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Versions: 01 RFC 2016

Internet-Draft                                              Leslie Daigle
draft-daigle-ura-01.txt                                     Peter Deutsch
November 22, 1995                                             Bill Heelan
                                                            Chris Alpaugh
                                                          Mary Maclachlan
                                          Bunyip Information Systems, Inc



                      Uniform Resource Agents (URAs)



----------------------------------------
Abstract
----------------------------------------

This paper presents an experimental architecture for an agent system that
provides sophisticated Internet information access and management.  Not a
generalized architecture for active objects that roam the Internet, these
agents are modeled as extensions of existing pieces of the Internet information
infrastructure.  The proposed agent technology focuses on the necessary
information structures to encapsulate Internet activities into objects that can
be activated, transformed, and combined into larger structured activities.




----------------------------------------
Status of this Memo
----------------------------------------

        This document is an Internet-Draft.  Internet-Drafts are working
        documents of the Internet Engineering Task Force (IETF), its areas,
        and its working groups.  Note that other groups may also distribute
        working documents as Internet-Drafts.

        Internet-Drafts are draft documents valid for a maximum of six
        months.  Internet-Drafts may be updated, replaced, or obsoleted by
        other documents at any time.  It is not appropriate to use
        Internet-Drafts as reference material or to cite them other than
        as a "working draft" or "work in progrss."

        To learn the current status of any Internet-Draft, please check the
        1id-abstracts.txt listing contained in the Internet-Drafts Shadow
        Directories on ds.internic.net, nic.nordu.net, venera.isi.edu, or
        munnari.oz.au.



----------------------------------------
Acknowledgements
----------------------------------------

Several people have shared throughts and viewpoints that have helped shape
the thinking behind this work over the past few years.  We'd like to thank,
in particular, Chris Weider, Patrik Faltstrom, Michael Mealling, Alan
Emtage, and the participants in the IETF URI Working Group for many
thought-provoking discussions.


----------------------------------------
Introduction
----------------------------------------

The evolution of Internet information systems has been characterized by
building upon successive layers of encapsulated technologies.  Machine address
numbers were devised, and then encapsulated in advertised machine names, which
has allowed the evolution of the Domain Name System (DNS) [RFC1034, RFC1035].
Protocols were developed for accessing Internet resources of various
descriptions, and then uniform mechanisms for specifying resource locations,
standardized across protocol types, were developed (URLs) [RFC1738].
Each layer of Internet information primitives has served as the building blocks
for the next level of abstraction and sophistication of information access,
location, discovery and management.

The work described in this paper is an experimental system designed to take
another step in encapsulation.  While TCP/IP protocols for routing, addressing,
etc, have permitted the connection and accessibility  of a plethora of
information services on the Internet, these must yet be considered a diverse
collection of heterogeneous resources.  The World Wide Web effort is the most
successful to date in attempting to knit these resources into a cohesive whole.
However, the activity best-supported by this structure is (human) browsing of
these resources as documents.  The Uniform Resource Agent (URA) initiative
explores the possibility of specifying an activity with the same kind of
precision accorded to resource naming and identification.

A fully-instantiated URA carries out a task delegated by an invoker (human or
otherwise).  The nature of the task is determined by the agent that the invoker
instantiates; that originating object encapsulates some knowledge of existence
of relevant Internet resources and information required in order to access them.
In this way, URAs can be used to allow invokers to carry out high-level
Internet resource activities while insulating them from the details of Internet
protocols, etc.  Also, by formally specifying a high-level Internet activity in
an agent, the activity can be repeated by the same or another invoker at a
later date,  the activity can be incorporated into a still higher-level
activity, the agent object can be modified to carry out a related task, etc.

More detail describing the underlying philosophy of this particular approach
can be found in [IIAW95].




