the blllog.

LXJS 2013

2013-10-06 18:50

The LXJS conference was a blast like last year. Well organized, great speakers, nice parties and an overwhelming overall atmosphere. It's definitely a conference that is in my regular schedule.

The talks

It was a pleasure to see such a variety of different talk styles. Whenever you get invited/accepted to give a talk at the LXJS, be sure your presentation style is outstanding. My two favourite ones were Michal Budzynski – Firefox OS army! and Jonathan Lipps – mobile automation made awesome. Playing games on stage or singing songs is something you won't see at many other conferences.

Another presentation I really enjoyed was one about designing for accessibility. Laura Kalbag did really get the message across and showed great examples.

Interesting was also the talk Digital Feudalism & How to Avoid It. It was about user experience and touched a lot of topics, from business models over privacy to the problems of open source. I really like the whole presentation, from the contents to the presentation style. But sadly only up to shortly before the end of the talk. Aral Balkan closed with his new startup that creates a new phone with overall great experience. As far as I know there's no information available on what Codename Prometheus will be based on. If it's based on Firefox OS I can see the point, if it's something custom I see doomed to fail.

A really enjoyable talk came from Vyacheslav Egorov. It was about microbenchmarking pitfalls and had great depth, while being super entertaining.

The people

I've met a lot new ones and plenty of people I already know. It was a good mixture with many great conversations. There's not really a point mentioning all of them, you know who you are.

On the boat trip I learned that Mountain View (that link is funnier than I've thought, given that's a blog about a JavaScript conference) not one of the most boring places but actually has something to over if you life there (recommend for young singles).

The conference itself

The conference was very well organized. Thanks David Dias and all the others that organized that event (here should be a link, but I couldn't found one to the organizers). Having a cinema as a venue is always nice. Comfortable seats and a big canvas for presentation.

Live streaming of the talks and having them available immediately afterwards on YouTube is really really nice. So even if you can't attend you still get all the great talks if you want to.

The only critique I have is the lunch. Those baguettes were OK and I didn't leave hungry, but the food last time was just so much better.


The LXJS 2013 was a great and I'm looking forward to see everyone again at this well organized conference next year!

Categories: en, JavaScript, conference

LXJS 2012

2012-10-01 22:27

The LXJS conference was really a blast. Well organized, great speakers, nice parties and an overwhelming overall atmosphere. My talk about bidirectional transformations also went well.

My talk

With my talk "Bidirectional transformations with lenses", it's been the first time I've talked about something not directly geo-related at a conference, though I couldn't leave out some references to the geo world. The whole topic would deserves a blog post on its own, hence I'll just leave a reference to the slides of my talk, the recording from LXJS and the Github repository of jslens.

The others talks

Most talks were of high quality and it was a great to learn about new things. Highlights for me were the talks about Fireworks (where there doesn't seem to be a recording of), the one about Helicopters, the one about how to manage open source projects properly and Jan's talk about Javascript's world domination that made me think.

All presentations were recorded, so you can watch them now to find out what you've missed out.

Format of the conference

It was the first single-track conference I've been to and I really liked it. Everyone got to see the same presentations and you don't feel like you've missed something. As a speaker you have the advantage of not having some well known person at the same time which draws away the attendees from your talk. Everything is focused around a single stage where everyone is excited about what is next.

The talks where always grouped into certain categories, that made a lot of sense. Though it was a bit strange to hear about new JavaScript based languages in two different slots.

The events around the conference

The conference had a pre, middle and after party. It was really good to get in touch with people there. I also liked the idea to not making a difference between the speakers and the attendees with a speakers dinner or something similar. For the after-after party a huge group of people just kept on having fun. The people didn't split as much as I would've expected it. This speaks for the great atmosphere and the nice group of attendees.


I really had a great time and it was fun to meet so many old friends from the CouchOne days, but also to meet a lot of interesting new people. I'm really looking forward to the 2013 edition of the LXJS.

Categories: en, JavaScript, conference

FOSS4G 2011: Report

2011-09-20 22:27

The FOSS4G 2011 is over now. Time for a small report. The crowd was amazing and it was again the ultimate gathering of the Free and Open Source for Geospatial developer tribe. Solid presentations and great evenings.

My talk: The State of GeoCouch

I'm really happy how my talk went, I really enjoyed it. The were lots of people (although there was a talk from Frank Warmerdam at the same time) asking interesting questions at the end.

