On Tue, Mar 4, 2008 at 6:36 PM, Fabio Mancinelli <
fabio.mancinelli@xwiki.com> wrote:
On 4 mars 08, at 13:27, Asiri Rathnayake wrote:
> First of all, I'm pretty new to this topic. But please help me clear
> some of my doubts. :)
>
> What functionality of XWiki will be exposed via the new WebService ?
> same stuff as in XMLRPC ? or more ?
>
Basically the idea is to make XWiki interoperable and addressable
using the REST architectural style principles.
At a high level of abstraction, yes the services will be provide the
same functionalities of XMLRPC.
But in a REST oriented solution the "interface" will be the one
provided by HTTP (the 4 verbs), not a custom API like the one already
present in the XMLRPC extension.
> And why REST and not SOAP ?
>
There is a long debate about REST vs. SOAP (the comparison here is a
bit wrong since REST is not a protocol), anyway REST and WS à la SOAP
are two ways of doing WebServices that exploit rather opposite
paradigms. So definitely I would say that we DO NOT want to do SOAP! :)
To be concise the idea, following rest principles, is:
1) Give every XWiki resource an ID (i.e., an URI)
2) Make everything accessible through a uniform interface (i.e. HTTP
or WebDAV)
This implies:
1) Do some "resource" engineering in order to well define the URI space
2) Think about resource representations
3) Build the "business logic" to map the new way of accessing resources.
Just an example for what it could look like.
GET http://site/spaces -> gets the list of the available spaces
POST http://site/spaces [SPACEINFO] -> create a new space
DELETE htp://site/spaces/foo -> delete space foo
PUT http://site/spaces/foo [SPACEINFO] -> Update space info (like
description, etc.)
etc.
The trick here is that you have all the relevant things directly
addressable and accessible through a uniform interface (i.e., HTTP or
WebDAV). You will be able, for example, to say something like
"GET http://site/space/page/object/field" and retrieve the value of
the field of the object associated with a given page on a given space.
Doing a PUT on that URI will set the value.
Currently you have to do something like:
XMLRPCClient
.getSpace
("space").getPage("page").getObject("Object").getField("field");
The uniform interface (HTTP) allows you also to write the previous URI
in a browser instead of compiling java code with brittle APIs :) An it
would work :)
Of course this is only the tip of the iceberg (and of the problems :))
> This can have
> some repercussions even on semantic features that Stèphane was
> proposing on the chat.
>
> Can we discuss those here as well ? :)
>
Yes :)
The foundation of RDF and all the semantic frameworks (à la semantic
web) are the fact that "things" can be expressed and referenced
through URI.
In RDF, in fact, triples that establish relationships between thing
are in the form
SubjectURI PredicateURI [ObjectURI | Literal]
To be more concrete I might say something like:
person://fabiomancinelli http://ontology/fullname "Fabio Mancinelli"
That basically states that my name is "Fabio Mancinelli", provided
that person://fabiomancinelli is the URI that identifies the "physical
person" that's me.
Now, by exposing XWiki resources in a RESTful way we are basically
exposing all the relevant XWiki "things" via a URI. We can use those
URI for describing semantic relationships. So we could say something
like
http://site/space/page http://ontology/tag http://ontology/Technology
http://site/space/page http://ontology/tag http://ontology/News
In order to state that a given page has the Technology and News tags.
Of course I've been very concise because it's not that easy and what
I've described requires a lot of effort despite its simplicity.
But if the engineering is done well this could result in a very
powerful extension.
It would be nice to send an email saying:
"Hey Asiri look at the paragraph http://site/space/page/paragraph/1
and review it", then you do a "PUT on http://site/page/paragraph/1"
and boom, the page will be updated reflecting the changes you did with
respect to that paragraph. :)
This sounds really cool.
Thanks a for the detailed explanation. :)
- Asiri
I hope that I've been clear.
I know that's a not easy topic and it has a lot of nuances.
Feel free to ask other questions.
> Thannks a lot.
You are welcome.