Internet Info 1997 December/Internet_Info_CD-ROM_Walnut_Creek_December_1997.iso/faqs/comp/answers/z-faq

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Summary: Information about the Z formal specification notation
URL: http://www.comlab.ox.ac.uk/archive/z.html
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Archive-name: z-faq
Last-modified: 29 September 1997
Maintainer: Jonathan Bowen <[e-mail]>
URL: ftp://ftp.comlab.ox.ac.uk/pub/Zforum/faq

NAME:     comp.specification.z
STATUS:   unmoderated
PURPOSE:  Discussion concerning the formal specification notation Z.

(If you have read this before, changed and new sections since the
previously issued version are marked with `|' in the left hand margin.)

Questions have been marked with "Subject:" at the start of the line to
allow some newsreaders to scan them easily (e.g., "^G" within "rn").

Subject: What is it?

Z (pronounced `zed') is a formal specification notation based on set
theory and first order predicate logic. It has been developed at the
Programming Research Group at the Oxford University Computing
Laboratory (OUCL) and elsewhere since the late 1970s.  It is used
by industry as part of the software (and hardware) development process
in Europe, USA and elsewhere. Currently it is undergoing international
ISO standardization.
  The comp.specification.z electronic USENET newsgroup was established
in June 1991 and is intended to handle messages concerned with Z.
It has an estimated readership of tens of thousands of people worldwide.
Comp.specification.z provides a convenient forum for messages concerned
with recent developments and the use of Z.  Pointers to and reviews of
recent books and articles are particularly encouraged. These may be
included in the Z bibliography (see below) if they appear in
comp.specification.z.

Subject: What if I do not have access to USENET news?

There is an associated Z FORUM electronic mailing list that was
initiated in January 1986 by Ruaridh Macdonald, RSRE, UK.  Articles are
now automatically cross-posted between comp.specification.z and the
mailing list for those whose do not have access to USENET news.  This
may apply especially to industrial Z users who are particularly
encouraged to subscribe and post their experiences to the list.  Please
contact <[e-mail]> with your name, address and
email address to join the mailing list (or if you change your email
address or wish to be removed from the list). Readers are strongly
urged to read the comp.specification.z newsgroup rather than the Z
FORUM mailing list if possible. Messages for submission to the Z FORUM
mailing list and the comp.specification.z newsgroup may be emailed to
<[e-mail]>.  This method of posting is particularly
recommended for important messages like announcements of meetings since
not all messages posted on comp.specification.z reach the OUCL.
  A mailing list for the Z User Meeting educational issues session has
been set by Neville Dean, Anglia Polytechnic University, UK.  Anyone
interested may join by emailing <[e-mail]> with
your contact details.
  A specialist electronic mailing for discussion of SAZ, a combination
of the structured method SSADM and Z existed for a while, but is now closed.

Subject: What if I do not have access to email?

If you wish to join the postal Z mailing list, please send your address
to Amanda Kingscote, Praxis Critical Systems Ltd, 20 Manvers Street,
Bath BA1 1PX, UK  (tel [phone], fax [phone], email
<[e-mail]>).  This will ensure you receive details of Z
meetings, etc., particularly for people without access to electronic
mail.

Subject: How can I join in?

If you are currently using Z, you are welcome to introduce yourself to
the newsgroup and Z FORUM list by describing your work with Z or
raising any questions you might have about Z which are not answered
here. You may also advertize publications concerning Z which you or
your colleagues produce. These may then be added to the master Z
bibliography maintained at the OUCL (see below).

Subject: Where are Z-related files archived?

Information on the World Wide Web (WWW) is available under the
http://www.comlab.ox.ac.uk/archive/z.html page.  See also the
http://www.comlab.ox.ac.uk/archive/formal-methods.html page on formal
methods in general. The WWW global hypermedia system is accessible using
the "netscape", "mosaic" or "lynx" programs for example. Contact your
system manager if WWW access is not available on your system.
  Some of the Z archive is also available via anonymous FTP under
ftp://ftp.comlab.ox.ac.uk/pub/Zforum (IP address 163.1.27.2 if you have
access problems). The README file provides some general information and
00index gives a list of the files. If you cannot access the Internet
directly, there is an automatic electronic mail-based electronic archive
server which allows access to some of the Z FTP archive. Send an email
message containing the command "help" to <[e-mail]>
for further information on how to use the server. If you have serious
trouble accessing the archive server, please contact the address
<[e-mail]>.

