ScalaMatsuri blog

This blog is about ScalaMatsuri preparation, and sponsored by Hatena, Inc.

ScalaMatsuri 2018 CFP is now open!

Hi, ScalaMatsuri organizer Kasuya (id:daiksy) here.

We are excited to announce that the fifth ScalaMatsuri will be held on March 16th (Fri), 17th (Sat), and 18th (Sun), 2018 at Tokyo International Exchange Center. Please submit your talk for the general sessions that will be held on 17th (Sat) or 18th (Sun).

Nakamura-san, who got voted the most last year

Here are the overview of the CFP:

  • CFP will close at December 16th 23:59 JST.
  • We are looking for topics that you think Scala community or new learners of Scala would be interested.
  • Session length: 10, 40, or 90 minutes.
  • You are allowed up to three submissions.
    • We'll ask you to select one talk even if multiple talks qualify.
  • Speakers will be decided using survey and SNS impact as references.
  • For those who request it, we have fixed-amount travel grants for speakers with most votes.
  • We require all participants to respect our Code of Conduct
  • See for more details.

Your talks make ScalaMatsuri a great event every year. Let's do this again for 2018!!

Here are some more details.

Session lengths

We've created 10, 40, and 90 minute sessions. Pick the length that fits your content the best -- from lighter talk to more involved lectures.

The new addition this year is the 90 minute length. This is intended to cover workshop and other formats different from lecture-style sessions that would have been difficult with the conventional 40 minute session. Conventionally these were covered by the Unconference, but we can now plan ahead for these types of sessions.

Of course, if you would have something to lecture using the whole 90 minutes, that is welcome as well. Surprise us with your new ideas.

SNS impact

Speakers will be decided by a selection committee using participant's voting as the primary reference, but we will take SNS impact into the account. The SNS impact will be calculated by quantifying the buzz (or share) on Twitter, Facebook, Hatena Bookmark etc to measure the excitement about the session.

We are planning to tally the number of times a session was shared to Twitter, Facebook, and Hatena Bookmark via the social buttons placed on each proposal page of the official ScalaMatsuri website.

This is intended to create buzz around ScalaMatsuri up front, and also to attract people to your proposals. Once your proposals get on the official ScalaMatsuri website, please share it on various media to advertise your proposal.

Travel grant

ScalaMatsuri wants diverse speakers from all over the world. To help break down the barriers, we're excited to offer travel grant.

Here are the only categories that can assist (because we are a non-profit):

  1. Airfare and other transportation to Tokyo.
  2. Other transportation during ScalaMatsuri
  3. Hotel fares during ScalaMatsuri general sessions. (three nights for March 16th, 17th, and 18th)

Any other expenses, including ones incurred from sightseeing or hotel fares (priced per person in Japan) for accompanying travellers, cannot be expensed by us. Please note that we expect hotel fees to be covered either by the speakers or from the travel grant. In other words, you must book the hotel and air travel on yourself.

The maximum amount of the travel grant is fixed by the origin of your travel:

  • Japan $800 USD
  • East Asia and Southeast Asia (China, Korea, Philippines etc) $900 USD
  • Other Asia (India, Turkey, Israel, etc) $1500 USD
  • Oceania $1300 USD
  • Europe $1500 USD
  • Africa $2000 USD
  • North America $1500 USD
  • South America $2000 USD

Note that the amount offered as travel grant will NOT exceed the actual travel expense. Suppose you've been approved for the grant and the travel expense was $1000 from Europe, the maximum amount the ScalaMatsuri will reimburse will be $1000.

All items must have either an email forward from an airline or scans/photos of a receipt. Please read for more details.

Session voting begins! (and about uncategorized voting)

Hi. This is @eed3si9n, one of the ScalaMatsuri staff. Although, I am a member of the Translation team, I like to participate in anything interesting from scheduling to swag items.


tl; dr. Here are the gist of this post.

  • The voting will close at December 1st, 23:59 JST. Based on the submitted sessions, we are going to change the previous voting system to an “uncategorized voting.”
  • The voting results will be interpreted more like a public opinion poll. In that, instead of picking the speakers purely based on the number of votes, ScalaMatsuri selection committee will pick up the mix of popular sessions, popular topics, as well as hand-picked sessions.
  • This year’s voting will be available directly from the ScalaMatsuri website after logging in.
  • If you’ve submitted a talk, and want to switch to another category, please let us know in the next few days via

A regional tech conference that's also global

As ScalaMatsuri made a huge progress in 2016, 2017 will continue to uphold the two major goals in a sustainable way:

  • Providing a space for Japanese Scala community to socialize, and present ideas to the international audience.
  • Make a global technical conference with the universal access, where people from various background such as languages, gender, or ethnicity, can be comfortable.

