The Web Collaborative Editing And Annotation Consistency Maintenance Of Technical Studies

In the age of Web2.0,people not only retrieve information by reading but also publish and modify existing contents on internet.Meanwhile,internet is not used in an isolated and independent way anymore,collaborative activities which is beyond geographic boundaries appears very often in daily life.The core mechanism and key technology of web based collaborative edit and annotation,which are fundamental components of many web2.0 applications(e.g.Internet Meeting,E-learning),is concurrency control and consistency maintenance.Based on existing research work and prototypes,this thesis focuses on web-based collaborative annotating and consistency maintenance technology to tree representation of the document.In detail:Web based collaborative annotation model with consistency maintenance algorithm.A light-weighted model for collaborative annotation is proposed,then the concurrency control algorithm supporting real-time collaboration is presented for the model.The "in-line" method of annotation makes people gain same annotating results through different terminals(laptop,PC,PDA etc.).Concurrency control algorithm is lock-free and supports users to make annotations freely to any part of the document at any time.Consistency maintenance technology to tree representation of documents, especially DOM documents.It is based on the idea of address space transformation and requires every participant site maintain a so-called DTree structure which has "mark" and "retrace" potentials.So when concurrent operations are received,they can be transformed through the "retrace" process.This method ensures the intention of operations and the consistency of the group editing system which adopts it to be respected.Additionally,DTree based policies for dynamic entering and leaving collaborative session is also covered,with which users can switch between online and offline modes expediently.A prototype based on the proposed collaborative annotation model.A real-time, multiuser collaborative annotating system called Co-Annotate is built on the base of two open-source projects:ShiftSpace and Usaproxy.It includes functional modules of session management,communication model,transparent agent based on http protocol and the storage model for annotation data in rdf/xml format.The concurrency control mechanism proposed in this thesis is also reflected in the prototype.