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\input texinfo                         @c -*-texinfo-*-
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@c $Id: Protocol-A.texi,v 1.7 1998/06/14 14:50:17 byers Exp $
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@c %**start of header
@setfilename protocol-a.info
@settitle LysKOM Protocol A
@setchapternewpage odd
@c %**end of header
@iftex
@parindent 0pt
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@font@tensltt=cmsltt10
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@begin tex
\global\def\rett#1{{\let\t\sltt\tt #1}}
\global\def\sltt#1{{\fam\ttfam\tensltt\let\t\rett #1}}
\global\let\t\sltt
@end tex
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@end iftex

@ifinfo
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This is the specification of LysKOM Protocol A v. 9.0
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Copyright @copyright{} 1995, 1996 Lysator ACS.
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Permission is granted to make and distribute verbatim copies of this
specification provided the copyright notice and this permission notice
are preserved on all copies.
@end ifinfo

@titlepage
@sp 10
@title{LysKOM Protocol A}
@sp 2
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@subtitle{Protocol version 10.0}
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@sp 2
@author by the LysKOM Developers

@page
@vskip 0pt plus 1filll
Copyright @copyright{} 1995 Lysator ACS

Permission is granted to make and distribute verbatim copies of this document
provided the copyright notice and this permission notice are preserved on all
copies.

Modified versions of this document may be redistributed with the added
condition that all modifications not cleared with the LysKOM development group
are clearly marked and that the entire modified work be redistributed under the
same conditions as the original.

Permission is granted to copy and distribute translations of this manual into
another language under the same conditions as for modified versions.

@end titlepage

@ifinfo
@node Top, Overview, (dir), (dir)
@comment node-name, next, previous, up
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This document specifies LysKOM Protocol A, version 9.0
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@menu
* Overview::
* Introduction::
* Data Types::
* Protocol Requests::
* Asynchronous Messages::
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* Error Codes::
* LysKOM Content Types::
* The User Area::
* Writing Clients::
* Indexes and Overviews::
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@end menu
@end ifinfo

@node Overview, Document Revision History, Top, Top
@chapter Overview

LysKOM is a conferencing system@footnote{Or in modern terms, enabling
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technology for Computer-Supported Cooperative Work (CSCW).}. Similar
systems were QZ-KOM and PortaCOM@footnote{Also known as ``PottaKOM'' and
``BortaKOM.''}. The LysKOM system is copyrighted by Lysator Academic
Computing Society and distributed under conditions of the GNU Public
License. LysKOM and its documentation is provided ``as is'' without
warranty of any kind.
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This document specifies version 10.0 of protocol A used between a LysKOM
client and a LysKOM server. Anything described here as ``unspecified''
is liable to change in future protocol versions.
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This specification is the work of several people. The main contributors have
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been
Per Cederqvist @code{<ceder@@lysator.liu.se>}, 
David Byers @code{<byers@@lysator.liu.se>},
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@ifinfo
Pr
@end ifinfo
@iftex
P@"ar
@end iftex
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Emanuelsson @code{<pell@@lysator.liu.se>},
Thomas Bellman @code{<bellman@@lysator.liu.se>}, 
Lars Aronsson @code{<aronsson@@lysator.liu.se>},
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Linus Tolke @code{<linus@@lysator.liu.se>} and
@ifinfo
Kent Engstrm
@end ifinfo
@iftex
Kent Eng@-str@"om@penalty-10000
@end iftex
@code{<kent@@lysator.liu.se>}.

The LysKOM developers can be reached by email to @code{lyskom@@lysator.liu.se}.

@menu 
* Document Revision History::
* Protocol Revision History::
* Protocol Design Principles::
* Notation::
@end menu

@node Document Revision History, Protocol Revision History, Overview, Overview
@section Document Revision History

@table @asis
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@item 9.0: @i{In progress}
Protocol version 9 is begin developed and this document needs to be
updated.

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@item 8.0: 1995-11-10
Protocol version 8 is being documented. This specification was translated to
English and converted to Texinfo by David Byers.