----------------------------------------
Motivation
----------------------------------------

As a very simple example, consider the client task of subscribing to a
mailing list.  There are many mechanisms for providing the user
information necessary to complete a subscription.   Currently, all
applications which provide the ability to subscribe to mailing lists
must contain net-aware code to carry out the task once the requisite personal
data has been solicited from the user.  Furthermore,  any application program
that embeds the ability to subscribe in its code necessarily limits the
set of mailing lists to which a client can subscribe (i.e, to those types
foreseen by the software's creators).  If, instead, there is an agent to which
this task can be delegated, all applications can make use of the agent,
and that agent becomes responsible for carrying out the necessary interactions
to complete the subscription.  Furthermore, that agent may be a client
to other agents which can supply particular information about how to
subscribe to new types of mail servers, etc.





----------------------------------------
Relationship to Other Internet Agents
----------------------------------------

A number of Internet-aware agent and transportable code systems have been
released recently -- Java [JAVA], TCL [TCL] and Safe-TCL, Telescript [TELE],
and the TACOMA system [TACOMA], to name a few of them.  Some of these systems,
like Java, focus on providing mechanisms for creating and distributing
(inter)active documents in the World Wide Web.  Others, like TACOMA, have more
general intentions of providing environments for mobile, interacting processes.

While each of these systems makes its individual contribution to solving the
transportation, communication, and security issues normally associated with
agent systems, they yield more objects that exist within the Internet
information space.  That is, while they may permit individual users to
have a more sophisticated interaction with a particular information resource,
they do not address the more general Internet problems of naming, identifying,
locating resources, and locating the same or similar resources again at
a later date. It is this set of problems that URAs specifically set out to
address.




----------------------------------------
The Experimental Architecture
----------------------------------------

At the centre of the URA architecture is the concept of a (persistent)
specification of an activity.  For purposes that should become clear
as the expected usage of URAs is described in more detail, we choose to support
this concept with the following requirements of the architecture:

        . there is a formalized environment in which these specifications
          are manipulated (examined, executed, etc).  This is referred to as a
          URAgency.

        . the activity specifications are modular, and independent of a
          given URAgency environment.  Thus, they exist as object constructs
          that can be shared amongst URAgencies.   There is a standardized
          _virtual_ structure of these URA objects, although different
          types may exist, with different underlying implementations.


Basic URAgency Requirements
---------------------------

A URAgency is a software system that manipulates URA objects.  In the
terminology of objects, a URAgency identifies the types of URAs it handles,
and is responsible for applying methods to objects of those types.   For the
purposes of this experimental work, the only methods it is required to support
are those to get information about a given URA, and to execute a URA.

The expected result of applying the "get information" method to a URA
is a description of some or all of the URA following the standardized
virtual structure of a URA object, outlined below.

The appropriate way to "execute" a URA is to supply information for the
individual URA data segments (in effect, to permit the creation of an instance
of a virtual object), or to identify a URA instance.  Again, the information
is to be supplied in accordance with the virtual structure below.

When a URAgency claims to handle a particular type of URA, it must have
the ability to map that URA type's implementation structure into and out
of the virtual, standard URA structure, it must know how to activate the URA,
and it must satisfy any runtime dependencies for that type of URA.

For example, a URA type may consist of a Pascal program binary which, when
run with particular command line arguments, yields information in the
standard URA object structure.  Activating this type of URA might consist of
executing the Pascal binary with an input file containing all the necessary
data segments.  A URAgency claiming to handle this sort of URA type must
first be able to provide an environment to execute the Pascal binary (for
whatever platform it was compiled), and also be able to interact with the Pascal
binary according to these conventions to get information about the URA, or
execute it.

As an alternative example, a URA type may consist of a script in some
interpreted language, with the URA object structure embedded as data structures
within the script.  A URAgency handling this type of URA might have to be
able to parse the script to pull out the standard URA object structure, and
provide the script language interpreter for the purposes of executing the
URA.




URA Object Structure
--------------------

In order to capture the necessary information for carrying out the type
of Internet activity described in the introductory paragraphs of this
document, six basic (virtual) components of a URA object have been identified.
Any implementation of a URA type is expected to be able to conform to
this structure within the context of a URAgency.