Subject: What tools are available?

Various tools for formatting, type-checking and aiding proofs in Z are
available.  A free LaTeX style file and documentation can be obtained from
the OUCL archive.  Access the ftp://ftp.comlab.ox.ac.uk/pub/Zforum/zed.sty
and ftp://ftp.comlab.ox.ac.uk/pub/Zforum/zguide.tex files.  A newer
style "csp_zed.sty" is available in the same location, which uses the
new font selection scheme and covers CSP and Z symbols. A style for
Object-Z "oz.sty" with a guide "oz.tex" is also accessible.  LaTeX2e
users may find "zed-csp.sty" and "zed2e.tex" useful.
  The FuZZ package, a syntax and type-checker with a LaTeX style option
and fonts, is available from the Spivey Partnership, 10 Warneford Road,
Oxford OX4 1LU, UK.  It is compatible with the 2nd edition of Spivey's Z
Reference Manual. Access http://www.comlab.ox.ac.uk/oucl/software/fuzz.html
for brief information including ordering.  Contact Mike Spivey (email
<[e-mail]>) for further information.
  CADiZ is a suite of integrated tools for preparing and type-checking
Z specifications as professional quality typeset documents.  The Z
dialect it recognizes is evolving in line with the standard.  The
typesetting can be performed by either troff or LaTeX for Unix or Word
for Windows.  The mouse can be used to interact with a view of the
typeset specification to inspect properties deduced by the type-checker,
to see the expansion of schema calculus expressions, and to reason
about conjectures such as proof obligations.  The PC version is
integrated with MS Word using OLE2, providing WYSIWYG editing of Z
paragraphs directly in Word documents.  (The troff and LaTeX versions
use ordinary text editors on ASCII mark-up.) Further development of the
tools is ongoing.  CADiZ is a BCS Award winning product available for
Sun, SGI and PC machines from York Software Engineering Ltd, The
Innovation Centre, York Science Park, Heslington, York, YO1 5DG, UK
(email <[e-mail]>, tel [phone], fax [phone]).
  ProofPower is a suite of tools supporting specification and proof in
Higher Order Logic (HOL) and in Z. As an option, ProofPower also supports
verification of SPARK-Ada programs against Z specifications using the
Compliance Notation designed by DERA.  Short courses on ProofPower-Z
are available as demand arises.  Information about ProofPower can be
obtained from http://www.trireme.demon.co.uk/ on the World Wide Web.
Please address enquiries to <[e-mail]> or to
Roger Jones, International Computers Ltd., Lovelace Road, Bracknell,
RG12 8SN, UK (tel [phone]).
  Zola is a commercial integrated support tool for Z on Sun workstations,
for automated assistance at all stages of the specification construction,
proving and maintenance process.  It is intended for system developers
and includes a WYSIWYG editor, type-checker and tactical theorem prover
suitable for the creation and maintenance of large specifications.  For
further information, contact Chris Paine, Imperial Software Technology
Ltd, Berkshire House, 252 Kings Road, Reading RG1 4HP, UK (tel
[phone], fax [phone], email <[e-mail]>), or see:
http://www.ist.co.uk/products/zola.html
  ZTC is a Z type-checker available free of charge for educational and
non-profit uses. It is intended to be compliant with the 2nd edition of
Spivey's Z Reference Manual. It accepts LaTeX with "zed" or "oz"
styles, and ZSL - an ASCII version of Z.  ZANS is a Z animator. It is a
research prototype that is still very crude.  Both ZTC and ZANS run on
Linux, SunOS 4.x, Solaris 2.x, HP-UX 9.0, DOS, and extended DOS. They
are available via anonymous FTP under ftp://ise.cs.depaul.edu/pub in
the directories ZANS-x.xx and ZTC-x.xx, where x.xx are version numbers.
Contact Xiaoping Jia <[e-mail]> for further information.
  Formaliser is a syntax-directed WYSIWYG Z editor and interactive type
checker, running under Microsoft Windows, available from Logica.
Contact Susan Stepney, Logica UK Limited, Cambridge Division, Betjeman
House, 104 Hills Road, Cambridge CB2 1LQ, UK  (tel [phone], fax
[phone], email <[e-mail]>) or see under
http://public.logica.com/~formaliser/formlsr/formlsr.htm on-line.
  DST-fuzz is a set of tools based on the fuzz package by Mike Spivey,
supplying a Motif based user interface for LaTeX based pretty printing,
syntax and type-checking. A CASE tool interface allows basic
functionality for combined application of Z together with structured
specifications. The tools are integrated into SoftBench. For further
information contact Hans-Martin Hoercher, DST Deutsche System-Techik
GmbH, Edisonstr. 3, D-24145 Kiel, Germany (tel [phone], fax
[phone], email <[e-mail]>).
  The B-Toolkit is a set of integrated tools which fully supports the
B-Method for formal software development and is available from B-Core
(UK) Limited, Magdalen Centre, The Oxford Science Park, Oxford OX4 4GA,
UK. For further details, contact Ib Sorensen (tel [phone],
fax [phone], email <[e-mail]>) or see
http://www.b-core.com/ on-line.
  Nitpick is a freely available tool for fully automatically analyzing
software specifications in (roughly) a subset of Z. See
http://www.cs.cmu.edu/~nitpick/
  Z/EVES is an analysis tool for Z specifications, that can be used to
check for syntax, type-correctness and "domain errors" (are functions
applied on their domain?), expand schemas, calculate preconditions and
check for totality, and state and prove conjectures, with the aid of a
heuristic theorem prover.  It supports the "zed"/"fuzz" style LaTeX
markup.  and runs on SunOS, OS/2, Linux, Windows 3.1, Windows'95 and,
with the appropriate compatibility package from Sun, Solaris.  It is
available electronically at no cost. Email [e-mail] or see:
http://www.ora.on.ca/distribution.html
  Z fonts for MS Windows and Macintosh are available on-line.  For
hyperlinks to these and other Z tool resources see the WWW Z page:
http://www.comlab.ox.ac.uk/archive/z.html#tools