@item 7.1: 1995-01-08.
Protocol and document revision history were added by Per Cederqvist. Outline
mode was used to make the document more manageable. This version was
distributed with lyskomd 1.7.1.

@item 7.0: 1994-12-31.
The first specification with a version number. All calls that had been added
since 1991-06-25 were documented. Pell and Per Cederqvist did the deed. This
version was distributed with lyskomd 1.7.0.

@item 1993-05-19.
Linus Tolke wrote comments for some calls that were without comments.

@item 1992-07-06.
Linus Tolke converted the document to ISO 8859-1.

@item 1991-08-12.
Per Cederqvist started using version control for documentation.

@item 1991-06-25.
Lars Aronsson documented the protocol that was in use at the time.
@end table

@node Protocol Revision History, Protocol Design Principles, Document Revision History, Overview
@section Protocol Revision History

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@subsection Protocol version 10.0
@table @asis
@item New Server Calls
@itemize @bullet
@item 85=get-collate-table
@item 86=create-text
@item 87=create-anonymous-text
@item 88=create-conf
@item 89=create-person
@item 90=get-text-stat
@item 91=get-conf-stat
@item 92=modify-text-info
@item 93=modify-conf-info
@item 94=get-info
@item 95=modify-system-info
@item 96=query-predefined-aux-items
@item 97=set-expire
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@item 98=query-read-texts
@item 99=get-membership
@item 100=add-member
@item 101=get-members
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@end itemize

@item Removed Server Calls
@itemize @bullet
@item  5=create-person
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@item  9=query-read-texts
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@item 10=create-conf
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@item 14=add-member
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@item 26=get-text-stat
@item 28=create-text
@item 36=get-info-old
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@item 46=get-membership-old
@item 48=get-members-old
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@item 50=get-conf-stat
@item 59=create-anonymous-text
@end itemize

@item New and New Modified Structures
@itemize @bullet
@item Aux-item
@item Aux-item-list
@item Conference
@item Info
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@item Member
@item Membership
@item Membership-Type
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@item Misc-info
@item Text-stat
@end itemize

@item New Asynchronous Messages
@itemize @bullet
@item async-deleted-text message
@item New async-new-text message
@end itemize
@end table

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@subsection Protocol version 9.0

@table @asis
@item Added Functionality
@itemize @bullet
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@item 79=set-info: Can change server information.
@item 80=accept-async: Can select asynchronous messages to receive.
@item 81=query-async: Can query which messages are being send.
@item 82=user-active
@item 83=who-is-on-dynamic
@item 84=get-static-session-info
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@end itemize
@end table

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@subsection Protocol version 8.0

@table @asis 
@item Added Functionality
@itemize @bullet
@item
30=add-recipient: Can change recpt to cc_recpt and vice versa.
@item
21=set-conf-type: Accepts Conf-Type and Extended-Conf-Type.
@item
10=create-conf: Accepts Conf-Type and Extended-Conf-Type.
@end itemize

@item New Commands
@itemize @bullet
@item
77=set-last-read
@item
78=get-uconf-stat
@end itemize
@end table

@subsection Protocol version 7 (first implemented in lyskomd 1.7.0)

@table @asis
@item Added Functionality
@itemize @bullet
@item
53=send-message: Recipient can be a conference or a person.
@end itemize

@item New Commands
@itemize @bullet
@item
74=re-z-lookup
@item
75=get_version_info
@item
76=lookup_z_name
@end itemize

@item Other
@itemize @bullet
@item
Det asynkrona meddelanded 1=i-am-off has been removed
@end itemize
@end table

@subsection Protocol Version 6 (first implemented in lyskomd 1.4.0)

@table @asis
@item New Calls
@itemize @bullet
@item
67=lookup_person
@item
68=lookup_conf
@item
69=set_client_version
@item
70=get_client_name
@item
71=get_client_version
@item
72=mark_text
@item
73=unmark_text
@end itemize
@end table


@subsection Protocol Version 5 (first implemented in lyskomd 1.3.0)

@table @asis
@item New Calls
@itemize @bullet
@item
65=re_lookup_person
@item
66=re_lookup_conf
@end itemize
@end table

