Protocol-A.texi

\input texinfo                         @c -*-texinfo-*-
@c
@c FIXME: Explain how the garb works with nice and keep-commented
@c FIXME: @i{Example:} is only used in front of some examples.
@c FIXME: @} in examples sometimes lack a leading space.
@c FIXME: Is there any ``Upright text in a reply''?
@c FIXME: @ref, @xref and @pxref are used wrongly.
@c FIXME: Make all types clickable in HTML (and info?)
@c FIXME: Check for @ifinfo that should be @ifnottex.
@c
@c $Id: Protocol-A.texi,v 1.112 2001/04/19 08:22:06 ceder Exp $
@c %**start of header
@setfilename protocol-a.info
@settitle LysKOM Protocol A
@setchapternewpage odd
@c @afourpaper
@c %**end of header

@set PROTOEDITION 10.4
@set PROTOVER 10
@set VERSION 1.0.4

@c @req{login} is used for protocol requests.
@macro req {n}
@code{\n\}
@end macro

@c @aux{mx-allow-filter} is used for aux-item names.
@macro aux {n}
@code{\n\}
@end macro

@c @async{async-login} is used for async names.
@macro async {n}
@code{\n\}
@end macro

@c @type{Conference} is used for LysKOM types.
@macro type {n}
@code{\n\}
@end macro

@c @priv{wheel} is used for privilege bits.
@macro priv {n}
@code{\n\}
@end macro

@c @conftype{rd-prot} is used for conference type bits.
@macro conftype {n}
@code{\n\}
@end macro

@c @misc{bcc-recpt} is used for misc-info names.
@macro misc {n}
@code{\n\}
@end macro

@c @rarg{passwd} is used to reference arguments of requests.  This is
@c *only* used in the nodes that defines the requests.
@macro rarg {n}
@code{\n\}
@end macro

@c @aarg{text-no} is used to reference arguments of asynchronous
@c messages.  This is *only* used in the nodes that defines the
@c relevant asynchronous message.
@macro aarg {n}
@code{\n\}
@end macro

@c @errorcode{no-such-text} is used to mark error codes.
@macro errorcode {n}
@code{\n\}
@end macro

@c @field{ident-user} is used to mark fields of struct types.
@macro field {n}
@code{\n\}
@end macro

@ifinfo
This is the LysKOM Protocol A specification, edition
@value{PROTOEDITION}.  It specifies version @value{PROTOVER} of the
protocol.  It corresponds to version @value{VERSION} of lyskomd.

Copyright @copyright{} 1995-2000 Lysator ACS.

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.

@ignore
Permission is granted to process this file through TeX
and print the results, provided the printed document
carries a copying permission notice identical to this
one except for the removal of this paragraph (this
paragraph not being relevant to the printed manual).
@end ignore

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 ifinfo

@c FIXME: What does this do?
@iftex
@parindent 0pt
@font@tensltt=cmsltt10
@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
@end iftex

@titlepage
@title{LysKOM Protocol A}
@subtitle{Protocol version @value{PROTOVER}}
@subtitle{Edition @value{PROTOEDITION}}
@subtitle{(lyskomd @value{VERSION})}
@author by the LysKOM Developers

@page
@vskip 0pt plus 1filll
Copyright @copyright{} 1995-2000 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
@ifnothtml
@contents
@end ifnothtml

@dircategory LysKOM
@direntry
* Protocol A: (protocol-a).             The LysKOM Protocol A specification.
@end direntry

@ifhtml
@html
<a href="http://www.lysator.liu.se/" ><img
src="http://www.lysator.liu.se/icons/lyslogo.gif" alt="Lysator"
width=40 border=0 height=40 align=left ></a>

<a href="http://www.lysator.liu.se/lyskom/" ><img
src="http://www.lysator.liu.se/icons/lyskom.gif" alt="LysKOM" width=40
border=0 height=40 align=left ></a>
<br clear=all>
@end html
@end ifhtml
@ifnottex
@node Top
@top LysKOM Protocol A

This document specifies version @value{PROTOVER} of LysKOM Protocol A.
This is edition @value{PROTOEDITION} of the specification.  It
corresponds to version @value{VERSION} of lyskomd.