Subject: How can I learn about Z?

There are a number of courses on Z run by industry and academia. Oxford
University offers industrial short courses in the use Z.  As well as
introductory courses, recent newly developed material includes advanced
Z-based courses on proof and refinement, partly based around the
B-Tool.  Courses are held in Oxford, or elsewhere (e.g., on a company's
premises) if there is enough demand. For further information, contact
Jim Woodcock (tel [phone], fax [phone], email
<[e-mail]>).
  Logica offer a five day course on Z at company sites.  Contact
Susan Stepney (tel [phone], fax [phone], email
<[e-mail]>) at Logica UK Limited, Betjeman House,
104 Hills Road, Cambridge CB2 1LQ, UK, or see on-line under
http://public.logica.com/~formaliser/services/zcourse.htm
  Praxis Critical Systems Ltd runs a range of Z (and other formal
methods) courses.  For details contact Anthony Hall on [phone]
or <[e-mail]>.
  Formal Systems (Europe) Ltd run a range of Z, CSP and other formal
methods courses, primarily in the US and with such lecturers as Jim
Woodcock and Bill Roscoe (both lecturers at the OUCL).  For dates and prices
contact Kate Pearson (tel [phone], fax [phone]) at
Formal Systems (Europe) Limited, 3 Alfred Street, Oxford OX1 4EH, UK.
  DST Deutsche System-Technik runs a collection of courses for either Z
or CSP, mainly in Germany. These courses range from half day
introductions to formal methods and Z to one week introductory or
advanced courses, held either at DST, or elsewhere.  For further
information contact Hans-Martin Hoercher, DST Deutsche System-Techik
GmbH, Edisonstr. 3, D-24145 Kiel, Germany (tel [phone], fax
[phone], email <[e-mail]>).

