💾 Archived View for gemini.bortzmeyer.org › rfc-mirror › rfc1835.txt captured on 2023-09-08 at 20:28:27.
⬅️ Previous capture (2021-11-30)
-=-=-=-=-=-=-
Network Working Group P. Deutsch
Request for Comments: 1835 BUNYIP INFORMATION SYSTEMS, Inc.
Category: Standards Track R. Schoultz
KTHNOC
P. Faltstrom
BUNYIP INFORMATION SYSTEMS, Inc.
C. Weider
BUNYIP INFORMATION SYSTEMS, Inc.
August 1995
Architecture of the WHOIS++ service
Status of this Memo
This document specifies an Internet standards track protocol for the
Internet community, and requests discussion and suggestions for
improvements. Please refer to the current edition of the "Internet
Official Protocol Standards" (STD 1) for the standardization state
and status of this protocol. Distribution of this memo is unlimited.
Abstract
This document describes WHOIS++, an extension to the trivial WHOIS
service described in RFC 954 to permit WHOIS-like servers to make
available more structured information to the Internet. We describe
an extension to the simple WHOIS data model and query protocol and a
companion extensible, distributed indexing service. A number of
options have also been added such as the use of multiple languages
and character sets, more advanced search expressions, structured data
and a number of other useful features. An optional authentication
mechanism for protecting all or part of the associated WHOIS++
information database from unauthorized access is also described.
Table of Contents
Part I - WHOIS++ Overview ................................. 3
1.1. Purpose and Motivation .............................. 3
1.2. Basic Information Model ............................. 4
1.2.1. Changes to the current WHOIS Model ................ 5
1.2.2. Registering WHOIS++ servers ....................... 5
1.2.3. The WHOIS++ Search Selection Mechanism ............ 7
1.2.4. The WHOIS++ Architecture .......................... 7
1.3. Indexing in WHOIS++ ................................. 8
1.4. Getting Help ........................................ 9
1.4.1. Minimum HELP Required ............................. 9
1.5. Options and Constraints ............................. 10
1.6. Formatting Responses ................................ 10
Deutsch, et al Standards Track [Page 1]
RFC 1835 Architecture of the WHOIS++ service August 1995
1.7. Reporting Warnings and Errors ....................... 11
1.8. Privacy and Security Issues ......................... 11
Part II - WHOIS++ Implementation .......................... 12
2.1. The WHOIS++ interaction model ....................... 12
2.2. The WHOIS++ Command set ............................. 12
2.2.1. System Commands ................................... 13
2.2.1.1. The COMMANDS command ............................ 14
2.2.1.2. The CONSTRAINTS command ......................... 15
2.2.1.3. The DESCRIBE command ............................ 15
2.2.1.4. The HELP command ................................ 15
2.2.1.5. The LIST command ................................ 15
2.2.1.6. The POLLED-BY command ........................... 15
2.2.1.7. The POLLED-FOR command .......................... 16
2.2.1.8. The SHOW command ................................ 16
2.2.1.9. The VERSION command ............................. 16
2.2.2. The Search Command ................................ 16
2.2.2.1. Format of a Search Term ......................... 17
2.2.2.2. Format of a Search String ....................... 18
2.3. WHOIS++ Constraints ................................. 19
2.3.1. Required Constraints .............................. 20
2.3.2. Optional CONSTRAINTS .............................. 21
2.3.2.1. The SEARCH Constraint ........................... 22
2.3.2.2. The FORMAT Constraint ........................... 22
2.3.2.3. The MAXFULL Constraint .......................... 22
2.3.2.4. The MAXHITS Constraint .......................... 23
2.3.2.5. The CASE Constraint ............................. 23
2.3.2.6. The AUTHENTICATE Constraint ..................... 23
2.3.2.7. The NAME Constraint ............................. 23
2.3.2.8. The PASSWORD Constraint ......................... 23
2.3.2.9. The LANGUAGE Constraint ......................... 23
2.3.2.10. The INCHARSET Constraint ....................... 24
2.3.2.11. The IGNORE Constraint .......................... 24
2.3.2.12. The INCLUDE Constraint ......................... 24
2.4. Server Response Modes ............................... 24
2.4.1. Default Responses ................................. 25
2.4.2. Format of Responses ............................... 25
2.4.3. Syntax of a Formatted Response .................... 26
2.4.3.1. A FULL format response .......................... 26
2.4.3.2. ABRIDGED Format Response ........................ 27
