Messages

Why is AGS not GPL (now that it's already open source)? What prevents AGS from being GPL? And what are the benefits and/or limitations of AGS being GPL?

IMHO, the problem of GPL is not with AGS it's self but with the games people make with AGS.   Most of the people that come here to make games don't have their own website.  They make their game and find free file hosting somewhere which is notoriously unreliable for an number of reasons.   The requirement of them having to provide source or offering to provide source for a period of three years is a major inconvenience.   A way around this is that they be allowed to offer source from the AGS or ScummVM website.  However, when I made this this suggestion on the ScummVM forum it was met with much negativity and summarily rejected.

The other potential obstacle to GPL is confusion over the status of the game file and if it is a derivative work or not.  The game file ought to be considered a separate work don't have confidence that this is true.  The obvious solution is to add a clause in the GPL explicitly stating so.  This suggestion was also rejected by the folks on the ScummVM forum.

And in any case, like it was mentioned above, what prevents ScummVM team from reverse-engineering AGS engine, just like all other angines they support?

I believe the Artistic License allows ScummVM to take the source and make a ScummVM GPL port.  CJ has also stated so on the ScummVM forum.

I don't think Tim is a troll.  He is making a noble attempt to try to bring to disparate communities together despite their cultural (as in cyber not ethnic) differences.  It's a near impossible and thankless task.

Tim thanks for the effort.

Perhaps you meant that the translation could be made from the data files, rather than the source, but then I would think that it would be just as easy - or hard - to support the old data format directly. I assume it's pretty much frozen now anyway. I have no idea what the situation is like in the currently developed versions.

This is similar to what I had in mind.  AGS has done a pretty good job over the years of being able to upgrade older games to new ones just by recompiling the source.  This would seem to suggest that the data format has changed but the old functionality remains.  The one thing that comes to mind that may be problematic is the strings are handled in the 2.x branch versus the 3.x branch. 

There is some discussion over here about making some degree of separation between editor, compiler, and runtime.  I suppose "separation" could mean a lot of things.  At minimum it would mean a formal definition/documentation of the editor-compiler and compiler-engine interfaces.   So my thoughts were that if these interfaces were well designed and formally defined  it would be possible to target multiple game-engine runtimes simply by making either compilers and/or translators. 

It seems to me that scummvm, the backend engine parts, likely already has almost all of the required functionality.   The missing middle part would be the data formats and VM instructions.   If AGS and ScummVM were able to use the same definitions then AGS could have it's own native engine and could also easily target ScummVM as a runtime target.  With this kind of cooperation , between the two communities, the planned refactoring of the AGS engine could be done in a way that makes it easier to port to ScummVM

But people on the ScummVM forum have said no. no, no we can't share API or anything because all our stuff is GPL and AGS is not.  They also said they don't want to work on something that is not GPL.   

That's how I see it, where we are.  Am I wrong?

. but when someone makes a sweeping generalization, basically saying "the scumm team doesn't want this, and you get banned for making suggestions"

I never said I got banned for making suggestions.  I said that the responses were negative and did  not address what I suggested. 

(Incidentally, he could very well be right about the "scumm team" since they would be the subset of the ScummVM team who work primarily on the SCUMM engine. But that doesn't really mean anything, does it?)

Pardon my ignorance on this point.  I was unaware there was a distinction between the two.

So... instead of explaining to them that they misunderstood you (which could certainly happen when you have people from around the world using English as their lingua franca) or were getting off topic, you just went away?

I have always been taught when you are a guest in someone else's house you should obey their house rules.  It wasn't my role to keep discussions in your forum on topic nor would I have any power to do so.

Btw, my wife's native language is Spanish, I help her run a medical interpretation business, and regularly present a "Working Through an Interpreter" seminar.  So I understand and am sensitive to the language issues you raise.  Thanks for calling my attention to scummvm's diverse demographics.   

I did ask about something I saw as either a drawback, or a gigantic misunderstanding on my part. I guess I could always have worded it better - if it came across as confrontational, I apologize - but I never saw any reply telling me that I had misunderstood, so I forgot about it.

I am not sure which post you are referring to.  But I also apologize if I took something you said the wrong way.  Frankly, I didn't perceive that anyone misunderstood but rather they were just being asses for the most part.  I don't mean to insult anyone but that is what I thought of the response I got.

Well, I know that I at least never intended to imply any such thing. Personally, I think you're seeing insults where none were intended.