@subsection Protocol Version 4 (first implemented in lyskomd 1.1.1)

@table @asis
@item New Calls
@itemize @bullet
@item
62=login
@item
63=who_is_on_ident
@item
64=get_session_info_ident
@end itemize
@end table

@subsection Protocol Version 3 (first implemented in lyskomd 1.1.0)

@table @asis
@item New Calls
@itemize @bullet
@item
61=find_previous_text_no
@item
60=find_next_text_no
@item
59=create_anonymous_text
@item
58=get_last_text
@end itemize
@end table

@subsection Protocol Version 2 (first implemented in lyskomd 0.30.0)

@table @asis
@item New Calls
@itemize @bullet
@item
57=set_user_area
@end itemize
@end table

@subsection Protocol Version 1 (first implemented in lyskomd 0.29.2)

@table @asis
@item New Calls
All calls from 0--56.
@end table


@node Protocol Design Principles, Notation, Protocol Revision History, Overview
@section Transport Protocol Requirements

LysKOM protocol A can be run on top of any reliable, bidirectional,
8-bit data stream. All current implementations use TCP/IP. At Lysator
port 4894 is used on the host @code{kom.lysator.liu.se}.

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Data in protocol A is ASCII clear text except within hollerith strings,
where arbitrary eight-bit characters are allowed. Data arguments are
separated by whitespace. The reason for this unorthodox design is that
the protocol should be usable from a text-only terminal, something that
is very useful during server and early client development.
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@node Notation, , Protocol Design Principles, Overview
@section Notation

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This specification uses a BNF-like grammar to describe the protocol and
its data elements. It does not use ASN.1 because we don't know ASN.1 and
probably wouldn't like it very much even if we did.
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Data fields have been given names that start with a lower-case letter.
Data types have names that start with an upper-case letter. The operator
@code{::=} defines the name to its left and @code{:} (a colon) specifies
a type. Comments start with @code{!} (exclamation mark) and alternatives
are separated by a @code{|} (vertical bar.) A @code{;} (semicolon)
terminates statements in the grammar. In some specifications there are
literal strings. There is to be no whitespace before or after literal
strings unless there is whitespace in the literal itself.
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@node Introduction, , , Top
@chapter Introduction

This chapter introduces the concepts used in LysKOM, such as articles,
conferences and sessions. 

@menu
* Articles ::
* Conferences ::
* Persons and Sessions ::
* The Misc-Info List ::
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* The Aux-Item List ::
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* Security ::
* Membership and Reading::
* Client-Server Dialog ::
@end menu


@node Articles, Conferences, , Introduction
@section Articles

An article is represented as a value of the type @code{Text-Stat} and a
string containing the article contents. An article will usually have one
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or more recipients and may be a comment or footnote to other articles.
Each article is kept in the database until it is older than the
@code{nice} value of each of its recipients and it is not marked by any
user.
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Currently there is a structure called a @code{Misc-Info-List} associated
with the @code{Text-Stat}. This list contains information about
recipients, senders, comments and footnotes. In the future the
information contained in the @code{Misc-Info-List} will be integrated
into the @code{Text-Stat}.
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Every article has at least one number, the global article number. Global
numbers are assigned in ascending order to new articles, and are never
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reused. If an article has recipients it will also have a local number
for each recipients. Local numbers are used in some data structures to
provide more compact storage and to provida an ordering of articles for
a particular recipient. Local numbers are assigned in ascending order
and are never reused for a particular recipient, though different
recipients will have articles with the same local numbers.
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Occasionally it is necessary to map between local and global numbers.
The server call @code{get-map} does this.
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@node Conferences, Persons and Sessions, Articles, Introduction
@section Conferences

