Eighth Symposium on Compositional Structures (SYCO 8)

Tallinn University of Technology, Tallinn, Estonia
13-14 December 2021

We are closely monitoring the coronavirus situation in Estonia.
Our current policy is in the "local information" section below.

The Symposium on Compositional Structures is a series of interdisciplinary meetings aiming to support the growing community of researchers interested in the phenomenon of compositionality, from both applied and abstract perspectives, and in particular where category theory serves as a unifying common language. We welcome submissions from researchers across computer science, mathematics, physics, philosophy, and beyond, with the aim of fostering friendly discussion, disseminating new ideas, and spreading knowledge between fields. Submission is encouraged for both mature research and work in progress, and by both established academics and junior researchers, including students.

Submission is easy, with no format requirements or page restrictions. The meeting does not have proceedings, so work can be submitted even if it has been submitted or published elsewhere. You could submit work-in-progress, or a recently completed paper, or even a PhD or Masters thesis.

While no list of topics could be exhaustive, SYCO welcomes submissions with a compositional focus related to any of the following areas, in particular from the perspective of category theory:

This new series aims to bring together the communities behind many previous successful events which have taken place over the last decade, including Categories, Logic and Physics, Categories, Logic and Physics (Scotland), Higher-Dimensional Rewriting and Applications, String Diagrams in Computational, Logic and Physics, Applied Category Theory, Simons Workshop on Compositionality, the Yorkshire and Midlands Category Theory Seminar and the Peripatetic Seminar in Sheaves and Logic.

This event follows SYCO 1 in Birmingham, SYCO 2 in Strathclyde, SYCO 3 in Oxford, SYCO 4 in California, SYCO 5 in Birmingham, and SYCO 6 in Leicester. It replaces SYCO 7 which was cancelled due to the pandemic.

Invited speakers

John van de Wetering Christine Tasson
Radboud University Nijmegen Sorbonne Université
Categorical approaches to reconstructing quantum theory A multicategorical approach to mixed linear-non-linear substitution

Important dates

All deadlines are 23:59 anywhere-on-earth on the given dates.

Accepted papers


Time Monday 13 December Tuesday 14 December
9:30–10:00 Invited talk: John van de Wetering, Categorical approaches to reconstructing quantum theory
10:30–11:00 Registration and Coffee Guillaume Boisseau and Robin Piedeleu, Graphical Piecewise-Linear Algebra
11:00–11:30 BREAK
11:30–12:00 Invited talk: Christine Tasson, A multicategorical approach to mixed linear-non-linear substitution Liliane-Joy Dandy, Emmanuel Jeandel and Vladimir Zamdzhiev , Qimaera: Type-safe (Variational) Quantum Programming in Idris
12:00–12:30 Matt Wilson and Augustin Vanrietvelde, Composable constraints
12:30–13:00 Stefan Zetzsche, Gerco van Heerdt, Matteo Sammartino and Alexandra Silva, Canonical automata via distributive law homomorphisms Davide Trotta, Matteo Spadetto and Valeria de Paiva, Dialectica Logical Principles
13:00–13:30 LUNCH LUNCH
14:00–14:30 Simon Henry and Nicholas Meadows, Higher Theories and Monads Simon Fortier-Garceau, Interventions and Counterfactuals for Categorical Models of Causality
14:30–15:00 Paulina Goedicke and Jamie Vicary, A Category Theoretical Description of Block Designs and Quantum Designs Vikraman Choudhury, Weighted sets and modalities
15:00–15:30 Vincent Wang-Mascianica and Bob Coecke, Talking Space: Inference from spatial linguistic meanings Elena Di Lavore and Pawel Sobocinski, Monoidal width
15:30–16:00 BREAK BREAK
16:00–16:30 Lukas Heidemann, Frames in pretriangulated dg-categories Dylan McDermott and Alan Mycroft, On the relation between call-by-value and call-by-name
16:30–17:00 Elena Di Lavore, Wilmer Leal and Valeria de Paiva, Dialectica Petri nets Olivier Peltre, Homological algebra for message-passing algorithms
17:00–17:30 George Kaye, Dan Ghica and David Sprunger, Normalisation by evaluation for digital circuits


Please register by filling in the registration form.
The registration deadline is Monday 6 December 2021, there is no registration fee.