2.4.3.3. HANDLE Format Response .......................... 27
2.4.3.4. SUMMARY Format Response ......................... 27
2.4.3.5. SERVERS-TO-ASK Response ......................... 28
2.4.4. System Generated Messages ......................... 28
2.5. Compatibility with Older WHOIS Servers .............. 29
3. Miscellaneous ......................................... 29
3.1. Acknowledgements .................................... 29
3.2. References .......................................... 29
3.3. Authors' Addresses .................................. 30
Deutsch, et al Standards Track [Page 2]
RFC 1835 Architecture of the WHOIS++ service August 1995
Appendix A - Some Sample Queries .......................... 31
Appendix B - Some sample responses ........................ 31
Appendix C - Sample responses to system commands .......... 33
Appendix D - Sample whois++ session ....................... 35
Appendix E - System messages .............................. 36
Appendix F - The WHOIS++ BNF Grammar ...................... 38
Appendix G - Description of Regular expressions ........... 40
1. Part I - WHOIS++ Overview
1.1. Purpose and Motivation
The current NIC WHOIS service [HARR85] is used to provide a very
limited directory service, serving information about a small number
of Internet users registered with the DDN NIC. Over time the basic
service has been expanded to serve additional information and similar
services have also been set up on other hosts. Unfortunately, these
additions and extensions have been done in an ad hoc and
uncoordinated manner.
The basic WHOIS information model represents each individual record
as a Rolodex-like collection of text. Each record has a unique
identifier (or handle), but otherwise is assumed to have little
structure. The current service allows users to issue searches for
individual strings within individual records, as well as searches for
individual record handles using a very simple query-response
protocol.
Despite its utility, the current NIC WHOIS service cannot function as
a general White Pages service for the entire Internet. Given the
inability of a single server to offer guaranteed response or
reliability, the huge volume of traffic that a full scale directory
service will generate and the potentially huge number of users of
such a service, such a trivial architecture is obviously unsuitable
for the current Internet's needs for information services.
This document describes the architecture and protocol for WHOIS++, a
simple, distributed and extensible information lookup service based
upon a small set of extensions to the original WHOIS information
model. These extensions allow the new service to address the
community's needs for a simple directory service, yet the extensible
architecture is expected to also allow it to find application in a
number of other information service areas.
Added features include an extension to the trivial WHOIS data model
and query protocol and a companion extensible, distributed indexing
service. A number of other options have also been added, like boolean
operators, more powerful search constraints and search methods, and
Deutsch, et al Standards Track [Page 3]
RFC 1835 Architecture of the WHOIS++ service August 1995
most specificly structured the data to make both the client and the
server part of the dialogue more stringent and parseable. An optional
authentication mechanism for protecting all or parts of the
associated WHOIS++ information database from unauthorized access is
also briefly described.
The basic architecture of WHOIS++ allows distributed maintenance of
the directory contents and the use of the WHOIS++ indexing service
for locating additional WHOIS++ servers. Although a general overview
of this service is included for completeness, the indexing extensions
are described in a separate paper.
1.2. Basic Information Model
The WHOIS++ service is centered in a recommendation to structure user
information around a series of standardized information templates.
Such templates consist of ordered sets of data elements (or
attribute-value pairs).
It is intended that adding such structured templates to a server and
subsequently identifying and searching them be simple tasks. The
creation and use of customized templates should also be possible with
little effort, although their use should be discouraged where
appropriate standardized templates exist.
We also offer methods to allow the user to constrain searches to
desired attributes or template types, in addition to the existing
commands for specifying handles or simple strings.
It is expected that the minimalist approach we have taken will find
application where the high cost of configuring and operating
traditional White Pages services can not currently be justified.
