In the last post i wrote about the decentralized structure of Retroshare. I said: similar features to Facebook are also possible in a decentralized manner. Now let’s have a closer look at those features.

Communication tools have the purpose to take a piece of information and transmit it. The question is who should receive it, when will it be received and to which next hop should the information be send.

Very simple forms of communcation are one to one messages. We have a clearly defined receiver which can be adresse by a RSA public key. This is very simple if we are directly connected to the receiver. If the receiver is not a direct neigbor, then Retroshare uses it’s distant tunnels. Current distant chat and distant messages only work when sender and receiver are online at the same time. Retroshare v0.6 will cache messages on neighbor nodes to deliver them when the receiver is online.

Retroshare can also do many to many communication. The Chatlobbies are for real time communication. If you don’t receive the message a few minutes after it was send you will never receive it. Messages are send to all neighbors in the chatlobby. RS keeps messages for a few minutes to prevent echos. Forums and channels offer persistant messages. This means messages are kept for a year in forums and a month in channels. The messages are not targeted at a person, but they belong to a context. This context is a chatlobby or a forum/channel. Users have to subscribe to the context.

Every message is bound to the context. It appears only at one place. In Retroshare forums and channels the context is a topic like “Developer’s Discussion” or “RetroShare Windows builds by Thunder”. In the social network plugin the posts are decoupled from a context. The context only stores a reference to the post. This allows posts to appear at different places. For example: a post can appear on the walls of user A and user B. And if i see the post and like it, i can forward it to my wall. Forwarding of specific posts only, increases the quality of the received content.

With forums and channels you first have to subscribe to them. Retroshare will then download the posts in it. The social network plugin automatically downloads the posts your friends like. And if your friends like it, then the probability is high that you also like it.

While forums are about a topic, a social network wall is about the user. It is a personal place where you can leave message for your friends, and your friends can leave messages for you. Still your are not limited to own content. If you want to share existing posts with your friends, just put it onto your wall.

Scope of the GSoC project

The goal of the GSoC project is to make a basic wall service. This includes the backend for message processing and the user interface. Chat and private messages are not planned for GSoC. But this is something that is very easy to add later.

Internally the social network plugin is based on the new Retroshare General Exchange System(GXS). GXS has two basic data structures: gxs-groups and gxs-messages. A gxs-message belongs to a gxs-group. If a gxs-group is marked as subscribed, then all messages in this group are downloaded. In the gxs-forums this mechanism is clearly visible to the user: gxs-groups are downloaded automatically, but the user has to subscribe to download the contained gxs-messages. The posts in the social network plugin should be independent. This requires that every root-post has its own gxs-group. The wall services automatically subscribes to interesting gxs-groups. Gxs-groups can be interesting because:

– the posts appears on a wall of a friend

– the user follows the author of the post or the user is friend with the author

– a friend made a comment on this post

So the interesting content is not defined by a forum title, but by the way friends interact with it.