ---------------------------------------------------------------------

   The query command submits a block of SQL queries to the SNQP server.
   Each SQL query must be terminated with a semi-colon, and the entire
   block is terminated with a line containing a single period.  Special
   characters in query string constants can be included using the C
   language conventions, e.g. "\n" is the newline character.

   Since a variety of cached information can be used in processing the
   SQL queries, the user may ask for answers that are more recent than
   <TIME>.  The SNQP server will endeavor to provide this information.
   Accepting requests to improve a t-bound is optional for SNQP servers.

   If a query command is already in process, the entire block is
   refused.  If multiple SQL queries are submitted in one block to a
   server that does not support multi-query blocks, an error is
   returned.  If <TIME> is submitted when t-bounds are not supported, an
   error is returned.

   ---------------------------------------------------------------------

      351 Partial response follows ended with .
      352 Beginning next query.  Previous query current through <TIME>.
      250 All queries processed.  Current through <TIME>.

      653 <Communications err> with <location> <location description>
      660 <Error> from <location> <location description>

      700 <SQL query parsing error>
      750 <SQL query semantic error>
      761 <Requirements Error> for <location> <location description>

   ---------------------------------------------------------------------





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   Responses are returned in blocks as they arrive from data
   repositories.  Reply 351 begins a response block.  Response blocks
   are terminated with periods.  Tuples are sent within the block as a
   list of attribute name and value pairs:

   ---------------------------------------------------------------------

   <attribute-name>: <attribute-value>
                   : <attribute-value>

   ---------------------------------------------------------------------

   Only the first line of a multi-line attribute returns the
   <attribute-name>.  Successive tuples are separated with blank lines.
   Attributes with null or blank values are suppressed at the option of
   the SNQP server.

   In between response blocks, error replies can be reported.  Replies
   653, 660 and 761 are examples of such errors.  Reply 653 reports a
   communication error with the data repository identified by the source
   location and described by the associated string. Reply 660 reports an
   error returned by a data repository.  Reply 761 reports a known
   requirement of the data repository that the query failed to satisfy.
   Reply 761 reflects comparison of the query with known characteristics
   of the data repository by the SNQP server.  For example, some data
   repositories refuse queries that do not contain a specific subset of
   attributes in the relation.  Other replies are possible.  It is best
   to check the the type and severity of the reply against the theory of
   reply codes in Section 4.

   When an SQL query in a block is successfully completed, the SNQP
   server sends Reply 352 to indicate that the next query is being
   started.  Reply 352 reports the t-bound of the previous query if it
   is available. Reply 352 is sent even if the previous query terminated
   due to permanent errors.   The one exception is that permanent errors
   generated by the next or stop command supersede Reply 352.

   When all SQL queries are complete, the SNQP server sends Reply 250 to
   indicate that all queries have been processed.  A query block
   containing one query that has no responses will only return Reply
   250.  Reply 250 reports the t-bound of the last SQL query in the
   block if it is available.  Reply 250 is sent even if the last query
   in the block terminated due to permanent errors.   The one exception
   is that permanent errors generated by the stop command supersede
   Reply 352.






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   Note that this command follows the convention that "intermediate"
   reply codes, as defined in Section 4, are used until the SQL query is
   complete.  Final query completion error codes abort the processing of
   the SQL query.  Examples of these errors include parsing errors
   (Reply 700) and semantic errors (Reply 750) in the SQL query.  The
   SNQP server will attempt to continue with the next query if possible.
   The block of queries will be terminated with Reply 250 or 251 (from
   the stop command) to indicate that another query will be accepted.
   Indicating the t-bound of a query response is optional for SNQP
   servers.

   ---------------------------------------------------------------------

      354-The query will contact <n> data repositories, ended with .
      <location> <location-description>

      355-There are <n> attributes that may constrain the query, ended with .
      <attribute-name>

      356-There are <n> possible values for "<attribute>", ended with .
      <attribute-value>

      357-There are <n> constraining values for "<attribute>", ended with .
      357-<attribute-value>
      357 <attribute-value>

      352 Beginning next query.  Previous query current through <TIME>.
      250 All queries processed.  Current through <TIME>.

      700 <SQL query parsing error>
      750 <SQL query semantic error>

   ---------------------------------------------------------------------

   Different kinds of advice are returned in different blocks.  Basic
   advice about the number, n, of data repositories that will be
   searched is returned with Reply 354.  Subsequent lines list location
   and location description for the data repositories that will be
   searched.  The data repository locations can be supplied to the SNQP
   server using the "source" attribute.  Each location is followed by a
   blank and a descriptive phrase for the data repository.

   Basic advice about the attributes that may constrain the query is
   returned with reply code 355.  The first line of the reply includes
   the number, n, of attributes.  Subsequent lines list the names of the
   attributes.  The specific values of the attribute will determine
   whether the query is constrained further.