The most up-to-date version if this document can always be found at 
@uref{http://www.lysator.liu.se/lyskom/protocol/}.
@end ifnottex

@menu
* Overview::                    
* Introduction::                
* Data Types::                  
* Protocol Requests::           
* Asynchronous Messages::       
* Error Codes::                 
* LysKOM Content Types::        
* The User Area::               
* Writing Clients::             
* Importing and Exporting E-Mail::  
* Type Index::                  
* Request Index::               
@end menu

@node Overview
@chapter Overview

@iftex
This document specifies version @value{PROTOVER} of LysKOM Protocol A.
This is edition @value{PROTOEDITION} of the specification.  It
corresponds to version @value{VERSION} of lyskomd.

The most up-to-date version if this document can always be found on
the web at @uref{http://www.lysator.liu.se/lyskom/protocol/}.
@end iftex

LysKOM is a conferencing system@footnote{Or in modern terms, enabling
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.

Anything described here as ``unspecified'' is liable to change in
future protocol versions.

This specification is the work of several people. The main contributors have
been
Per Cederqvist @email{ceder@@lysator.liu.se}, 
David Byers @email{byers@@lysator.liu.se},
@ifinfo
Pär
@end ifinfo
@iftex
P@"ar
@end iftex
Emanuelsson @email{pell@@lysator.liu.se},
Thomas Bellman @email{bellman@@lysator.liu.se}, 
Lars Aronsson @email{aronsson@@lysator.liu.se},
Linus Tolke @email{linus@@lysator.liu.se} and
@ifinfo
Kent Engström
@end ifinfo
@iftex
Kent Eng@-str@"om@penalty-10000
@end iftex
@email{kent@@lysator.liu.se}.

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

@menu
* Document Edition History::   
* Protocol Version History::    
* Notation::                    
@end menu

@node Document Edition History
@section Document Edition History

@table @asis

@item 10.4: 2001-04-07
Editorial changes needed to publish an online version on the web at
@uref{http://www.lysator.liu.se/lyskom/protocol/}.

@item 10.3: 2000-09-09
Several aux-items can be set on letterboxes and not only conferences.  A
few can now be set on the server.  The @aux{allowed-content-type} and
@aux{recommended-conf} aux-items were added.  The
@aux{mx-allow-filter} and @aux{mx-reject-forward} aux-items are marked
obsolete.  Text regarding mail import was improved, based on actual
experience in writing an email importer.  Reserved a range of aux-items
for komimportmail.  Several minor corrections and clarifications made.
Distributed with lyskomd 2.0.4.

@item 10.2: 1999-07-23
Some typos and other minor errors were fixed.  Distributed with lyskomd
2.0.2.

@item 10.1: 1999-07-12
Call @req{sub-comment} was incorrectly marked obsolete. This has been
corrected. Regexps are case sensitive.  The Info-Type enumeration was
introduced in the description of the protocol.  (Previous versions of
the protocol had broken definitions of add-recipient,
async-new-recipient and async-sub-recipient.)  Distributed with lyskomd
2.0.1.

@item 10.0: 1999-06-27
The specification was translated to English and converted to Texinfo by
David Byers.  Protocol version 10.  Distributed with lyskomd 2.0.0.
Note: this edition incorrectly marked the @req{sub-comment} call as
obsolete, and stated that regexp lookup was case insensitive.  Both
statements were wrong, and has since been fixed.

@item 9.0: 1996-08-04
Protocol version 9.  Distributed with lyskomd 1.9.0.

@item 8.0: 1995-11-10
Protocol version 8.  Distributed with lyskomd 1.8.0.

@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 Version History
@section Protocol Version History

@subsection Protocol version 10 (first implemented in lyskomd 2.0.0)

@table @asis

@item Error codes

The error codes are now documented.  Several error codes were changed to
more sane values while documenting the new behaviour.

