People
Yasushi Kodama
Professor; Director, Data Science Center
Hosei University, Tokyo, Japan
Principal investigator. Language design, the Rocq (Coq) development,
the measurement harnesses.
Affiliation, on the public record: the Data Science Center of Hosei
University lists Yasushi Kodama as its Director —
www.dsc.hosei.ac.jp
(appointment notice, 1 April 2024).
He is a Professor in the Faculty of Business Administration; his research is in
programming languages and formal verification.
The group is the principal investigator together with students in his
laboratory at Hosei University. Faculty collaborators at other
universities are joining as named co-investigators.
Hosei University is an accredited private university in Tokyo. This is
academic, non-commercial research; the code and the proofs are released
publicly.
What we work on
A language where the AI call is typed
AIPL is an actor language whose type system tracks side effects as
capabilities — !{ai, net, io, mut, time, mem, fs, log}.
Effects propagate through now and await, so a method
that does not declare ai cannot reach a model call even
indirectly.
Guarantees that are machine-checked
Type soundness, type safety and deadlock freedom are proved in Rocq (Coq)
across three fragments. The boundary of the guarantee is formal too: for the
largest fragment we proved that deadlock is admitted, rather than
quietly leaving it out.
Measuring agent graphs
When does a graph of small, individually verified LLM nodes beat one large
prompt? We derived the break-even conditions and measured them —
including the case where a per-node verifier detects a defect but cannot
repair it.
Systems that leave the browser
AIPL runs on bare metal: Embedded Xinu on Raspberry Pi 3/4/5, with a small
language model resident in the kernel, and a real multi-hop wireless MANET
used for disaster-evacuation research.
Selected results
-
One specification, three implementations. OCaml (the reference), Python
and browser JavaScript, held to a shared corpus of about 590 programs so that
the specification — not any one implementation — is the ground truth.
-
40 machine-checked theorems, every one closed under the global context
with no admitted axiom.
-
Deadlock attacked on three paths, because there are three. Obligation
levels for cyclic waiting; linearity of reply targets for a request that is
never answered; deadlines plus a sender-existence check for waiting on a message
nobody will send.
-
Break-even for agent graphs. A graph wins when
k·p^(k-1) < 1 under per-call pricing, and whenever
k ≥ 2 and p < 1 under token pricing — with the
caveat we state ourselves: the formula assumes failures are independent, and says
nothing about a defect that recurs at the same node every time.
-
Decomposition improves quality on its own (per-unit success 0.905 →
0.971), while parallel fan-out is capped by generation throughput (~135
tokens/s) and gave no speed-up at all on a real task (17.5 s → 17.4 s).
-
AIPL on bare metal. Compiled on-board to AArch64 and executed under
Embedded Xinu on a Raspberry Pi 5, with an in-kernel language model so that
ai_call returns in about 0.4 s with no network at all.
-
From simulation to real radios. A disaster-evacuation MANET study on a
real road network (266 vertices and four real shelters in Arakawa, Tokyo),
carried from simulation to measurements on physical wireless links.
Things you can open
-
github.com/yaskodama/abclcp
— the OCaml implementation. The Rocq development is in
coq/ on the make-src-base branch.
-
/manual.html ·
/actor.html
— the user manual, and an AIPL runtime you can type into, running in your browser.
-
/apps.html
— three applications written in AIPL: a 6-axis arm doing line work, a
23-joint humanoid walking, and a fire-evacuation MANET on a real road network.
All run entirely in the browser and show the AIPL source line that is executing.
-
Dining philosophers
— the actor scheduler and its live dashboard, in a single page.
Reports
The group has written about 84 technical reports (roughly 990 pages), most of them
in Japanese. A selection:
- Type soundness of AIPL, 4th edition (25 pp., August 2026) — the machine-checked development described above.
- The AIPL specification paper, 3rd edition (30 pp.) — the current definition of the language.
- Agent graphs: effectiveness, method, and an applied case (three reports, August 2026).
- A field experiment for evacuation-support MANET, 2nd edition (13 pp., August 2026).
The full report archive is access-controlled. PDFs are available on request.
Contact
Yasushi Kodama, Data Science Center, Hosei University, Tokyo, Japan —
yass@hosei.ac.jp.
You can also register on this site to reach the members area.