Also note that the architecture makes no assumptions about the search
and retrieval mechanisms used within individual servers. Operators
are free to use dedicated database formats, fast indexing software or
even provide gateways to other directory services to store and
retrieve information, if desired.
The WHOIS++ server simply functions as a known front end, offering a
simple data model and communicating through a well known port and
query protocol. The format of both queries and replies has been
structured to allow the use of client software for generating
searches and displaying the results. At the same time, some effort
has been made to keep responses at least to some degree readible by
humans, to ensure low entry cost and to ease debugging.
Deutsch, et al Standards Track [Page 4]
RFC 1835 Architecture of the WHOIS++ service August 1995
The actual implemention details of an individual WHOIS++ search
engine are left to the imagination of the implementor and it is hoped
that the simple, extensible approach taken will encourage
experimentation and the development of improved search engines.
1.2.1. Changes to the current WHOIS Model
The current WHOIS service is based upon an extremely simple data
model. The NIC WHOIS database consists of a series of individual
records, each of which is identified by a single unique identifer
(the "handle"). Each record contains one or more lines of
information. Currently, there is no structure or implicit ordering of
this information, although by implication each record is concerned
with information about a single user or service.
We have implemented two basic changes to this model. First, we have
structured the information within the database as collections of data
elements, or simple attribute/value pairs. Each individual record
contains a specified ordered set of these data elements.
Secondly, we have introduced typing of the database records. In
effect, each record is based upon one of a specified set of
templates, each containing a finite and specified number of data
elements. This allow users to easily limit searches to specific
collections of information, such as information about users,
services, abstracts of papers, descriptions of software, and so on.
As a final extension, we require that each individual WHOIS++
database on the Internet be assigned a unique handle, analogous to
the handle associated with each database record.
The WHOIS++ database structure is shown in Fig. 1.
1.2.2. Registering WHOIS++ servers
We propose that individual database handles be registered through the
Internet Assigned Numbers Authority (the IANA), ensuring their
uniqueness. This will allow us to specify each WHOIS++ entry on the
Internet as a unique pair consisting of a server handle and a record
handle.
A unique registered handle is preferable to using the host's IP
address, since it is conceivable that the WHOIS++ server for a
particular domain may move over time. If we preserve the unique
WHOIS++ handle in such cases we have the option of using it for
resource discovery and networked information retrieval (see [IIIR]
for a discussion of resource and discovery and support issues).
Deutsch, et al Standards Track [Page 5]
RFC 1835 Architecture of the WHOIS++ service August 1995
There are many ways of guaranteeing uniqueness of server handles; we
will discuss them in a separate paper.
We believe that organizing information around a series of such
templates will make it easier for administrators to gather and
maintain this information and thus encourage them to make such
information available. At the same time, as users become more
familiar with the data elements available within specific templates
they will be better able to specify their searches, leading to a more
useful service.
______________________________________________________________________
| |
| + Single unique WHOIS++ database handle |
| |
| _______ _______ _______ |
| handle3 |.. .. | handle6 |.. .. | handle9 |.. .. | |
| _______ | _______ | _______ | |
| handle2 |.. .. | handle5 |.. .. | handle8 |.. .. | |
| _______ | _______ | _______ | |
| handle1 |.. .. | handle4 |.. .. | handle7 |.. .. | |
| |.. .. | |.. .. | |.. .. | |
| ------- ------- ------- |
| Template Template Template |
| Type 1 Type 2 Type 3 |
| |
| |
| |
| |
| Fig.1 - Structure of a WHOIS++ database. |
| |
| Notes: - Entire database is identified by a single unique WHOIS |
| handle. |
| - Each record has a single unique handle and a specific set |
| of attributes, determined by the template type used. |
| - Each value associated with an attribute can be any ASCII |
| string up to a specified length. |
|______________________________________________________________________|
Deutsch, et al Standards Track [Page 6]
RFC 1835 Architecture of the WHOIS++ service August 1995
1.2.3. The WHOIS++ Search Selection Mechanism
The WHOIS++ search mechanism is intended to be extremely simple. A
search command consists of one or more search terms, with an optional
set of global constraints (specifiers that modify or control a
search).