The six basic components of a URA object are:

URA HEADER:
        Identification of the URA object, including a URA name, type and
        abstract, creator name, resources required by the URA, etc.


ACTIVATION DATA:
        Specification of the data elements required to carry out the URA
        activity.  For example, in the case of an Internet search for
        "people", this could include specification of fields for person
        name, organization, e-mail address, etc.


TARGETS:
        Specification of the URL/URN's to be accessed to carry out the
        activity.  Note that, until URN's are in common use, the ability
        to tweak URL's will be necessary.  A key issue for URAs is the
        ability to transport them and activate them far from the creator's
        originating site.  This may have implications in terms of
        accessibility of resource sites.  For example, a software search
        created in Canada will likely access a Canadian Archie server, and
        North American ftp sites.  However,  an invoker in Australia should
        not be obliged to edit the URA object in order to render it
        relevant in Australia.  The creator, then, can use this section to
        specify the expected type of service, with variables for the parts
        that can be modified in context (e.g., the host name for an Archie
        server, or a mirror ftp site).


EXPERIENCE INFORMATION:
        Specification of data elements that are not strictly involved in
        conversing with the targets in order to carry out the agent's
        activity.  This space can be used to store information from one
        invocation of a URA instance to the next.  This kind of information
        could include date of last execution, or URLs of resources located
        on a previous invocation of the agent.


ACTIVITY:
        If URAs were strictly data objects, specifying required data and
        URL/URN's would suffice to capture the essence of the composite
        net interaction.  However,  the variability of Internet resource
        accesses and the scope of what URAs could accomplish in the net
        environment seem to suggest the need to give the creator some
        means of organizing the instantiation of the component URL/URN's.
        Thus, the body of the URA should contain a scripting mechanism
        that minimally allows conditional instantiation of individual
        URL/URN's.  These conditions could be based on which (content)
        data elements the user provided, or accessibility of one URL/URN,
        etc.  It also provides a mechanism for suggesting scheduling of
        URL/URN instantiation.

        The activity is specified by a script or program in a language specified
        by the URA type, or by the URA header information.  All the required
        activation data, targets, and experience information are referenced
        by their specification names.

RESPONSE FILTER:
        The main purpose of the ACTIVITY module is to specify the steps
        necessary to take the ACTIVATION DATA, contact the TARGETS, and
        collect responses from those services.  The purpose of the RESPONSE
        FILTER module is to transform those responses into the result of
        the URA invocation.  This transformation may be along the lines of
        reformatting some text, or it may be a more elaborate interpretation
        (e.g., providing a relevance rating for a retrieved HTML page).

        The response filter is specified by a script or program in a language
        specified by the URA type, or by the URA header information.  All the
        required activation data, targets, and experience information are
        referenced by their specification names.



See Appendix 1 for a more detailed description of the components of a URA.
Appendix 2 contains a sample virtual URA structure.



The Architecture in Action
--------------------------

Having introduced the required capabilities of the URAgency and virtual
structure of URA objects, it is now time to elaborate on the tasks and
interactions that are best supported by URAs.

URAs are constructed by identifying net-based resources of interest (targets)
to carry out a particular task.  The activation data component of a URA is the
author's mechanism for specifying (to the invoker) the elements of information
that are required for successful execution .  An invoker creates an instance
of a URA object by providing data that is consistent with, or fills in, this
template.  Such an instance encapsulates everything that the agent "needs to
know" in order to contact the specified target(s), make a requrest of the
resource ("get", or "search", etc) and return a result to the invoker.  This
encapsulation is a sophisticated identification of the task results.

For exmaple, in the case of a mailing list subscription URA, the creator will
identify the target URL for a resource that handles list subscription (e.g., an
HTML form), and specify the data required by that resource (user name, user
mail address, mailing list identifier, etc).  When an invoker provides that
information and instantiates the URA, the resulting object completely
encapsulates all that is needed in order to subscribe the user -- the
subscription result is identified.