The talk is not only about GeoCouch but also gives you an overview of some of the features it leverages from Apache CouchDB. In the end you should have an overview why you might want to use GeoCouch for your next project.

You can get the slides right here.

Other talks

I was happy to see that there was another talk about GeoCouch. Other talks I really enjoyed were:

And of course there were also great talks from in the plenary sessions from Paul Ramsey about Why do you do that? An exploration of open source business models and Schuyler Erle's so funny lightning talk about Pivoting to Monetize Mobile Hyperlocal Social Gamification by Going Viral

Code Sprint

At the code sprint I was working on MapQuery together with Steven Ottens and Justin Penka. Steven was working on TMS support, Justin on a 6 minutes tutorial and I on making manual adding of features possible.

The OpenLayers developers did the migration from Subversion to Git for their development. OpenLayers is now available on Github.

And luckily there was a fire alarm in between to take a group photograph.

Future of the FOSS4G

I really hope there won't be a yearly FOSS4G conference for the whole of the US. There should be regional events, as I think one big one would draw the attention away from the international conference. Why should you fly to Beijing for the FOSS4G 2012 if you can meet the majority of the developers in the US as well?

Final words

The FOSS4G was great. It was organized well and people were always out in the evenings. The only minor nitpick is that many people working remote had the city of their company in the name badge and not the one they live in. It seems that the original for you had to fill was confusing. So for next year it should perhaps say “Location where you live”. Hence I still don't believe that there were more Dutch than German people at the conference (Tik hem aan, ouwe! ;)

Categories: en, CouchDB, GeoCouch, MapQuery, Erlang, JavaScript, geo

Bolsena hacking event

2010-06-11 22:27

The OSGeo hacking event in Bolsena/Italy was great. Many interesting people sitting the whole day in front of their laptops surrounded by a beautiful scenery and nice warm sunny weather. It gets even better when you get meat for lunch and dinner.

I had the chance to tell people a bit more about CouchDB and Couchapps,

One project I haven't heard that much before of was Degree. They build the whole stack of OGC services you could imagine. For me it was of interest that they have a blob storage in their upcoming 3.0 release. The data isn't flattened into SQL tables but stored as blobs. This sounds like good use for a CouchDB backend in the future.

I was working with Simon Pigot on a GeoNetwork re-implementation based on CouchDB using Couchapp. We got the basic stuff like putting an XML document into the database, editing it and returning the new document, as well as fulltext indexing with couchdb-lucene work. Next steps are improving the JSON to XML mapping and integrating spatial search based on GeoCouch.

The event was really enjoyable, thanks Couchio for sponsoring the trip, thanks Jeroen for organizing it, and thanks all other hackers that made it such a awesome event. Hope to see you next year!

Categories: en, CouchDB, JavaScript, geo

Drag as long as you want

2009-11-11 22:27

It has been a very long outstanding bug (officially it was a missing feature) in OpenLayers that annoyed me from the first time I’ve been using OpenLayers. I’m talking about ticket #39: “Allow pan-dragging while outside map until mouseup”.

Normally when you drag the map in OpenLayers it will stop dragging as soon as you hit the edge of the map viewport (the div that contains the map). Whenever you have a small map, but a huge window and a loooong way to drag, it can get quite annoying, as the maximum distance you can drag at once is the size of that viewport.

But yesterday it finally happend. A patch to fix it landed in trunk. A first rough cut was made at the OpenLayers code sprint at the FOSS4G. Andreas Hocevar reviewed the code and made a more unobtrusive version of it (thanks, again).

Try these two examples to see the difference. Click on the map an drag it a long way to the right and back to the left again (you might need to zoom it a bit to see the full effect):

As it is a new feature, it isn’t enabled by default (and only available on current SVN trunk, it will be available in OpenLayers 2.9). To enable it on your map, just use the following code to add the documentDrag parameter to the DragPan control (you obviously need a recent SVN checkout).

Update (2009-11-18): It got even easier with r9805:

// Use default controls but with documentDrag enabled.
var controls = [
    new OpenLayers.Control.Navigation({documentDrag: true}),
    new OpenLayers.Control.PanZoom(),
    new OpenLayers.Control.ArgParser(),
    new OpenLayers.Control.Attribution()]
map = new OpenLayers.Map('map', {controls: controls});

For a full working version have a look at the source of the documentDrag example.

