Skip to main content

Flex client-server data exchange

Flex programming is much like classic client-server stuff (at least, compared to a web app). So, here's a challenge we faced when designing viibee:

The user modifies data on the client and these mutations shall, of course, propagate to the server. The question is: shall the data be modified locally (on the client) before the server received the changes or shall the client modify the data only after the server has persisted the changes? Let's call these two scenarios "optimistic" and "pessimistic", respectively.

In the pessimistic model there is less chance of an inconsistency of the data between server and client. Also, the user can always be sure that his changes have really been persisted. But you loose a lot of responsiveness of the UI (and this is why you chose to do a RIA, isn't it?).

In the optimistic model you have a much more responsive UI. But you might need to implement certain logic twice, especially some data validation will have to be done on the client and maybe on the server again. Plus, you will have to handle the case that errors occur on the server.

We thought of the pessimistic model as a "banking app" and the optimistic model as "GMail". Interestingly enough, Adobe has described the optimistic model here and describe it in terms of a banking application.

In the end, we have chosen the optimistic model and have not looked back so far.

Comments

Popular posts from this blog

NoSQL talk at Developer Summit

Three days ago I had to chance to talk about NoSQL at the Internet Briefing's Developer Summit. On top of general ideas and concepts like the CAP theorem I chose to talk about Apache Jackrabbit, CouchDB and Cassandra. My slides are embedded below.
It was a really good event with interesting speakers and a knowledgeable audience. I was especially pleased that when I talked about CouchDB's HTTP API someone from the audience mentioned that Apache Sling does something very similar for Jackrabbit.
Special kudos to Christian Stocker of Liip for daring to do a live demo of the "real-time web" - he took a picture from his phone and had it pop up on Jabber and Twitter in about 5 secs.
Vlad Trifa has posted a good summary of the whole event (part 1, part 2) - he also gave a great presentation about the application of the REST architectural style to the "Web of Things".

No SqlView more presentations from mmarth.

NoSQL: A long-time relation(ship) comes to an end

(cross-posting from here)

OK, I admit it, declaring that "the RDBMS is dead" is a meme that has been going around the software industry for a while. Remember object-oriented data bases that were supposed to replace the relational ones? Well, guess who is still here. However, despite the RDBMS's amazing survival skills I would like to propose a related prediction:

I believe that the year 2009 will go down in history as the year when the "relational model default" ended. The term "relational model default" was coined by me to describe a peculiar thing that goes on in application development: start talking to your average application developer about some arbitrary business requirement and chances are that simultaneously he mentally constructs a relational model to fit those requirements.
That relational approach to modeling your problem may or may not be suitable. The real problem is that all too often this default does not get challenged. As a consequence,…