Local information

The local organiser is Amar Hadzihasanovic (amar@cs.ioc.ee).

Conference venue

The meeting will take place in the Crown Hall of the historical Teachers' House (Õpetajate Maja), in the heart of the Old Town of Tallinn.

The annual Christmas Market will be taking place at the same time, right in front of the conference venue.

Coffee and lunch will be served on location during the meeting hours. Beyond that, the Old Town offers plenty of cafés and restaurants. Within walking distance, the Balti Jaam market has a selection of food stalls, and Telliskivi creative city has bars, cafés, and independent shops.


Tallinn is conveniently served by Tallinn airport, which is reachable in about 20 minutes from the city centre with public transport (tram line 4 and bus line 2).

Electronic tickets for public transport can be purchased with the Pilet.ee app (Android, iPhone). Alternatively, there are rechargeable travel cards that can be purchased in every R-kiosk. Affordable private rides are provided by Bolt.

Online participation

The meeting will have an online component and all talks will be broadcast on Zoom. Registered online participants will be contacted by e-mail, closer to the meeting date, with the virtual coordinates.

COVID-19 situation in Estonia

UPDATE (30/11): The number of cases in Estonia is still steadily declining, so for now things are still looking good locally. We are aware of the new Omicron variant. According to the WHO it is too early to draw any conclusions on how dangerous it is compared to the Delta variant. For fully vaccinated people there are as yet no indications of concern, but we invite everyone to check their own country's regulations regarding travelling.

UPDATE (17/11): The number of cases is dropping again. We will of course keep monitoring the situation, but for now things are looking up!

UPDATE (05/11): In the last weeks, there has been a concerning rise in the number of COVID-19 cases and hospitalisations in Estonia. A considerable majority of serious cases concern the unvaccinated, and so far the government of Estonia has not introduced major restrictions on those who can prove recovery and/or vaccination with an EU-approved vaccine.

In light of that, at the moment we are carrying on with the event in a hybrid form, as planned, and inviting those who are willing, and have proof of recovery and/or vaccination, to participate in person.

At the moment, for the UK, EU, and Schengen countries, proof of vaccination or recovery, and the filling of a passenger locator form, is sufficient to avoid self-isolation on arrival to Estonia. Please consult the government web page for the latest regulations.

In the unlikely event of new restrictions that make it impossible to hold the event as planned, we will send out an update on mailing lists and on this website no later than the beginning of December.


The meeting is supported by the ESF funded Estonian IT Academy research measure (project 2014-2020.4.05.19-0001).


The intention is for SYCO to be a community meeting, where people have enough time to explain their ideas, and with a friendly and non-competitive atmosphere. To encourage this, in the event that more submissions are received of an acceptable standard than can be accommodated in the timetable, the programme committee may choose to defer some submissions to a future meeting, rather than reject them. This would be done based largely on submission order, giving an incentive for early submission, but would also take into account other requirements, such as ensuring a broad and inclusive scientific programme. Deferred submissions can then be re-submitted to any future SYCO meeting, where they will be prioritised for inclusion in the programme, and where they will not need to be re-reviewed. Meetings are held sufficiently frequently to avoid a backlog of deferred papers.


Submission is by EasyChair, via the SYCO 8 submission page.

Submissions should present research results in sufficient detail to allow them to be properly considered by members of the programme committee, who will assess their interest to the SYCO community. We encourage the submission of work in progress, as well as mature results. There are no proceedings, so work can be submitted even if it has been previously published, or has been submitted for consideration elsewhere. There is no specific formatting requirement, and no page limit, although for long submissions authors should be aware that reviewers will not be able to read the entire document in detail. Think creatively—you could submit a recent paper, draft notes of a project in progress, or even a recent Masters or PhD thesis.

If you have a submission which was deferred from a previous SYCO meeting, it will not automatically be considered for SYCO 8; you still need to submit it again through EasyChair. Such a submission will be prioritised for inclusion in the SYCO 8 programme. When submitting, append the words "DEFERRED FROM SYCO X" to the title of your paper, replacing "X" with the appropriate meeting number. There is no need to attach any documents.

Programme committee

Steering committee

The symposium is managed by the following people. If you have a general question about SYCO, or if you want to propose to host a future version, please get in touch with a member of the steering committee.