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From Joseph Gentle <jose...@gmail.com>
Subject Re: Future of Apache wave [Was: Re: Advantages of P2P messaging?]
Date Thu, 13 Jun 2013 19:34:24 GMT
Interesting...

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.

-J


On Thu, Jun 13, 2013 at 12:05 PM, Michael MacFadden
<michael.macfadden@gmail.com> 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, in
> 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 recommends
> 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 how
> the parameters of the operations interact; such as positional arguments
> for insert and delete style operations.  The OT Stack doesn't need to know
> 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 knows
> that if one insert happens before another it has to increment the index of
> the second operation.
>
> If things are decoupled in this way, the whole OT stack becomes much more
> flexible.  As one of the founders of OT says almost every time I see him,
> "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" <josephg@gmail.com> wrote:
>
>>So you're imagining storing rich text like this?
>>
>>{doc: 'hi there!', annotations: [{from:0, to:2, bold:true}]} or something?
>>
>>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.
>>
>>-J
>>
>>
>>On Thu, Jun 13, 2013 at 1:19 AM, Michael MacFadden
>><michael.macfadden@gmail.com> wrote:
>>> Joseph,
>>>
>>> I disagree.  The annotations themselves are just another data structure.
>>> You add them, remove them and modify them like anything else.  You can
>>> manage annotations as another structure within the blip model.  There is
>>> no reason why you can interface them though a JSON Style operations
>>> structure.
>>>
>>> ~Michael
>>>
>>> On 6/13/13 12:11 AM, "Joseph Gentle" <josephg@gmail.com> 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.
>>>>
>>>>-J
>>>>
>>>>
>>>>On Wed, Jun 12, 2013 at 4:06 PM, Michael MacFadden
>>>><michael.macfadden@gmail.com> wrote:
>>>>> Actually I just went and took a look at your operations.  The JSON OT
>>>>>type
>>>>> is probably the closest to what I would suggest we use.  JSON Objects
>>>>>are
>>>>> not just for javascript.  They define arbitrary objects structures.
>>>>>We
>>>>> don't need a specific wave XML type, we could use the JSNO operations
>>>>>to
>>>>> modify the conversation model
>>>>>
>>>>> Potentially.
>>>>>
>>>>>
>>>>> On 6/12/13 10:55 PM, "Joseph Gentle" <josephg@gmail.com> wrote:
>>>>>
>>>>>>Really?
>>>>>>
>>>>>>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. Then
>>>>>>people can just pick which one based on what kind of data they have.
>>>>>>
>>>>>>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 have
>>>>>>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 type
as
>>>>>>the root of all wavelets and support subdocuments at arbitrary paths
>>>>>>(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).
>>>>>>
>>>>>>-J
>>>>>>
>>>>>>
>>>>>>On Wed, Jun 12, 2013 at 2:41 PM, Michael MacFadden
>>>>>><michael.macfadden@gmail.com> wrote:
>>>>>>> You have stumbled upon one of the weaknesses of wave OT.  Best
>>>>>>>practices
>>>>>>> would say to NOT bind your OT directly to the data type, because
>>>>>>>then
>>>>>>>you
>>>>>>> don't have an extendable model. For example if you have all of
your
>>>>>>> operations figured out and validated, and then you need to change
>>>>>>>your
>>>>>>> data model, you have to go back and mess with your transformation
>>>>>>> functions.  Not good.  Or you have to try to bend new data models
in
>>>>>>>to
>>>>>>> the existing one, also not good.
>>>>>>>
>>>>>>> Best practice is to create a generic OT model and operate on
that.
>>>>>>>There
>>>>>>> is debate as to what the model should be, but most agree on the
>>>>>>>concept.
>>>>>>>
>>>>>>> For example in wave they tried to create a map like collection
that
>>>>>>>OT
>>>>>>> could operate on. Essentially though that had to implement the
map
>>>>>>>as
>>>>>>>if
