Implementation and Extension of a Webclient to Access a CalDav Server

DAViCal is a calendar server suited to store personal and shared calendars. It is an open source implementation of the CalDav protocol, which has been designed for storing calendar resources on a remote server, similarly as the IMAP protocol does for e-mail. 

There are many client applications that allow a user to interact with CalDav servers, such as the Mozilla Calendar/Mail, Evolution, Mulberry or Apple's iCal. Most of these applications also allow users to access their e-mail, thus, providing a combined interface for e-mail communication and scheduling of tasks and meetings.

However, for accessing mail and calendars from arbitrary computers, it is often much more convenient to use browser-based interfaces instead of native applications. Roundcube is such a browser-based mail application (for webmail). It is multi-lingual, supports multiple indentities and multiple address books (using databases or LDAP-directories as storage). As it is open source and conforming to standards, roundcube is usable with any IMAP server. Through its plugin-API, roundcube is easily extensible. Many plugins have already been developed, e.g., to manage sieve mail filtering rules. Roundcube has been used for several years at the Department of Informatics (IFI) at the University of Zurich.

For CalDav, there exist a few browser-based solutions. However, they are either part of larger groupware solutions (such as open eXchange or Horde), they are not free (Atmail CalDav client), read-only (PHP iCalendar), or not maintained anymore (Webical).

To enable IFI’s webmail users to access not only their e-mail but also their calendars from arbitrary computers, it has been decided, to develop a roundcube plugin, that allows the access of personal and shared calendars directly from roundcube. With this the IFI will be able to provide its users with a browser-based solution, that combines e-mail communication and scheduling of tasks and meetings.

Description of Work

This assignment consists of a number of key contributions to be made. Contributions originate from two areas of work. First, the existing implementation base of a previous completed assignment shall be extended. Foreseen extensions embrace those functional parts of a previous assignment that were planned for a complete implementation, but not achieved within the frame of that assignment. This assignment, hence, will complete the full set of functional requirements as outlined in the thesis goals list and the activities list, respectively.

Second, and after completing the implementation functionality-wise, the design, implementation, and evaluation of a GUI (Graphical User Interface) component shall be addressed. The primary focus in this second contribution is two-fold. On the one hand, all the functionality implemented shall be made available via this GUI component. On the other hand, access to functionality shall happen in a highly user friendly manner. Thus, usability and functionality access provide equally for the key focus here.

Accordingly, the student should familiarize him or herself with the implementation base that is already available. For all extensions—functionality completion and GUI component—envisioned, the state-of-the-art and related work shall be documented. Based on this review, the system design shall be determined and documented clearly, covering the key design decisions taken in terms of by using which tools/techniques a roundcube plugin for calendaring—including the GUI component—is best implemented, in terms of flexibility, maintainability and usability. The student needs to develop a suited evaluation procedure to substantiate a certain level of usability being achieved. Finally, such a function-wise complete calendar plugin, including its GUI component, is to be implemented, tested, and the implementation and evaluation results have to be documented.

Thesis Goals

The main goal of this work is the implementation of a working webclient to access a CalDav server. The webclient will be implemented as a roundcube plugin and provides the necessary functions that allow users to perform the following actions:

• To add, edit, and remove appointments.
• To schedule meetings. This includes inviting participants through CalDav directly on the server or indirectly by e-mail and displaying of busy/free times of the participants.
• To accept and reject meeting invitations.
• Automatic discovery of accessible calendars.
• Creation, deletion, and renaming of calendars.
• Configuration of calenders, e.g., setting access rights, colors.
• The user interface should be intuitive to use, e.g., supporting double-clicking to edit appointments, re-scheduling appointments by drag-and-drop.

Since this work bases on an existing implementation, all functional extensions and the GUI component shall integrate well with the existing implementation. This assignment will reach its goals if the final implementation successfully proves to address all of the above functions.

Activities

Based on the description of work the following activities—some in parallel—are recommended:

• Study the existing implementation as well as other relevant technology and standards needed.
• Develop a detailed concept of the required data structures, data flows and processes. Develop a detailed concept of the implementation of the webclient.
• Implement the so far open or only partially addressed features described under "Goals" in a step-by-step fashion, including testing the implemented features continuously. Consult the report of the respective previous assignment for a detailed assessment of functions that are not yet (fully) implemented.
• A strong focus of the GUI component is usability. Determine the suited set of usability-oriented metrics and an appropriate evaluation approach for substantiating a certain degree of usability being achieved.
• An essential part of the work is the documentation of all architectural decisions concerning the implementation and the documentation of the code. The documentation has to be sufficiently detailed, such that people not previously involved in the project are able to understand the code and can continue working on it.