For a customer we want to realize a relatively large project. What I want to do is the following and my question is: Can this be done with TYPO3?
I'm sure there are extensions which enable a standard TYPO3 installation to handle blog data or wiki data. If this doesn't exist yet, we want to write a job database extension and a project database extension etc.
The thing is: The data should be stored in clear objects like WIKIPAGE, BLOGPOST, PROJECT, JOB and form a graph.
This object-graph should be accessible through a RESTful API. Is it correct that the Flow Framework provides this functionality?
Is there a way to create a template like a HTML wireframe which allows me to put the bits of dynamic code at the right place?
I'll split my answer up in three parts, to make a little clearer how TYPO3 works:
The REST API: There is no native REST support in T3 yet, so will have to write that yourself. In the past I found this complicated but possible. Be prepared to get a rather deep look into the workings of T3 because you might have to create your own dispatcher or work on top of somebody else's extension to make this possible. I'm pretty sure it's doable, but might be more work than in a framework where you get the finished REST module delivered.
Regarding Extensions: In the so called Extbase framework (that's a backport of FLOW3, now called Flow Framework, a MVC PHP framework originally created by the T3 community) you can create this rather easily. Making MVC based extensions is a charm, you even get a nice GUI (called Extension Builder) to create the skeleton. The framework is really powerful, but can be a little limiting at times, especially when you have to do something out of the ordinary. But to create a simple blog will be really quick if you know what you are doing. Be careful though if you use extensions by other people. They might be really good but overpowered for your use case, and lots of stuff in the TER (TYPO3 extension repository) is still base on the old extension architecture.
HTML Template wireframe: I don't know exactly what you mean by that, but I suspect you mean something like Fluid, that's the current T3 templating engine. It's pretty powerful, and it works roughly like you described (you create the HTML, split it in partials, input some variables).
Final words: T3 is 100% suitable for a large project, it was always created as an enterprise content management system and has kept that idea. Actually I often find it to be over the top for smaller projects, but of course we also did that. There is no lack of notable examples of international companies that have used T3 for their sites. I think it's suitable for your needs, but be prepared to learn a lot about T3s inner workings. With the new MVC framework that's not a CMS where you just start coding, you better know what you are doing before that.
Hope that helps, oh and also don't confuse TYPO3 CMS with the Flow Framework, those are totally different things, even if they were started in the same community.