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Proposed topics for discussion |
Minutes of the meeting are now available
(last updated 17th January 2007).
Annie Liu has made some
The 62nd meeting of IFIP WG2.1
will be held at
Hotel "Château de Namur",
from 11th to 15th December 2006:
Hotel "Château de Namur"
To book a room, please send an e-mail to
by November 15, 2006. After this date, the availability of rooms is
not guaranteed. Do mention "Meeting UCL-IFIP WG2.1".
Avenue de l'Ermitage, 1
B-5000 Namur, Belgium
Tel + 32 81 72 99 00
Fax + 32 81 72 99 99
In the registration, indicate your special wishes, if any: for instance,
you may choose
See the options below.
- to share a twin or double room, and with whom;
- to skip meals, and which ones.
No credit number and no advance payment is needed; but don't cancel your
reservation at the last minute.
Here is an estimate of the costs:
The costs (A) are payable to the hotel; credit cards are accepted.
The costs (B) should be paid in cash to the host during the meeting.
There are ATM machines at the airport and in town, but not near the hotel.
Room and breakfast: €97 per person/day.
If a twin or double room is shared: €62.5 per person/day.
Lunches (€34) and dinners (€42): €76 per person/day.
Meeting facilities: €95 per participant/week.
Excursion and banquet: about €50.
A dinner is scheduled at the hotel on Sunday 10 evening; people will be
served up to 9 p.m. The banquet is scheduled for Thursday evening.
No lunch is organized on Friday noon; interested people may request this
lunch, onMonday morning. If you intend to skip a scheduled meal, and
do not want to pay for it, indicate this in your registration,
The hotel is rather isolated. There is one café-restaurant nearby,
closed in the evening.
One needs around 30 minutes for walking down to the city centre. Note
downtownis really "down": the city is at the river level, whereas the
hotel is on top of the citadel hill.
There is a Wifi network in the hotel. Access cards for 1 hour (€10), 24
hours (€20) or 5 days (€50) may be purchased. The periods cannot be
interrupted, and each card is associated with a unique computer.
If you arrive at Brussels airport, you may take a train to Brussels,
then to Namur, and from there a taxi to the hotel.
Here are train timetables.
The airport station is identified by bruxelles nat airport.
In Namur, there is also a bus (number 3) from the train station to the
hotel; the terminus is close to the hotel. This bus runs once per hour,
every day. If you travel by car, "unlimited" parking is available, as
Here a few additional links:
For hotel matters,
ask the hotel.
For general requests, ask
he will help Michel Sintzoff.
sits on top of the
Citadel of Namur
fortress). It is some distance away from downtown Namur,
about a half-hour walk downhill (and more uphill). The
Citadel is a public space and is open to walkers all year
round, seven days a week. Joggers are welcome, good shoes
We will start at 9:30 on Monday and finish around noon on
Friday. See schedule for further details.
The hotel is a 15' drive away from the Namur train station,
and the train ride is about an hour and a half from the
airport (via Brussels North). You can get detailed
look for NAMUR and BRUXELLES NAT AIRPORT.
Bus route 3
connects the station and the hotel, every hour
or so, until 7pm. Past that time, you will have to take a
On Wednesday afternoon, we will visit the Citadel's vast
network of underground passages, and the Delforge perfume
factory, established in Citadel buildings. Both sites are
within walking distance of the hotel and the tour will take
us halfway down to the old city center. Those who wish to
do so can then go downtown for dinner and maybe some
Christmas shopping (the Christmas Village starts this
week-end). We will consider transportation options for the
way back on Monday, depending on the number of interested
parties. The hike uphill is a sportive but healthy
The visits will cost 8€/person, transportation not
included. A registration list will be circulated on Monday.
The banquet will take place on Thursday night in a charming
little downtown restaurant. Vegetarian or other dietary
restrictions can be arranged. Transportation options will be
decided on Monday. (Note that you therefore probably do not
need dinner in the hotel on Thursday.)
The banquet will cost 40€/person, transportation not
included. A registration list will be circulated on Monday.
Belgium features a "temperate maritime" climate, which
translates into a fair chance of rain and a risk of frost or
snow in this season. Extended forecasts predict showers and
high temperatures around 10 degrees C...
The following talks have been proposed and will be ready for presentation
at the start of the meeting. The first few talks may be selected from this
- Symbolic generation of optimal discrete control
The extensional, state-based generation of policies for optimal discrete
control is impractical
when there are very many states since its complexity is polynomial in the
number of states.
To avoid this drawback, an intensional approach is proposed: optimal control
guards of actions are generated by a symbolic iteration. The domain of
states is stratified into domain strata,
viz. sets of states having the same optimal value. The optimal guards are
stratified into guard strata which are subsets of domain strata. The
optimal values are generated by greedy iteration steps.
The strata are generated by iteration steps which are guided by the greedy
ones and are asynchronous:
the guard strata for an action with an increasing cost depend on domain
strata with decreasing ranks. The complexity of this symbolic technique is
compared to that of symbolic methods for generating
domains of discrete reachability.
- Test-driven development
I would like to introduce the topic of
Test Driven Development.
It is a simple and pragmatic way of letting the tests drive
interactively the development of programs. It's not really research
for me, just an everyday practice I found very effective. I think
there is room for research into making TDD more effective with
mathematical reasoning, or conversely making program derivation more
effective with TDD.
- From clear specifications to efficient implementations
Two major concerns of study rest at the center of computer science:
what to compute, and how to compute efficiently. Problem solving
involves going from clear specifications for the "what" to efficient
implementations for the "how". This is challenging because clear
specifications usually correspond to straightforward implementations,
not at all efficient, while efficient implementations are usually
difficult to understand, not at all clear.