Search terms allow the user to specify template type, attribute,
value or handle that any record returns must satisfy. Each search
term can have an optional set of local constraints that apply to only
that term.
A WHOIS++ database may be seen as a single rolodex-like collection of
typed records. Each term specifies a further constraint that the
selected set of output records must satisfy. Each term may thus be
thought of as performing a subtractive selection, in the sense that
any record that does not fulfil the term is discarded from the result
set. Boolean searches are possible by the use of AND, OR, NOT and
parenthesis.
1.2.4. The WHOIS++ Architecture
The WHOIS++ directory service has an architecture which is separated
into two components; the base level server, which is described in
this paper, and a indexing server. A single physical server can act
as both a base level server and an indexing server.
A base level server is one which contains only filled templates. An
indexing server is one which contains forward knowledge (q.v.) and
pointers to other indexing servers or base level servers.
Deutsch, et al Standards Track [Page 7]
RFC 1835 Architecture of the WHOIS++ service August 1995
1.3. Indexing in WHOIS++
Indexing in WHOIS++ is used to tie together many base level servers
and index servers into a unified directory service.
Each base level server and index server which wishes to participate
in the unified directory service must generate "forward knowledge"
for the entries it contains. One type of forward knowledge is the
"centroid".
An example of a centroid is as follows: if a whois++ server contained
exactly three records, as follows:
Record 1 Record 2
Template: Person Template: Person
First-Name: John First-Name: Joe
Last-Name: Smith Last-Name: Smith
Favourite-Drink: Labatt Beer Favourite-Drink: Molson Beer
Record 3
Template: Domain
Domain-Name: foo.edu
Contact-Name: Mike Foobar
the centroid for this server would be
Template: Person
First-Name: Joe
John
Last-Name: Smith
Favourite-Drink:Beer
Labatt
Molson
Template: Domain
Domain-Name: foo.edu
Contact-Name: Mike
Foobar
An index server would then collect this centroid for this server as
forward knowledge.
Index servers can collect forward knowledge for any servers it
wishes. In effect, all of the servers that the index server knows
about can be searched with a single query to the index server; the
index server holds the forward knowledge along with pointers to the
servers it indexes, and can refer the query to servers which might
hold information which satisfies the query.
Deutsch, et al Standards Track [Page 8]
RFC 1835 Architecture of the WHOIS++ service August 1995
Implementors of this protocol are strongly encouraged to incorporate
centroid generation abilities into their servers.
-------------------------------------------------------------------
____ ____
top level | | | |
whois index | | | |
servers ---- ----
____ ____
first level | | | |
whois index | | | |
servers ---- ----
____ ____ ____
individual | | | | | |
whois servers | | | | | |
---- ---- ----
Fig. 2 - Indexing system architecture.
-------------------------------------------------------------------
1.4. Getting Help
Another extension to the basic WHOIS service is the requirement that
all servers support at least a minimal set of help commands, allowing
users to find out information about both the individual server and
the entire WHOIS++ service itself. This is done in the context of the
new extended information model by defining two specific template
formats and requiring each server to offer at least one example of
each record using these formats. The operator of each WHOIS service
is therefor expected to have, as a minimum, a single example of
SERVICES and HELP records, which can be accessed through appropriate
commands.
1.4.1. Minimum HELP Required
Executing the command:
DESCRIBE
gives a brief information about the WHOIS++ server.
Deutsch, et al Standards Track [Page 9]
RFC 1835 Architecture of the WHOIS++ service August 1995
Executing the command:
HELP
gives a brief description of the WHOIS++ service itself.
The text of both required helped records should contain pointers to
additional help subjects that are available.
Executing the command:
HELP <searchstring>
may give information on any topic.
1.5. Options and Constraints
The WHOIS++ service is based upon a minimal core set of commands and
controlling constraints. A small set of additional optional commands
and constraints can be supported. These would allow users to perform
such tasks as provide security options, modify the information
contents of a server or add multilingual support. The required set of
WHOIS++ commands are summarized in section 2.2. WHOIS++ constraints
are described in section 2.3. Optional constraints are described in
section 2.3.2.
