Let D be a set of datatypes, with, for each d ∈ D, a set of possible datavalues x:d. Let L be a set of labels. We consider finite labelled trees t:T with labelled, typed values x:d as leaves. Our trees have nodes of two flavours: ordered and unordered, and are subject to the restriction that the labels of the children of an unordered node must be distinct.


Formally, a tree is constructed inductively as one of three cases

  • a leaf nodet = L(l, x:d) where x:d is a typed data value
    an ordered nodet = O(l, xs)where xs is a list of trees
    an unordered nodet = U(l, a)where a: L ⇒ T is a finite partial map from labels to trees
    In each case, the label l is called the rootlabel of the tree t, denoted l = #t.

    Our model for access to the nodes allows selection of a child of an unordered node by label, and traversal of the children of an ordered node in order.

    Given a suitable representation of the underlying datavalues, such a labelled tree can be represented by an xml document, with labels as tags, and an optional attribute "unordered".

    <profile unordered="unordered">
      <institutes unordered="unordered">
        <ICCS /> <CISA /> <LFCS />
        <child>paula< /child>
        <child>maximillian< /child>
        <child>robin< /child>

    We describe a system of types s:S for such trees, and corresponding schemata for the corresponding xml documents, together with orderings ≥, the "extension" orderings on trees and schemata, such that:

    If t'≥t, t:s and s≥s' then t':s'

    First, we define the extension ordering on trees inductively t ≥ t (reflexive) O(l, x::xs) ≥ O(l, y::ys) iff x ≥ y andalso O(l, xs) ≥ O(l, ys) U(l, a) ≥ U(l, b) iff ∀ m:L. a(m) ≥ b(m) (meaning that if b(m) is defined then so is a(m), and the ordering condition holds)



    • L(l, x:d):L(l, d)
    • O(l, []):O(l, d)
    • O(l, h::xs):O(l, d) provided h:d andalso O(l, xs):O(l, d)
    • U(l, af):U(l, df) provided ∀ m. af(m):df(m) (meaning that if af(m) is defined then so is df(m), and the typing condition holds)
    • x:A(af) iff x:af(#x)

    First we suppose given a partial order ≥ on D, such that if x:d and d ≥ d' then x:d'


    man chfn

    CHPASS(1)                 BSD General Commands Manual                CHPASS(1)


         chpass, chfn, chsh, -- add or change user database information


         chpass [-a list] [-p encpass] [-e expiretime] [-s newshell] [user]


         The chpass utility allows editing of the user database information asso-
         ciated with user or, by default, the current user.
         The chfn, and chsh utilities behave identically to chpass.  (There is
         only one program.)
         The information is formatted and supplied to an editor for changes.
         Only the information that the user is allowed to change is displayed.
         The options are as follows:
         -a      The super-user is allowed to directly supply a user database
                 entry, in the format specified by passwd(5), as an argument.
                 This argument must be a colon (``:'') separated list of all the
                 user database fields, although they may be empty.  [Note that
                 this only changes the user database, master.passwd.]
         -p      The super-user is allowed to directly supply an encrypted pass-
                 word field, in the format used by crypt(3), as an argument.  [See
                 the discussion in getpwent(3) about types of passwords; this
                 option may not be appropriate.]
         -e expiretime
                 Change the account expire time.  This option is used to set the
                 expire time from a script as if it was done in the interactive
         -s newshell
                 Attempt to change the user's shell to newshell.
         Possible display items are as follows:
               Login:              user's login name
               Password:           user's encrypted password [do not use this to
                                   change a password; use passwd(1) instead]
               Uid:                user's login
               Gid:                user's login group
               Class:              user's general classification
               Change:             password change time
               Expire:             account expiration time
               Full Name:          user's real name (*)
               Home Directory:     user's home directory
               Shell:              user's login shell
               NOTE(*) -           Historically, the so-call "GECOS" field in the
                                   user database entry contain the full name plus
                                   other information.  Only the full name is cur-
                                   rently supported.
         The login field is the user name used to access the computer account.
         The password field contains the encrypted form of the user's password.
         Do not use this to change a password; use passwd(1) instead.
         The uid field is the number associated with the login field.  Both of
         these fields should be unique across the system (and often across a group
         of systems) as they control file access.
         While it is possible to have multiple entries with identical login names
         and/or identical user id's, it is usually a mistake to do so.  Routines
         that manipulate these files will often return only one of the multiple
         entries, and that one by random selection.
         The group field is the group that the user will be placed in at login.
         Since BSD supports multiple groups (see groups(1)) this field currently
         has little special meaning.  This field may be filled in with either a
         number or a group name (see group(5)).
         The class field references class descriptions in /etc/login.conf and is
         typically used to initialize the user's system resource limits when they
         The change field is the date by which the password must be changed.
         The expire field is the date on which the account expires.
         Both the change and expire fields should be entered in the form ``month
         day year'' where month is the month name (the first three characters are
         sufficient), day is the day of the month, and year is the year.
         The full name field contains the full name of the user.
         The user's home directory is the full UNIX path name where the user will
         be placed at login.
         The shell field is the command interpreter the user prefers.  If the
         shell field is empty, the Bourne shell, /bin/sh, is assumed.  When alter-
         ing a login shell, and not the super-user, the user may not change from a
         non-standard shell or to a non-standard shell.  Non-standard is defined
         as a shell not found in /etc/shells.
         Once the information has been verified, chpass uses pwd_mkdb(8) to update
         the user database.


         User database entries (among other things) are under the control of
         lookupd(8) and may be physically located in many different places,
         including local and remote netinfo(5) databases, directory service agents
         such as LDAP servers and flat file databases such as master.passwd.  This
         version of chpass is currently limited to changing user database entries
         in the flat file and local netinfo databases.