Thank you for saying so.  I wasn't insulted, I just didn't see how anything could be accomplished by continuing the discussion with people who seem so intransigent.   

What do suggest the two communities cooperate?

[I]

But let's do a little thought experiment to get some clarity.  Suppose there is a GPL media player program that display a PNG file and plays an OGG file.  The programmer was very clever and so the binary and the source don't take up much space so the source, binary, and everything can be easily distributed together.   No I come along with a fabulous photo of myself and an OGG recording of me doing the funniest ever stand-up comedy routine.

I'm certainly no licensing expert, but I don't see any difference between the six cases you mention. In each of them, the player, the photo and the recording are separate works. The photo and the recording are yours to distribute, and the GPL allows you to distribute the player. You can even charge money for the whole thing, if you want to. Depending on the license of the photo and the recording, I may not be able to redistribute copies of the whole thing, but I should still be able to redistribute the player or request a copy of the source code for it.

What you describe, as I understand it, are different forms of distribution and I don't see why it would make any difference if you distribute on CD, as an ISO image, by carrier pigeon, or lovingly engraved on stone tablets. Even the self-extracting ZIP file should be ok. The GNU licensing FAQ explicitly says that an installer and the files it installs are separate works. I would guess that what the person you quoted meant is that if you embed the image and/or recording into the player itself, that could be a problem because then they would no longer separate. Your license could be violating the player's license by trying to impose additional restrictions on it.

But, as I said, I'm no expert on this.

I'm glad you agree with me on this.

@Wyz: Neat-0    didn't know about  the google one

Python: http://python.org/
CINT: http://root.cern.ch/drupal/content/cint

Rick, I agree with most of what you write, but are you certain about these two points? My understanding of the GPL is that you can at least argue that if you create and distribute a binary that contains GPL code, everything else that goes into the binary must also be released under the GPL, including any data.

I believe what the GPL refers to is data required in order for the program to function properly.  They are trying to protect against someone crippling an open source program by requiring people to purchase a key for example.   I'm not 100% certain nor am I an attorney.  Who knows what kind of hay could be made of this in some court in some country?  

But let's do a little thought experiment to get some clarity.  Suppose there is a GPL media player program that display a PNG file and plays an OGG file.  The programmer was very clever and so the binary and the source don't take up much space so the source, binary, and everything can be easily distributed together.   No I come along with a fabulous photo of myself and an OGG recording of me doing the funniest ever stand-up comedy routine.  

1.  Does the GPL allow me to distribute a CD containing my copyrighted non-GPL photo and audio recording along with the GPL media player?  

2.  Now I write a little non-gpl program that invokes the player and passes the OGG and PNG filenames.  I then make it an auto-play CD that runs my invocation program.  Does that make a difference?

3.  Postage is expensive so suppose I distribute an ISO image file instead.  Does GPL allow that?   Why?  It's a  distribution of a binary file containing both gpl and non-gpl works?  

4. It could be said that the ISO isn't directly executable and thats what makes the difference.  But things like Virtualbox do this very thing with ISO files all the time.  This same functionality could be integrated into (or is already present) any modern operating system.  So this isn't a persuasive answer to #3.

5. I get tired of arguing with people and so decide to distribute the gpl-player and my non-gpl PNG and OGG files in a zip file.  Does the GPL permit this?

6. I discover there is such a thing as executable ZIP files.  So now I use I decide to make my zipfile executable so that when executed it launchs the player program and passes the OGG and PNG file names.  Is this permitted?  

IMHO, If would be absurd to say that it's not possible to mix gpl and non-gpl materials on the same disk (CD or otherwise).  I would be absurd to say that it's ok to put that stuff on a disk but it's not ok to make an ISO image.  It would be absurd to say that you couldn't put those same materials in a zip file.  It would be absurd to say that it's ok to put them in a zip file but not ok to extract the program and other files to memory and execute the program.   The law is not supposed to produce absurd results and so this is how I justify my opinion.  

Secondly, I thought the GPL notion of "distributing source" accepted "providing a URL to somewhere the source can be downloaded from" as valid. Or am I missing your point?

Your are correct about the offer to distribute.  The problem is that you have to know what version of source that was actually used to make the binary you are distributing.  You would then have to extract that version of the source from scummvm repository and post it on your website.  You would also have to get copies of the correct versions of any libraries and their source used to by that version of the binary.  You would have to do this for each platform you distribute your game for.   Now if you make another game you will have to do this all over again.  This is an insurmountable task for many AGS users.

