Protocol-A.texi

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@setfilename protocol-a.info
@settitle LysKOM Protocol A
@setchapternewpage odd
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@ifinfo
This is the specification of LysKOM Protocol A v. 9.0

Copyright @copyright{} 1995-1999 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.
@end ifinfo

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

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

@page
@vskip 0pt plus 1filll
Copyright @copyright{} 1995-1999 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
This document specifies LysKOM Protocol A, version 9.0.

FIXME: This document is not yet published.  The document you are looking
at has the version numbers all wrong.  This will be fixed before
publication.

@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
@end ifinfo

@node Overview, Introduction, Top, Top
@chapter Overview

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.

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.

This specification is the work of several people. The main contributors have
been
Per Cederqvist @code{<ceder@@lysator.liu.se>}, 
David Byers @code{<byers@@lysator.liu.se>},
@ifinfo
Pär
@end ifinfo
@iftex
P@"ar
@end iftex
Emanuelsson @code{<pell@@lysator.liu.se>},
Thomas Bellman @code{<bellman@@lysator.liu.se>}, 
Lars Aronsson @code{<aronsson@@lysator.liu.se>},
Linus Tolke @code{<linus@@lysator.liu.se>} and
@ifinfo
Kent Engström
@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
@section Document Revision History

@table @asis

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

@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

@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
@item 98=query-read-texts
@item 99=get-membership
@item 100=add-member
@item 101=get-members
@item 102=local-to-global
@item 103=map-created-texts
@item 105=set-keep-commented
@end itemize

@item Removed Server Calls
@itemize @bullet
@item  5=create-person
@item  9=query-read-texts
@item 10=create-conf
@item 14=add-member
@item 26=get-text-stat
@item 28=create-text
@item 36=get-info-old
@item 46=get-membership-old
@item 48=get-members-old
@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-Input
@item Conference
@item Info
@item Member
@item Membership
@item Membership-Type
@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

@item Notes
@itemize @bullet
@item Since protocol version 9 setting a priority of zero in 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 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 9.0

@table @asis
@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
@end table

@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
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 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}.

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.


@node Notation, , Protocol Design Principles, Overview
@section Notation

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.

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

Fundamental data types have names in all-caps (such as @code{INT32} and
@code{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: @code{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, Data Types, Overview, 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 ::
* The Aux-Item List ::
* 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
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.

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}.

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 @code{local-to-global} does this.



@node Conferences, Persons and Sessions, Articles, Introduction
@section Conferences

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 mailbox
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.

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

@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
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 of 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



@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
@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.

Connections to the server are represented as values of the type
@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.


@node The Misc-Info List, The Aux-Item List, Persons and Sessions, Introduction
@section The Misc-Info List

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; 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 @code
@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
@code{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 @code
@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
@code{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 involed text and the
conference status of the involved conference.  (That is, as long as the
conference isn't secret everybody is allowed to se the carbon-copy
recipient group.)

A BCC recipient group is only visible to members and supervisors of the
recipient.  This is enforced by the server.

This type of group was introduced in protocol version 10.  When
old-style calls such as @xref{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 @code
@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
@code{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 @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


@subsection Footnote To

@table @code
@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 is was added as a footnote.
@end table


@subsection Comment in

@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


@subsection Footnote in

@table @code
@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, 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 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, 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 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 (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. 

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)
Data is a cross-reference to something else. The contents consist of a
letter, a number, 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!".

The inherit bit is automatically cleared and the item can always be
deleted. 


@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. Clients should never ever create
this item without an explicit confirmation from the user that the text
has indeed been read.

The hide-creator, secret and inherit bits are automatically cleared.
Once created an item of this type cannot be deleted.


@item redirect [8] (conference)

This item indicates that texts should not be sent to the conference,
but be directed to some other target instead. Clients should notify
users that attempt to send texts to the conference of the redirect and
offer to send the text to the target of the redirect instead. A typical
use of this item would be a user that does not read LysKOM very often
and would like to advise other users to send e-mail instead.

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 forwarding mechanism
later.

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


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

Data is a string that the client may use as an alternate to the name of
a conference or the subject of a text. Note that the server does not
match against this name when performing name lookups. Clients should
only display alternate names created by the user currently logged on.

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" in PGP 2.6.2 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 rule is currently not enforced.