         The vi(1) editor will be used unless the environment variable EDITOR is
         set to an alternate editor.  When the editor terminates, the information
         is re-read and used to update the user database itself.  Only the user,
         or the super-user, may edit the information associated with the user.
         See pwd_mkdb(8) for an explanation of the impact of setting the
         PW_SCAN_BIG_IDS environment variable.


         /etc/master.passwd  the user database
         /etc/passwd         a Version 7 format password file
         /etc/chpass.XXXXXX  temporary copy of the password file
         /etc/shells         the list of approved shells


         finger(1), login(1), passwd(1), getusershell(3), login.conf(5),
         passwd(5), pwd_mkdb(8), vipw(8)
         and Robert Morris and Ken Thompson, UNIX Password security.


         User information should (and eventually will) be stored elsewhere.


         The chpass utility appeared in 4.3BSD-Reno.
    BSD                            December 30, 1993                           BSD

    man finger

    FINGER(1)                 BSD General Commands Manual                FINGER(1)


         finger -- user information lookup program


         finger [-46glmpshoT] [user ...] [user@host ...]


         The finger utility displays information about the system users.
         Options are:
         -4      Forces finger to use IPv4 addresses only.
         -6      Forces finger to use IPv6 addresses only.
         -s      Display the user's login name, real name, terminal name and write
                 status (as a ``*'' before the terminal name if write permission
                 is denied), idle time, login time, and either office location and
                 office phone number, or the remote host.  If -o is given, the
                 office location and office phone number is printed (the default).
                 If -h is given, the remote host is printed instead.
                 Idle time is in minutes if it is a single integer, hours and min-
                 utes if a ``:'' is present, or days if a ``d'' is present.  If it
                 is an ``*'', the login time indicates the time of last login.
                 Login time is displayed as the day name if less than 6 days, else
                 month, day; hours and minutes, unless more than six months ago,
                 in which case the year is displayed rather than the hours and
                 Unknown devices as well as nonexistent idle and login times are
                 displayed as single asterisks.
         -h      When used in conjunction with the -s option, the name of the
                 remote host is displayed instead of the office location and
                 office phone.
         -o      When used in conjunction with the -s option, the office location
                 and office phone information is displayed instead of the name of
                 the remote host.
         -g      This option restricts the gecos output to only the users' real
                 name. It also has the side-effect of restricting the output of
                 the remote host when used in conjunction with the -h option.
         -l      Produce a multi-line format displaying all of the information
                 described for the -s option as well as the user's home directory,
                 home phone number, login shell, mail status, and the contents of
                 the files .forward, .plan, .project and .pubkey from the user's
                 home directory.
                 If idle time is at least a minute and less than a day, it is pre-
                 sented in the form ``hh:mm''.  Idle times greater than a day are
                 presented as ``d day[s]hh:mm''.
                 Phone numbers specified as eleven digits are printed as ``+N-NNN-
                 NNN-NNNN''.  Numbers specified as ten or seven digits are printed
                 as the appropriate subset of that string.  Numbers specified as
                 five digits are printed as ``xN-NNNN''.  Numbers specified as
                 four digits are printed as ``xNNNN''.
                 If write permission is denied to the device, the phrase ``(mes-
                 sages off)'' is appended to the line containing the device name.
                 One entry per user is displayed with the -l option; if a user is
                 logged on multiple times, terminal information is repeated once
                 per login.
                 Mail status is shown as ``No Mail.'' if there is no mail at all,
                 ``Mail last read DDD MMM ## HH:MM YYYY (TZ)'' if the person has
                 looked at their mailbox since new mail arriving, or ``New mail
                 received ...'', ``Unread since ...'' if they have new mail.
         -p      Prevent the -l option of finger from displaying the contents of
                 the .forward, .plan, .project and .pubkey files.
         -m      Prevent matching of user names.  User is usually a login name;
                 however, matching will also be done on the users' real names,
                 unless the -m option is supplied.  All name matching performed by
                 finger is case insensitive.
         -T      Disable the piggybacking of data on the initial connection
                 request.  This option is needed to finger hosts with a broken TCP
         If no options are specified, finger defaults to the -l style output if
         operands are provided, otherwise to the -s style.  Note that some fields
         may be missing, in either format, if information is not available for
         If no arguments are specified, finger will print an entry for each user
         currently logged into the system.
         The finger utility may be used to look up users on a remote machine.  The
         format is to specify a user as ``user@host'', or ``@host'', where the
         default output format for the former is the -l style, and the default
         output format for the latter is the -s style.  The -l option is the only
         option that may be passed to a remote machine.
         If the file .nofinger exists in the user's home directory, finger behaves
         as if the user in question does not exist.
         The optional finger.conf(5) configuration file can be used to specify
         aliases.  Since finger is invoked by fingerd(8), aliases will work for
         both local and network queries.


         The finger utility utilizes the following environment variable, if it
         FINGER      This variable may be set with favored options to finger.


         /etc/finger.conf  alias definition data base
         /var/log/lastlog  last login data base


         chpass(1), w(1), who(1), finger.conf(5), fingerd(8)
         D. Zimmerman, The Finger User Information Protocol, RFC 1288, December,


         The finger command appeared in 3.0BSD.


         The current FINGER protocol RFC requires that the client keep the connec-
         tion fully open until the server closes.  This prevents the use of the
         optimal three-packet T/TCP exchange.  (Servers which depend on this
         requirement are bogus but have nonetheless been observed in the Internet
         at large.)
    BSD                              July 22, 2002                             BSD