Subject: What has been published about Z?

A searchable on-line Z bibliography is available on the World Wide Web
under http://www.comlab.ox.ac.uk/archive/z/bib.html in BibTeX format.
  The following books largely concerning Z have been or are due to be
published (in approximate chronological order):

  I.Hayes (ed.), Specification Case Studies, Prentice Hall International
      Series in Computer Science, 1987. (2nd ed., 1993)
      URL: http://www.prenhall.com/013/832543/ptr/83254-3.html
  J.M.Spivey, Understanding Z: A specification language and its formal
      semantics, Cambridge University Press, 1988.
  D.Ince, An Introduction to Discrete Mathematics, Formal System
      Specification and Z, Oxford University Press, 1988. (2nd ed., 1993)
  J.C.P.Woodcock & M.Loomes, Software Engineering Mathematics: Formal
      Methods Demystified, Pitman, 1998. (Also Addision-Wesley, 1989)
  J.M.Spivey, The Z Notation: A reference manual, Prentice Hall
      International Series in Computer Science, 1989. (2nd ed., 1992)
      [Widely used as a de facto standard for Z. Often known as ZRM2.]
  A.Diller, Z: An introduction to formal methods, Wiley, 1990.
  J.E.Nicholls (ed.), Z user workshop, Oxford 1989, Springer-Verlag,
      Workshops in Computing, 1990.
  B.Potter, J.Sinclair & D.Till, An Introduction to Formal Specification
      and Z, Prentice Hall International Series in Computer Science, 1991.
      (2nd ed., 1996)
      URL: http://www.prenhall.com/013/242206/ptr/24220-6.html
  D.Lightfoot, Formal Specification using Z, MacMillan, 1991.
  A.Norcliffe & G.Slater, Mathematics for Software Construction,
      Ellis Horwood, 1991.
  J.E.Nicholls (ed.), Z User Workshop, Oxford 1990, Springer-Verlag,
      Workshops in Computing, 1991.
  I.Craig, The Formal Specification of Advanced AI Architectures,
      Ellis Horwood, 1991.
  M.Imperato, An Introduction to Z, Chartwell-Bratt, 1991.
  J.B.Wordsworth, Software Development with Z, Addison-Wesley, 1992.
      URL: http://www.aw.com/cseng/authors/wordsworth/softdev/
  S.Stepney, R.Barden & D.Cooper (eds.), Object Orientation in Z,
      Springer-Verlag, Workshops in Computing, August 1992.
      URL: http://public.logica.com/~stepneys/bib/ss/ooz.htm
  J.E.Nicholls (ed.), Z User Workshop, York 1991, Springer-Verlag,
      Workshops in Computing, 1992.
      URL: http://www.imi.gla.ac.uk/springer/eWiC/Abstracts/9.html
  D.Edmond, Information Modeling: Specification and implementation,
      Prentice Hall, 1992.
  J.P.Bowen & J.E.Nicholls (eds.), Z User Workshop, London 1992,
      Springer-Verlag, Workshops in Computing, 1993.
      URL: http://www.comlab.ox.ac.uk/archive/z/zum92.html
  S.Stepney, High Integrity Compilation: A case study, Prentice Hall, 1993.
      URL: http://public.logica.com/~stepneys/bib/ss/hic.htm
  M.McMorran & S.Powell, Z Guide for Beginners, Blackwell Scientific, 1993.
  K.C.Lano & H.Haughton (eds.), Object-oriented Specification Case Studies,
      Prentice Hall International Object-Oriented Series, 1993.
  B.Ratcliff, Introducing Specification using Z: A practical case study
      approach, McGraw-Hill, 1994.
  A.Diller, Z: An introduction to formal methods, 2nd ed., Wiley, 1994.
  J.P.Bowen & J.A.Hall (eds.), Z User Workshop, Cambridge 1994,
      Springer-Verlag, Workshops in Computing, 1994.
      URL: http://www.comlab.ox.ac.uk/archive/z/zum94.html
  R.Barden, S.Stepney & D.Cooper, Z in Practice, Prentice Hall
      BCS Practitioner Series, 1994.
      URL: http://public.logica.com/~stepneys/bib/ss/zip.htm
  D.Rann, J.Turner & J.Whitworth, Z: A beginner's guide. Chapman & Hall, 1994.
  D.Heath, D.Allum & L.Dunckley, Introductory Logic and Formal Methods.
      A.Waller, Henley-on-Thames, 1994.
  L.Bottaci and J.Jones, Formal Specification using Z: A modelling approach.
      International Thomson Publishing, 1995.
  D.Sheppard, An Introduction to Formal Specification with Z and VDM.
      McGraw Hill International Series in Software Engineering, 1995.
  J.P.Bowen & M.G.Hinchey (eds.), ZUM'95: The Z Formal Specification
      Notation, Springer-Verlag, Lecture Notes in Computer Science,
      volume 967, 1995.
      URL: http://www.comlab.ox.ac.uk/archive/z/zum95.html
  J.P.Bowen, Formal Specification and Documentation using Z: A Case Study
      Approach, International Thomson Compress Press, 1996.
      URL: http://www.comlab.ox.ac.uk/oucl/users/jonathan.bowen/zbook.html
  J.C.P.Woodcock & J.Davies, Using Z: Specification, proof and refinement,
      Prentice Hall International Series in Computer Science, 1996.
      URL: http://www.comlab.ox.ac.uk/usingz.html
  A.Harry, Formal Methods Fact File: VDM and Z, Wiley, 1996.
  J.Jacky, The Way of Z: Practical Programming with Formal Methods,
      Cambridge University Press, 1997.
      URL: http://www.radonc.washington.edu/prostaff/jon/z-book/
  J.P.Bowen, M.G.Hinchey & D.Till (eds.), ZUM'97: The Z Formal Specification
      Notation, Springer-Verlag, Lecture Notes in Computer Science,
      volume 1212, 1997.  URL: http://www.cs.reading.ac.uk/zum97/
Announced:
  L.Semmens, Z for Software Engineers, Ellis Horwood Series in Computers
      and Their Applications, December 1996.