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   Advice for a particular attribute has two forms.  First, the advice
   may list the n possible values for the attribute in reply 356.  The
   list is complete; no other values for the attribute exist within the
   context of the query.  Second, the advice may list the n values for
   the attribute that are known to constrain the query.  The list is
   incomplete; other values of the attribute may exist within the
   context of the query.

   When advice for an SQL query in a block is successfully completed,
   the SNQP server sends reply 352 to indicate that the next query is
   being started.  Reply 352 reports the t-bound of the advice for the
   previous query if it is available. Reply 352 is sent even if the
   previous query terminated due to permanent errors.   The one
   exception is that permanent errors generated by the next or stop
   command supersede Reply 352.

   When all SQL queries are complete, the SNQP server sends Reply 250 to
   indicate that all queries have been processed.  Reply 250 reports the
   t-bound of the last SQL query in the block if it is available.  Reply
   250 is sent even if the last query in the block terminated due to
   permanent errors.   The one exception is that permanent errors
   generated by the stop command supersede Reply 352.

   Final query completion error codes abort the processing of the SQL
   query.  Examples of these errors include parsing errors and semantic
   errors in the SQL query.  The SNQP server will attempt to continue
   with the next query if possible. The block of queries will be
   terminated with Reply 250 or 251 (from the stop command) to indicate
   that another query will be accepted.  Indicating the t-bound of
   advice is optional for SNQP servers.

3.10 Relations

   ---------------------------------------------------------------------

      RELATIONS <TIME>
      211-There are <n> relations defined:
      211-<Relation-name>
      211-<Relation-name>
      211 Current through <TIME>.

      556 T-bounds not supported

   ---------------------------------------------------------------------

   The relations command lists the currently available relation names.
   Since characteristics of relations can be cached, the user may ask
   for an answer that is more recent than <TIME>.  The SNQP server will



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   endeavor to provide this information.  The first line of the reply
   notes the number of relations <n>.  Subsequent lines list the
   relation names. The information in the response is current through
   the time returned, but may have changed after that time.  Accepting
   requests to improve a t-bound and indicating the t-bound of the
   result are optional for SNQP servers.

   If <TIME> is submitted when t-bounds are not supported, an error is
   returned.

3.11 Stop

   ---------------------------------------------------------------------

      STOP
      251 All pending queries and responses discarded

      450 No query in progress

   ---------------------------------------------------------------------

   The stop command ends processing of the current SQL query, and
   cancels any that may have followed it in the last query command.  An
   error is returned if no queries are in progress.

3.12 Quit

   ---------------------------------------------------------------------

      QUIT
      221 <domain-name> closing transmission channel

   ---------------------------------------------------------------------

   The quit command ends the session.  It closes the TCP connection
   after signing off with the domain name of the SNQP server.

4. Replies

   Most SNQP replies are short.  They have a rely code followed by a
   continuation character and reply text.  If the continuation character
   is blank, the reply is complete.  If the continuation character is a
   dash ("-"), the reply continues on the next line.  Text within the
   reply can vary, but the reply code remains the same.  A two line
   reply example is given below:






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   ---------------------------------------------------------------------

      nnn-Message1
      nnn Message2

   ---------------------------------------------------------------------

   In some cases commands or replies may be long, so these
   commands/replies use the '.'-terminated block structure that is used
   for message bodies in SMTP. Blocks are comprised of lines of text
   that constitute the command/reply.  Blocks are terminated with a
   period on a line by itself.

   The theory of reply codes explained for SMTP in RFC-821 is used here.
   Table 2 defines the reply code structure.  Reply codes are three
   digits, xyz.  The x digit indicates the command status.  The y digit
   indicates the component of the system that generated the reply.  The
   z digit allows for further distinctions within replies from the same
   component.

   ---------------------------------------------------------------------
      Code  Interpretation
   ---------------------------------------------------------------------

      1yz   Positive preliminary reply (not used in SNQP)
      2yz   Positive completion reply
      3yz   Positive intermediate reply
      4yz   Transient negative completion reply
      5yz   Permanent negative completion reply
      6yx   Transient negative intermediate reply
      7yx   Permanent negative intermediate reply

      x0z   Syntax or semantic problem
      x1z   Informational reply
      x2z   Related to transmission channel
      x3z   Formatted (location coded) report for GUI
      x4z   Status message to be displayed by GUI
      x5z   Related to query resolver
      x6z   Related to data repository
      x9z   Component generating the error is unknown or suspect

                     Table 2: Reply Code Structure

   ---------------------------------------------------------------------







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   The GUI-related reply codes are only used if the server has been
   informed that it is communicating with a graphical user interface,
   via the imagui command.   For such codes in the x3z space, digit "z"
   takes on the role of digit "y" in other codes. I.e. 735 are permanent
   negative intermediate replies about the query resolver.

