The subject is great, but I found the text a little bit confusing...One may say I don´t have enough knowledge of some concepts to understand the text, but I would reply "people who have it can learn something from it?".
Let´s put this way, as the Philadelphia´s lawyer would say: "explain it as if I were 2 years old". :-) 2009/3/6 Gervas Douglas <[email protected]> > <<*The SearchSOA.com community has asked **"What is the difference > between RESTful transactions and Web Services transactions?"* > > First, it's helpful to define the terms a bit here, because people often > have a reaction to the term "transaction" that doesn't distinguish between > local and global transactions. Local transactions are used in every almost > every database operation today, and this is exactly the same for both Web > services and RESTful applications. > > The question therefore really pertains to global transactions -- those that > involve more than one database, potentially on different computers -- since > that's where things are very different. (I should also clarify that Web > services are a technology while REST is an architectural approach, so this > is going to be a bit of an apples-to-oranges comparison.) > > Web services transactions (as defined in the OASIS WS-Transactions set of > specifications) are intended to be compatible with existing TP > infrastructures, which basically evolved from mainframe systems. The REST > approach, on the other hand, evolved from the Web, which is based on an > entirely different technology stream. Some of the key differences derive > from the very different assumptions behind mainframe systems and Web based > systems. > > Mainframe systems were designed assuming an environment for resources and > users under the control of a single organization. Web based systems on the > other hand were designed assuming a world wide network of independent but > cooperating systems under the control of different organizations and > individuals. Today's corporate IT systems can be more or less divided > between those developed before the Web and those developed for the Web. > Systems designed for the Web have much less control over things like > workload, uptime, the need to provide a good experience to users, etc. These > different assumptions impact transactions because they result in very > different solutions to the requirement for distributed access to shared > data, or shared state. > > At the technical level the biggest manifestation of the difference is in > the design of the communications system. Transactional communications > mechanisms that evolved from mainframe designs use persistent sessions to > share state between programs. The communications protocol used in REST > oriented systems, HTTP, does not support persistent sessions because they > negatively impact scalability. If you are operating in a carefully > controlled environment, that impact is manageable. > > For compatibility with existing shared state mechanisms, Web services > transactions propagate shared transactional context among participants in a > global transaction so that each participant's access to shared state can be > coordinated with the others. REST based transactions assume that only one > party to a global transaction accesses the shared state at any given time, > sort of like passing a token. The other participants have no knowledge of > what's going on at another participant and their operations on shared state > can't be coordinated. They are responsible only for knowing what they must > do when they receive the shared state – when it's their turn. This creates > is a very different design requirement for handling failure and recovery, > since it cannot be automated, the trade off in additional application level > design and coding pays results in a system better suited to the assumptions > of the Web. > > *Eric Newcomer is a distributed computing specialist and independent > consultant. Newcomer is a chair of the OSGi Alliance Enterprise Expert Group > and former CTO of IONA Technologies. He writes a blog on OSGi > matters<http://modualrit.blogspot.com/> > .>> > * > > *You can find this at: > http://searchsoa.techtarget.com/news/article/0,289142,sid26_gci1350094,00.html > * > > *Gervas > * > > -- Marcelo Augusto Costa