Categories: en, OpenLayers, JavaScript, geo

Poor man’s bounding box queries with CouchDB

2009-07-19 22:27

Several people store geographical points within CouchDB and would like to make a bounding box query on them. This isn’t possible with plain CouchDB _views. But there’s light at the end of the tunnel. One solution will be GeoCouch (which can do a lot more than simple bounding box queries), once there’s a new release, the other one is already there: you can use a the list/show API (Warning: the current wiki page (as at 2009-07-19) applies to CouchDB 0.9, I use the new 0.10 API).

You can either add a _list function as described in the documentation or use my futon-list branch which includes an interface for easier _list function creation/editing.

Your data

The _list function needs to match your data, thus I expect documents with a field named location which contains an array with the coordinates. Here’s a simple example document:

   "_id": "00001aef7b72e90b991975ef2a7e1fa7",
   "_rev": "1-4063357886",
   "name": "Augsburg",
   "location": [
   "some extra data": "Zirbelnuss"

The _list function

We aim at creating a _list function that returns the same response as a normal _view would return, but filtered with a bounding box. Let’s start with a _list function which returns the same results as plain _view (no bounding box filtering, yet). The whitespaces of the output differ slightly.

function(head, req) {
    var row, sep = '\n';

    // Send the same Content-Type as CouchDB would
    if (req.headers.Accept.indexOf('application/json')!=-1)
      start({"headers":{"Content-Type" : "application/json"}});
      start({"headers":{"Content-Type" : "text/plain"}});

    send('{"total_rows":' + head.total_rows +
    while (row = getRow()) {
        send(sep + toJSON(row));
        sep = ',\n';
    return "\n]}";

The _list API allows to you add any arbitrary query string to the URL. In our case that will be bbox=west,south,east,north (adapted from the OpenSearch Geo Extension). Parsing the bounding box is really easy. The query parameters of the request are stored in the property req.query as key/value pairs. Get the bounding box, split it into separate values and compare it with the values of every row.

var row, location, bbox = req.query.bbox.split(',');
while (row = getRow()) {
    location = row.value.location;
    if (location[0]>bbox[0] && location[0]<bbox[2] &&
            location[1]>bbox[1] && location[1]<bbox[3]) {
        send(sep + toJSON(row));
        sep = ',\n';

And finally we make sure that no error message is thrown when the bbox query parameter is omitted. Here’s the final result:

function(head, req) {
    var row, bbox, location, sep = '\n';

    // Send the same Content-Type as CouchDB would
    if (req.headers.Accept.indexOf('application/json')!=-1)
      start({"headers":{"Content-Type" : "application/json"}});
      start({"headers":{"Content-Type" : "text/plain"}});

    if (req.query.bbox)
        bbox = req.query.bbox.split(',');

    send('{"total_rows":' + head.total_rows +
    while (row = getRow()) {
        location = row.value.location;
        if (!bbox || (location[0]>bbox[0] && location[0]<bbox[2] &&
                      location[1]>bbox[1] && location[1]<bbox[3])) {
            send(sep + toJSON(row));
            sep = ',\n';
    return "\n]}";

An example how to access your _list function would be: http://localhost:5984/geodata/_design/designdoc/_list/bbox/viewname?bbox=10,0,120,90&limit=10000

Now you should be able to filter any of your point clouds with a bounding box. The performance should be alright for a reasonable number of points. A usual use-case would something like displaying a few points on a map, where you don’t want to see zillions of them anyway.

Stay tuned for a follow-up posting about displaying points with OpenLayers.

Categories: en, CouchDB, JavaScript, geo

List function editing in Futon

2009-07-19 22:27

Futon is the graphical administration interface for CouchDB. It’s nice and slick for browsing and editing views, but there is one feature missing: you can’t edit _list functions in similar fashion. You need to edit them as JSON strings.

As I wanted to play a bit with _list, I’ve created a branch which implements such an interface. Its usage should be quite self-explanatory. Just select a _view, from there you can switch to the "List" tab to create or edit a _list function.

You can get my futon-list branch at GitHub. Instead of using git, you can also download the share/wwww directory (click on the download button within the ‘share/www’ directory) and unpack it over your current source.

In case you wonder why your _list function doesn’t work, the API has changed for CouchDB 0.10.

Screenshot of the _list interface in Futon

Screenshot of the _list interface in Futon

Categories: en, CouchDB, JavaScript

By Volker Mische

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