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Conferences hold articles. They are represented in the protocol as a
data type called @code{Conference}. Each conference has a
@emph{creator}, the person who created the conference, and a
@emph{supervisor}, a conference whose members can modify the conference.
If the supervisor is a person, the members of that person's letterbox
are supervisors, which in most cases is only that person. We have also
introduced a type called @code{UConference} (pronounced micro-conf-stat)
which holds a subset of the information contained in the full
@code{Conference} type. Use the @code{UConference} type whenever
possible since it places a much smaller load on the LysKOM server.
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Each conference has a type, which is essentially a collection of boolean
flags. Currently the types @code{rd-prot}, @code{letterbox},
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@code{secret}, @code{original} and @code{allow-anonymous} are defined.
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@table @code
@item rd-prot
The conference is protected from reading by non-members. Persons become
members by having one of the existing members or supervisors add him or
her to the conference. This restriction is enforced by the server.
@item original
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Conferences of this type are intended for original articles only.
Comments are to be redirected to the super-conference instead. This
restriction is currently not enforced by the server; clients must
implement this functionality.
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@item letterbox
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Conferences of this type are connected to persons. Letters to a person
are sent to the letterbox and the name of the letterbox is synchronised
with the person name. It is currently not possible to explicitly set or
clear this flag on a conference.
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@item secret
Conferences of this type are secret. The server will not divulge any
information of the existence of the conference to persons who are not
members or supervisors of the conference. If a letterbox is made secret,
that person cannot log in using the person name, but must specify a
person number instead.
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@item allow-anonymous
Conferences of this type accept anonymous articles. Other conferences
will reject anonymous articles.
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@end table



@node Persons and Sessions, The Misc-Info List, Conferences, Introduction
@subsection Persons and Sessions

Persons are represented in the protocol by values of the type
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@code{Person}. Associated with persons are statistics, a set of personal
flags and a set of privileges (@pxref{Security}.) Persons are also
associated with a conference that has the same number as the person and
the @code{letterbox} bit set.
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Connections to the server are represented as values of the type
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@code{Static-Session-Info}, @code{Session-Info-Ident} or
@code{Session-Info}. Sessions have session number that are unique for
each session in the lifetime of the server execution. A single user can
have several sessions running at once. The session is not released until
the network connection is closed; a user can log in and out repeatedly
in a single session.
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@node The Misc-Info List, The Aux-Item List, Persons and Sessions, Introduction
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@section The Misc-Info List

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The @code{Misc-Info} list contains tagged data. The fields are sent in
groups pertaining to a particular type of information: information about
recipient; carbon copy recipient, comment to; footnote to; comment in
and footnote in. The information groups may be sent in any order and
there may be any number of groups. Within each group the elements are
always sent in the order listed below.
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@subsection Recipient
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@table @code
@item recpt
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Starts a recipient group. It contains the conference number of a
recipient of the article.
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@item loc-no
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Always present within a recipient group. It contains the local text
number of the article in the conference specified by the preceding
@code{recpt} field.
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@item rec-time
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If the recipient is a person, this element is added by the server when
the recipient marks the article as read. It contains the time when the
text was read.
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@item sent-by
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Present when the recipient was added by a person other than the author
(after the article was created.) It contains the person number of the
person who added the recipient.
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@item sent-at
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Present when the recipient was added after the article was created. It
contains the time when the recipient was added.
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@end table


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@subsection Carbon Copy (CC) Recipient
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The carbon-copy recipient group is identical to the recipient group
above. The difference is how new comments to an article with a recipient
or carbon-copy recipient are treated. A comment to an article is sent to
all recipients, but not to carbon-copy recipients of the original
article.
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@table @code
@item cc-recpt
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Starts a carbon-copy recipient group. It contains the conference number
of a carbon-copy recipient of the article.
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@item loc-no
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Always present in a CC recipient group. It contains the local text
number of the article in the conference specified by the most recent
@code{cc-recpt} field.
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@item rec-time
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Present after the CC recipient has read the article. It contains the
time when the article was read.
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@item sent-by
Present when a CC recipient was added by a person other than the author
after the article had been created. It contains the person number of the
person who added the cc recipient.
@item sent-at
Present when a CC recipient was added after the article had been
created. It is the time when the CC recipient was added.
@end table