   Table 3a and Table 3b list the defined regular (non-GUI) reply codes.
   Text messages for the reply codes may vary.  The codes are sorted
   numerically.

   ---------------------------------------------------------------------

      210-The following commands are available:
      211-There are <n> relations defined:
      212-There are <n> attributes in relation "<relation>":
      213 Performing <comparison-type> type equality comparisons
      214 Basic advice enabled.  Query responses disabled.
      214 Advice enabled for "<attribute>" in "<relation>"
      215 GUI responses enabled
      215 GUI responses disabled
      216 Query responses enabled.  Advice disabled.

      220 <domain-name> <snqp-service-name> Query Service ready
      221 <domain-name> closing transmission channel

      250 All queries processed
      250 All queries processed.  Current through <time>.
      251 All pending queries and responses discarded

      340 Searching <n> data repositories
      350 Send the query text, end with .
      351 Partial response follows, ended with .
      352 Beginning next query in batch
      352 Beginning next query in batch.  Previous current through <time>.
      353 Starting next query. Any pending responses discarded.
      354 The query will contact <n> data repositories, ended with .
      355 There are <n> attributes that may constrain the query, ended with .
      356 There are <n> possible values for attribute "<attribute>":
      357 There are <n> constraining values for attribute "<attribute>":

      420 Too many connections in progress. Try later.
      421 Error in communicating with <snqp-service-name>
      450 No query in progress
      451 Cancel ignored

                        Table 3a: Reply Codes

   ---------------------------------------------------------------------



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   ---------------------------------------------------------------------

      450 Query already in progress
      490 Internal error: Invalid query reference number
      491 System error: <error number or message>
      492 Internal error: Out of client table space
      499 <snqp-service-name> shutting down
      500 Sorry, no help is available for "<command>"
      501 Unknown command
      502 Too many arguments for this command
      502 Not enough arguments for this command

      514 Advice not available
      514 Advice not available on <attribute>

      552 Query blocks are limited to one SQL query
      553 Unknown relation
      553 Unknown relation.  Current through <TIME>.
      554 Unknown attribute
      555 Unknown comparison type
      556 T-bounds not supported
      557 Will not list more than <n> data repositories
      557 Will not list more than <n> attribute values
      557 Will not list more than <n> responses
      557 Too many data repositories to list
      557 Too many attribute values to list
      557 Too many responses to list
      557 Too many data repositories to search

      651 <Error message from query resolver>
      653 <Communications error> with <location> <location description>
      660 <Error> from <location> <location description>

      700 <SQL parse error message>
      750 <SQL semantic error message>
      751 <Error message from query resolver>
      761 <Requirements error> for <location> <location description>

      790 Internal error: <fatal error from SNQP server>


                        Table 3b: Reply Codes
                                  (Continued)

   ---------------------------------------------------------------------






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   Table 4 lists the defined GUI reply codes.  Text messages for the
   reply codes may vary.  The codes are sorted numerically.  An
   explanation of the codes follows the table.

   ---------------------------------------------------------------------

      331 nnnnnnn! <message>
      331 nnnnnnn.mmmmmm <message>
      331 nnnnnnn-mmmmmm <message>
      730 nnnnnnnammmmmm e <parse error message>
      735 nnnnnnnammmmmm e <semantic error message>
      340 <status>

                        Table 4: GUI Reply Codes

   ---------------------------------------------------------------------

   In Table 4, nnnnnnn is the line number in a query block, and mmmmmm
   is the column in the line.  Both numbers begin counting with 1.  The
   exclamation point response directs the program to list information
   after line n.  The period response directs the program to break line
   n at column m.  The hyphen response directs the program to flag line
   n at column m.  Replies 730 and 735 direct the GUI to indicate the
   parsing or semantic error at line n, column m.  Response 340 provides
   status information that can be displayed immediately in the GUI's
   status line.  A sample status message is one that indicates which
   data repository is being contacted.

5. Protocol Requirements

   SQL queries may often have more functionality then a server supports
   or an application demands.  Moreover, query blocks larger than one
   SQL query, advice on query costs, some types of comparison operations
   or t-bounds need not be supported by a particular server.  SNQP
   defines a minimal subset of functionality for a working SNQP
   protocol.  Functionality beyond this subset is optional.  Servers
   that do not support optional functionality must return replies that
   indicate this to the user.

   Table 5 lists the minimum functionality for an SNQP server.











