Replicating memes

I made some documentation about our SPARQL-IN feature that we recently added. I added some interesting use-cases like doing an insert and a delete based on in values.

For the new class signal API that we’re developing this and next week, we’ll probably emit the IDs that tracker:id() would give you if you’d use that on a resource. This means that IN is very useful for the purpose of giving you metadata of resources that are in the list of IDs that you just received from the class signal.

We never documented tracker:id() very much, as it’s not an RDF standard; rather it’s something Tracker specific. But neither are the class signals a RDF standard; they are Tracker specific too. I guess here that makes it usable in combo and turns the status of ‘internal API’, irrelevant.

We’re right now prototyping the new class signals API. It’ll probably be a “sa(iii)a(iii)”:

That’s class-name and two arrays of subject-id, predicate-id, object-id. The class-name is to allow D-Bus filtering. The first array are the deletes and the second are the inserts. We’ll only give you object-ids of non-literal objects (literal objects have no internal object-id). This means that we don’t throw literals to you in the signal (you need to make a query to get them, we’ll throw 0 to you in the signal).

We give you the object-ids because of a use-case that we didn’t cover yet:

Given triple <a> nie:isLogicalPartOf <b>. When <a> is deleted, how do you know <b> during the signal? So the feature request was to do a select ?b { <a> nie:isLogicalPartOf ?b } when <a> is deleted (so the client couldn’t do that query anymore).

With the new signal we’ll give you the ID of <b> when <a> is deleted. We’ll also implement a tracker:uri(integer id) allowing you to get <b> out of that ID. It’ll do something like this, but then much faster: select ?subject { ?subject a rdfs:Resource . FILTER (tracker:id(?subject) IN (%d)) }

I know there will be people screaming for all objects, also literals, in the signals, but we don’t want to flood your D-Bus daemon with all that data. Scream all you want. Really, we don’t. Just do a roundtrip query.

I recently stumbled upon this marvelous piece. I title the quote “making an excuse“:

Saying that you’re forced to do something when you really aren’t is a failure to take responsibility for your actions. I generally don’t think users of proprietary software are primarily to blame for the challenges of software freedom — nearly all the blame lies with those who write, market, and distribute proprietary software. However, I think that software users should be clear about why they are using the software. It’s quite rare for someone to be compelled under threat of economic (or other) harm to use proprietary software. Therefore, only rarely is it justifiable to say you have to use proprietary software. In most cases, saying so is just making an excuse.

Bradley M. Kuhn - 2010, on his blog

I’ll translate this for you to Catholicism. You can definitely adapt this to most religions (for some, add death penalties like stoning here and there):

Saying that you’re forced by your nature to masturbate when you really aren’t is a failure to take responsibility for your actions. The church generally doesn’t think masturbaters are primarily to blame for the challenges of sexuality — nearly all the blame lies with pornography. However, I think that people who masturbate should be clear about why they have sex with themselves: It’s quite rare for someone to be compelled under the desire of sexual pleasure. Therefore, only rarely is it justifiable to say you have to masturbate. In most cases, saying so is just making an excuse.

The translation

There you go.

Busy handling

I made an article about reporting busy status in Tracker before.

But then it wasn’t yet possible to queue a query while Tracker’s RDF store is busy. We’re making this possible following next unstable release. Yeah I know you guys hate that Tracker’s RDF store can be busy. But you tell us what else to do while restoring a backup, or while replaying a journal?

While we are replaying the journal, or restoring a backup, we’ll accept your result-hungry queries into our queue. Meanwhile you get progress and status indication over a DBus signal. Some documentation about this is available here.

SPARQL 1.1 Draft features: IN and NOT IN

We had a feature requests for supporting SPARQL IN and NOT IN. As usual, we’re ahead of the SPARQL Draft specification. But I don’t think IN and NOT IN will look much different in the end. Anyway, it was straightforward so I just implemented both.

