You are presented with multiple paper abstracts, alongside the associated literature review and chapter titles. Given the provided information, you are going to do a literature review. Please generate a coherent literature review that synthesizes the content, draws connections between different works, highlights major findings, and identifies any gaps in the existing research.

Literature Review Title: Virtual Learning Environments-A Survey 
Chapter Title:  A. Webct (Course Tools) or Blackboard Learning System 
1. Abstract of Cited Paper (BIB001):  Collaborative learning models are widely used in educational institutions. These models require a high interaction level among students and are mainly oriented towards in-class scenarios. But when collaborative models are deployed in a distant scenario, user expressiveness is significantly reduced thus creating a gap that hinders the effectiveness of this collaboration. A computer-supported model provides a set of tools to compensate for the distant scenario and reduce this gap. This paper presents the issues and solutions derived from the design and deployment of a complex collaborative model in a distant scenario. The course structure was captured using the Learning Design specification, and an architecture based on virtual network computing was used to provide the required collaborative tools. The course was included as part of a regular undergraduate program in three higher educational institutions.

Literature Review:
According to the team that developed WebCT it is " a tool that facilitates the production of sophisticated Webbased educational environments." It can be used flexibly to establish complete online courses, or to publish materials that add existing courses. All communication with WebCT come about through a web browser.. Essentially a webCT course comprises of a series of linked HTML pages that define a path or "road-map" through the course material. The course content is supplemented by webCT tools which can be built into the course design by simply dragging the appropriate tool icon onto the web page. This creates an active link to a 'toolpage' BIB001 . There are three main aspects to webCT: 1. A presentation tool that allows the designer to customise the look and feel of the course pages. 2. A set of student tools that can optionally be integrated anywhere in the course. 3. A set of administrative tools to aid the tutor manage the course when it is in progress. A webCT course centres around a single course homepage, which appears whenever a student logs on to their course. This page contains links to the various course pages and the tools. The learner tools in webCT include: asynchronous communications tools (e-mail and conferencing) and also a chat facility; student evaluation and self-evaluation tools such as online quizzes and MCQs; an image repository; a glossary database; learner collaboration and presentation areas; content annotation, homepage generation, course navigation and searching tools. Tutors can track student progress including the number of times and when they have accessed the course. Technology: This is a client-server system with all interaction through a web browser client. Supported server platforms are currently only Unix but an NT 4.0 version is to be announced. The proposed framework fails to meet all guidelines for accessibility. WebCT's user interface has been criticized as needlessly complex and unintuitive. The "Vista" version of the product represented an attempt to derive balance between flexibility and ease of use, however it has also been the target of ease-of-use criticisms. Some WebCT criticisms which were apparent consist of difficulties deploying it in multiple tabs or browser windows, large dependence on Java for its user experience, BIB001 practice of too many browser framesets, concerns with some features requiring pop-up blockers to be turned off, and difficulties using standard browser navigation tools (i.e. the Back and Forward commands). B. Virtual-U Virtual-University BIB002 like the other systems described is a server based integrated environment for education that uses a web client. One of the major differences between Virtual-U and other systems is the use of a campus metaphor within which locations and objects are used to represent the different tools and activities. The homepage contains a map of the Virtual_U campus which consists of :  A Course Room -containing details of the courses  A Library -containing resources and links to library pages and search engines  A Gallery -for presentation of multimedia resources  A Conference Building -from which conferences can be accessed  A Café -another conference space for more casual student or staff interaction  A Personal Workspace -The workspace provides links to all other areas of the campus and also includes a number of tools for managing your own work. These tools include a calendar for personal time planning, a submissions box for viewing assignments, a grade-book allowing students to view their own performance or for instructors to monitor student progress, a glossary and preference options. Additionally, there is also a detailed help system providing course designers with pedagogical guidelines for the use of the system. Technology: Web browser client, Server software runs on Unix or NT.