See also an on-line list of Z books from Blackwells Bookshop under:
http://www.blackwell.co.uk/cgi-bin/bb_catsel?09_IBY
  "Formal Methods: A Survey" by S.Austin & G.I.Parkin, March 1993
includes information on the use and teaching of Z in industry and
academia.  Contact DITC Office, Formal Methods Survey, National
Laboratory, Teddington, Middlesex TW11 0LW, UK (tel [phone],
fax [phone]) for a copy.
  OUCL Technical Monographs and Reports, including many on Z, is
available from the OUCL librarian (tel [phone], fax
[phone], email <[e-mail]>).
  For information on formal methods publications in general, see:
http://www.comlab.ox.ac.uk/archive/formal-methods/pubs.html

Subject: What is object-oriented Z?

Several object-oriented extensions to or versions of Z have been
proposed.  The book "Object orientation in Z", listed above, is a
collection of papers describing various OOZ approaches - Hall, ZERO,
MooZ, Object-Z, OOZE, Schuman&Pitt, Z++, ZEST and Fresco (an OO VDM
method) - in the main written by the methods' inventors, and all
specifying the same two examples. A more recent book entitled
"Object-oriented specification case studies" surveys the principal
methods and languages for formal object-oriented specification,
including Z-based approaches.

Subject: How can I run Z?

Z is a (non-executable in general) specification language, so there is
no such thing as a Z compiler/linker/etc. as you would expect for a
programming language. Some people have looked at animating subsets of Z
for rapid prototyping purposes, using logic and functional programming
for example, but this is not really the major point of Z, which is to
increase human understandability of the specified system and allow the
possibility of formal reasoning and development. However, Prolog seems
to be the main favoured language for Z prototyping and some references
may be found in the Z bibliography (see above).