URAs are manipulated through the application of methods.  This, in turn , is
governed by the URAgency with which the invoker is interacting.   However,
because the virtual structure of URAs is represented consistently across
URA types and URAgencies, a URAgency can act as one of the targets of a URA.
Since methods can be applied to URAs remotely, URAs can act as invokers of URAs.
This can yield a complex structure of task modules.

For example, a URA designed to carry out a generalized search of book-selling
resources might make use of individual URAs tailored to each resource.  Thus,
the top-level URA becomes the orchastrating URA for access to a number of
disparate resources, while being insulated from the minute details of
accessing those resources.



----------------------------------------
A Prototype Implementation
----------------------------------------

The experimental work with URAs includes a prototype implementation of URA
objects.  These are written in the Tcl scripting language.  A sample prototype
Tcl URA can be found in Appendix 3.

The URAgency that was created to handle these URAs is part of the Silk
Desktop Internet Resource Discovery tool. Silk provides a graphical user
interface environment that allows the user to access and search for
Internet information without having to know where to look or how to look.
Silk presents a list of the available URAs to carry out these activities
(e.g., "search for tech reports", "hotlist", etc).  For each activity, the
user is prompted for the activation data, and Silk's URAgency executes the
URA.  The Silk software also supports the creation and maintenance of URA
object instances.  Users can add new URAs by creating new Tcl scripts (per
the guidelines in the "URA Writer's Guide", available with the Silk software.
See [SILK]).  The Silk graphical interface hides some of the mechanics of the
underlying URAgency.  A more directly-accessible version of this URAgency
will become available.



----------------------------------------
Conclusions
----------------------------------------

This work was originally conceived as an extension to the family of
Uniform Resource Identifiers -- URLs, and the proposed Uniform Resource
Names (URNs), and Uniform Resource Characteristics (URCs).  The approach
of formalizing the characteristics of an information task in a standardized
object structure is seen as a means of identifying a class of resources,
and contributes to the level of abstraction with which users can refer
to Internet resources.

Although still in experimental stages, this work has already evoked interest
and shown promise in the area of providing mechanisms for building more
advanced tools to interact with the Internet at a more sophisticated level than
just browsing web pages.

One of the major difficulties that has been faced in developing a collection
of URAs is the brittleness induced by interacting with services that are
primarily geared towards human-users.  Small changes in output formats
(easily discernable by the human eye) can be entirely disruptive to a
software client that must apply a parsing and interpretation mechanism
based on placement of cues in the text.  This problem is certainly not
unique to URAs -- any software acting upon results from such a service
is affected.  Perhaps there is the need for an evolution of "service entrances"
to information servers on the Internet -- mechanisms for getting "just
the facts" from an information server.  Of course, one way to provide
such access is for the service provider to develop and distribute a URA
that interacts with the service.  When the service's interface changes,
the service provider will be moved to update the URA that was built to
access it reliably.

Work will continue to develop new types of URAs, as well as other URAgencies.
This will necessitate the creation of URAgency interaction standards --
the "common virtual URA object structure" is the first step towards defining
a lingua franca among URAs of disparate types and intention.



----------------------------------------
References
----------------------------------------

   [IIAW95] Leslie L. Daigle, Peter Deutsch, "Agents for Internet Information
      Clients", CIKM'95 Intelligent Information Agents Workshop, December 1995.
      Available from
        <http://www.bunyip.com/products/silk/silktree/uratree/iiaw95.ps>

   [JAVA] "The Java Language: A White Paper" Available from
        <http://java.sun.com/1.0alpha2/doc/overview/java/index.html>

   [RFC1034] P.V. Mockapetris, "Domain Names - Concepts and Facilities",
      RFC 1034, November 1987.

   [RFC1035] P.V. Mockapetris, "Domain Names - Implementation and
      Specification", RFC 1035, November 1987.

   [RFC1738] T. Berners-Lee, L. Masinter, M. McCahill, "Uniform Resource
      Locators (URL)", RFC 1738, December 1994.