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


@item e-mail-address [13] (conference, letterbox, server)

Data is an RFC 822-style email address. When set on a mailbox, it
should be the email address of the person. If the person has multiple
email addresses he may set serveral e-mail-address aux-items.

The meaning of this aux-item when set on a conference that isn't a
mailbox is vague. For a conference that is used as to import a mailing
list this should be the email address of the list. For other conferences 
we haven't really defined a sensible use.

When this aux-item is set on the server it shold contain the email
address of the administrator (or administrators).

This aux-item can only be set by the supervisor of a conference or the
server administrator. The creator cannot be hidden.


@item faq-text [14] (conference, server)

Data is a decimal text number, which is a FAQ for the conference (or
server).  This aux-item can only be set by the administrator. Adding
this item to a conference or to the server automatically marks the text.
Deleting the item unmarks the text. 

This item can only be set by the supervisor or server administrator. The 
hide-creator, secret, and inherit bits are automatically cleared.


@item creating-software [15] (text)

Data is the name and version number of the client that created the
text.  This aux-item can only be set by the author of the text.  Once
set, it cannot be removed or changed.  A typical value would be
@samp{elisp-client 0.47.3}.  Setting the creating-software aux-item is
optional.

The data should be the client name, a space, and the client version used
in the @code{set-client-version} call.  The server may enforce this
restriction.

@item mx-author [16] (text)

Data is a string containing the name of the author of an imported
e-mail. Clients should display this instead of the actual author of the
text, which will be an importer ID.


@item mx-from [17] (text)

Data is the e-mail address extracted from the @code{From} header of an
imported e-mail. This field can be used by clients to construct an
address for personal (e-mail) replies to an imported message.


@item mx-reply-to [18] (text)

Data is the e-mail address extracted from the @code{Reply-To} header of
an imported e-mail. Clients should use this for constructing replies to
imported messages.


@item mx-to [19] (text)

Data is a single e-mail address, and must be valid as the contents of an
e-mail @code{To} header. Multiple @code{mx-o} items may be present. For
imported messages, these items contain the @code{To} header of the
messages.

On messages created by a LysKOM person, the @code{mx-to} items are used
by the exporter to determine that the message is to be exported and
where to send it.

@item mx-cc [20] (text)

Same as @code{mx-to}, but applies to the @code{CC} header rather than
the @code{To} header.


@item mx-date [21] (text)

Data is the send data of an imported e-mail. Its format is "YYYY-MM-DD
hh:mm:ss TZ". YYYY is the year the message was sent, MM is the month, DD 
is the day, hh is the hour, mm is the minute and ss is the second. This
date and time are given in the timezone where the message was sent. TZ
is the timezone the date is valid for. It must be of the form "+hhmm" or 
"-hhmm", where hh is the number of hours offset from UTC and mm is the
number of minutes offset. Symbolic timezones are not permitted. The
timezone specification is recommended but optional, since it is not
always available.

Clients should display this date as the date a text was written since
the imported text will have been created at a later date. 


@item mx-message-id [22] (text)

Data is the @code{Message-ID} header of an imported e-mail. This is used 
by e-mail importers. 


@item mx-in-reply-to [23] (text)

Data is a string containing one item from the @code{In-Reply-To} header
of an imported e-mail. If the @code{In-Reply-To} header contains several 
items, there will be several @code{mx-in-reply-to} items.


@item mx-misc [24] (text)

Data is a string that contains all of the headers, including
@code{Subject}, and including whose that are redundantly stored in other
aux-items. It is set by the importer. The fields are concatenated with
"\n". In other words, this item contains all headers of an imported
e-mail as they appear in the message.

@item mx-allow-filter [25] (conference)

Data is a regexp string which allows a sender (a field in the
email-header) to import the message. If none is present, the text is
imported. Several filters can exist, however, it is enough if one
positive filter matches (OR) and none negative dissallows (AND)
import. The order is of no importance. Can be set by an organizer of the
conference.

The regexp is case insensitive, and use a glob-pat style, it allows
[^]?*+(|) as constructs. Note that "." is literal. The importer is
required to check these when adding recipient of an imported text and
comply. Example of usage: (positive filter) "From:*.liu.se*",
"From:*jsk*". "From:*(jonas|jonka|jsk)*" Tests are not made on the
text-body.

However, if the string starts with a "!" the email will be rejected if
the there is a match (negative filter), even if one of the filter allowed it.  Example:
"!From:*aol*", "!Subject:*money*". 