1.6. Formatting Responses
The output returned by a WHOIS++ server is structured to allow
machine parsing and automated handling. Of particular interest in the
ability to return summary information about a search (without having
to return the entire results).
All output of searches will be returned in one of five output
formats, which will be one of FULL, ABRIDGED, HANDLE, SUMMARY or
SERVER-TO-ASK. Note that a conforming server is only required to
support the first four formats.
When available, SERVER-TO-ASK format is used to indicate that a
search cannot be completed but that one or more alternative WHOIS++
servers may be able to perform the search.
Details of each output format are specified in section 2.4.
Deutsch, et al Standards Track [Page 10]
RFC 1835 Architecture of the WHOIS++ service August 1995
1.7. Reporting Warnings and Errors
The formatted response of WHOIS++ commands allows the encoding of
warning or error messages to simplify parsing and machine handling.
The syntax of output formats are described in detail in section 2.4,
and details of WHOIS++ warnings and error conditions are given in
Appendix E.
All system messages are numerical, but can be tagged with text. It is
the clients decision if the text is presented to the user.
1.8. Privacy and Security Issues
The basic WHOIS++ service was conceived as a simple, unauthenticated
information lookup service, but there are occasions when
authentication mechanisms are required. To handle such cases, an
optional mechanism is provided for authenticating each WHOIS++
transaction.
The current identified authentication mechanism is PASSWORD, which
uses simple password authentication. Any other scheme name used must
begin with the characters "X-" and should thus be regarded as
experimental and non-standard.
Note that the WHOIS++ authentication mechanism does not dictate the
actual authentication scheme used, it merely provides a framework for
indicating that a particular transaction is to be authenticated, and
the appropriate mechanisms to use. This mechanism is extensible and
individual implementors are free to add additional mechanisms.
This document includes a very simple authentication scheme where a
combination of username and password is sent together with the search
string so the server can verify that the user have access to the
information. Note that this is NOT by any means a method recommended
to secure the data itself because both password and information are
tranferred unencrypted over the network.
Given the unauthenticated nature that default services like white
pages services are, it is easy to either forget the implications of
this and just show all data to the public Internet, or think that
Internet is so dangerous that information is hidden from the Internet
so the whole idea of a global white pages service is lost. Therefore
the type of authentication scheme selected and the public nature of
the Internet environment must still be taken into consideration when
assessing the security and authentication of the information served.
A more detailed exposition on security is outside the scope of this
document.
Deutsch, et al Standards Track [Page 11]
RFC 1835 Architecture of the WHOIS++ service August 1995
2. Part II - WHOIS++ Implementation
2.1. The WHOIS++ interaction model
A WHOIS++ server will normally listen for a TCP connections on the
allocated WHOIS++ port (although a WHOIS++ server can be accessed
over any TCP connection). Once a connection is established, the
server issues a banner message, and listens for input. The command
specified in this input is processed and the results returned
including an ending system message. If the optional HOLD constraint
has not been specified the connection is then terminated.
If the server supports the optional HOLD constraint, and this
constraint is specified as part of any command, the server continues
to listen on the connection for another line of input. This cycle
continues as long as the sender continues to append the required HOLD
constraint to each subsequent command.
At the same time, each server is permitted to set an optional timeout
value (which should be indicated in the response to the CONSTRAINTS
command). If set, the server is free to terminate an idle connection
at any time after this delay has passed with no input from the
client. If the server terminates the connection due to timeout, it
will be indicated by the system message. The timeout value is not
changeable by the client.
2.2. The WHOIS++ Command set
There are two types of WHOIS++ commands - system commands and the
WHOIS++ search command.
The WHOIS++ command set consists of a core set of required systems
commands, a single required search command and an set of optional
system commands which support features that are not required by all
servers. The set of required WHOIS++ system commands are listed in
Table I. Details of the allowable search terms for the search command
are included in Table II.
Each WHOIS++ command also allows the use of one or more controlling
constraints, when selected can be used to override defaults or
otherwise modify server behavior. There is a core set of constraints
that must be supported by all conforming servers. These include
SEARCH (which controls the type of search performed), FORMAT (which
determines the output format used) and MAXHITS (which determines the
maximum number of matches that a search can return).
