Wei-Che Huang [HREF1], Master Student, School of Software Engineering & Data Communications[HREF2], Faculty of Information Technology, Queensland University Of Technology[HREF3], Brisbane, 4000. Email: w2.huang@student.qut.edu.au
Associate Professor Paul Roe [HREF4], Deputy Head of School, School of Software Engineering & Data Communications[HREF2], Faculty of Information Technology, Queensland University Of Technology[HREF3], Brisbane, 4000. p.roe@qut.edu.au
Dr On Wong [HREF5], Lecturer, School of Software Engineering & Data Communications[HREF2], Faculty of Information Technology, Queensland University Of Technology[HREF3], Brisbane, 4000. o.wong@qut.edu.au
Wikis are a popular collaboration technology. They support the collaborative editing of web pages through a simple mark-up language. The wikipedia site is perhaps the best example of how wikis can be used. There are lots of different wikis, all with their own special extended features over the basic collaborative editing of web pages. In this paper we investigate how wikis can be made mobile; that is how wiki forms of collaborative editing can be achieved through mobile devices such as smart phones. Mobile devices are becoming ubiquitous and powerful. Thus it is advantageous for people to get the benefits of wikis in a mobile setting. However, mobile devices present their own challenges such as limited screen size, bandwidth and battery life; they also have intermittent connectivity. We have investigated and built a prototype mobile wiki which addresses these issues and which enables collaboration through mobile devices. The system comprises a cut down wiki which runs on the mobile device. This communicated with a main central wiki to cache pages for off line use. This hoarding process also enables new pages to be created. On re-connection edited and new pages are synchronized with a main wiki server. Communication and hence hoarding is adaptive depending on the characteristics of the mobile device. When sitting in a powered cradle, eager downloading and synchronization of pages is supported. During mobile operation, pages are cached lazily on demand to minimize power use and to save the limited and expensive bandwidth. Finally a pluggable page rendering engine enables pages to be rendered in different ways to suit different sized screens. This enables simple collaborative working whilst on and offline through smart mobile devices. The prototype system has been implemented using .NET.
The first wiki web site was created by Ward Cunningham in 1995. The original idea was to develop collaborative web pages on the project group’s intranet server that allowed any member to make instant changes of information and associations freely to the online documentation just by using their web browsers [1]. Put simply, a wiki consists of web pages that can be edited by any user over time. Each page is stored in a centralized server which allows pages to be reviewed and compared to previous versions by any team member. Users have the ability to both edit the content on the page and to create the structure of the wiki website by using the wiki page link syntax. As such it is a collaborative workspace allowing people from all around the world to, add, alter and organize shared documents. This has proved to be a very popular collaborative system due to its simplicity and easy web access by any user [1, 2, 3]. Wikis have become important community building tools for document management, project planing, information sharing, and discussion forums.
With the enormous progress of mobile computing and wireless communication capabilities of small devices such as smart phones, PDAs, and wireless enabled laptops, we are beginning to see an emergence of various applications supporting mobile collaboration. These hand-held devices are becoming much more powerful than before, thereby attracting people to use them in their work and social lives. Mobile services that allow people anywhere, anytime to access needed resources have become a vital requirement in today’s fast paced environment. With the flexibility offered by these smart devices people can frequently work while on the move. For example, it has become very common to see people using their laptops or PDAs on the street or at meetings to take notes, reply to e-mails, and stay up-to-date. Providing a more sophisticated platform for supporting effective mobile collaboration has led to series of investigation and research issues [4, 5, 6].
Unlike the fixed wire line network used by desktop/laptop computers that normally require people to stay at one location to perform their tasks, developing a mobile collaborative system needs to consider the opportunities and constraints of mobile devices including: small user interfaces, limited computing capacity, limited bandwidth, intermittent network connect, connection expense, power constraints and the distributed resources in the mobile environment [7, 8].
Wikis are convenient and powerful systems for collaboration and mobile devices offer unique opportunities for mobile work. This paper investigates how wikis can be made mobile, taking into account the limitations of mobile devices, whilst providing a seamless collaboration experience to users. A mobile wiki system has been researched and a prototype system has been implemented, called Pocket RikWik. This paper presents theses along with techniques employed to achieve these goals including adaptive communication, hoarding and pluggable page rendering.