It goes like this:

SELECT ?abc { ?abc a nie:InformationElement ;
                   nie:title ?title .
               FILTER (?title IN ('abc', 'def')) }

SELECT ?abc { ?abc a nie:InformationElement ;
                   nie:title ?title .
               FILTER (?title NOT IN ('xyz', 'def')) }

It’s particularly useful to get metadata about a defined set of resources (give me the author of this, this and that file)

Direct access

This work is progressing nicely. Most of the guys on the team are working on this, and it’s going to be awesome thanks to SQLite’s WAL journal mode. SQLite’s WAL mode is still under development and probably unstable here and there, but we’re trusting the SQLite guys with this anyway.

What is left to do for direct-access is cleaning up a bit, getting the small nasty things right. You know. The basics are all in place now.

We’re doing most of the library code in Vala, but clever people can easily imagine the C API valac makes from the .vala files here. That’s the abstract API that client developers will use. Unless you use a higher level API like libqttracker, QSparql, Hormiga or sparql-glib.

All of which still need to be adapted to the direct-access work that we’re doing. But we’re in close contact with all of the developers involved in those libraries. And they’re all thrilled to implement backends for the new stuff.

Plans

We plan to change the signals-on-changes or class-signals feature a bit so that the three signals are merged into one. The problem with three is that you can’t reliably identify a change-transaction this way (a rename of a file, for example).

Another thing on our list is merging Zeitgeist’s ontology. To the other team members at Tracker: guys, Zeitgeist has been waiting for three months now. Let’s just get this done!

Oh there are a lot of plans, to be honest.

I wonder when, if ever, we go in feature freeze. Hehe. I guess we’ll just have very short feature-freeze periods. Whatever, it’s fun.

MeeGo in cars

Hey BMW & co, if you guys want to learn how to write music players and playlists for car entertainment on MeeGo, get in touch! This Tracker that I’m talking about is on that MeeGo OS; being the Music’s metadata database is among its purposes.

I can’t wait to have a better music player playlist my car.

Or maybe some integration with the in-car GPS and the car owner’s appointments and meetings? With geo-tagged photos on the car owner’s phone? Automatic and instant synchronization with Nokia’s future phones? Sounds all very doable, even easy, to me. I’d want all that stuff. Use-cases!

Let’s talk!

Een zelfstandige in België hoort zijn sociale bijdrage (bv. per kwartaal) vooraf te betalen. Je bent een debiel als je dat niet doet, want dan vragen ze na vier jaar lekker veel interest op het hele bedrag.

Iedereen die je tegen het lijf loopt wanneer je je firma opstart zal het je ook opnieuw zeggen. De mensen bij Unizo, op de cursus boekhouden, mijn boekhouder, de mensen van de bank en zelfs mijn notaris was het aan het uitleggen bij de oprichting. En allemaal met een dringende toon: doe dit, vergeet dat niet. Vergeet dat écht niet. Écht niet!

Je bent dus onwenselijk dom als je het toch niet doet. Maarja, dat er domme mensen bestaan is geen nieuws.

Wat weinig mensen weten is dat je het zelfs kan omdraaien: in tegenstelling tot voorafbetalingen van vennootschapsbelastingen, krijg je voor voorafbetalingen van je sociale bijdrage wél interest op het teveel betaalde bedrag.

En dat is een interest die momenteel hoger ligt dan wat je op een ferme spaarrekening krijgt.

Uiteraard moet je gokken wat je zoal gemiddeld zal verdienen op vier jaar. Dus uiteraard mag je dat vrij hoog inschatten. Weet jij misschien precies hoeveel meer winst je over enkele jaren zal maken? Nou ik niet. En ik geef mezelf uiteraard meer salaris wanneer er meer winst is, meneer de controleur. Maar ik kon het niet weten dat er na vier jaar toch niet zoveel winst was! Tja!

Dus, schat je dat vrij hoog in. En betaal je vier jaar lang te veel sociale bijdrage. Na vier jaar storten ze het teveel terug, mét een hoge interest.