In my hypothetical example I suggested that this requirement be fulfilled by including a license.txt file containing an offer of source code from the scummvm website with  the approriate url.  The suggestion was met with scorn and ridicule which was really uncalled for.  Again my hypothetical examples were given to illustrate the possibility of how easily some of the issues may be resolved.  

I was surprised that a benign statement paraphrasing the GPL itself provoked such vitriolic responses.  I think the so called newbie made an accurate assessment when he said "...No, won't happen - the scumm devs have other things to attend to..."

[edit]
In case anyone is wondering why I didn't argue these points on the scummvm forum and I am doing so here:

Tim kindly invited me to participate in the thread on the scummvm forum.  I took the time to register and to post a couple of what I believed to be helpful and fairly benign suggestions.  The response was very negative ("Man I don't dig them negative waves.." - Donald Sutherland, Kellys Heroes). 

I didn't argue these points overt here because:
1) I considered myself a guest on their forums. 
2) I did see how any good could come from me pointing out fallacies in their response

I took the time to relate the experience I had over there to people over here because:
1) Tim made some comments that made people over here curious about the people over there
2) I thought people over here would like to know

Oh, and skip season 1's The Menagerie which is a 2-part butchered and padded out version of the pilot.

I agree.  Watch all the other episodes first and then watch the Menagerie last.

Btw, one of my favorite episodes is "A Picece of the Action".  I would recommend watching a couple of old 30s-40s gangster movies, especially with Eduard G Robinson,  first for historical reference  and to get into the proper frame of mind?

I think air date would give you the most authentic experience.    There isn't a storyline as much as there is character development from episode to episode.    I think production dates were/are governed more by what's less expensive, what talent is available (i.e. if guest star prior commitments), etc.   

I would also recommend watching the pilot first.  If you watch closely you will see Shatner as a lowly ensign   

Enjoy!

So what do you all have to say about this? The ScummVM Team follows AGS too, and some of the most skilled people in the team do it

Tim, the two responses you quote were not responsive to my suggestion, the quote I choose was where the poster "Well it seems plausible but the scumm team just doesn't seem to want to chase this pipe dream ...
Simple answer: No, won't happen - the scumm devs have other things to attend to..." and nobody disagreed with this assessment.  

I asked the folks over there to opine on the idea of documenting a game file format common to both AGS and ScummVM not to do any work.   Instead of discussing the relative merits, potential benefits, and problems all I got was pretty much "Nobody wants to work on this."   It's as if they didn't even read my post or didn't understand what I said.  

I made an earlier suggestion to help the discussion along when everyone was bickering about license incompatibilities.   I suggested that perhaps CJ choose the AL because of concerns he had for AGS users rather than concern for the AGS source code and that further discussion with CJ would be better than just ranting and speculating about his decision.

Again the responses were non-responsive.  Instead of someone stepping up and contacting CJ they instead focused on the details of a hypothetical example that was given to illustrate the process and not the outcome.  

I'm sorry Tim but interactions over there have been very negative.  It seems to me that anything I have to say is not taken seriously as if I were some kind of retard.  

Other than that, people still don't get the Copyleft philosophy.

Some do; some don't in both communities.   In the thread I referred to earlier there were a couple of beauties

Assertion: GPL prevents non-GPL code from using scumVM API
Fact: There are legal precedents where API's are found not to be copyrightable

Assertion: The scummVM documentation/website can contradict the terms of it's license agreement.
Fact: If it did in fact say that people could do X and then sue someone for doing X because doing so violates the license agreement they would be guilty of fraud and copyright abuse and because of that the license agreement would be unenforceable.

Assertion: Data used by a GPL executable must also be GPL if it is stored in the same file.  
Fact: This is true for data that exists in the GPL source code.  However, this is not true for externally generated data regardless of where it's stored especially when the function of the exe is to view/play the data.  

It should also be noted that the GPL is not adequate in all circumstances.  That's why, if you read the GPL it says that people are free to add their own clauses to the basic license.   ScummVM has itself, IMHO, made a serious error in the beginning by making it impractical to package and distribute a game file with it's runtime.  How is it impractical?  It's impractical because the GPL insists that source code and everything else needed to recreate the binary also be distributed.  This requires much more disk space, careful attention to engine versions and theoir dependencies, etc.   A clause could have been added to their license that simply allowed game files and  scummVM runtime, scummVM license.txt, one or more game files be distributed together with out the source code requirement.  Game players aren't interested in re-building the runtime.  if they were they would go to the scummVM site anyway.  So all you need is the license.txt that contains the scummVM url.  In fact the exe itself could write a duplicate of this file if for some reason it did not exist.