The rest of this paper is organized as follows. Section 2 describes wiki systems and how they support collaboration. The characteristics of mobile computing are presented in Section 3. In Section 4 our non-mobile wiki system, RikWik, is briefly described. Section 5 discusses Pocket RikWik, its functionality and architecture particularly for addressing the constraints of mobile devices. Section 6 reviews related work including the mobile support provided by some wiki systems. The final section describes our future work and conclusions of this paper.
Wiki-based systems have been around for over ten years and they have become popular community building tools. One of the largest and most popular wiki websites is the Wikipedia that is successfully and collaboratively created as a free, web-based encyclopaedia and is based entirely on voluntary contributions. It also offers content exporting for offline reading and (one) page uploading for an offline created article [9].
Wikis allow pages to be either viewed as HTML or edited using a simple textual mark-up language. A wiki system comprises a rendering engine that turns page data (wiki markup or XML format) into a display format (HTML or XHTML), wiki logic to determine components that deal with client requests, plug-ins that enhance users’ collaborative work and a centralized storage system (database or files) [1, 2, 3]. The rendering engine sometimes provides several parsers for converting stored page format into different display forms such as HTML, XHTML, XML and pure readable text. Besides the content, the wiki page also consists of a header that displays the name of the page, a title menu and several links that are specific to particular internal/external web pages. A standard web browser can be used to view different formats of wiki page content.
Wiki logic resides in a central web server like IIS or Apache, which is response for managing client requests and activating the appropriate supporting components to execute the operation. Instead of parsing wiki page data into a displayed form for presentation, page data is converted as the simple textual markup in a text area field in an HTML form with a “save” and a “cancel” buttons after clicking the “edit”. The modified page content will be immediately translated into underlying page data and stored as a new revision, which replaces the previous version on the web browser after the user submits the edited page.
Wikis store multiple revisions for every page. This page versioning feature allows previous revisions of wiki pages to remain available for reference, comparison and rollback. The user can reload a particular page version for any purpose while the system always forwards the latest version for viewing. It allows users to review previous content as well as prevents from unfavourable editing because usually wikis are open for anyone to edit a page.
Moreover, an important transformation of wiki editing is the wiki page link syntax, which is the syntax used for creating hypertext links to other internal pages as well as new wiki pages that link directly to the edit form having that new page title. Typically, a word or phrase enclosed by double square brackets will be converted into a link to a wiki page with the same title. In addition to this, “SmashedWords” or “WikiWord” (It is a combination of letters with at least two capitals) are also parsed as a page link with that page title.
According to the nature of wiki, multiple users may be involved in editing process at the same time. The same version of a wiki page edited by a user may be modifying by other users. The conflict will occur when they submit their changes. Some wikis offer the ability of merging two conflict pages while others allow users to participate in resolving conflicts by displaying these two page contents on the same web page.
In order to facilitate better collaboration work, a number of wiki clones like TikiWiki, Twiki, Openwiki, MediaWiki, and MoinMoin have been created with different extensions such as search (a full text search and a page title search), file attachment, access control, WYSIWYG editing and custom styling [10, 11, 12, 13,14]. TWiki aims to be an enterprise collaboration platform that offers rich features while TikiWiki also provides a full featured wiki-based collaborative system as well as the content access from a variety of mobile devices. Besides, offline read and write support have been discussing in TWiki [15] and MoinMoin [16]. Due to wiki’s group-editable nature, and the fact that changes made by anyone at anytime, anywhere can be accessed immediately online, the wiki approach has been quite successful in many organizations for document/information management and project planning as well as for discussion forums [17, 18, 19]. Since there is no standardisation of wiki features, the exact set of features supported by wiki systems varies. Wiki maintainers (administrators) may have added further plug-ins as well as extra services for improving wiki functionality. However, these wiki engines do not offer full support for mobile devices nor basic wiki features like editing and creating in offline situations.
Mobile computing is becoming ubiquitous in the form of notebooks and converged devices such as smartphones. Mobile computing presents many opportunities for collaboration, for example mobile devices are always with the user. However the characteristics of mobile devices and that of their environment raise challenges.
