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From Michael MacFadden <>
Subject Re: Future of Apache wave [Was: Re: Advantages of P2P messaging?]
Date Thu, 13 Jun 2013 19:45:34 GMT

We are almost in sync now.  Lets go one step further.  Let's so you were
designing an application to be a rich text editor.  Forget OT, you just
making an editor.  I assume your editor has to have some sort of model
right?  Let's temporarily forget the persistence format.  You may save the
rich text to xml, or rtf, or whatever, but I am not worried about that.  I
am saying what is the in memory model that your editor uses to interact
with the document?  Build that.  Build it any way you like.

Ok so now you have a rich text object model.  Your editor is going to
interact with that though some sort of object model API.  When the user
selects some text and presses the bold button, the editor makes some API
call to the model and says, make this part bold.  For the sake of
conversation, I don't care how that internally happens in the object data

OK.  So now if we have a sufficiently powerful OT operation set can
describe manipulating objects, we can manipulate the object model with OT.
 Really what OT services are, are robust message busses that describe how
one user is changing the objects to another user, and accounting for
context transformations along the way.  So if you can build an abstract OT
operation set that lets you mess with objects and objects structures, then
you have a shot at then adapting that operation set to a whole slew of

This is actually an ongoing area of research, that I presented a paper on
to the collaborative editing workshop at the ACM CSCW conference last year.


On 6/13/13 8:34 PM, "Joseph Gentle" <> wrote:

