Workshop on Effects and Type Theory, EffTT

Tallinn, Estonia, 13-14 December 2007
a "small workshop" of the TYPES project


Abstracts and slides of talks

List of participants

Practical information

Some photos by Marino and Tarmo

New: Special issue of Fundamenta Informaticae for EffTT and DTP 2008,
submission deadline 1 October 2008


The syntax and semantics of impurities of computation known as effects have been an important challenge for functional programming. Today, we tend to employ categorically inspired tools such as monads, Lavwere theories, applicative functors and arrows, but also more pragmatic approaches such as uniqueness typing.

Effects are an issue also for type-theoretic programming and reasoning, where a number of aspects make them specifically interesting. First, we do not yet know what the best dependently typed generalizations of our simply typed tools are, although we hope they would reinforce the dual utility of type-theoretic calculi as programming languages and logics. Second, this duality specifically forces that pure computations must terminate, so even nontermination is an impurity and potentially an effect. Third, is it not likely that the type-theoretic glasses can help us see more clearly the particularities of external-world effects such as true destructively updatable state and true interactive input-output?

Thus, this workshop is exactly about effects and type theory. Topics of interest include

Invited speakers

Our invited speakers are Paul Levy (Birmingham) and Aleksandar Nanevski (Microsoft Research, Cambridge).

Contributing a talk

The rest of the programme will be based on contributed talks and discussions. If you would like to contribute a talk, send a title and abstract to efftt(at) by 21 November 2007.


The workshop organizers are Thorsten Altenkirch, Marino Miculan and Tarmo Uustalu.


The workshop will take place in the building of the Estonian Academy of Sciences (the palace of the Ungern-Sternbergs), Kohtu 6. This is on Tallinn's Dome Hill in the historical city center and at walking (well, climbing) distance from all central hotels.

The workshop dates are during the Tallinn Christmas market and the Christmas Jazz festival of Jazzkaar.


To express your intent to participate, please drop an email to efftt(at) as soon as possible, but no later than 21 November 2007 (knowing who will be coming early on will help us plan the workshop better).

Our host institution, the Institute of Cybernetics (IoC), charges a registration fee of 1400 EEK / 90 EUR to cover lunches and coffees during the two days and a dinner in the evening of 13 December. To pay, please fill out this form, sign the generated pdf document and fax it to +372 620 4151 or alternatively email a scanned copy to efftt(at) Please do so by 5 December 2007.

Attendance is by no means confined to people involved in the TYPES project; the workshop is open to anyone interested.


Tallinn is not the best connected city on this continent. There are direct flights to Tallinn airport from Amsterdam, Berlin Schönefeld, Brussels, Copenhagen, Dublin, Frankfurt, Gothenburg, Hamburg, Helsinki, Kiev, London Gatwick and Stansted, Milan Malpensa, Moscow, Oslo, Prague, Riga, Stockholm Arlanda, Vienna, Vilnius, and Warsaw. The hubs for connecting from other cities are Copenhagen and Stockholm (SAS/Estonian Air), Helsinki (Finnair), Amsterdam (KLM/Air France), Prague (CSA), Frankfurt (Lufthansa).


We can suggest the following hotels with whom IoC has loyal customer agreements:

Both of these hotels are in the Old Town (the historical city center).

We will start at 9.00 on Thu 13 December and finish not later than by 17.00 on Fri 14 December, so you should arrive during Wed.

Tarmo Uustalu
Last update 30 June 2008