Subject: Where can I meet other Z people?

|The 11th International Conference of Z Users (ZUM'98) will be held in
|Berlin, Germany, 24-25 September 1998. A Call for Papers has been
|issued. For further information, please contact the Connference Chair:
|Mike Hinchey, New Jersey Institute of Technology, Department of
|Computer and Information Science, University Heights, Newark, NJ
|07102-1982, USA (email <[e-mail]>, tel [phone], fax
|[phone]).  URL: http://www.cs.reading.ac.uk/archive/z/zum98/
|  Information on Z User Meetings is issued on newsgroups including
|comp.specification.z, the Z postal mailing list and various specialist
|electronic mailing lists.
|  Previous proceedings for Z User Meetings have been published in the
|Springer-Verlag LNCS and Workshops in Computing series since the 4th
|meeting in 1989.  For further on-line information on previous meetings,
|see the URL http://www.comlab.ox.ac.uk/archive/z/zum.html
|  For a list of meetings with a formal methods content, see:
| http://www.comlab.ox.ac.uk/archive/formal-methods/meetings.html

Subject: What is the Z User Group?

The Z User Group was set up in 1992 to oversee Z-related activities,
and the Z User Meetings in particular.  As a subscriber to either
comp.specification.z, ZFORUM or the postal mailing list, you may
consider yourself a member of the Z User Group.  There are currently
no charges for membership, although this is subject to review if
necessary.  Contact <[e-mail]> for further
information.

Subject: How can I obtain the draft Z standard?

The proposed Z standard under ISO/IEC JTC1/SC22 is available on-line.
See under http://www.comlab.ox.ac.uk/oucl/groups/zstandards/ for the
latest information and locations.  An early version is also available
in printed form from the OUCL librarian (tel [phone], fax
[phone], email <[e-mail]>) by requesting
Technical Monograph number PRG-107.

Subject: Where else is Z discussed?

The BCS-FACS (British Computer Society Formal Aspects of Computer
Science special interest group) and FME (Formal Methods Europe) are two
organizations interested in formal methods in general. Contact BCS
FACS, Dept of Computer Studies, Loughborough University of Technology,
Loughborough, Leicester LE11 3TU, UK (tel [phone], fax
[phone], email <[e-mail]>) for further information.
  A "FACS Europe" newsletter is issued to members of FACS and FME.
Please send suitable Z-related material to the Z column editor, David
Till, Dept of Computer Science, City University, Northampton Square,
London, EC1V 0HB, UK (tel [phone], email <[e-mail]>)
for possible publication.  Material from articles appearing on the
comp.specification.z newsgroup may be included if considered of
sufficient interest (with permission from the originator if possible).
It would be helpful for posters of articles on comp.specification.z to
indicate if they do not want further distribution for any reason.

Subject: How does VDM compare with Z?

See I.J.Hayes, C.B.Jones & J.E.Nicholls, Understanding the differences
between VDM and Z, FACS Europe, series I, 1(1):7-30, Autumn 1993
available as an on-line Technical Report from Manchester under
ftp://ftp.cs.man.ac.uk/pub/TR/UMCS-93-8-1.ps.Z and I.J.Hayes, VDM and Z:
A comparative case study, Formal Aspects of Computing, 4(1):76-99, 1992.
VDM is discussed on the (unmoderated) VDM FORUM mailing list.  Send a
message containing the command "join vdm-forum <name>" where <name> is
your real name to <[e-mail]>. To contact the list
administrator, email John Fitzgerald on <[e-mail]>.

Subject: How does the B-Method compare with Z?

B is a tool-based formal method for software development, conceived by
the originator of Z, Jean-Raymond Abrial, whereas Z is designed mainly
for specification. See http://www.b-core.com/ZVdmB.html for a comparison.
See also http://www.comlab.ox.ac.uk/archive/formal-methods/b.html for
further information on B.

Subject: What if I have spotted a mistake or an omission?

Please send corrections or new relevant information about meetings,
books, tools, etc., to <[e-mail]>.  New questions and
model answers are also gratefully received!

--
Jonathan Bowen <[e-mail]>
Department of Computer Science, University of Reading, UK
URL: http://www.cs.reading.ac.uk/people/jpb/