>>>>>>> its underlying model was a bunch of XMLish type tags.  This we
very
>>>>>>> convoluted.
>>>>>>>
>>>>>>> ~Michael
>>>>>>>
>>>>>>> On 6/12/13 10:26 PM, "Joseph Gentle" <josephg@gmail.com>
wrote:
>>>>>>>
>>>>>>>>Yeah exactly. The google wave OT code uses special operations
that
>>>>>>>>can
>>>>>>>>understand the XML structure. It doesn't just edit the plaintext.
>>>>>>>>Formatting annotations are stored in a special way - operations
can
>>>>>>>>say something like "At position 10 add bold. At position 20
stop
>>>>>>>>adding bold".
>>>>>>>>
>>>>>>>>-J
>>>>>>>>
>>>>>>>>On Wed, Jun 12, 2013 at 1:56 PM, Bruno Gonzalez (aka stenyak)
>>>>>>>><stenyak@gmail.com> wrote:
>>>>>>>>> I suspected something like that. I assume it also correctly
>>>>>>>>>handles
>>>>>>>>> variable-length UTF8 characters, so it's not necessarily
1-byte
>>>>>>>>>patches?
>>>>>>>>>
>>>>>>>>> This starts to make sense. OT can only compute conflict-free
>>>>>>>>>merges
>>>>>>>>>using
>>>>>>>>> the "character" primitive (because that's how Wave was
originally
>>>>>>>>> designed). As an unfortunate consequence, you can then
only
>>>>>>>>>OT-operate
>>>>>>>>>on
>>>>>>>>> plain text. Otherwise you could get conflict-free xml
text that
>>>>>>>>><loo<ks
>>>>>>>>> li<>ke>this>, and that of course isn't legal
xml.
>>>>>>>>> But we still want rich text in Google Wave, therefore
all the
>>>>>>>>>formatting
>>>>>>>>> stuff is stored some place else, specifically in the
blip
>>>>>>>>>annotations.
>>>>>>>>>The
>>>>>>>>> modifications to annotations are (sometimes) simply derived
from
>>>>>>>>>the
>>>>>>>>> transformations that the plain text suffers after merges?
>>>>>>>>>
>>>>>>>>> I suppose there could be other OT algorithms that don't
use a
>>>>>>>>>"character"
>>>>>>>>> primitive, but rather an "xml tag" primitive, a json
item, a
>>>>>>>>>"pixel",
>>>>>>>>>or
>>>>>>>>> anything else, right?
>>>>>>>>>
>>>>>>>>> (sorry for only contributing with questions... :-)
>>>>>>>>>
>>>>>>>>>
>>>>>>>>> On Wed, Jun 12, 2013 at 10:27 PM, Joseph Gentle
>>>>>>>>><josephg@gmail.com>
>>>>>>>>>wrote:
>>>>>>>>>
>>>>>>>>>> On Wed, Jun 12, 2013 at 12:13 PM, Bruno Gonzalez
(aka stenyak)
>>>>>>>>>> <stenyak@gmail.com> wrote:
>>>>>>>>>> > My assumption was that conflicts were simply
mathematically
>>>>>>>>>>inevitable
>>>>>>>>>> in a
>>>>>>>>>> > DVCSs, that's why your mention about lack of
conflict markers
>>>>>>>>>>sparked my
>>>>>>>>>> > interest... you mention conflicts like they
can be optional? If
>>>>>>>>>>so,
>>>>>>>>>>are
>>>>>>>>>> > conflicts "eliminated" by choosing an arbitrary
merging
>>>>>>>>>>strategy
>>>>>>>>>>when
>>>>>>>>>> > conflicts *do* happen (e.g. "choose the last
timestamped patch
>>>>>>>>>>and
>>>>>>>>>>lose
>>>>>>>>>> > information on the way, we don't care"), or
can they be
>>>>>>>>>>prevented
>>>>>>>>>>from
>>>>>>>>>> ever
>>>>>>>>>> > happening in the first place?
>>>>>>>>>>
>>>>>>>>>> They're inevitable in patch based systems because
patches usually
>>>>>>>>>>have
>>>>>>>>>> a line level granularity. OT usually uses individual
character
>>>>>>>>>> positions. In OT, if two operations both delete the
same
>>>>>>>>>>character,
>>>>>>>>>> the character gets deleted once. If two clients insert
a
>>>>>>>>>>character
>>>>>>>>>>at
>>>>>>>>>> the same position, one of the characters will be
first in the
>>>>>>>>>> resultant document and one will be second. Conflict
markers just
>>>>>>>>>> aren't necessary.
>>>>>>>>>>
>>>>>>>>>> -J
>>>>>>>>>>
>>>>>>>>>> > --
>>>>>>>>>> > Saludos,
>>>>>>>>>> >      Bruno González
>>>>>>>>>> >
>>>>>>>>>> > _______________________________________________
>>>>>>>>>> > Jabber: stenyak AT gmail.com
>>>>>>>>>> > http://www.stenyak.com
>>>>>>>>>>
>>>>>>>>>
>>>>>>>>>
>>>>>>>>>
>>>>>>>>> --
>>>>>>>>> Saludos,
>>>>>>>>>      Bruno González
>>>>>>>>>
>>>>>>>>> _______________________________________________
>>>>>>>>> Jabber: stenyak AT gmail.com
>>>>>>>>> http://www.stenyak.com
>>>>>>>
>>>>>>>
>>>>>
>>>>>
>>>
>>>
>
>

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