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   ---------------------------------------------------------------------
      Command       Limitations
   ---------------------------------------------------------------------
      advice        Not supported.
      attributes    List the attributes for a relation.
      compare       List type of comparison operation.  At least
                    one of CCSO and default comparison types must
                    be supported.  Wildcards in SQL query strings
                    can be rejected by the query command with an
                    appropriate semantic error message.
      help          Explain the available SNQP commands.
      imagui        Not supported.
      next          Not supported.
      noadvice      Supported, but has no effect since advice
                    is not supported.
      noimagui      Supported, but has no effect since imagui
                    is not supported.
      query         Submit a block containing one SQL query statement.
                    The minimum supported SQL query statement is
                    a selection query that performs equality
                    comparisons between attribute values and
                    constant strings.  Conjunctions of such comparisons
                    are supported.  The minimum SQL query does not allow
                    projections, but returns all the attributes
                    for matching tuples.
      relations     List the relations available through the SNQP
                    server.
      stop          End processing of current query.
      quit          Terminate the query session.


                 Table 5: Minimum  SNQP Server Requirements
                          (Commands do not support t-bounds)

   ---------------------------------------------------------------------

6. Security Considerations

   SNQP clients and servers depend on the Domain Name Service.  They are
   subject to all the security issues that arise in that context.  This
   version of the SNQP protocol does not define procedures for
   protecting the information communicated to and from an SNQP server.









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RFC 2259                          SNQP                      January 1998


7. References

   [1]   American National Standards Institute. "SQL," ANSI Standard
         X3.135-1989.  1989.

   [2]   H. Garcia-Molina, G. Wiederhold. "Read-Only Transactions in
         a Distributed Database,"  ACM Transactions on Database Systems
         7(2), pp. 209-234.  June 1982.

   [3]   S. Dorner, P. Pomes. "The CCSO Nameserver: A Description,"
         Computer and Communications Services Office Technical Report,
         University of Illinois, Urbana, USA. 1992. Available in the
         current "qi" distribution from
         <URL:ftp://uiarchive.cso.uiuc.edu/local/packages/ph>

   [4]   J. Levine, T. Mason, D. Brown. "Parsing SQL," lex  yacc, 2nd
         ed.  O'Reilly and Associates, Inc. 1992.

   [5]   Ordille, J., "The Internet Nomenclator Project", RFC 2258,
         January 1998.

   [6]   J. Ordille. "Descriptive Name Services for Large Internets,"
         Ph. D. Dissertation. University of Wisconsin. 1993.
         <URL:http://cm.bell-labs.com/cm/cs/doc/93/12-01.ps.gz>

   [7]   J. Ordille, B. Miller. "Distributed Active Catalogs and
         Meta-Data Caching in Descriptive Name Services," Thirteenth
         International IEEE Conference on Distributed Computing Systems,
         pp. 120-129.  May 1993.
         <URL:http://cm.bell-labs.com/cm/cs/doc/93/5-01.ps.gz>

   [8]   J. Ordille. "Nomenclator Home Page." 1997.
         <URL:http://cm.bell-labs.com/cm/cs/what/nomenclator/>

   [9]   Postel, J., "Simple Mail Transfer Protocol", STD 10, RFC 821,
         August 1982.

   [10   Yeong, W., Howes, T., and S. Kille.  "Lightweight Directory
         Access Protocol", RFC 1777, March 1995.












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RFC 2259                          SNQP                      January 1998


8. Authors' Addresses

   Jim Elliott
   Epic Systems Corporation
   5301 Tokay Boulevard
   Madison, WI 53711  USA

   EMail: jim@apocalypse.org


   Joann J. Ordille
   Bell Labs, Lucent Technologies
   Computing Sciences Research Center
   700 Mountain Avenue, Rm 2C-301
   Murray Hill, NJ 07974  USA

   EMail: joann@bell-labs.com


































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9.  Full Copyright Statement

   Copyright (C) The Internet Society (1998).  All Rights Reserved.

   This document and translations of it may be copied and furnished to
   others, and derivative works that comment on or otherwise explain it
   or assist in its implementation may be prepared, copied, published
   and distributed, in whole or in part, without restriction of any
   kind, provided that the above copyright notice and this paragraph are
   included on all such copies and derivative works.  However, this
   document itself may not be modified in any way, such as by removing
   the copyright notice or references to the Internet Society or other
   Internet organizations, except as needed for the purpose of
   developing Internet standards in which case the procedures for
   copyrights defined in the Internet Standards process must be
   followed, or as required to translate it into languages other than
   English.

   The limited permissions granted above are perpetual and will not be
   revoked by the Internet Society or its successors or assigns.

   This document and the information contained herein is provided on an
   "AS IS" basis and THE INTERNET SOCIETY AND THE INTERNET ENGINEERING
   TASK FORCE DISCLAIMS ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING
   BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION
   HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF
   MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.
























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