@item New Server Calls

These new calls have status Recommended.

@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 98=query-read-texts
@item 99=get-membership
@item 100=add-member
@item 101=get-members
@item 102=set-membership-type
@item 103=local-to-global
@item 104=map-created-texts
@item 106=set-pers-flags
@end itemize

These new calls have status Experimental.

@itemize @bullet
@item 97=set-expire
@item 105=set-keep-commented
@end itemize

@item Name changes

@multitable {59=create-anonymous-text} {59=create-anonymous-text-old}
@item Old name                 @tab New name
@item 5=create-person          @tab 5=create-person-old
@item 9=query-read-texts       @tab 9=query-read-texts-old
@item 10=create-conf           @tab 10=create-conf-old
@item 13=get-conf-stat-old     @tab 13=get-conf-stat-older
@item 14=add-member            @tab 14=add-member-old
@item 26=get-text-stat         @tab 26=get-text-stat-old
@item 28=create-text           @tab 28=create-text-old
@item 36=get-info              @tab 36=get-info-old
@item 46=get-membership        @tab 46=get-membership-old
@item 48=get-members           @tab 48=get-members-old
@item 50=get-conf-stat         @tab 50=get-conf-stat-old
@item 59=create-anonymous-text @tab 59=create-anonymous-text-old
@end multitable

@item Status change

The following calls have change status from Experimental to Recommended.

@itemize @bullet
@item 58=get-last-text
@item 77=set-last-read
@item 78=get-uconf-stat
@end itemize

The following calls have changed status from Recommended or
Experimental to Obsolete.

@itemize @bullet
@item 5=create-person-old
@item 9=query-read-texts-old
@item 10=create-conf-old
@item 14=add-member-old
@item 26=get-text-stat-old
@item 28=create-text-old
@item 36=get-info-old
@item 46=get-membership-old
@item 47=get-created-texts
@item 48=get-members-old
@item 50=get-conf-stat-old
@item 59=create-anonymous-text-old
@end itemize

@item New and Modified Structures
@itemize @bullet
@item Aux-Item
@item Aux-Item-Input
@item Conference
@item Info
@item Member
@item Membership
@item Membership-Type
@item Misc-Info
@item Text-Stat
@end itemize

@item Renamed Asynchronous Messages
A @samp{async-} prefix has been added to the name of all asynchronous
messages.  In addition, 0=new-text has been renamed to
0=async-new-text-old, and it is now considered obsolete.  Clients should
use 80=accept-async to listen to 15=async-new-text instead.

@item New Asynchronous Messages
@itemize @bullet
@item 14=async-deleted-text
@item 15=async-new-text
@item 16=async-new-recipient
@item 17=async-sub-recipient
@item 18=async-new-membership
@end itemize

@item Notes
@itemize @bullet
@item Since protocol version 9 setting a priority of zero for a
conference was supposed to indicate passive membership in a conference. 
It was largely up to the client to implement this. True passive
memberships have been introduced in this protocol version through the
Membership-type extension to the Membership type. In order to maintain
compatibility with clients that interpret priority 0 as passive
membership, the old calls @pxref{add-member-old} and
@pxref{get-membership-old} perform magic, translating between priorities 
and membership types. The magic is documented with each call.
@end itemize
@end table


@subsection Protocol version 9 (first implemented in lyskomd 1.9.0)

@table @asis
@item New functionality
@itemize @bullet
@item The server shall now reply with error @errorcode{not-implemented} when
a client attempts to use an unimplemented call.  This feature requires
that the client uses newline as call terminator.
@end itemize
@item Added Commands
@itemize @bullet
@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
@end itemize
@item Changed names
@itemize @bullet
@item @req{change-conference} was previously called @code{pepsi}.  The
name was changed, but not the functionality.
@end itemize
@item Status change
@itemize @bullet
@item 63=@req{who-is-on-ident} is now considered obsolete.
@item 64=@req{get-session-info-ident} is now considered obsolete.
@end itemize
@end table