Netjes toch?

Ik denk dat ik dit ga moeten vieren!

Nu niet teveel van jullie freelancers dit gaan doen he! Ik wil nog een paar jaartjes genieten van hun “probleem” ;-)

I try to avoid posting about the same subject twice in a row. But I also really think that Wikileaks is worth violating about any such rule in existence. Maybe I should make a category on my blog just for Wikileaks?

So TED has decided to do an interview with Julian Assange:

I’d like to point out that I congratulate and thank everybody, not just but also Julian, who’s involved. Thank you.

Today is the day the world is witnessing the most significant military leak in the history of mankind, so I have a feeling that today ’s gonna be a good day.

To all the people at Wikileaks, and to all whistle blowers in past, present and future: you are heroes. You guy’s ideas will be with us for centuries ahead of us. You’ll be remembered in history books. Let’s make sure you guys will.

I’m into Lars Von Trier’s movies last few days. First with Dear Wendy, then The boss of it all and yesterday I was watching Manderlay together with a girlfriend.

It wasn’t the first time that I saw the movie; I think the third time or something. But I’m still convinced that the movie is even better than Dogville, about which I wrote a few years ago that it’s the best movie I ever saw.

Don’t listen to the U.S. critics. In their struggle not to see the world from a U.S. point of view, they don’t understand what it’s about (it’s not really about slavery). I guess Lars Von Trier carefully selects his audience.

The movie Manderlay, like Dogville, has a (hidden) morality. Even more than Dogville, which is basically about the moral necessity of assertiveness, is Manderlay a movie that tries to make you think. In my case about the failure of only using assertiveness to educate people (about) a new reality. Also about the failure of using democratic voting for every issue (ownership of a tool). And about the necessity of a law system: no matter how moral, or, immoral; it’s still better than absolute freedom - people need a law -. But with “freedom” being some sort of piece of shit ideological word among many readers of my blog, I’m sure many wont understand what I mean with that. I try to carefully select my audience. I’m not against “freedom”, just against its naive interpretations. Especially the “anarchy”-ones.

So Manderlay dances with the morals in Dogville. Both movies are part of a trilogy, so I guess that makes sense.

I’m grateful that Lars carefully selects his audience. You don’t create art by appeasement.

Looking forward to Wasington, the last part of this trilogy.

In 4.57 billion years our solar system went from creating simple bacteria to a large group of species. Several of which highly capable of making fairly intelligent decisions, one of which capable of having the indulgence of believing that it can think. That’s us.

The sun has an estimated 5 billion years to go before it turns into a Red Giant that in its very early stages will wipe out truly every single idea that exists inside at least our own solar system.

Unless radio waves that our planet started emitting since we invented radio are seen and understood (which requires a recipient in the first place), that will be the ultimate end of all of our ideas and culture. Unless we figure out a way to let the ideas cultivate outside of our solar system. Just the ideas would already be an insane achievement.

But imagine going from bacteria to beings, colonized by bacteria, that think that they can think, in far less time than the current age of our sun. Unless, of course, bacteria somehow arrived into our solar system from outside (unlikely, but perhaps equally unlikely than us ever exporting our ideas and culture to another solar system).

Imagine what could happen in the next 5 billion years …

The support for domain specific indexes is, awaiting review / finished. Although we can further optimize it now. More on that later in this post. Image that you have this ontology:

nie:InformationElement a rdfs:Class .

nie:title a rdf:Property ;
  nrl:maxCardinality 1 ;
  rdfs:domain nie:InformationElement ;
  rdfs:range xsd:string .

nmm:MusicPiece a rdfs:Class ;
  rdfs:subClassOf nie:InformationElement .

nmm:beatsPerMinute a rdf:Property ;
  nrl:maxCardinality 1 ;
  rdfs:domain nmm:MusicPiece ;
  rdfs:range xsd:integer .

