PREFACE
Introduction
The fourth in a series of International Conferences on Accelerator and Large Experimental Physics
Control Systems was held at the Swissôtel in Chicago from October 30 to November 3 1995. This series
had been preceeded by a number of conferences on accelerator control systems dating to 1983, and it hadlater been decided to widen the scope to include other large experimental devices, such as telescopes,
tokamaks and high energy physics experiments themselves, which have similar control problems.
The pre-conference announcements and circulars emphasized that certain aspects of the field would
receive more stress at this conference than in the past. These areas were controls hardware; nonaccelerator control systems, particularly those of physics experiments and telescopes; and operational
aspects of controls. Oral sessions were devoted to each of these topics, two sessions in the case of
hardware. Additionally, the topic of the opening plenary session talk was operational aspects. At ameeting held just after the conference closing the International Scientific Advisory Committee expressedthe viewpoint that emphasis in these areas should be continued in the future. This will require particulareffort in the areas of physics experiments and telescopes, where ICALEPCS is still not well known. At
the same meeting the committee was divided on the value of continuing parallel sessions, which were
held in Chicago for the first time.

Paper breakdown by topic
It is interesting to note the breakdown of the papers at this conference. The record 195 contained in these
Proceedings have been categorized, including each paper no more than twice, as the following:
Accelerators
105
Physics experiments
17
Telescopes
5
Hardware
18Operations
11
EPICS
12
Commercial and industrial
19
User interfaces
12
Distributed computing
12
AI and advanced techniques 9OO techniques
11Databases
7
Software sharing
3
The breadth of this distribution, as compared with that at early conferences, is notable and, speaking forthe organizers, gratifying. A major new trend was noticed in the contributed papers - 36 of them could beclassified as 'Control of subsystems.' A large fraction of these pertain to the extension of an existing
control system to a new area, the upgrading of one part of an overall system, or control support forextension of machine functionality. The ability to make such changes indicates a major strength of thecontrol system 'Standard Model', namely that it is modular and that additions or changes can be made inparticular areas and then easily integrated into the overall system.

Commercial systems
One general impression of the progress presented at this conference is the greater readiness to adopt both
hardware and software coming from outside the immediate community. There are several reasons forthis. One is that the controls industry can now provide systems that meet the requirements for the control

of many components, not just utilities, from their standard lines. Another is that many laboratories aresuffering from reductions in staff and can no longer indulge in the luxury of in-house development.
Several papers show that such imports can be used with advantage for reducing the amount of in-houseeffort required in providing for the control of many of the support systems needed for an accelerator, butthat they do have limitations. Many commercial control systems use proprietary networking and require
their own separate networks. This may not create a major problem for small machines, but may involve
extra expense for large ones, particularly if competitive tendering results in different suppliers for someof the subsystems. Commercial systems are not usually able to cope with the sub-millisecond timing
required for instrumentation and RF.

Sharing of Software
As was the case at the 1993 ICALEPCS, a one-day workshop on the topic of sharing control system
software was held after the completion of the conference. Compared with the first formal discussion atICALEPCS 91, considerable progress in software sharing (SOSH) has been made. The EPICS
collaboration, plus some smaller groupings of European laboratories, exists explicitly for this purpose. Asis often pointed out, purchase of commercial software products as noted above is also a mode of sharing
development costs. However some major laboratories, with large in-house-developed proprietary control
systems, effectively cannot participate via such channels.
The conclusion of a previous workshop was that where sharing would have the most impact is in thematter of application software. There has been developed at CEBAF a product called CDEV which could
serve as an interface between different application programming schemes on a high level and different
control infrastructures and protocols on a lower plane. Several laboratories have investigated thepossibility of such a product to interface their software to that of others and the results appear promising,although with obstacles. A major part of the Chicago workshop concerned specific detailed matters which
would be involved in implementing such a scheme.
A separate effort involves sharing at a lower level in the controls model, namely a protocol at the level ofthe network or hardware bus serving similarly as a software bus. These discussions center primarily on
the use of the CORBA method of object oriented communications. Such investigations continue.

On site computer center
One of the interesting features of the conference was the computer center which was constructed in theSwissôtel, primarily by members of the Fermilab Computer Division, for the use of all conference
attendees and exhibitors. This center consisted of Macintosh and PC computers plus high end Xterminals, printers and a scanner. All were connected by an Ethernet LAN, with some wireless nodes
attached. Wide area networking via a T1 link provided adequate bandwidth for the remote operation ofvarious control systems. Some of the 'poster' presentations were actually made on X-terminals withoutside connections. Additionally a projection system with connection to a computer or terminal at thepodium allowed the visual aids of oral presentations to exist on computer screens, as opposed totransparencies. One of the hotel employees expressed surprise that for a technology conference thisoption was chosen by relatively few presenters. His remark can stand as a challenge to organizers of andpresenters at future ICALEPCS.

Proceedings on CD-ROM
These Proceedings have been prepared in both paper and CD-ROM versions, 40% of the attendees having
chosen the former and 60% the latter. It is clear that given the nature of the material we have received,
CD-ROM is the more appropriate medium for this conference. Many authors have included detailed orcolored figures and photographs, which are only approximated in the paper version. Additionally, thepapers in a form appropriate for CD-ROM were also automatically appropriate for the World Wide Web,and thus were able to begin appearing in their final form within a month of conference completion.
Some comments on technical matters concerning the papers are appropriate. The instructions for authors
sent before the conference stated rather explicitly how text was to be handled. As a result there were only
minimal problems in preparing the text parts of papers for electronic media and with a consistency offormat. However the same is not true of figures. These have been produced using a wide variety ofsoftware tools and in a variety of modes and formats. The result has been considerable work on our partto integrate all figures, and in a few cases with resulting quality and uniformity verging on inadequate.

Nomenclature
In the preface to the Proceedings of the last conference in this series, one of us pointed out that one of theremaining things that restricts the exchange of information between the laboratories and institutes is theplethora of names given to different parts of the systems.
The first that comes to mind is the names for the computers at the second or third layers of the standard
model. We now have even more, not fewer, this time:-DIC, Device Interface Computer
DSC, Device Stub Controller
ECA, Equipment Control Assembly
EIU, Equipment Interface Units
FEC, Front End Computer (Controller)
FFE, Far Front End
IDC, Intelligent Device Controller
ILC, Intelligent Local Controller (Computer),IOC, Input/Output Controller,LPC, Local Process Controller (Computer) andPCA, Process Control Assembly.

It would help if agreement could be obtained on a common name.

Acknowledgments
The smooth running of the conference depended on a number of people who devoted large amounts oftime to ensuring its success. The names of the Local and International Committees can be found in theintroductory pages. Also particularly noted are the efforts of Ms. Lisa Lopez who served as conference
executive secretary and Ms. Donna Lamore who organized the construction and operation of the local
computer center. We speak for all the organizers in expressing our hopes that all the conference
participants enjoyed and profited from their visit to Chicago and that these Proceedings will be of value
to them and to those who were unable to attend.
The production of the Proceedings was generously supported by the United States Department of Energy
and the Hewlett-Packard Corporation. The organizers sincerely thank both organizations for their support.
Michael Crowley-MillingPeter Lucas
Paul Schoessow