@subsection Protocol version 8 (first implemented in lyskomd 1.8.0)

@table @asis
@item Added Functionality
@itemize @bullet
@item
30=add-recipient: Can change @misc{recpt} to @misc{cc-recpt} and vice versa.
@item
21=set-conf-type: Accepts @type{Conf-Type} and @type{Extended-Conf-Type}.
@item
10=create-conf: Accepts @type{Conf-Type} and @type{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
The asynchronous message 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 Notation
@section Notation

This specification uses a BNF-like grammar to describe the protocol and
its data elements.

Data fields have been given names that start with a lower-case letter.

Fundamental data types have names in all-caps (such as @type{INT32} and
@type{ARRAY}).

Derived data types have names that start with an upper-case letter. (If
the type contains more than one word, all words start with an upper-case
letter, like this: @type{Text-Stat}.)  The operator @code{::=} defines
the name to its left.

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.


@node Introduction
@chapter Introduction

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

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


@node Articles
@section Articles

An article is represented as a value of the type @type{Text-Stat} and a
string containing the article contents. An article will usually have one
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
@field{nice} value of each of its recipients and it is not marked by any
user.

Currently there is an array of @type{Misc-Info} included in the
@type{Text-Stat}. This array contains information about recipients,
senders, comments and footnotes. In the future the information
contained in the @type{Misc-Info} array will be integrated into the
@type{Text-Stat}.

Every article has at least one number, the global article number. Global
numbers are assigned in ascending order to new articles, and are never
reused. If an article has recipients it will also have a local number
for each recipient. Local numbers are used in some data structures to
provide more compact storage and to provide 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.

Occasionally it is necessary to map between local and global numbers.
The server call @req{local-to-global} does this.



@node Conferences
@section Conferences

Conferences hold articles. They are represented in the protocol as a
data type called @type{Conference}. Each conference has a
@dfn{creator}, the person who created the conference, and a
@dfn{supervisor}, a conference whose members can modify the conference.
If the supervisor is a person, the members of that person's mailbox
are supervisors, which in most cases is only that person. We have also
introduced a type called @type{UConference} (pronounced micro-conf-stat)
which holds a subset of the information contained in the full
@type{Conference} type. Use the @type{UConference} type whenever
possible since it places a much smaller load on the LysKOM server.

Each conference has a type, which is essentially a collection of
boolean flags. Currently the flags @conftype{rd-prot},
@conftype{letterbox}, @conftype{secret}, @conftype{original},
@conftype{allow-anonymous} and @conftype{forbid-secret} are defined.

@table @conftype
@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
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.
@item letterbox
Conferences of this type are connected to persons. Letters to a person
are sent to the mailbox and the name of the mailbox is synchronized
with the person name. It is currently not possible to explicitly set or
clear this flag on a conference.
@item secret
Conferences of this type are secret. The server will not divulge any
information about the existence of the conference to persons who are not
members or supervisors of the conference. If a mailbox is made secret,
that person cannot log in using the person name, but must specify a
person number instead.
@item allow-anonymous
Conferences of this type accept anonymous articles. Other conferences
will reject anonymous articles.
@item forbid-secret
Conferences of this type do not allow secret members. If a conference is 
changed to this type, preexisting secret members remain secret.
@end table



@menu
* Persons and Sessions::        
@end menu

@node Persons and Sessions
@subsection Persons and Sessions

Persons are represented in the protocol by values of the type
@type{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 @conftype{letterbox} bit set.

Connections to the server are represented as values of the type
@type{Static-Session-Info}, @type{Session-Info-Ident} or
@type{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.


@node The Misc-Info List
@section The Misc-Info List

The @type{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; blank 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.