This talk gives an overview of a general and systematic method for
transforming clear specifications into efficient implementations. We
will present the method through examples, taken from problems in
hardware design and image processing expressed using loops and array,
in query processing and access control expressed using set operations,
in sequence processing and math puzzles expressed using recursive
functions, in program analysis and trust management expressed using
logic rules, and in building software components expressed using
objects. We summarize our ongoing projects on a number of fronts.
- Generic and Indexed Programming
At Oxford, we have just started a 42-month EPSRC-funded project on Generic and
Indexed Programming, a continuation of the recently-completed
Datatype-Generic Programming project.
The `indexed' aspect of this project is about expressing more of the
structure (specifically, invariants) of a program in the types. We have in
mind things like the shape of a data structure, the state of a component,
and some property of a represented value.
Mechanisms such as Haskell's generalized algebraic datatypes
can be used to provide a kind of lightweight dependently-typed
programming. Similar ideas are expressible in modern OO languages such as
Java and C#. In this talk, I will outline the aims of the project.
(Joint work with Bruno Oliveira.)
- Parametric Datatype-Genericity
Datatype-generic programs are programs parametrized by a datatype or
type functor. There are two main styles of datatype-generic
programming: the Algebra of Programming approach, characterized by
structured recursion operators parametrized by a shape functor, and
the Generic Haskell approach, characterized by case analysis
over the structure of a datatype. We show that the former enjoys a
kind of parametricity, relating the behaviours of generic functions at
different types; in contrast, the latter is more ad hoc, with no
coherence required or provided between the various clauses.
(Joint work with Ross Paterson.)
- CancerGrid: Model- and Metadata-Driven Clinical Trials Informatics
The CancerGrid project (www.cancergrid.org) is developing a software
architecture for `tissue-plus-data' clinical trials. The project is
using a model- and metadata-driven approach that makes the semantics
of clinical trials explicit, facilitating dataset discovery and reuse.
The architecture is based on open standards for the composition of
appropriate services, such as: randomization, minimization, clinician
identity, serious adverse events relay, remote data capture, drug
allocation and warehousing, form validation.
The project has developed a CONSORT-compliant model for clinical
trials, parameterized by clinical data elements hosted in metadata
repositories. A model instance can be used to generate and configure
services to run the trial it describes.
This talk will describe the model, the services, and the technology
employed: from XML databases to Office add-ins.
(Joint work with Jim Davies, Steve Harris, and the rest of the
- Proving Properties of Constraint Logic Programs
by Eliminating Existential Variables
We propose a method for proving first order
properties of constraint logic programs which
manipulate finite lists of real numbers.
Constraints are linear equations and
inequations over reals. Our method consists in
converting any given first order formula into a stratified
constraint logic program and then applying a suitable
unfold/fold transformation strategy that preserves the
perfect model. Our strategy is based on the elimination
of existential variables, that is, variables which occur in
the body of a clause and not in its head. Since, in general,
the first order properties of the class of programs
we consider are undecidable, our strategy is necessarily
incomplete. However, experiments show that it is powerful
enough to prove several non-trivial program properties.
(Joint work with Maurizio Proietti and Valerio Senni.)
- The unfold/fold automatic derivation of winning
strategies for solving some impartial games
- Polymorphic Algebraic Data Type Reconstruction
(Tom Schrijvers - local observer)
Traditional type inference aims at reconstructing type declarations given
some type definitions. We present a rule-based constraint rewriting
algorithm that reconstructs both type declarations and type definitions.
Our algorithm reconstructs uniform polymorphic definitions of algebraic
data types and simultaneously infers the types of all expressions and
functions (supporting polymorphic recursion) in the program. The
declarative nature of the algorithm allows us to easily show that it has a
number of highly desirable properties such as soundness, completeness and
various optimality properties. Moreover, we show how to easily extend and
adapt it to suit a number of different language constructs and type system
- Data dependency theory made generic -- by calculation
(Jose Nuno Oliveira)
Classical computer science theories (eg. transition systems, parsing,
databases) are written pointwise. What do we gain by replaying
them in the (relational) pointfree style? This talk will try
to answer this question by picking one such widespread theory
-- relational database theory (in fact, the data dependency part
of it, as far as this talk is concerned) -- and refactoring it in a
"let the symbols do the work" style. It can be observed that clear-cut
patterns replace long-winded formulae and semi-formal
proofs (full of "..." notation, case analyses and English words)
give way to compact, agile calculations (namely, that of the
"lossless decomposition" theorem); disparate definitions are shown
to be equivalent, and so on.
Above all, the theory becomes generic: sets of tuples become binary
relations, attributes generalize to arbitrary functions and
injectivity is shown to be "what matters" after all.
(Also a pro: students like it!)
There are, however, some difficulties. Feedback from the meeting is
welcome concerning some hard bits, namely how to make attribute-set
complementation (required in some MVD axioms) functional and generic.
- Core Role-Based Access Control: Efficient Implementations by Transformations
This talk describes a transformational method applied to the core
component of role-based access control (RBAC), to derive efficient
implementations from a specification based on the ANSI standard for
RBAC. The method is based on the idea of incrementally maintaining
the result of expensive set operations, where a new method is
described and used for systematically deriving incrementalization
rules. We calculate precise complexities for three variants of
efficient implementations as well as for a straightforward
implementation based on the specification. We describe successful
prototypes and experiments for the efficient implementations and for
automatically generating efficient implementations from
Joint work with C. Wang, M. Gorbovitski, T. Rothamel, Y. Cheng,
Y. Zhao, and J. Zhang
- December 2006