Wireless network connections can be intermittent or non-existent, inconvenient or expensive. The unstable nature of wireless networks may result from the user’s mobility or the coverage of the network. Therefore mobile devices must cater for intermittent connectivity; since the user may not connect to Internet even when the network is available. In addition to the problems of network availability and connection cost, mobile devices are further constrained by limited battery power [20]. This compounds with limited bandwidth to prevent optimistic caching of information for offline use since this potentially uses a lot of power. We can not expect users to spend time looking for particular wiki pages and specifying them for download instead of retrieving these pages directly and performing critical tasks while they need to stay online on the move. Thus, if those resources can be packaged and arranged to be locally available after being adapted to user profiles, the network connection can be dispensed with for a time. Offline operation will be a critical issue in this situation.
Storage space is another limiting factor of mobile devices. In addition to the wiki page content and the associated properties, different revisions and attachments are also stored in the storage space. Revision control is another issue that consumes a certain amount of space. If the system saves every revision of each wiki page, the storage for a wiki page will increase the amount of times the user edits it for, even if the user just adds a word or deletes a sentence. The growth of storage space will be very dramatic when the number of participative users is continually increasing [21, 22]. However, there is really no need to store all pages on a portable computer. The problem of selecting necessary pages should be figured out and solved.
Delivering web pages to personal digital assistants (PDAs) has become an important task when considering a web-based collaborative system with mobile support. Mobile devices have small screens and limited memory capacities. Generally, web pages designed for PCs require extensive amounts of scrolling, both horizontally and vertically on such small screens. This easily leads users to disorientation within the page and makes it difficult to focus on particular content (e.g. the content has been scattered.) as a result of the design of web pages with the assumption that they will be showed on a standard desktop screen [23, 24].
A wiki engine, RikWik, has been created by researchers at QUT. RikWik aims to have an easier flexible, extensible and secure environment by leveraging XML to the full with a pluggable architecture which offers extra services for enhancing collaborative work [25]. An important feature of RikWik is the provision of web services which enable pages to be created and edited programmatically. RikWik is implemented using Microsoft's ASP.NET framework.
A RikWik page represents a single wiki document within the RikWik site, which is stored as XML and can be viewed in different formats. Viewing pages in RikWik requires them to be converted from their underlying XML form into a display format such as HTML, XML and plain text. Cascading Style Sheets (CSS) can also be used for document styling that allows the user to view pages in their preferred format (See Figure 4-1). The rendering of a RikWik page consists of three steps: The page data is firstly retrieved from the database in XML form. Macros (for example for listing recently changed pages) existed within page XML will be extracted and executed before the revised XML document is translated into the target format for viewing. The rendering pipeline is pluggable enabling custom renders to be easily added.
The default editing on RikWik uses a conventional simple wiki markup language. An HTML textbox is filled with wiki markup of a pages content which is provided to the user for editing. On the server this markup is converted to the RikWik XML form before it is submitted into the database. In addition, a JavaScript WYSIWYG editor has been created for offering an advanced editing experience, which generates XML directly and sends it to the server. This is particularly helpful for non-technical users who do not want to learn wiki markup.
RikWik provides a web service interface to the wiki client (See Figure 4-1). This interface can be used to retrieve pages in their XML form and to submit revisions to pages. The provision of web services makes RikWik flexible and extensible. External programs can be extended to interact with the RikWik server such as getting, editing and uploading pages and receiving notification of page updates. Moreover, web services can also be used as the basis for offline operation. Copies of pages can be taken for offline reading or editing and subsequently pushed back to the server. A conflict resolution mechanism can be utilized to deal with conflicts.
RikWik was designed at the outset to be easily extended for supporting mobile devices and offline operation. Extensive research has been done to realize the use of RikWik and obtaining the functionality that are necessary to support on the mobile devices. This include the use of offline operations in order to keep the mobile users’ experiences as close to the experiences with the real RikWik system accessed by their desktop/laptop computers.
The architecture of Pocket RikWik is shown in Figure 5-1. The two main issues of mobile collaboration for Pocket RikWik are offline operation and devices' small screen size. Offline operation is handled by caching copies of pages locally. Since pages may be edited locally as well as viewed we cannot simply cache the HTML representation of pages; we need to cache the XML pages themselves and to support the editing of such pages. This means that we effectively need to run RikWik locally on the device. Thus the overall architecture of Pocket RickWik comprises two wikis which communicate - the main wiki server and a local wiki server running on the device. To maintain the same user interface look and feel and seamless navigation from wiki pages to external resources the mobile wiki pages are hosted in a web browser.