@subsection Recipient

@table @misc
@item recpt
Starts a recipient group. It contains the conference number of a
recipient of the article.
@item loc-no
Always present within a recipient group. It contains the local text
number of the article in the conference specified by the preceding
@misc{recpt} field.
@item rec-time
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.
@item sent-by
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.
@item sent-at
Present when the recipient was added after the article was created. It
contains the time when the recipient was added.
@end table


@subsection Carbon Copy (CC) Recipient

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. This difference is enforced by the clients.

@table @misc
@item cc-recpt
Starts a carbon-copy recipient group. It contains the conference number
of a carbon-copy recipient of the article.
@item loc-no
Always present in a CC recipient group. It contains the local text
number of the article in the conference specified by the most recent
@misc{cc-recpt} field.
@item rec-time
Present after the CC recipient has read the article. It contains the
time when the article was read. Since only persons can read articles
this will only be seen if the CC recipient is a person.
@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


@subsection Blank Carbon Copy (BCC) Recipient

The blank carbon-copy recipient group is identical to the carbon-copy
recipient group above. The difference is the visibility of the
information. A carbon-copy recipient group is visible to anyone that is
allowed to fetch both the text status of the involved text and the
conference status of the involved conference.  (That is, as long as the
conference isn't secret everybody is allowed to see the carbon-copy
recipient group.)

A BCC recipient group is basically only visible to members and
supervisors of the recipient.  Persons that have the right to become a
member of the recipient can also see it, as can the author of the text
(unless the recipient is secret to him).  This is enforced by the
server.

This type of group was introduced in protocol version 10.  When
old-style calls such as get-text-stat-old (@pxref{get-text-stat-old})
are used this will be converted to a CC recipient group by the server
for the benefit of clients that don't understand this group.

@table @misc
@item bcc-recpt
Starts a blank carbon-copy recipient group. It contains the conference
number of a blank carbon-copy recipient of the article.
@item loc-no
Always present in a BCC recipient group. It contains the local text
number of the article in the conference specified by the most recent
@misc{bcc-recpt} field.
@item rec-time
Present after the BCC recipient has read the article. It contains the
time when the article was read. Since only persons can read articles
this will only be seen if the BCC recipient is a person.
@item sent-by
Present when a BCC 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 BCC recipient.
@item sent-at
Present when a BCC recipient was added after the article had been
created. It is the time when the BCC recipient was added.
@end table


@subsection Comment To

@table @misc
@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 it was added as a comment.
@end table


@subsection Footnote To

@table @misc
@item footn-to
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 it was added as a footnote.
@end table


@subsection Comment in

@table @misc
@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


@subsection Footnote in

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


@node The Aux-Item List
@section 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
@subsection 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 mailbox 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 identifies 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
@subsection Predefined Aux-Item Types

Predefined Aux-Item types are part of Protocol A, and clients should
support all of them. As with other parts of the protocol, changes to
these definitions will be made backwards-compatible, if possible.

Creation and deletion of items with a predefined type can cause
arbitrarily complex and wonderous behavior in the server. Furthermore,
the server may place constraints on the items with regard to content,
flags, who can create them, to what objects they can be attached and
so forth. The server may also silently enforce specific values for any
field of an item, regardless of what the client requests.

All items with tags in the range 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 (illegal-aux-item.)

Some of the aux-items below (mostly the ones that begin with "mx-") are
used by mail importers. For information about supplementary aux-items
introduced by @command{komimportmail}, see @ref{komimportmail Aux-Item Types}.

@table @samp
@item content-type [1] (text)
Specifies the content type of a text. Data is a valid MIME type or 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. 

An item of this type will never be inherited, can always be deleted, is
never anonymous and is never secret.


@item cross-reference [3] (text, conference, letterbox)
Data is a cross-reference to something else. The contents consist of a
letter, a number, and optionally a space and a descriptive text. The
letter must be one
of T, C or P. T specifies that the cross-reference points to a text; C
that it points to a conference; and P that it points to a person. The
number is the id of the target of the cross reference. The descriptive
text is simly that, a text that describes the cross-reference. For
example, "T15 Check this out!" is a cross reference to text 15 with a
description that reads "Check this out!", and "T17" is a cross reference
without a description.