Kerika

Kerika is a proprietary, cross-platform, peer-to-peer software package, written in Java that works on Macs, Windows and Linux computers. (And Kerika is also the name of the company that produces this software.)
Kerika facilitates collaboration within distributed teams, particularly where team members are using a variety of computers and are located in different organizations or locations.
The software is an application, not a Web 2.0-style hosted service, so it needs to be downloaded and installed on a user's computer. And because the software is based upon a peer-to-peer model, all the project information are stored locally on the user's computer (e.g. personal laptop), rather than on a central server.
The software is offered as a subscription service to commercial users, but is free for educational/academic users.
Graphical Wiki
Kerika supports a visual approach to collaboration: users set up projects using Idea Pages, which are digital canvases that can accommodate a variety of items, such as drawings of process flows, documents, pictures, Web links, software, etc. Process flows are represented using simple graphical shapes (e.g. ellipses, lines, arrows, etc.).
Idea Pages can contain other Idea Pages, so that a large project can be set up as a collection of nested Idea Pages, each of which represents a different sub-project or focus area.
Projects can be shared by adding email addresses to the project's team list. Kerika examines each email address that is added to a project's team list and processes it as follows:
* If the email address references another Kerika user, this person gets a copy of all the project information that exists, as well as copies of future updates.
* If the email address references someone who is not a Kerika user, this person gets project updates sent by email instead. These emails include a picture snapshot of the Idea Page and copies of any documents that have been modified by any member of the team since the last time an update was sent.
This feature allows individual members of a project team to start using Kerika without waiting for the rest of the team to also adopt the software. (This is one way to deal with the network effect dilemma: new collaboration tools have a tough time getting off the ground because not enough people are using it in the early stages, and, conversely, established collaboration tools enjoy the benefits of incumbency.)
Once Idea Pages have been set up and shared with other Kerika users, the software essentially functions like a kind of "graphical Wiki": whenever an item is moved, changed, or deleted from an Idea Page, this change is reflected for all the other members of the team. Unlike conventional Wikis, however, all the project files are stored locally on the computers of individual team members rather than on a central server, which helps avoid the single point of failure weakness that is inherent in Web 2.0 services.
Kerika uses the Piccolo user interface toolkit that was developed at the University of Maryland Human-Computer Interaction Lab.
Networking
Kerika uses the JXTA open-source networking protocol for implementing its hybrid peer-to-peer network:
* There is a central rendezvous server: every Kerika application automatically checks in here when the user starts up Kerika on his/her computer. The Kerika application registers the user's current IP address and gets the IP addresses of other Kerika users who are online. Thereafter, communications between one Kerika client and another is generally done directly, without any intermediaries.
* If a user is hidden behind a NAT or firewall, the client application uses the relay server, which is really another instance of the rendezvous server, to help connect to other clients. In these cases connections take place using HTTP over port 80.
* If a user is offline at a time when another user wants to connect to it (e.g. to provide a team member with some project updates), a storage server holds the messages for the offline user. In such cases Kerika works on store and forward model similar to email systems.
Document Management
Kerika uses a relatively simple model for document management, which mimics the sequence of interactions that take place when people write a document and then email it to a group of colleagues for review:
* Users can attach notes to documents, thereby providing commentary. These notes are stored separately from the documents, so that the document is not actually modified as a consequence of someone attaching a note to it.
* If a team member modifies a shared document, this automatically creates a new version of that document which is electronically tagged as belonging to that person. This new version is then sent to everyone else on the team, and filed locally on their computer. Modifying a document does not overwrite anyone else's copy, nor is there a "check-out/edit/check-in" process that is commonly found in traditional document management systems. Instead, separate versions are simulteneously maintained to correspond to each team member's edits; this decentralized approach reflects the peer-to-peer model of Kerika.
Privacy
Web 2.0 hosted services raise privacy concerns, since the business model of nearly all Web 2.0 companies is to make money by displaying targeted advertisements; the most well-known example being Google's AdSense program which automatically scans text in Web pages and messages to determine the subject matter. The loss of privacy inherent with Web 2.0 is a significant trade-off for some users who have generally turned to other solutions, such as peer-to-peer networks. Kerika deals with this problem by allow users to set up their own storage server (i.e. "private server"). A private server holds messages for a defined set of Kerika users, which enables teams to create a ring of trust.

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