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@subsection Comment To
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@table @code
@item comm-to
Always present when the article is a comment to another article.
@item sent-by
Present when the article was added as a comment by a person other than
the author, after the article had been created. It contains the person
number of the person who added the article as a comment.
@item sent-at
Present when the article was added as a comment after the article had
been created. It contains the time when is was added as a comment.
@end table


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@subsection Footnote To
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@table @code
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@item footn-to
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Always present when the article is a footnote to another article.
@item sent-at
Present when the article was added as a footnote after the article had
been created. It contains the time when is was added as a footnote.
@end table


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@subsection Comment in
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@table @code
@item comm-in
Present when there are comments to this article. It contains the article
number which is a comment to this article.
@end table


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@subsection Footnote in
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@table @code
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@item footn-in
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Present when there are footnotes to this article. It contains the
article number which is a footnote to this article.
@end table


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@node The Aux-Item List, Security, The Misc-Info List, Introduction
@subsection The Aux-Item List

The aux-item list is used as a generic extension mechanism in the LysKOM
server and in protocol A. 

@menu
* About Aux-Items ::
* Predefined Aux-Item Types ::
* Client-Specific Aux-Item Types ::
* Experimental Aux-Item Types ::
* Defining New Aux-Item Types ::
@end menu

@node About Aux-Items, Predefined Aux-Item Types, , The Aux-Item List
@subsubsection About Aux-Items

Aux-items were introduced in protocol version 10 as a mechanism for
extending the conference, text and server information structures without
changing the protocol. Persons were excluded since nobody could figure
out a case where setting an aux-item on the letterbox wasn't as good as
setting it on the person (another reason was that I was fed up writing
aux-item code by the time they were working on texts and conferences.)

The exact structure of an aux item is specified elsewhere (@pxref{LysKOM
Data Types}). The important fields here are the aux-no, tag and data
fields.

The aux-no field is used to identify an item. The aux-no together with a
text or conference number uniquely identifies a particular aux item.
Items are numbered from one and up within each item list Once assigned,
the aux-no for an item is never changed. New items are guaranteed to
be assigned numbers that have never been used before within a particular
list.

The tag field ideintifies the type of aux item. It is used by the server
and by clients to figure out how to interpret the data field, and by the
server to decide if the item needs special treatment.

The data field is a simple string. The meaning of the string is
determined by the tag field, but since it is a string, clients that have
no understanding of the contents can successfully parse the item anyway
(in contrast to items in the misc-info list.)



@node Predefined Aux-Item Types, Client-Specific Aux-Item Types, About Aux-Items, The Aux-Item List
@subsubsection Predefined Aux-Item Types

Predefined Aux-Item types are part of Protocol A, and clients are
encouraged to support all of them. As with other parts of the protocol,
changes to these item types will probably always be
backwards-compatible.

Predefined types can case serious magic to be invoked in the server.
There is no limit to the strangeness that may be associated with this
type of item. The server may also place limits on who may create
predefined items, might verify the data field, and can force any field
in the item to a specific value, no matter what the client specified.

All items with tags in the rande 1-9999 and 30000 and up are considered
predefined. If a client attempts to create an item with a tag in this
range, but the server has no idea what that tag means, the server will
return an error (KOM_ILL_AUX.)



@table @samp
@item content-type [1] (text)
Specifies the content type of a text. Data is a valid MIME type of one
of the special LysKOM types (@pxref{LysKOM Content Types}.)

This item may only be set by the author of a text. The inherit, secret
and hide-owner bits are cleared. Only one content-type item can be
created per creator.


@item fast-reply [2] (text)
Data is a string that constitutes a brief comment to the text. This
comment should be displayed immediately after the text body. 

The inherit bit is automatically cleared.


@item cross-reference [3] (text, conference)
Data is a cross-reference to something else. The contents must match
"\(T\|C\|P\)\([0-9]+\) \(.*\)", where \1 specifies if the cross
reference leads to a text, conference or person, \2 specified the number
of the target (text-no, conf-no or pers-no) and \3 is simply descriptive
text.

The inherit bit is automatically cleared.


@item no-comments [4] (text)
When this item is set, the author requests that nobody comments the
text. This is advisory only; it is still possible to write comments, but
clients should advise the user that this is contrary to the author's
wishes. Data should be empty.