With that ontology there are three tables called “Resource”, “nmo:MusicPiece” and “nie:InformationElement” in SQLite’s schema:

• The “Resource” table has ID and the subject string
• The “nie:InformationElement” has ID and “nie:title”
• The “nmm:MusicPiece” one has ID and “nmm:beatsPerMinute”

That’s fairly simple, right? The problem is that when you ORDER BY “nie:title” that you’ll cause a full table scan on “nie:InformationElement”. That’s not good, because there are less “nmm:MusicPiece” records than “nie:InformationElement” ones.

Imagine that we do this SPARQL query:

SELECT ?title WHERE {
   ?resource a nmm:MusicPiece ;
             nie:title ?title
} ORDER BY ?title

We translate that, for you, to this SQL on our schema:

SELECT   "title_u" FROM (
  SELECT "nmm:MusicPiece1"."ID" AS "resource_u",
         "nie:InformationElement2"."nie:title" AS "title_u"
  FROM   "nmm:MusicPiece" AS "nmm:MusicPiece1",
         "nie:InformationElement" AS "nie:InformationElement2"
  WHERE  "nmm:MusicPiece1"."ID" = "nie:InformationElement2"."ID"
  AND    "title_u" IS NOT NULL
) ORDER BY "title_u"

OK, so with support for domain indexes we change the ontology like this:

nmm:MusicPiece a rdfs:Class ;
  rdfs:subClassOf nie:InformationElement ;
  tracker:domainIndex nie:title .

Now we’ll have the three tables called “Resource”, “nmo:MusicPiece” and “nie:InformationElement” in SQLite’s schema. But they will look like this:

• The “Resource” table has ID and the subject string
• The “nie:InformationElement” has ID and “nie:title”
• The “nmm:MusicPiece” table now has three columns called ID, “nmm:beatsPerMinute” and “nie:title”

The same data, for titles of music pieces, will be in both “nie:InformationElement” and “nmm:MusicPiece”. We copy to the mirror column during ontology change coping, and when new inserts happen.

When now the rdf:type is known in the SPARQL query as a nmm:MusicPiece, like in the query mentioned earlier, we know that we can use the “nie:title” from the “nmm:MusicPiece” table in SQLite. That allows us to generate you this SQL query:

SELECT   "title_u" FROM (
  SELECT "nmm:MusicPiece1"."ID" AS "resource_u",
         "nmm:MusicPiece1"."nie:title" AS "title_u"
  FROM   "nmm:MusicPiece" AS "nmm:MusicPiece1"
  WHERE  "title_u" IS NOT NULL
) ORDER BY "title_u"

A remaining optimization is when you request a rdf:type that is a subclass of nmm:MusicPiece, like this:

SELECT ?title WHERE {
  ?resource a nmm:MusicPiece, nie:InformationElement ;
            nie:title ?title
} ORDER BY ?title

It’s still not as bad as now the “nie:title” is still taken from the “nmm:MusicPiece” table. But the join with “nie:InformationElement” is still needlessly there (we could just do the earlier SQL query in this case):

SELECT   "title_u" FROM (
  SELECT "nmm:MusicPiece1"."ID" AS "resource_u",
         "nmm:MusicPiece1"."nie:title" AS "title_u"
  FROM   "nmm:MusicPiece" AS "nmm:MusicPiece1",
         "nie:InformationElement" AS "nie:InformationElement2"
  WHERE  "nmm:MusicPiece1"."ID" = "nie:InformationElement2"."ID"
  AND    "title_u" IS NOT NULL
) ORDER BY "title_u"

We will probably optimize this specific use-case further later this week.

In followup on the RSA animation videos here’s the original talk by Barbara Ehrenreich titled Smile or Die.

I think part of GNOME’s crisis is caused by the same atmosphere of “go with the program, don’t complain, or you’re out”. I wrote about this before:

It’s not popular to be critical about a (the leader of a) popular idea. This is illustrated by the intellectually absurd criticisms David Schlesinger receives.

Yet is the critic who monitors the organs of a society key to that organ either producing for its stakeholders, or failing and dragging the entire society it serves down with it.