We chose to implement Pocket RikWik using the .NET Compact Framework; this enabled us to reuse some of the RikWik server code and to leverage the Compact Frameworks powerful set of classes, including support for web services. Windows mobile devices which run the .NET compact Framework such as PocketPCs and some smartphones come with a built in web browser (Pocket Internet Explorer). The final missing piece to the overall architecture is a local web server to serve pages. We constructed a simple web server capable of serving HTML wiki pages to Pocket Internet Explorer.
In order to achieve the goal of being a compact wiki system working on the PDA, Pocket RikWik is divided into the following distinct components:
In general it is not possible to cache all wiki pages on a mobile device. Even with large flash memories most users do not want to cache lots of unnecessary pages on a mobile device; particularly if they will only access a regular and small subset of these pages. Thus in order to fit in with the limited storage of mobile devices, the selection of replicated pages must only cover what the user needs. Our goal is to provide an efficient page hoarding strategy, taking into account use preferences, and adaptive fetching. A web service interface provided by RikWik server is used for querying online pages and for downloading pages for offline use.
To provide seamless offline access to RikWik pages, page XML data and associated properties is automatically retrieved and stored in the client's device prior to it disconnecting. The method for getting needed pages from the server is based on a simple mechanism that finds all accessible RikWik pages for a particular user and filters out the unnecessary pages according to user preferences set up on a “User Preferences” page. For example, users can specify that they wants those pages that were edited in last ten days. Moreover, additional data can also be retrieved manually including different revisions, custom style sheets and file attachments.
In order to keep local pages up to date, page XML will be retrieved from the server to be rendered for display when viewing RikWik pages on the PDA online (See Figure 5-2). Local modification will be reflected to the server immediately and updated page data will be forwarded into the user’s mobile device as well. Offline changes will be stored in the local database. When the network connection resumes, these local changes will be pushed back in the server, updates need to propagate to clients and conflicts have to be solved no matter where they happened.
Uploading local changes that have been edited by other users on the server side can produce conflicts. According to the settings (overwrite or report conflicts) on the PDA, the process of conflict resolution is different and it is shown in Figure 5-3 below. Local modified pages are saved as a new revision to replace the current version for viewing on the server side when the “overwrite” option is chosen. Otherwise, the conflict page's underlying XML is retrieved from the sever database and then forwarded to the client side. This allows the user to compare both versions and trim the content carefully.
In order to keep the Pocket RikWik user experience close to the online RikWik experience, a pocket browser is used as an interface to Pocket RikWik. The user can view wiki pages by either accessing RikWik server via Internet or getting local pages that have been retrieved and stored in the user’s device.
Underlying page data for the Pocket RikWik system are stored as XML. Viewing wiki pages requires them to be converted from XML into a viewable format. Due to the RikWik page schema that is based on the standard web markup dialect, XHTML, it is easy for us to convert into different formats (e.g. HTML, XML and plain text) and to make up the interface to fit with Pocket PC screen (See Figure 5-4).
Furthermore, Pocket RikWik also supports the generation of dynamic content using macros listed below for facilitating navigation of pages while the RikWik server offers a wider range of macros.
There are several wiki-like systems/applications for use on mobile devices.
One of them is the WikiPad application for PalmOS. WikiPad is a simple note taking application and uses “WikiWord” syntax to define links between pages so the user can navigate from one page to another by clicking on underlined hyperlinks. However, it only supports one piece of Wiki syntax: WikiWord, which contains a mixture of lowercase letters and more than one uppercase letter. Each WikiWord would be displayed as a link to a page with the same name when the user saves the page. WikiPad is easy to use and is suitable for creating daily entries. However, it has no desktop version and is not targeted as a collaboration tool but personal content management instead. In addition, it is also missing some important functionality such as page deletion, and wiki heading and formatting syntax [26].
ArcoWiki is a hypertext browsing and authoring application for PalmOS. It supports basic wiki syntax such as font style, lists, links, and navigation history and basic editing function. Furthermore, ArcoWiki also offers some basic wiki features like help index, page renaming, and search. The user can export the page content to the desktop computer and publish them online using one of the wiki engines [27]. However, it can not be accessed by multiple users for group work and there is no desktop version as well.