This item may only be set by the author. The secret, hide-creator and
inherit bits are automatically cleared.


@item personal-comment [5] (text)
When this item is set, the author requests only personal comments. This
is advisory only; it is still possible to create regular comments, but
clients should advise the user that the author prefers a personal
comment. Data should be empty.

This item may only be set by the author. The secret, hide-creator and
inherit bits are automatically cleared.


@item request-confirmation [6] (text)
The author requests that everyone who reads the text confirms having
done so by creating read-confirmation items on the text. Clients should
ask users if they wish to confirm having read the text when it is
displayed. Data should be empty.

The hide-creator, secret and inherit bits are automatically cleared.


@item read-confirm [7] (text)
This item can be taken as confirmation that the item creator has read
the text to which the item is attached. 

The hide-creator, secret and inherit bits are automatically cleared.


@item redirect [8] (conference)

When set, messages sent directly to the conference should really be
sent elsewhere. Data is PROTOCOL:ADDRESS where PROTOCOL is either
"E-mail" or "LysKOM", and ADDRESS is either an e-mail address or a
LysKOM conference. Hopefully we'll be able to replace this with a
forwardning mechanism later.

This item can only be set by the conference supervisor or in the case of
a letterbox, the person attached to the letterbox. The hide-creator and
secret bits are cleared automatically. Only one redirect can be
specified.


@item x-face [9] (conference)

Data is the face of the person in compface format. Cool, innit?

This item can only be set by the conference supervisor or in the case of
a letterbox, the person attached to the letterbox. The hide-creator and
secret bits are cleared automatically. 


@item alternate-name [10] (text, conferece)

Data is a string that the client may use as an alternate to the name of
a conference or the subject of a text. 

The inherit flag is automatically cleared.


@item pgp-signature [11] (text)

Data is a PGP signature of the text. The signature should be the
equivalent of what "pgp -sba" generates.

The secret, hide-creator and inherit bits are automatically cleared.
Signatures cannot be deleted once they have been created.


@item pgp-public-key [12] (letterbox)

Data is the public key of the person. It is desirable that the public
key contains a userid of the format "LysKOM <p\([0-9]\)@@\(.*\)>+", where
\1 is the number of the person in the LysKOM server specified in \2.

This item can only be set by the person himself. The hide-creator,
secret and inherit bits are automatically cleared.


@end table




@node Client-Specific Aux-Item Types, Experimental Aux-Item Types, Predefined Aux-Item Types, The Aux-Item List
@subsubsection Client-Specific Aux-Item Types

Client-specific items do not cause the server to perform any magic. All
the flags (except the delete flag) are left untouched, the data is not
validated in any way, and anyone can create any item. If you need more
server support than this, your item should be on the predefined list.

All tags in the range 10000-19999 are reserved for clients. Blocks of
100 numbers at a time can be assigned to specific clients. A client
should never create items with tags in a range assigned to another
client or in an unassigned range. Assigned ranges will never change.

Currently, the following ranges are assigned to clients:
@itemize @bullet
@item 10000-10099: The Elisp Client
@end itemize

If you want a range of numbers, send e-mail to the LysKOM development
group.


@node Experimental Aux-Item Types, Defining New Aux-Item Types, Client-Specific Aux-Item Types, The Aux-Item List
@subsubsection Experimental Aux-Item Types

Experimental numbers are free for all. Use 'em any way you want. All
numbers in the range 20000-29999 are for experimental use. 



@node Defining New Aux-Item Types, , Experimental Aux-Item Types, The Aux-Item List
@subsubsection Defining New Aux-Item Types

If you want a new predifined item type, just document what it does, what
the data format looks like and what the server is to do with the item
and send this to the LysKOM development group. We'll assign a number to
oooyour item and put the documentation in this document. 

If you're not sure what you want the data to look like yet, make a note
in your documentation that the data format might change. Once you have a
data format you're happy with, update the documentation so others may
use your item.

If you need serious magic in the server (more than can be specified with
the lyskomd configuration file), you'll probably have to write the code
yourself, or hope that the development group thinks your idea is so cool
we do the job for you.