Acknowledging the problem and changing course is what I seek in a candidate this year.

OK, two is enough. Back to technical articles.

Today after I brought Tinne to the airport I drove around Zürichsee. She can’t stay in Switzerland the entire month; she has to go back to school on Monday.

While driving on the Seestrasse I started counting luxury cars. After I reached two for Lamborgini and three for Ferrari I started thinking: Zimmerberg Sihltal and Pfannenstiel must be expensive districts too… And yes, they are.

I was lucky today that it was nice weather. But wow, what a nice view on the mountain tops when you look south over Zürichsee. People from Zürich, you guys are so lucky! Such immense calming feeling the view gives me! For me, it beats sauna. And I’m a real sauna fan.

I’m thinking to check it out south of Zürich. But not the canton. I think the house prices are just exaggerated high in the canton of Zürich. I was thinking Sankt Gallen, Toggenburg. I’ve never been there; I’ll check it out tomorrow.

Hmmr, meteoswiss gives rain for tomorrow. Doesn’t matter.

Actually, when I came back from the airport the first thing I really did was fix coping with property changes in ontologies for Tracker. Yesterday it wasn’t my day, I think. I couldn’t find this damn problem in my code! And in the evening I lost three chess games in a row against Tinne. That’s really a bad score for me. Maybe after two weeks of playing chess almost every evening, she got better than me? Hmmrr, that’s a troubling idea.

Anyway, so when I got back from the airport I couldn’t resist beating the code problem that I didn’t find on Friday. I found it! It works!

I guess I’m both a dreamer and a realist programmer. But don’t tell my customers that I’m such a dreamer.

Today Tinne and I visited Switzerland’s capital, Bern.

We were really surprised; we’d never imagined that a capital city could offer so much peace and calm. It felt good to be there.

The fountains, the old houses, the river and the snowy mountain peaks give the city an idyllic image.

Standing on the bridge, you see the roofs of all these lovely small houses.

The bear is the symbol of Bern. Near the House of Parliament there was this statue of a bear. Tinne just couldn’t resist to give it a hug. Bern has also got real bears. Unfortunately, Tinne was not allowed to cuddle those bears.

The House of Parliament is a truly impressive building. It looks over the snowy mountains, its people and its treasury, the National Bank of Switzerland.

As you can imagine, the National Bank building is a master piece as well. And even more impressive; it issues a world leading currency.

On the market square in Oerlikon we first saw this chess board on the street; black and white stones and giant chess pieces. In Bern there was also a giant chess board in the backyard of the House of Parliament. Tinne couldn’t resist to challenge me for a game of chess. (*edit*, Armin noted in a comment that the initial position of knight and bishop are swapped. And OMG, he’s right!)

And she won!

At the House of Parliament you get a stunning, idyllic view on the mountains of Switzerland.

It’s crossing my mind to move here in ~ two years.

Today we visited Zug; it has a Ferrari shop.

Zug, where an apartment costs far more than a villa in Belgium. Briefly a million euros.

It also comforts me. I could be here. Zug has a volière with exotic birds and a lake.

When Tinne and me were driving back to Oerlikon, we listened to Karoliina’s Symphonic dream.

The music; a canvas for the paint, Switzerland.

Die Lichter auf dem Berg. Die sind alle Seelen.

Congratulations to Mr. Van Rompuy for helping the EU powers to find a compromise.

Diplomats credit him with a shrewd sense of deal-making and a determination that is belied by his quiet anti-charisma, and he has already begun to win plaudits from Paris, Berlin and other capitals.

– Financial Times, Saturday Mar 27 2010 (alt. link)

Finally a politician to be proud of as a Belgian!

The mouse is dull grey
It steps into the sunshine
The mouse is snow white

Let’s discuss this abstract quote about mailing lists:

At the end of the day, there are some people who deserve to be unpopular and we have no way to do that.

– Luis Villa March 17 2010, on his blog