The Python programming language had these same kinds of issues so they created their own licnese that addressed the needs of developers and end users.   The GPL is unclear about programs that are used to write other programs.   It does not adequately address the disposition of the final product and it should.   Many people want to believe that programs written using GPL tools must also be GPL but this is an absurd outcome.  It would be the same as telling the ghost of Ernest Hemmingway that his latest novel from the here-after is owned by Microsoft because he wrote it using Word and so it is a derivative work.

That's all I have to say.  I'm sorry that the ScummVM folks have left me with such a negative impression.   I'm sure they are all (or mostly so) nice people in real life but unfortunately they are not fun to talk to on the internet.   

How about  AGS Platformer Engine or APE.   

I don't think Tim is trolling ; There is just a culture clash between the two groups.  Here is a thread on their forums where I've made a couple of positive suggestions to find ways of working together and the responses are typically negative such as this...

Well it seems plausible but the scumm team just doesn't seem to want to chase this pipe dream with evidence of this thread being in the junk yard portion of the forum and banning people who bother to suggest about the PSP ported model as being proof that it is possible.

Right now, AGS seems to have an android port in the making but who knows how far that is coming along, also as stated above, there is a PSP ported fully finished if you want to play stuff like Six Days a Stranger on the go...

Simple answer: No, won't happen - the scumm devs have other things to attend to...

[rSomeOtherRoom]

@Monsieur OUXX:  No, no, no you you are missing the cool part of this.  The structure is static at design time and changes dynamically at runtime.   So the following only means that rSomeRoom has cNpcCharacter when the game is first started.  

Code: ags

gMyGame
     rSomeRoom
          oSomeObject
          hThisHotspot
          cNpcCharacter
     rSomeOtherRoom

However, when cNpcCharacter moves to rSomeOtherRoom we can then say that rSomeRoom no longer has cNpcCharacter and that now rSomeOtherRomm has cNpcCharacter like this.

Code: ags

gMyGame
     rSomeRoom
          oSomeObject
          hThisHotspot
     rSomeOtherRoom
          cNpcCharacter

Now consider what happens when there is an inventory item, iSomeItem, and the player character in rSomeRoom.  We can say that rSomeRoom has iSomeItem and cPlayerCharacter like this.

Code: ags

gMyGame
     rSomeRoom
          iSomeItem
          oSomeObject
          hThisHotspot
          cPlayerCharacter
     rSomeOtherRoom
          cNpcCharacter

Now suppose the player clicks PickUp on iSomeItem.  The event handlers are executed in the order iSomeItem, rSomeRoom, gMygame.  Further lets suppose one of the handlers moves iSomeItem from rSomeRoom to cPlayerCharacter.  So now we would have the following structure.  

Code: ags

gMyGame
     rSomeRoom
          oSomeObject
          hThisHotspot
          cPlayerCharacter
               iSomeItem
     rSomeOtherRoom
          cNpcCharacter

Now clicking on iSomeItem would execute event handlers in the order iSomeItem, cPlayerCharacter, rSomeRoom, gMyGame.  

If cPlayerCharacter moves to rSomeOtherRoom the rSomeOtherRoom would have cPlayerCharacter which would have iSomeItem like this.

Code: ags

gMyGame
     rSomeRoom
          oSomeObject
          hThisHotspot
     rSomeOtherRoom
          cNpcCharacter
          cPlayerCharacter
               iSomeItem

Now event handlers execute in the order iSomeItem, cPlayerCharacter, rSomeOtherRoom, gMyGame.   And if the player dropped the item in the current room then we would have the followoing and event handlers would execute in the order iSomeItem, rSomeOtherRoom, gMyGame

Code: ags

gMyGame
     rSomeRoom
          oSomeObject
          hThisHotspot
          cPlayerCharacter
               iSomeItem
     rSomeOtherRoom
          cNpcCharacter
          cPlayerCharacter
          iSomeItem

@Wyz:  I agree with you that the three of us are trying to achieve the same ends but and are struggling to find a simple and elegant means.  After reading your comments and thinking through the above example some more things or quirks come to mind.  

When you were talking about categorizing events it occurred to me that  one event could have a number of interpretations.  For example, a LookAt cursor click on iSomeItem could be interpreted as "LookAt iSomeItem", "LookAt any item", "LookAt anything", "Mouse Click", "?".    It seems to me none of us have addressed or even mentioned this situation.  I think generally what happens now is that we get a generic LookAt event and then in the event handler we can lookup what is under the cursor and then use a giant if-else thing to decode the event to whatever degree of specificity  is required.  It would be nice if we could come up with something better.