@item mx-reject-forward [26] (conference)

Data is a string with either an email name on the same format as
aux-info rediret [8]. The mail is forwarded to this address if it was
rejected by "mx-import-filter".

@item notify-comments [27] (letterbox)

Data is a decimal text number that the user is interested in. Clients
should monitor this text for unread comments and present these to the
user in some convenient manner. This is typically used by users that
want to read comments to some text of theirs as soon as they arrive,
rather than in the normal reading order.

This item can only be set by the owner of the letterbox. No flags are
forced or 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 predefined 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
your 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
@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

Persons' memberships in conferences are represented in the protocol as
arrays of @code{Membership}-typed values. This structure contains
information about how and when the membership was created and which
texts have been read in the conference.

There are two kinds of memberships. An active membership indicates that
the person is actively participating in the conference, wants to know if 
there are unread texts and wants to receive messages send to the
conference. A passive membership is similar to no membership at all. The 
person is still a member but will not receive messages sent to the
conference and will not be notified when there are new texts. From the
user's perspective, passive membership should be like no membership at
all, but the server still remembers what the user has read in the
conference while he or she was an active member. Since protocol version
10 a bit in the membership type field of the membership structure
indicates the type of membership. Previously the server did not support
passive memberships, but there was a convention that clients should
treat the priority level zero as a passive membership.

The membership record indicates which texts have been read through the
@code{last-text-read} and @code{read-texts} fields. All texts with local 
numbers up to @code{last-text-read} have been read. In addition, all
texts with local numbers contained in the @code{read-texts} array have
been read.

Finding out which articles a person has read in a particular conference
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:

@enumerate
@item Fetch the membership to get the @code{last-text-read}
@item Use @pxref{local-to-global} to translate a number of local numbers 
to global numbers. 
@item Remove the global numbers corresponding to local numbers contained 
in @code{read-texts} from the result
@item Get and translate more texts as needed.
@end enumerate

The process is complicated because of the translation between local and
global text numbers. If the server does not implement the
@pxref{local-to-global} call, it is possible to use the less
efficient but perfectly serviceable @pxref{get-map} call instead.


@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
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 newline character.

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

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. The call @i{must} be terminated with a newline
character, but extra newlines @i{within} the call are permitted.

@example
        server-call ::=
                ( ref-no        :       INT32;
                  request       :       Protocol-Request;
                )
@end example

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.

@example
        server-reply ::= ok-reply | error-reply;

        ok-reply ::=
                ( "="
                  ref-no        :       INT32;
                  reply-data;
                )

        error-reply ::=
                ( "%"
                  ref-no        :       INT32;
                  error-no      :       Error-No;
                  error-status  :       INT32;
                )

        error-no ::= INT32;
@end example

Our notation is not flexible enough to specify the two-way nature of the
communication. @code{ref-no} in the reply is always the same as
@code{ref-no} in the corresponding request. @code{reply-data} depends on
which request was made and is specified together with each request.

Please note that there is no whitespace after the initial indicator in
the reply.

Error reporting is covered in more detail in chapter @ref{Error Codes}.


@node Data Types, Protocol Requests, Introduction, Top
@chapter Data Types

The data types in protocol A come in two flavors. The first (vanilla)
are the simple data types from which the LysKOM (chocolate) data types
are built. Simple data types include things like integers and strings
while complex data types include things such as conferences and people.

@menu
* Simple Data Types::
* LysKOM Data Types::
* Name Expansion::
@end menu

@node Simple Data Types, LysKOM Data Types, Data Types, Data Types
@section Simple Data Types

Data elements are sent from client to server separated by one or more
ASCII spaces (0x20), tab characters (0x09), line feeds (0x0A) or
carriage returns (0x0D.) In messages from server to client the data
elements are separated by exactly one space character and the entire
message terminated with a line feed.


@subsection Integers

@tindex INT32
@tindex INT16
@tindex INT8
@tindex BOOL
@dfn{INT32}, @dfn{INT16}, @dfn{INT8} and @dfn{BOOL} are non-negative
integers which must fit in 32, 16, 8 and 1 bits, respectively. They are
transmitted to the server in ASCII-encoded decimal notation.