These required constraints are summarized in Table III.
Deutsch, et al Standards Track [Page 12]
RFC 1835 Architecture of the WHOIS++ service August 1995
An additional set of optional constraints are used to provide support
for different character sets, indicate the need and type of
authentication to perform on a transaction, and permit multiple
transactions during a single communications session. These optional
constraints are listed in Table IV.
It is possible, using the required COMMANDS and CONSTRAINTS system
commands, to query any WHOIS++ server for its list of supported
commands and constraints.
2.2.1. System Commands
System commands are commands to the server for information or to
control its operation. These include commands to list the template
types available from individual servers, to obtain a single blank
template of any available type, and commands to obtain the list of
valid commands and constraints supported on a server.
There are also commands to obtain the current version of the WHOIS++
protocol supported, to access a simple help subsystem, to obtain a
brief description of the service (which is intended, among other
things, to support the automated registration of the service by
yellow pages directory services). All of these commands are required
from a conforming WHOIS++ server.
Deutsch, et al Standards Track [Page 13]
RFC 1835 Architecture of the WHOIS++ service August 1995
------------------------------------------------------------------------
Short Long Form Functionality
----- --------- -------------
COMMANDS [ ':' HOLD ] list valid WHOIS++ commands
supported by this server
CONSTRAINTS [ ':' HOLD ] List valid constraints
supported by this server
DESCRIBE [ ':' HOLD ] Describe this server,
formating the response
using a standard
"Services" template
'?' HELP [<string> [':' <cnstrnts>]] System help, using a "Help"
template
LIST [':' <cnstrnts>] List templates supported
by this system
POLLED-BY [ ':' HOLD ] List indexing servers
that are know to track
this server
POLLED-FOR [ ':' HOLD ] List information about
what this server is
tracking for
SHOW <string> [':' <cnstrnts>] Show contents of templates
specified
VERSION [ ':' HOLD ] return current version of
the protocol supported.
Table I - Required WHOIS++ SYSTEM commands.
------------------------------------------------------------------------
Below follows a descriptions for each command. Examples of responses
to each command is in Appendix C.
2.2.1.1. The COMMANDS command
The COMMANDS command returns a list of commands that the server
supports. The response is formatted as a FULL response.
Deutsch, et al Standards Track [Page 14]
RFC 1835 Architecture of the WHOIS++ service August 1995
2.2.1.2. The CONSTRAINTS command
The CONSTRAINTS command returns a list of constraints and the values
of those that the server supports. The response is formatted as a
FULL response, where every constraint is represented as a separate
record. The template name for these records is CONSTRAINT. No
attention is paid to handles. Each record has, as a minimum, the
following two fields:
- "Constraint", which contains the attribute name described -
"Default", which shows the default value for this constraint.
If the client is permitted to change the value of the constraint,
there is also:
- "Range" field, which contains a list of values that this
server supports, as a comma separated list; Or, if the range
is numerical, as a pair of numbers separated with a hyphen.
2.2.1.3. The DESCRIBE command
The DESCRIBE command gives a brief description about the server in a
"Services" template. The result is formatted as a FULL response.
2.2.1.4. The HELP command
The HELP command takes an optional argument as subject to get help
for.
2.2.1.5. The LIST command
The LIST command returns the name of the templates available on the
server. The answer is formatted FULL format response.
2.2.1.6. The POLLED-BY command
The POLLED-BY command returns a list of servers and the templates and
attribute names that those server polled as centroids from this
server. The format is in FULL format with two attributes, Template
and Field. Each of these is a list of names of the templates or
fields polled. An empty result means either that the server is not
polled by anyone, or that it doesn't support indexing.
Deutsch, et al Standards Track [Page 15]
RFC 1835 Architecture of the WHOIS++ service August 1995
2.2.1.7. The POLLED-FOR command
The POLLED-FOR command returns a list of servers that this server has
polled, and the template and attribute names for each of those. The
answer is in FULL format with two attributes, Template and Field. An
empty result means either that the server is not polling anyone, or
that it doesn't support indexing.