The concrete actions taken for these goals are documented in my last year’s post A regional tech conference that's also global, but here are the hightlights:

  • Establishing Code of Conduct, and making an intro video for it.
  • Public CFP, travel support, and translations of the submitted session abstracts.
  • Public voting of the sessions.
  • Subtitles on the slide decks and professional two-way interpretation.

My thoughts on how these went are written up in ScalaMatsuri as a lifestyle.

Revisiting the public voting

The ideas of public CFP and voting were adopted with inspiration from nescala, but for ScalaMatsuri that has many sessions over multiple tracks, we don’t think pure ballot yields the best result.

As it was the first trial, we first determined the number of sessions per each category of Japanese and English - sessions of 15 and 40 minute length. As we were too focused on making the language ratio 1:1, I think we ended up missing many of the 15 minutes talks that were popular.

Till date, there are 43 of 40 minute English proposals, 16 of 40 minute Japanese proposals, 9 of 15 minute English proposals, and 13 of 15 minutes Japanese proposals. I don’t think it would be best to fixate on picking eight 40 minute sessions and three 15 minute sessions.

Instead of determining the number of sessions up front per category, we might be able to schedule six 40 minute talks and eight 15 minute talks for Japanese given there are almost equal number of proposals. Really, the criteria that matters is “what the audience wants to see on the day of the conference.”

Uncategorized voting

To research “what the audience wants to see on the day of the conference,” ScalaMatsuri 2017 will adopt uncategorized voting. In other words, we will remove the categorization of English/Japanese 40/15 minutes, and you can pick whatever you want to see from all the proposals. One of the reasons we are even able to consider this, is because we have successfully implemented two-way interpretation. We no longer have to be nervous about the language barrier issue.

Because we reused the session proposal list from the last year, the page contains the “About voting” section, which states “The voting will be done for the following categories separately.” If you’ve submitted a talk, and want to switch to another category, please let us know in the next few days via

Public opinion poll

One point I want to clarify before we begin the voting this year, is that this year’s voting will be considered a public opinion poll.

Last year we observed that when hundreds of people try to select 22 sessions, the selected talks end up forming a cluster of similar topics. This is actually an obvious outcome because the voters did not talk to each other to coordinate “hey, let’s pick that talk for intro to fp.”

Another observation we made is that there was a pack of 6 or 8 talks that clearly got more votes than the others, but then the curve flattens to one or two votes difference.


In short, there was a clear top cluster of a few sessions that everyone wants to see, and the rest spread out widely. Combining these points, instead of picking talks from the top mathematically, we think the conference would be far more enjoyable if we treated the voting more like a public opinion poll to infer topics and trends. ScalaMatsuri selection committee will pick up the mix of popular sessions, popular topics, as well as hand-picked sessions with some degree of subjectiveness.

Voting program

One of the things we couldn’t do last year due to lack of time, was creating our own voting program. This year we commissioned Tech to Value to make the voting program. After logging in, you can now vote from the ScalaMatsuri website’s session proposal list.


You can vote by clicking on the ☆ icon. Since there are many sessions, you can first pin some of the candidates first using the pushpin icon.

How to vote

Participants who bought a ticket, sponsor companies and ScalaMatsuri staffs are eligible for voting. This article covers how participants can vote.

1.) Confirm your e-mail address that you used to buy the ticket, and the reception number in the e-mail you have received from DoorKeeper.


The email you have received from Doorkeeper contains the QR code with your reception number (your 6 digits number below the QR code). You will be asked to enter the reception number when you sign in. We will verify this code later to match up with your Google, Twitter, or Github account that you use to sign in.

If you haven't made the purchase yet, there are a few more tickets available from the following page:

2.) From the top right of the proposal list page, press the “Sign-in” button and sign in using your Google, Twitter, or GitHub account. (This will pop up an Authorize application dialog)

When you sign in, please enter the DoorKeeper reception number. This is it for the preparation.

Select the sessions you would like to see. The number of votes per person is limited to 10. The remaining votes will be displayed at the top of the proposal list page.

There are toggles to display only the voted and/or pinned sessions. f:id:mocolog:20161125125159p:plain

The voting will close on 1st, Dec. 23:59 JST. Any votes afterwards will be invalid, so please be sure to vote early.

3.) Get psyched waiting for the voting result!

Voting FAQ

Q.How will the voting result be announced?