The idea is not to reject any type of item, unless there's already an
item type that does the job just as well. Adding item types should be a
much less painful process than adding new calls.





@node Security, Membership and Reading, The Aux-Item List, Introduction
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@subsection Security

Security in LysKOM is based on two components. Each person has a set of
privileges and each session has a security level. Rights in the system
require both the sufficient privileges and a sufficient security
level. The privileges currently available are wheel, admin, statistic,
create-conf, create-pers and change-name. Security levels range from 0
to 255.


@table @code
@item wheel
@emph{Normally not assigned}
@table @asis
@item Level 0
Person may always log in, even when LysKOM is crowded.
@item Level 6
Person may set Priv-Bits for all persons.
@item Level 7
Person may set password for all persons.
@item Level 8
Person acts as supervisor for everything.
@item Level 10
Person can read all articles.
@end table

@item admin
@emph{Normally not assigned}
@table @asis
@item Level 1
Shut down the server@*
Set motd_of_kom@*
Read last_login
@item Level 2
Read status of secret conferences and persons@*
Read the protected parts of person and conference statuses@*
Read the entire text status, even when there are secret recipients
@item Level 3
Change everybody's names
@item Level 4
Add/remove members@*
Add/remove recipients to articles
@item Level 5
Set super-conference@*
Remove articles
@item Level 6
Set administrator
@end table

@item statistic
@emph{Normally not assigned}
@table @asis
@item Level 2
Read the statistics portions of persons, even if protected
@end table

@item create_conf
@emph{Normally assigned}
@table @asis
@item Level 0
Create conferences
@end table

@item create_pers
@emph{Normally assigned}
@table @asis
@item Level 0
Create persons
@end table

@end table


@node Membership and Reading, Client-Server Dialog, Security, Introduction
@section Membership and Reading

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Persons' memberships in conferences are represented in the protocol as
arrays of @code{Membership}-typed values. This structure contains a
record of what the person has read in that conference.
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The first part of the record is the @code{last-text-read} field. It
contains the highest local text number such that the person has read
every text with an equal or lower local number. The second part of the
record is the @code{read-texts} array, which contains the local text
numbers higher than @code{last-text-read} that are also read.
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Finding out which articles a person has read in a particular conference
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requires a few calls. Normally, a client will retrieve a batch of
perhaps 50 articles at a time. The outline of the process is as follows:
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@enumerate
@item Fetch the membership to get the @code{last-text-read}
@item Translate 50 local numbers starting as @code{last-text-read} to global
numbers.
@item Remove the local numbers that are in @code{read-texts} from the result
@item Get and translate more texts as needed.
@end enumerate

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The process is complicated because of the translation between local and
global text numbers. In the future there will hopefully be a single call
that does this work in the server.
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@node Client-Server Dialog, ,Membership and Reading , Introduction
@section Client-Server Dialog

The client-server dialog consists of two phases, establishing the connection
and the LysKOM session itself.

@subsection Connecting to the Server

A connection to the server is initiated by connecting to the appropriate
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network port@footnote{The default port for a LysKOM server is 4894} and
sending a single letter which is used to select a protocol version
followed by connection information required by that protocol. In
protocol A the connection information is a Hollerith string saying who
the user connecting is followed by a hewline character.
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When the server has accepted the connection its reply is
protocol-dependent. Protocol A servers will reply with the string
@code{LysKOM} on a single line.

@example
        % telnet kom.lysator.liu.se
        Trying 130.236.254.151 ...
        Connected to varg.lysator.liu.se.
        Escape character is '^]'.
        A5Hbyers
        LysKOM
@end example

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After connecting, calls to the server can be made. Most calls require
the user to log in, but some calls can be made without a log-in. Calls
to the server are made by sending a reference number followed by the
call as specified.
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@example
        server-call ::=
                ( ref-no        :       INT32;
                  request       :       Protocol-Request;
                )
@end example

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At some future point the server will reply with the result of the
request or an error code preceded by an indicator and the reference
number.
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@example