@subsection Strings

@tindex HOLLERITH
@dfn{HOLLERITH} denotes character strings of arbitrary length. They are
transmitted as @code{<n>H<text>} where @code{<text>} is the string and
@code{<n>} is the number of characters in @code{<text>} in decimal
notation. All byte values are allowed in the string itself, including
nulls.

Long live FORTRAN!



@subsection Bit Strings

@tindex BITSTRING
@dfn{BITSTRING} is a string of bits, commonly used for a set of
boolean-valued flags. Bit strings are denoted as

@example
        BITSTRING ( name-1; name-2; name-3; ... )
@end example

in this specification. They are transmitted as a sequence of ASCII ones
and zeroes in the order the fields are listed.

For instance, given the specification

@example
        shape-of-world : BITSTRING (
                is-flat;
                is-round;
                is-2d;
                is-3d;
        )
@end example

most peoples idea of @code{shape-of-world} would be sent as @code{0101}
(round and three-dimensional.)


@subsection Enumerations

@tindex ENUMERATION
@dfn{ENUMERATION} is an integer constant. It is transmitted as an INT32, 
but only fixed values are permitted. Clients should be prepared to
receive numbers outside the enumeration and either handle this
gracefully as an error or use a reasonable default value in place of an
invalid enumeration value.

An enumeration is specified as 

@example
        ENUMERATION ( 
                name-1=value-1;
                name-2=value-2;
                name-3=value-3;
                ...
        )
@end example

This specification states that name-1 is represented by the integer
value-1, name-2 is represented by value-2 and name-3 is represented by
value-3. 

For example, in the following specification, the constant guwal will be
transmitted as the integer 2, ciokwe as the integer 3, and hopi as the
integer 5.

@example
        language : ENUMERATION ( hakka      = 1;
                                 guwal      = 2;
                                 ciokwe     = 3;
                                 yoruba     = 4;
                                 hopi       = 5;
                )
@end example




@subsection Arrays

@tindex ARRAY
@dfn{ARRAY} is a list of a fixed number of elements of a single type.
The specification for an array is @code{ARRAY <type>} where
@code{<type>} is the type of the array elements.

Arrays are transmitted as an @code{<n> @{ <element> <element> ... @}}
where @code{<n>} is the number of elements and each @code{<element>} is
an element of the array. A special case is when the array is empty, in
which case the server transmits it as @code{0 *}. Note that the client
must always transmit empty arrays as @code{0 @{ @}}.

In some calls the client can ask the server not to send the array
contents, only its length. In these cases the array is transmitted as
@code{<n> *} where @code{<n>} is the number of elements in the array.


@subsection Selection

@tindex SELECTION
@dfn{SELECTION} is tagged data. It consists of an INT32 selector
followed by a tail of an arbitrary type and is specified as

@example
        SELECTION (
                <n>=<name>        <tail> : <type>;
                <n>=<name>        <tail> : <type>;
                ...
        )
@end example

where each @code{<n>} is the selector value, @code{<name>} the selector
name and @code{<tail>} the name of the selector tail and @code{<type>}
its type.

When transmitted, the selector is transmitted as an INT32 followed by
the tail belonging to that selector. For instance, given the
specification

@example
        phrase : SELECTION (
               1=hello          name : HOLLERITH;
               2=howdy          ;
        )
@end example

two legal messages of the type @code{phrase} are @samp{1 4HJohn} and
@samp{2}.


@subsection RPC

@tindex RPC
@dfn{RPC} is a notation used to specify calls to the server. An RPC
specification has the following form:

@example
        RPC (
                <call> <<n>> ( <request> ) -> ( <reply> ) ;
                <call> <<n>> ( <request> ) -> ( <reply> ) ;
        )
@end example

where each @code{<call>} is the name of a call, @code{<n>} is the call
number, @code{<request>} is a single data element sent as a request and
@code{<reply>} is a single data element sent in reply from the server.

RPC calls are transmitted as @code{<n> <request>} where @code{<n>} and
@code{<request>} have the same meaning as above. Note that in the
client-server dialog a reference number must also be supplied with each
request. This reference number is not part of the RPC itself, but is
required for communications @xref{Client-Server Dialog}.



@subsection Structure

Structures are collections of several data items. In the specification
they are written as

@example
        ( <name> : <type> ;
          <name> : <type> ;
          ...
        )
@end example

where each @code{<name>} is the name of a data field and the
corresponding @code{<type>} is its type.

Structures are transmitted as a sequence of their fields.