A.We will announce the result at the ScalaMatsuri website.

We will also announce on the Twitter, so this might a good chance to start following us.

  1. Is there any extra chance to talk what if my proposal is not accepted?

You can propose your talk for our Unconference, which will be held on the second day of the conference (February 26, 2017). The talks are proposed and assigned on the day of the Unconference in the morning. We tend to have more sessions during the Unconference, so please bring your talks.

Please remember to vote!

CFP closes, and session voting opens!

photo by Just Us 3

Hi, this is @OE_uia, an organizer of ScalaMatsuri.

We've closed CFP on 14th Oct. and got final count of 117 proposals, which is the highest in ScalaMatsuri history. Huge thanks to all the candidates!

Although all sessions sounds attractive, we'll have a voting session to determine speakers as we communicated in last article.

A regional tech conference that's also global - ScalaMatsuri blog

All the sessions in conference part will be chosen by this session voting. This means it determines whether you'll be able to enjoy Scala Matsuri fully, or be a bit disappointed at it.

You'll want to see the proposal list one by one. It would be helpful to filter sessions by tags you're interested in.

Links to Twitter or GitHub accounts help you to understand candidates. Discussion at Official Gitter Channel or at Twitter may give another insight with you.

We expect you to choose sessions which you really want to see. It would definitely make ScalaMatsuri enjoyable.

How to vote:

This voting session is for participants who bought a ticket, sponsor companies and ScalaMatsuri staffs. This article covers how participants can vote.

1.) Confirm your e-mail address which you use to buy ticket, and check-in code in a ticket e-mail.

You can check mails from Doorkeeper and it has QR code with check-in code (your 6 digits number below QR code).


You need to input this reception number, your name as well as e-mail address in the voting form. We'll verify your votes using reception number and your name, and your e-mail address.

If you haven't made the purchase yet, Ninja sponsor is still available. With this sponsorship, you can join session voting as well as ScalaMatsuri 2016, and will be called Ninja!

2.) Fill this form with your e-mail address which you used in vote.

Suffix of each line stands for difficulties:: +:Beginner, ++:Intermediate, +++:Advanced.

ScalaMatsuri 2016 Session Voting

Here are abstracts of candidates. You can filter candidates with tag.

Proposal List - ScalaMatsuri 2016

In this form, you'll need to choose following number of sessions by category (language, length).

  • English 40min ... 12 sessions out of 48 candidates
  • English 15min ... 3 sessions out of 12 candidates
  • Japanese 40min ... 7 sessions out of 27 candidates
  • Japanese 15min ... 8 sessions out of 30 candidates

This session voting will be closed at 23:59 JST on 30th Oct.

(Note: Professional translation services are available in main two halls.)

3.) Get psyched waiting for the voting result!

Voting FAQ

Q.How will voting result be announced?

A.We will announce at ScalaMatsuri Website.

Q. Why are the number of votes different among the session categories?

A.This is for room allocation. Comparing popularity of each session beforehand is very important to assign appropriate room to them. However, it's not very straight forward to compare since they're under different competition rate.

So we standardize weight of votes, and will be able to just compare number of votes which each session gets.

Number of sessions in each language will be almost same.

Q. Is there any extra chance to talk what if my proposal is not accepted?
  1. You can propose your talk for our Unconference, which is planned to be 2nd day of ScalaMatsuri 2016 (31st Jan in 2016).

Proposals Talks are gathered and assigned at the morning session of the day. Number of sessions in unconference is a bit more than conference part.

Gitter channels open now

We've opend gitter channels for ScalaMatsuri, in English or Japanese. You can ask any question about ScalaMatsuri, or discuss session voting, logistics etc.

This gitter channel is inspired from Scala World.

Japanese channel scalamatsuri/scalamatsuri-ja

English channel scalamatsuri/scalamatsuri-en

Enjoy ScalaMatsuri session voting!

A regional tech conference that's also global

Hi. This is @eed3si9n, one of the ScalaMatsuri staff. Supposedly I am a member of the Translation team, but I’m getting involved in anything interesting from planning to swag items.

Two major goals that I consider ScalaMatsuri 2016 has are:

  • Providing a space for Japanese Scala community to socialize, and present ideas to the international audience.
  • Making a global technical conference with the universal access, where people from various background such as languages, gender, or ethnicity, can be comfortable.

Of course part of the fun is planning the conference itself, thinking about these things. After last year’s conference I thought about those goals and wrote up a blog post towards universal access at a conference.

