Report available via FTP

Report available via FTP

[agate!howland.reston.ans.net!zaphod.mps.ohio-state.edu!cs.utexas.edu!utnu]

The following report has just been published and is available via FTP:

%T HRT-HOOD: A Design Method for Hard Real-time Ada
%A A. Burns
%A A.J. Wellings
%I Department of Computer Science, University of York
%D May 1993
%R YCS199

The report is stored in compressed postscript format in

/pub/realtime/papers/YCS199.ps.Z

at minster.york.ac.uk (144.32.128.41)

Remember to use the binary mode when getting the file. The file
/pub/realtime/papers/INDEX contains information on all the reports and papers
stored in the realtime archive. Additionally, the directory /reports
contains the most recent reports of the Department of Computer Science at
York.

The abstract of the report is as follows:

"Most structured design methods claim to address the needs of hard
real-time systems.  However, few contain abstractions which directly
relate to common hard real-time activities, such as periodic or sporadic
processes. Furthermore, the methods do not constrain the designer to
produce systems which can be analysed for their timing properties.  In
this paper we present a structured design method called HRT-HOOD (Hard
Real-Time Hierarchical Object Oriented Design).  HRT-HOOD is an
extension of HOOD, and includes object types which enable common hard
real-time abstractions to be represented.  The method is presented in
the context of a hard real-time system life cycle, which enables issues
of timeliness and dependability to be addressed much earlier on in the
development process. We argue that this will enable dependable
real-time systems to be engineered in a more cost effective manner than
the current practise, which in effect treats these topics as
performance issues.  To illustrate our approach we present a simple
case study of a Mine Drainage Control System, and show how it can be
designed using the abstractions presented in the paper."

--
Ken Tindell             Internet      : ken@minster.york.ac.uk
Computer Science Dept., Local FTP site: minster.york.ac.uk
York University,        Tel.          : +44-904-433244         
YO1 5DD, UK             Fax.          : +44-904-432708

Report available via FTP

[cis.ohio-state.edu!magnus.acs.ohio-state.edu!usenet.ins.cwru.edu!howland.]

A report entitled "Implementing Analysable Hard Real-time Sporadic Tasks in
Ada 9X", by A. Burns and A.J. Wellings is available by FTP from the following 
site:

minster.york.ac.uk (IP address 144.32.128.41)

in the directory:

/pub/realtime/papers

in the file:

YCS209.ps.Z

The file is stored in compressed postscript format so be sure to set binary
mode when FTPing the report. The abstract of the report is as follows:

              In this paper we illustrate how systems containing hard
              real-time  sporadic  tasks  can  be  analysed for their
              worst case  behaviour.   In  order  to  undertake  this
              schedulability  analysis, it is necessary to define the
              minimum  inter-arrival  time  and/or  maximum   arrival
              frequency  of  sporadic tasks. Furthermore, at run-time
              it is essential to ensure that sporadic tasks  are  not
              invoked  more  often  than  has  been guaranteed by the
              analysis. We  assume  that  sporadics  are  invoked  by
              interrupts  and  that  interrupts  can  be masked under
              software control.

                   Sporadic tasks are often analysed using the notion
              of  bandwidth  preserving  sporadic  servers within the
              Rate Monotonic Scheduling Analysis scheme.  At run-time
              this  requires the underlying kernel to support complex
              execution time  monitoring  mechanisms.   Unfortunately
              such  mechanisms are not generally supported by Ada 9X.
              This paper  shows  that  by  using  Deadline  Monotonic
              Scheduling  Analysis  there  is  no  need  to resort to
              bandwidth  preserving   sporadic   servers,   and   the
              facilities available in Ada 9X can be used.

A number of other papers and reports written by the Real-Time Systems
Research Group at York are also available; the file INDEX in the directory
/pub/realtime/papers lists these.

--
Ken Tindell             Internet      : ken@minster.york.ac.uk
Computer Science Dept., Local FTP site: minster.york.ac.uk
University of York,     Tel.          : +44-904-433244         
YO1 5DD, UK             Fax.          : +44-904-432708