NoteStudio is the most comprehensive mobile supported wiki-like system when comparing with the two others described above. NoteStudio offers the different versions for PC, Mac (OSX), and Palm separately. But it does not support for using on the Pocket PC. NoteStudio mainly target as a personal wiki. The user can write personal content and encrypt the “page” on the PDA (or Desktop computer) using wiki syntax and synchronize the content with each other. Moreover, you can export the content as HTML style with specified style sheet (CSS) from the user’s Palm [28]. However, it is still targeted as a personal wiki-based system instead of a collaborative platform.
Another notable example is Mobile Tiki (a mobile version of TikiWiki) that provides the ability for WAP enabled mobile devices to access the content of all mobile Tiki enabled websites. Nowadays users can browse the wiki pages, blogs, articles, and forums by using their mobile devices [29]. The main purpose of the Mobile Tiki project is to offer the ability of accessing the wiki content instead of providing the basic features, such as editing and creating pages, for users to manipulate wiki on their mobile device.
The following table provides an overview of the existing wiki mobile applications and their features. These mobile wiki systems either provide only the ability of accessing its wiki server pages on the mobile devices for reading or offer a personal notes taking tool using the wiki markup on the PalmOS. NoteStudio is the featured wiki-like system, which supports both desktop and mobile versions. Users can use their mobile devices to import/export wiki articles to/from desktop version. But it is still targeted as a personal wiki application and not a web-based collaborative system. Pocket RikWik is a compact version of RikWik running on the mobile devices. Users can use a standard pocket web browser to manipulate with RikWik services no matter whether it is online or offline. All mechanisms such as getting pages, uploading changes, propagating updates and conflict resolution will be performed automatically.
Table 6-1 The Comparison of the existing Wiki mobile applications
| Pocket RikWik | Mobile Tiki | WikiPad | AcroWiki | NoteStudio | |
| Web-based System | Y | Y | N (Win App) |
N (Win App) |
N (Win App) |
| Multiple Users Access | Y | Y | N | N | N |
| Desktop Server Companion | Y | Y | N | N | Y (Single User) |
| Auto and Manu retrieving server pages | Y | N | N | N | N |
| Mobile pages Editing (Online & Offline) |
Y | N | Y | Y | Y |
| Providing Wiki-markup Editing | Y (Rich markup) |
N (Read only) |
Y (Basic markup) |
Y (Basic markup) |
Y |
| Creating Offline Pages | Y | N | Y | Y | Y |
| Mobile Revision Control | Y | N | N | N | N |
| Mechanisms of Upload and Conflict Resolution | Y (Multiple Users) |
N | N | N | Y (Single User) |
| Support Pocket PCs or PalmOS | Pocket PCs | Pocket PCs & PalmOS |
PalmOS | PalmOS | PalmOS |
The principal objective of this paper is present a novel wiki which supports mobile collaboration. This goes beyond current systems which only allow offline viewing of pages, by supporting offline page editing. The architecture comprises a central wiki server and a subservient mini-wiki running on the mobile device which can cache, render and edit pages. The system supports the hoarding of pages to enable offline page viewing and editing. A prototype has been developed using the Microsoft .NET Compact Framework; however the general architecture could be implemented using other technologies such as J2ME, especially given that the interface to the wiki server uses web services.
The current approach to conflict resolution (no matter whether it is on the server or the client side) is to provide an interface allowing users to decide how to deal with conflicts. However, a merge mechanism such as Harmony (An XML Synchronization protocol) would provide a finer level of conflict resolution through the fine grained merging of changed page contents [30].The mechanism for selecting and retrieving required pages will be evaluated and improved to fit in with different requirements.
An interesting avenue for further investigation is to generalise the architecture further through a true Peer to Peer relationship between Pocket RikWik and the wiki server. This would enable many interesting features including general mobile wiki federation and would obviate the need for a centralised wiki server. In order to achieve this the Pocket Web Server would need to be extended to support web services [31].
Another critical aspect of mobile scenarios that has not been focused on is the appropriate security mechanism. The transmission of data between server and client via web services is insecure. Therefore, an appropriate security approach should be provided in the future work, probably based on WS-Security.
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