   [SILK] Bunyip's Silk project homepage:
        <http://www.bunyip.com/products/silk/>

   [SILKURA] Silk URA information:
        <http://www.bunyip.com/products/silk/silktree/uraintro.html>

   [TACOMA] Johansen, D. van Renesse, R. Schneider, F. B., "An Introduction to
      the TACOMA Distributed System", Technical Report 95-23, Department of
      Computer Science, University of Tromso, Norway, June 1995.

   [TCL] Ousterhout, J. K. "Tcl and the Tk Toolkit", Addison Wesley, 1994.

   [TELE]  White, J. E., "Telescript Technology:  The Foundation for the
      Electronic Marketplace", General Magic White Paper, General Magic Inc.,
      1994.





----------------------------------------
Authors' Address
----------------------------------------

Leslie Daigle
Peter Deutsch
Bill Heelan
Chris Alpaugh
Mary Maclachlan

Bunyip Information Systems, Inc.
310 St. Catherine St. West
Suite 300
Montreal, Quebec, CANADA
H2X 2A1

Phone:  (514) 875-8611

E-mail: ura-bunyip@bunyip.com



----------------------------------------
Appendix 1 -- Virtual URA Structure
----------------------------------------


This appendix contains a BNF-style description of the expected virtual
structure of a URA object.  This "virtual structure" acts as the canonical
representation of the information encapsulated in a given URA.  It is expected
that more information may optionally be contained in the elements of the
components --  the elements listed here are offered as the "minimum" or
"standard" set.

N.B.:
        []-delimited items are optional
        %% denotes a comment
        \0 represents the empty string
        |  is "or"
        {} are literal characters

This form is used for convenience and clarity of expression -- whitespace and
ordering of individual elements are not considered significant.


<VIRTUAL_URA> := {<virtual-ura-structure>}

<virtual-ura-structure> := { URAHDR <ura-header> }
                           { ACTDATA <activation-data> }
                           { TARG <targets> }
                           { EXPINFO <experience information> }
                           { ACTSPEC <activity> }
                           { RESPFILT <response filter> }

<ura-header> := { name <ura-name> }
                { author <ura-author> }
                { version <ura-version> }
                [ { lang <lang-dependencies> } ]
                [ { parent <parent-of-instance> } ]



<activation-data> := <act-data-element><activation-data> | \0

<act-data-element> := {
                       { name <data-elt-name> }
                       { response <data-elt-value> }
                       { prompt <data-elt-prompt> }
                       [ { required <boolean> } ]
                       [ { default <data-default-val> } ]
                      }

<targets> := <target-service><targets> | \0

<target-service> := {
                     { name <targ-url> }
                     { protocol <url-protocol> }
                     { url <url-spec> }
                     [ { <url-type-specific-data> } ]
                    }

<url-spec> :=  <complete-url> | <url-constructor>

<complete-url> := %% a complete, valid URL string (e.g., http://www.bunyip.com/)

<url-constructor> := {
                      { scheme <url-scheme-spec> }
                      { host <url-host-spec> }
                      [ { port <url-port-spec> } ]
                      { selector <url-selector-spec> }
                     }

<url-scheme-spec> := {
                      { name <scheme-name> }
                      { response <scheme-value> }
                      { prompt <scheme-prompt> }
                     }
<url-host-spec> := {
                      { name <host-name> }
                      { response <host-value> }
                      { prompt <host-prompt> }
                   }
<url-port-spec> := {
                      { name <port-name> }
                      { response <port-value> }
                      { prompt <port-prompt> }
                   }
<url-selector-spec> := {
                      { name <selector-name> }
                      { response <selector-value> }
                      { prompt <selector-prompt> }
                       }


<experience information> := {
                             { name <data-elt-name> }
                             { response <data-elt-value> }
                            }

<activity> :=  <compound-string>

<response filter> := <compound-string>


%% Without requiring more detail...