>The abstraction I use is to have a bunch of data types. Each data type
>defines what documents look like, what operations look like and they
>define a set of OT functions (transform, compose, apply, etc). Eg,
>Text documents are strings and their operations are lists of {skip:5},
>{insert:'hi'}, {delete:10}, etc. JSON documents are JSON and their
>operations are lists of path+what to do there. Eg, [{path: ['hi'],
>delete list element 5}, ...]
>It sounds like you're saying we should abstract over the ideas of
>ot-for-lists, ot-for-sets and so on. Is that right?
>... But rich text isn't quite a list or a set. You can make annotation
>markers or something, but then they take up space. Maybe its possible
>to ignore the final document space that an annotation takes up for the
>purpose of transformation?
>Another architecture I've thought about using is making all documents
>use the JSON OT code. Specialized type like rich text can exist as
>leaves in the JSON structure - and let you embed a rich text operation
>inside a JSON operation.
>On Thu, Jun 13, 2013 at 12:05 PM, Michael MacFadden
><> wrote:
>> As a follow up.  The reason you are struggling with the concept is that
>> you have tied the operation language directly to a specific data model,
>> much the way wave did.  They created a conversation model and a specific
>> set of operations that act on that model.  When you do that your
>> operations a making assumptions on how the object model works.  This
>> coupling is not a good idea.  Much of the OT community strongly
>> avoiding this.
>> Rather great a generic set of operations that manipulate things in an
>> abstract way, and then let the application sort out what to do with the
>> operations when it receives it.  The OT stack only needs to understand
>> the parameters of the operations interact; such as positional arguments
>> for insert and delete style operations.  The OT Stack doesn't need to
>> that the thing you are inserting is a character, a contact card, a
>> database record, or an object in a list.  It doesn't care.  It just
>> that if one insert happens before another it has to increment the index
>> the second operation.
>> If things are decoupled in this way, the whole OT stack becomes much
>> flexible.  As one of the founders of OT says almost every time I see
>> "Let OT focus on what it is good at, and let it ignore everything else".
>> ~Michael
>> On 6/13/13 7:54 PM, "Joseph Gentle" <> wrote:
>>>So you're imagining storing rich text like this?
>>>{doc: 'hi there!', annotations: [{from:0, to:2, bold:true}]} or
>>>Every change to the document is going to need to manually update every
>>>single annotation which has start / end points after the edit. But it
>>>wouldn't work - if you insert some text and I edit an annotation later
>>>in the document, my annotation will float forwards / backwards when I
>>>get your op because I don't know how I should change it.
>>>This idea comes up about every 6 months on the sharejs mailing list.
>>>Several solutions have been proposed, but none of them work correctly.
>>>I think we just need a separate set of transform / apply / ...
>>>functions for rich text.
>>>On Thu, Jun 13, 2013 at 1:19 AM, Michael MacFadden
>>><> wrote:
>>>> Joseph,
>>>> I disagree.  The annotations themselves are just another data
>>>> You add them, remove them and modify them like anything else.  You can
>>>> manage annotations as another structure within the blip model.  There
>>>> no reason why you can interface them though a JSON Style operations
>>>> structure.
>>>> ~Michael
>>>> On 6/13/13 12:11 AM, "Joseph Gentle" <> wrote:
>>>>>The conversation *model* yes, but not the rich text documents
>>>>>themselves. You can't really make text annotations work properly on
>>>>>top of JSON operations. We should keep something like the current
>>>>>system for actual blips.
>>>>>On Wed, Jun 12, 2013 at 4:06 PM, Michael MacFadden
>>>>><> wrote:
>>>>>> Actually I just went and took a look at your operations.  The JSON
>>>>>> is probably the closest to what I would suggest we use.  JSON
>>>>>> not just for javascript.  They define arbitrary objects structures.
>>>>>> don't need a specific wave XML type, we could use the JSNO
>>>>>> modify the conversation model
>>>>>> Potentially.
>>>>>> On 6/12/13 10:55 PM, "Joseph Gentle" <> wrote:
>>>>>>>My method for ShareJS was to simply have a JSON OT type and a
>>>>>>>plaintext OT type. I'd like to add a rich text OT type as well.
>>>>>>>people can just pick which one based on what kind of data they
>>>>>>>For Wave I'd like to be able to do something similar - JSON is
>>>>>>>obviously useful for storing application data. It'd be nice to
>>>>>>>some sort of hybrid for wavelets where we can put multiple different
>>>>>>>kinds of data inside a wavelet. One option is to use a JSON OT
>>>>>>>the root of all wavelets and support subdocuments at arbitrary
>>>>>>>(so the object could be:
>>>>>>>{projectName:"ruby on rails", files:[{name:'foo/bar.rb', ...}],
>>>>>>>documentation:{_type:richtext, _data:"<Rich text data>"}}
>>>>>>>Or wavelets could simply each have a type (defaulting to the current
>>>>>>>wavey XML type).
>>>>>>>On Wed, Jun 12, 2013 at 2:41 PM, Michael MacFadden
>>>>>>><> wrote:
>>>>>>>> You have stumbled upon one of the weaknesses of wave OT.
>>>>>>>> would say to NOT bind your OT directly to the data type,
>>>>>>>> don't have an extendable model. For example if you have all
>>>>>>>> operations figured out and validated, and then you need to
>>>>>>>> data model, you have to go back and mess with your transformation
>>>>>>>> functions.  Not good.  Or you have to try to bend new data
>>>>>>>> the existing one, also not good.
>>>>>>>> Best practice is to create a generic OT model and operate
on that.
>>>>>>>> is debate as to what the model should be, but most agree
on the
>>>>>>>> For example in wave they tried to create a map like collection
>>>>>>>> could operate on. Essentially though that had to implement
the map
>>>>>>>> its underlying model was a bunch of XMLish type tags.  This
>>>>>>>> convoluted.
>>>>>>>> ~Michael
>>>>>>>> On 6/12/13 10:26 PM, "Joseph Gentle" <>
>>>>>>>>>Yeah exactly. The google wave OT code uses special operations
>>>>>>>>>understand the XML structure. It doesn't just edit the
>>>>>>>>>Formatting annotations are stored in a special way - operations
>>>>>>>>>say something like "At position 10 add bold. At position
20 stop
>>>>>>>>>adding bold".
>>>>>>>>>On Wed, Jun 12, 2013 at 1:56 PM, Bruno Gonzalez (aka stenyak)
>>>>>>>>><> wrote:
>>>>>>>>>> I suspected something like that. I assume it also
>>>>>>>>>> variable-length UTF8 characters, so it's not necessarily
>>>>>>>>>> This starts to make sense. OT can only compute conflict-free
>>>>>>>>>> the "character" primitive (because that's how Wave
>>>>>>>>>> designed). As an unfortunate consequence, you can
then only
>>>>>>>>>> plain text. Otherwise you could get conflict-free
xml text that
>>>>>>>>>> li<>ke>this>, and that of course isn't
legal xml.
>>>>>>>>>> But we still want rich text in Google Wave, therefore
all the
>>>>>>>>>> stuff is stored some place else, specifically in
the blip
>>>>>>>>>> modifications to annotations are (sometimes) simply
derived from
>>>>>>>>>> transformations that the plain text suffers after
>>>>>>>>>> I suppose there could be other OT algorithms that
don't use a
>>>>>>>>>> primitive, but rather an "xml tag" primitive, a json
item, a
>>>>>>>>>> anything else, right?
>>>>>>>>>> (sorry for only contributing with questions... :-)
>>>>>>>>>> On Wed, Jun 12, 2013 at 10:27 PM, Joseph Gentle
>>>>>>>>>>> On Wed, Jun 12, 2013 at 12:13 PM, Bruno Gonzalez
(aka stenyak)
>>>>>>>>>>> <> wrote:
>>>>>>>>>>> > My assumption was that conflicts were simply
>>>>>>>>>>> in a
>>>>>>>>>>> > DVCSs, that's why your mention about lack
of conflict markers
>>>>>>>>>>>sparked my
>>>>>>>>>>> > interest... you mention conflicts like they
can be optional?
>>>>>>>>>>> > conflicts "eliminated" by choosing an arbitrary
>>>>>>>>>>> > conflicts *do* happen (e.g. "choose the
last timestamped
>>>>>>>>>>> > information on the way, we don't care"),
or can they be
>>>>>>>>>>> ever
>>>>>>>>>>> > happening in the first place?
>>>>>>>>>>> They're inevitable in patch based systems because
>>>>>>>>>>> a line level granularity. OT usually uses individual
>>>>>>>>>>> positions. In OT, if two operations both delete
the same
>>>>>>>>>>> the character gets deleted once. If two clients
insert a
>>>>>>>>>>> the same position, one of the characters will
be first in the
>>>>>>>>>>> resultant document and one will be second. Conflict
>>>>>>>>>>> aren't necessary.
>>>>>>>>>>> -J
>>>>>>>>>>> > --
>>>>>>>>>>> > Saludos,
>>>>>>>>>>> >      Bruno González
>>>>>>>>>>> >
>>>>>>>>>>> > _______________________________________________
>>>>>>>>>>> > Jabber: stenyak AT
>>>>>>>>>>> >
>>>>>>>>>> --
>>>>>>>>>> Saludos,
>>>>>>>>>>      Bruno González
>>>>>>>>>> _______________________________________________
>>>>>>>>>> Jabber: stenyak AT

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