I haven't given this a lot of thought but to move the discussion along perhaps I can pickup from what Wyz said about classifications.  

Let's assume we have one big set that contains all possible events in a game called Events. We can immediately name subsets like: player events, room events, screen events, sound events. We can divide it some more: npc1 events, 'lotion' events. We can divide it differently: 'give' events, 'talkto' events, 'interact' events. This said let's see how an user would like to map these event

.  

Perhaps it's all in how we name events?  Suppose events were named in a hierarchical manner, from general to specific.  So to answer my own question we would have the following possible interpretations of a mouse click on iSomeItem

• Mouse
  
• Mouse.LookAt
  
• Mouse.LookAt.Item
  
• Mouse.LookAt.Item.iSomeItem
  
  Event handler functions could be declared something like the following. All of these would respond to a the LookAt iSomeItem event.  The handle keyword informs the compiler that these are event handlers so that it can use the function name to connect the function to the actual events.  This would negate the need for all that pointy and clicky stuff and would mean that events could be added or removed simply by cutting or pasting  snippets of script code.  The pointy and clicky stuff could be retained but would only be a wizardly thing that pastes an appropriate template into the script.
  
  

  Code: ags

  
  handle Mouse(button id, entity type, entity id) {
  }
  
  handle Mouse.LookAt(entity type, entity id) {
  }
  
  handle Mouse.LookAt.iSomeItem(ntity type, entity id) {
  }
  

  
  
  There was one other issue I had with my first examples and I am not sure of the correct answer.  In the case of events such as LookAt, PickUp, etc that are actions being performed by the player character, I wonder if the player character's script should have first crack at handling the events?   If the answer is yes then when there is a LookAt iSomeItem when player character has iSomeItem the event will be propagated to cPlayerCharacter twice.  What to do about that?  
  
  [edit]
  Monsieur OUXX I hate you for making this interesting thread and I hate Ryan Timothy for making all the pretty pictures!  Damm you guys!  :'(     No, just kidding of course.  
  
  Here is a document I made over the last few days and thought you (MX, RT, WZX, et al) may enjoy looking at.  I'm sorry for PDF but that was the easiest way to get a web viewable document from my version of Visio.
  
  http://img28.imageshack.us/img28/9957/entityconcept.pdf

I like the way script modules deal with events and believe it's similar to listeners.  For example, one or more module scripts and the global script can have mouse event handlers.   Event handlers are executed in the same order as the scripts appear in the AGS editor.  Any of the event handlers may prevent further propagation by executing the ClaimEvent() function.  

Now lets suppose we expanded upon this concept.  Imagine that rooms, objects, characters, guis, etc are all sub-classes of entity where each entity can have it's own script and script modules.  A character for example would have a character script and optional modules similar to the way AGS game script is now organized.

Code: ags

gMyGame
     rSomeRoom
          oSomeObject
          hThisHotspot
          cNpcCharacter
     rSomeOtherRoom

Now suppose it were possible to organize entities in a hierarchical structure as shown above and that the player talks to cNpcCharacter.    The TalkTo event handler in cNpcCharacter is executed first.  If the event handler executes ClaimEvent()  then it is not prograted any further.  If there is no handler defined in cNpcCharacter or it it's handler does  not ClaimEvent() then the event is propagated  to rSomeRoom's event handler.  The event is finally proprogated to the gMygame event handler.

Now here is the cool thing about this.  Suppose cNpcCharacter moves to rSomeOtherRoom.  Now if the player talks to cNpcCharacter the event handlers are executed in this order cNpcCharacter, rSomeOtherRoom, gMyGame rather than cNpcCharacter, rSomeRoom, gMyGame.  The context is autoimatically and dynamically changed at runtime.

I think this also covers agregated and inherited functionality discussed above.

[edit]
spelling

@Monsieur OUXX:  Inheriting behavior is an interesting idea.  What do you think about dynamically inheriting behavior based on context?  For example if a character is at the beach he may want to talk about the ocean, fishing and ships but if he were somewhere else he may want to talk about entirely different things.   Contextual behaviors are not limited to dialog; if the character was on the beach he would walk, if he were in the ocean he would swim.   A politician character may not take bribe money in a public place but he may do so in a dark alley (i.e. responds to exactly same event  differently depending on location).   Behavior is not limited to characters right?