<compound-string> := <string>\n<compound-string> | \0
<boolean> := 0 | 1
<ura-name> := <string>
<ura-author> := <string>
<ura-version> := <string>
<lang-dependencies> := <string>
<parent-of-instance> := <string>
<data-elt-name> := <string>
<data-elt-value> := <string>
<data-elt-prompt> := <string>
<data-elt-default> := <string>
<data-default-val> := <string>
<targ-url> := <string>
<url-protocol> := http-get | http-post | ...
<url-type-specific-data> := <string>
<scheme-name> := <string>
<scheme-value> := <string>
<scheme-prompt> := <string>
<host-name> := <string>
<host-value> := <string>
<host-prompt> := <string>
<port-name> := <string>
<port-value> := <string>
<port-prompt> := <string>
<url-selector-name> := <string>
<url-selector-value> := <string>
<url-selector-prompt> := <string>




----------------------------------------
Appendix 2  -- Sample Virtual URA
               Representation
----------------------------------------

A valid virtual representation of a Silk Tcl URA is presented below. The
actual URA from which it was drawn is given in Appendix 3.


{
   {URAHDR
      {name {DejaNews Search}}
      {author {Leslie Daigle}}
      {version  {1.0}}
   }

   {ACTDATA
      {name        {Topic Keywords}}
      {prompt      {Topic Keywords}}
      {response    {}}
   }

   {EXPINFO
      {name        {Comments}}
      {prompt      {Comments}}
      {response    {}}
   }

   {ACTSPEC
       {proc mapResponsesToDejanews {} {
           set resp ""
           if {[uraAreResponsesSet {Topic Keywords}]} {
             lappend resp [list query [uraGetSpecResponse {Topic Keywords}]]
           }

           return $resp

         }
      proc uraRun {} {
        global errorInfo

        foreach serv [uraListOfServices] {
          set u [uraGetServiceURL $serv]

          switch -- $serv {
            dejanews {
              if [catch {
                set query [mapResponsesToDejanews]
                if {$query != {}} {
                    set result [uraHTTPPostSearch $u $query]
                    if {$result != ""} {
                      set list [dejanews_uraHTTPPostCanonicalize $result]
                      puts $list
                    }
                  }
              }] {
                puts stderr $errorInfo
              }
            }

            default {
              # can't handle other searches, yet.
            } } } }
      }
   }

   {RESPFILT
      {
       proc dejanews_uraHTTPPostCanonicalize {htmlRes} {

         set result {}
         set lines {}
         set clause {}
         set garb1 ""
         set garb2 ""


         # Get the body of the result page -- throw away leading and
         # trailing URLs

         regexp {([^<PRE>]*)<PRE>(.*)</PRE>.*} $htmlRes garb1 garb2 mainres

         set lines [split $mainres "\n"]

         foreach clause $lines {

           if [regexp {<DT>.*(..\/..).*<A HREF="([^"]*)">([^<]*)</A>.*<B>([^<]*).*} \
                $clause garb1 dt relurl desc grp] {

             lappend r [list HEADLINE [format "%s    (%s, %s)" [string trim $desc] \
                 [string trim  $grp] $dt]]
             lappend r [list URL [format "http://www.dejanews.com/cgi-bin/%s" $relurl]]
             lappend r [list TYPE "text/plain"]

             lappend result $r
           }
         }
         return $result
       }
      }


   }

}


----------------------------------------
Appendix 3  -- Sample Silk Tcl URA
----------------------------------------

The following is a valid Silk Tcl URA.  For more information on the
implementation and structure of Silk-specific URAs, see the "URA Writers
Guide" that accompanies the distribution of the Silk software (available
from <http://www.bunyip.com/products/silk>).