Today I want to talk about what we have been doing to make both regional and global conference, and introduce the background of the ideas presented in the “towards universal access” post, like the Code of Conduct, public CFP, and voting. The ideas themselves have been around, but getting them to materialize required many discussions on different parameters such as making sure that the conference is enjoyable to the attendees, leaving in the Japanese flavors, increasing more participants from overseas including nearby Asian countries, and improving the technical level of the conference.

What’s a harassment?

Most of us think of ourselves as the good guys. In a way, it could be similar to a method that thinks it should throw exception when something bad happens. In reality, such assumption could end up bothering others. For example, statements like “despite being a man|woman …” or “such and such country people are …” would be stereotyping, and would be considered discriminatory.

ScalaMatsuri has adopted a Code of Conduct since the last time, but this time we are explicitly forbidding asking other participants out (comments about appearance, romantic or sexual interest). You would think “there’s no way anyone would do this,” but there has been regular reports of harassments in the recent conferences including Scala related ones. We think there is an urgent need to specify the type to define a safe space for those who are unfamiliar with the general culture in Japan, do not interact with our community often, and especially female hackers from both Japan and overseas.

Please treat each other with respect as a hacker. Thanks for your cooperation.

Public CFP

In the past two conferences, the organizers have selected the invited speakers. The first has saw 4 members from Typesafe, and the second one had Martin Odersky as the keynote. As a method of further improving the technical level of the sessions, we are venturing into long-term public CFP, and providing maximum $2000 travel support.

The 40-minute English session in particular has total 32 session ideas. This level of competition would not have been possible with the conventional method through the organizers. Fortunately, we have many sponsors this year, so we will be able to fund the travel supports as planned. Thank you!

With the session candidates on both languages with such range and depth, the conference will be interesting with any of them selected. With professional interpreters on two halls, providing the translation both from English-Japanese, and Japanese-English, our hope is that we can learn from the talks this year.


As the mechanism of reflecting the opinions from the attendees we’ve adopted the voting to decide the sessions by the first round ticket purchasers, sponsors, and staff. This is also aimed to distribute the limited travel support fairly.

The session voting will start on October 16th, which the next day of CFP deadline, and the voting will close at 23:59pm of October 30th JST.

The voting rules are public at the CFP page.

  • The voting will be done for the following categories separately: 40-minute talks in English, 40-minute talks in Japanese, 15-minute talks in English, and 15-minute talks in Japanese.
  • We will try to select eight 40-minute talks and three 15-minute talks for both the languages. The number may vary depending on the travel budgets.
  • Two slots for 40-minute talks in Japanese will be reserved for Beginner talks. No reservation will be placed for English talks.
  • Only one session will be offered per person.

There a few variables that we tweaked in the above rules. One of them was setting the language ratio of the winners to 1:1. As of today, there are way more applicants on the English-speaking side, but there is a finite limit on the travel budget; majority of the conference participants would be from Japan; and we would like leave in some regional flavors. In the end, we settle with 1:1, which means 8 slots each for 40 minutes sessions, and 3 slots each for the 15-minute sessions.

Starting this CFP, we started asking the speakers of the sessions intended audiences (beginner, intermediate, and advanced). Likely most of the speakers and participants from oversea is going to be intermediate and above, but there will be beginner participants from the domestic side. We wanted to have some numbers of session in Japanese that do not require prior knowledge, so we are making two fixed beginner slots for the 40-minute sessions in Japanese.

After voting is done, the sessions will be selected provisionally in the order of the gained votes, but the travel support will be given out from the speakers with the most votes, so the final result may not reflect the number of votes, and we will not know the language ratio until the end.

CFP translations

Since we would like both English and Japanese speakers to vote on both the English and Japanese sessions, the on-going task that’s happening is CFP translations. The translation team translates the title and the abstract of all 58 submitted sessions into Japanese if the original was in English, and to English if the original was in Japanese.

Many of the conference talks and computer science in general is filled with catchy titles like “dining philosophers” and “scrap your boilerplate” with requires a rich sense of the language. The translation team tries to keep the playfulness even when the topic is serious.

Ideas to make ScalaMatsuri more fun

Your sessions are the main contents of ScalaMatsuri. If you have an idea of “I want go to such and such kind of conference” or “I want to hear somesuch sessions” please tweet with #scalamatsuri, or submit your talk by October 15th 00:00 JST.

There will also be an unconference on day 2. You can propose a topic on the spot to do a round table. Or start hacking on a program for a surprising demo. The contents of the conference is determined by you on the day. Since the venue will have many rooms, day 2 should accommodate more nerdy topics, so start thinking about them.