Just wondering in light of the above comments; is inheriting behavior different than OO class inheritance?

@Ryan Timothy:

Also has anyone used another engine that manages lots of sprites? I've never really been a fan of the magic numbering we use for sprites. You literally have to check up what that sprite is every time you're checking older code.  Would an OO system be more user friendly?  Sprites.Folder1.Sprite9?

It's sort of what I had in mind earlier in the thread.  Each entity could own it's own resources (sprites, sounds, etc) so you could have something like cEgo.Sprite.FolderWalk.Left1

Here is what Qt says about it:
http://qt.nokia.com/about/licensing/frequently-asked-questions#what-is-the-lgpl
http://qt.nokia.com/about/licensing

The LGPL does permit users to license software programs that merely link with the LGPL licensed library under different license terms provided certain requirements are met. In essence this means that Qt users may create proprietary applications that dynamically link to the LGPL-licensed Qt libraries provided he or she adheres to the requirements of the LGPL.

- Dynamically link to the library
- Qt copyright notice, LGP, GPL text in distribution files
- Offer to provide QT libs from QT or AGS websites

If this gets more serious consideration it wouldn't hurt to send an inquiry asking for confirmation/clarification in AGS specific situation.  

[edit]
@Calin:

A better idea IMO would be to seperate the editor and the compiler. If the compiler were pure C++ instead of the mixed mode assembly it currently is then the editor could be run in mono which is native to Mac, linux and windows. Then we just compile the compiler to be native to each os and attach the editor to the game exe similar to the way that gdb does. That way we can leave alot of the editor code alone and preserve the pretty clean codebase.

I think this is a good idea.  There would need to be a well defined and easy to work with output from the editor.  There would also need to be seamless integration with the native engine to maintain the current fast and edit-compile-test cycle.  Conceivably a compiler could be made that produces ScummVM compatible game binaries.

if what I am proposing comes through then will there be licencing issues?

Presumably:  Commercial License != Artistic License Comparability.

But seriously, if there's any commercial library out there that could really make development a lot easier, I'm sure we could scrape together a few hundred bucks for a license.)

IMHO, QT is a better choice, no fee, LGPL license which is compatible with Artistic License according to gnu.org

Artistic License 2.0 (#ArtisticLicense2) - This license is a free software license, compatible with the GPL thanks to the relicensing option in section 4(c)(ii).

http://www.gnu.org/licenses/license-list.html#Introduction

No no no. I was first made aware of the leak 12 months ago and I fixed it immediately. I fixed the leak (or at least stopped the water) within minutes of learning of the leak.

Hehe, no wonder you were so adamant about not being negligent  .   So yeah i would think you have a fairly strong case.  You didn't do anything to cause the leak and when you became aware of it you immediate took action to remedy the situation.  You didn't install the pipes or have any say in who did the install, how they did it, how much they got paid to do it or what materials they used.  

I don't think this is the case. For a start the flat below and I *share* the same insurance because it is part of the buildings insurance which is part of the freeholders insurance which covers the development.

Right. So if the insurance covers such events and you and the other residents are jointly paying the premiums then they ought to pay.  You should contact them to let them know what's going on and to ask how to file a claim in this situation.  

Just out of curiosity, this sounds like this is a condo sort of a deal.  Is there an owners association, yearly maintenance fees, etc.  When you say "letting agency" are they the ones who developed and/or marketed the building to people like yourself? 

Carefully read everything (insurance, contracts, etc) and see if situations like this are explicitly and clearly addressed.  How much is the damage anyway? $200-300?  Is the guy downstairs trying to cash-in for more or just wanting to have the plaster fixed? 

Most lawyers (at least in the US) offer a free initial consultation.  If so take advantage of that but be prepared before you go in.  Ask him to explain who is responsible for what in this situation.  Ask if you are responsible for the buildings mechanical systems and if the plumbing is included.  You may even be due compensation for making the plumbing repairs, who knows?  Ask about the insurance and what role they should be playing. Who should file the claim and on whose behalf.  How to determine the appropriate value of the damage.  What documentation do you need to collect? (receipts/quotations for the repair work, insurance documents, contracts, photos of the damage, etc).   Conceivably you can glean enough advice to prevail in small claims court on your own.  It may come to that if you have all the facts and know what you are doing.

I'm on there and find it useful.   I do automation consulting and if you join the right discussion groups you can find out what projects are going on etc.