# -----------------------------------------------------------------------------
#
#                             URA initialization
#
# -----------------------------------------------------------------------------

#
# Initialize the URA, its search specs and searchable services.
#

# URA init.

set uraDebug 1

uraInit {
  {name {DejaNews Search}}
  {author {Leslie Daigle}}
  {version {1.0}}
  {description "This URA will search for UseNet News articles."}
  {help "This is help on UseNet News search script."}
}

#
# bug: handling of choices/labels is kind of gross.
#

# Search spec. init.

foreach item {
  {
    {name        {Topic Keywords}}
    {field       Topic}
    {tag         STRING}
    {description {Keywords to search for in news articles}}
    {prompt      {Topic Keywords}}
    {help        {Symbols to look up, separated by spaces.}}
    {type        STRING}
    {subtype     {}}
    {allowed     .*}
    {numvals     1}
    {required    0}
    {response    {}}
    {respset     0}
  }
} {
  uraSearchSpecInit $item
}

uraAnnotationInit {
  {help        {Enter comments to store with an instance}}
  {numvals     1}
  {subtype     {}}
  {response    {}}
  {name        Comments}
  {required    0}
  {class       ANNOTATION}
  {type        TEXT}
  {description {General comments about this URA.}}
  {respset     1}
  {prompt      Comments}
  {field       {}}
  {allowed     .*}
}

uraResultInit {
  {name {Related Pages}}
  {contents { {
    {HEADLINE {The DejaNews UseNet search service}}
    {TYPE text/plain}
    {URL http://www.dejanews.com}
} }}
}


foreach item {
  {
    {name dejanews}
    {protocol http-post}
    {url http://marge.dejanews.com/cgi-bin/nph-dnquery}
  }
} {
  uraServicesInit $item
}


proc dejanews_uraHTTPPostCanonicalize {htmlRes} {

  set result {}
  set lines {}
  set clause {}
  set garb1 ""
  set garb2 ""


  # Get the body of the result page -- throw away leading and trailing URLs
  regexp {([^<PRE>]*)<PRE>(.*)</PRE>.*} $htmlRes garb1 garb2 mainres

  set lines [split $mainres "\n"]

  foreach clause $lines {

    uraDebugPuts stderr [format "Line: %s" $clause]

    if [regexp {<DT>.*(..\/..).*<A HREF="([^"]*)">([^<]*)</A>.*<B>([^<]*).*} \
         $clause garb1 dt relurl desc grp] {
      uraDebugPuts stderr [format "Date: %s Rel URL: %s Desc: %s Group: %s" \
             $dt $relurl $desc $grp]

      lappend r [list HEADLINE [format "%s    (%s, %s)" [string trim $desc] \
          [string trim  $grp] $dt]]
      lappend r [list URL [format "http://www.dejanews.com/cgi-bin/%s" $relurl]]
      lappend r [list TYPE "text/plain"]

      lappend result $r
    }
  }
  return $result

}


# -----------------------------------------------------------------------------
#
#                             Mapping procedures
#
# -----------------------------------------------------------------------------

#
# There is one procedure, for each searchable service, to map the search
# spec responses to a form suitable for inclusion into a search URL (or
# whatever form the particular query procedure accepts).
#

#
#
proc mapResponsesToDejanews {} {
  set resp ""
  if {[uraAreResponsesSet {Topic Keywords}]} {
    lappend resp [list query [uraGetSpecResponse {Topic Keywords}]]
  }

  return $resp

}


#
# bug: need better error reporting (i.e. which searches didn't work and why, etc.)
#
proc uraRun {} {
  global errorInfo

  foreach serv [uraListOfServices] {
    set u [uraGetServiceURL $serv]

    switch -- $serv {
      dejanews {
        if [catch {
          set query [mapResponsesToDejanews]
          uraDebugPuts stderr [format "%s: query is `%s'." $serv $query]
          if {$query != {}} {
              set result [uraHTTPPostSearch $u $query]
              if {$result != ""} {
                uraDebugPuts stderr [format "%s: result is `%s'." $serv $result]
                set list [dejanews_uraHTTPPostCanonicalize $result]
                uraDebugPuts stderr [format "%s: list is `%s'." $serv $list]
                puts $list
              }
            }
        }] {
          puts stderr $errorInfo
        }
      }

      default {
        # can't handle other searches, yet.
      }
    }
  }
}







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

"The Relentless Pursuit of Perfection                   Leslie Daigle
   is a depth-first search of the infinitely deep       leslie@bunyip.com
      tree of life's experiences."                      Montreal, Canada
                                        -- ThinkingCat

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


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