2.2.1.8. The SHOW command
The SHOW command takes a template name as argument and returns
information about a specific template, formatted as a FULL response.
The answer is formatted as a blank template with the requested name.
2.2.1.9. The VERSION command
The output format is a FULL response containg a record with template
name VERSION. The record must have attribute name "Version", which
value is "1.0" for this version of the protocol. The record may also
have the additional fields "Program-Name" and "Program-Version" which
gives information about the server implementation if the server so
desires.
2.2.2. The Search Command
A search command consists of one or more search terms, which might
each have local constraints, followed by an optional colon with a set
of global search constraints.
Each attribute value in the WHOIS++ database is divided into one or
more words separated by whitespace. Each search term operates on
every word in the attribute value.
Two or more search terms may be combined with boolean operators AND,
OR or NOT (other than the implied AND between terms). The operator
AND has higher precedence than the operator OR, but this can be
changed by the use of parentheses.
Search constraints that apply to every search term are specified as
global constraints. Local constraints override global constraints for
the search term they are bound to. The search terms and the global
constraints are separated with a colon (':'). Additional global
constraints are appended to the end of the search command delimited
with a semicolon ';'.
If different search constraints can not be fulfilled, or the
combination of different search constraints is uncombinable, the
server may choose to ignore some constraints, but still do the search
Deutsch, et al Standards Track [Page 16]
RFC 1835 Architecture of the WHOIS++ service August 1995
and return some records.
The set of required constraints are summarized in Table III. The set
of optional constraints are summarized in Table IV.
As an option, the server may accept specifications for attributes for
either inclusion or exclusion from a reply. Thus, users could specify
-only- those attributes to return, or specific attributes to filter
out, thus creating custom views.
2.2.2.1. Format of a Search Term
Each search term consists of one of the following:
1) A search string, followed by an optional semicolon and set of
semicolon-separated local constraints.
2) A search term specifier (as listed in Table II), followed by a
'=', followed by a search string, an optional semicolon and a
set of semicolon-separate local constraints.
3) An abbreviated search term specifier, followed by a search
string, followed by an optional semicolon and set of
semicolon-separated local constraints.
4) A combination of attribute name, followed by '=', followed by
a search string, followed by an optional semicolon and set of
semicolon-separate local constraints.
If no term identifier is provided, then the search will be applied to
attribute values only. This corresponds to an identifier of VALUE.
If a SEARCH-ALL specifier is used then the search will be applied to
all template names, handles, attribute names and attribute values.
When the user specifies the search term using the form:
"<attribute_name> = <value>"
this is considered to be an ATTRIBUTE-VALUE search.
For discussion of the system reply format, and selecting the
appropriate reply format, see section 2.4.
Deutsch, et al Standards Track [Page 17]
RFC 1835 Architecture of the WHOIS++ service August 1995
-------------------------------------------------------------------
Valid specifiers:
-----------------
Name Functionality
---- -------------
ATTRIBUTE-VALUE [ ';' <constrnt>]* allows combining
attribute and value
specifiers in one term.
HANDLE [ ';' <constrnt>]* Confine search to handles.
SEARCH-ALL [ ';' <constrnt>]* Search everything.
TEMPLATE [ ';' <constrnt>]* Confine search to
template names.
VALUE [ ';' <constrnt>]* Confine search to attribute
values. This is the default.
(Note: The name HANDLE can be replaced with the shortname '!')
Acceptable forms of a search specifier:
---------------------------------------
1) <searchstring> [';' <constraint>]*
2) <specifier> = <searchstring> [';' <constraint>]*
3) <shortspecifier> <searchstring> [';' <constraint>]*
4) <attribute_name> = <searchstring> [';' <constraint>]*
(Note: A <constraint> is a name of a valid local constraint.)
Table II - Valid search command term specifiers.
-------------------------------------------------------------------
2.2.2.2. Format of a Search String
Special characters that need to be quoted are preceeded by a
backslash, '\'.
Special characters are space ' ', tab, equal sign '=', comma ',',
colon ':', backslash '\', semicolon ';', asterisk '*', period '.',
parenthesis '()', square brackets '[]', dollar sign '