This plan does not represent the current status of the project, rather it is an overview of the features that HLS (Helsinki Learning System) should have. 

Table of contents

• Overview of components
  1. Databases and data structures
  2. Applications
• Technical overview
• Installing
• Current status

Overview of components

HLS has the following components, each described later. 

1. Databases and data structures

The data structures of the HLS system are xml documents stored in an xml database. The structure of these data bases is specified by xml document type definitions (dtds). There are following data bases in HLS:

• ccd, course content dictionary. Defines the topical hierarchy of the content. Defines also additional information concerning topics.
• problems. Problems which can be of type multiple choice, yes or no, string and essay.
• exercises. Exercises consist of several problems and information about in which order the system offers them to the user. Also hints and other feedback concerning problems are stored in exercises.
• userdb. User data base stores user accounts to the system.

1.1 CCD

Course content dictionary contains the topic hierarchy of courses. Each course has an entry in the ccd. The topics covered in the course are listed under that course. The topic hierarchy is recursive, i.e. each topic has its subtopics as topic subelements. Courses and topics contain also additional description data. This data is not yet specified. The use of ccd in problem and exercise data bases is pictured below.

1.2 Meta data

• TimeStamp. When the document was last modified.
• Author. The author of the document and the url to the author.
• Copyright owner. Copyright owner of the document.
• Level. Level of difficulty of the problem or exercise. A percentage of the successful attempts of solving it.
• Relevant text. A standard text book which covers the topic of the document.
• Course. A reference to the course in the ccd to which the problem or exercise belongs.
• Topic. A reference to the topic in the ccd to which the problem or exercise belong.

1.3 Problems

All types of problems have problem text. Problem can contain several language versions. Different types of problems contain specific data:

• Multiple choice:
  • All the choices and the information whether they are correct or false.
• Yes or no:
  • The correct answer as yes or no.
• String:
  • The correct answer as a string.
  • Encoding of the answer, e.g. Maple or Mathematica.
  • Evaluation guide, which tells how the user's answer and the correct answer should be compared.
• Essay:  Not yet specified.

1.4 Exercises

Exercises consist of sequences of problems. Each member of the sequence is a reference to a problem in the problem data base with additional information. There are three different types of user actions, correct answer, wrong answer, and I don't know answer. For each of these types of actions there is stored the following information:

• Feedback, which the system should displays to the user.
• Reference to a problem which the system displays next to the user. Can also be left empty, when it means that the exercise ends.
• Information whether to display the correct solution.

1.5 Users

According to the privileges there are different types of users, the higher types have all the privileges of the lower types:

• administrator. Can freely modify all the content of the databases. Can create new user accounts.
• lecturer. Can create ccd's, modify their own ccd's, modify all problems and exercises of their own courses. Can create new user accounts on levels lecturer and editor.
• editor. The default level. Can create and modify their own problems and exercises. Can create and modify their own user accounts.
• Users without privileges can view the content of the problem and exercise data bases.

2. Applications

There are two applications of the data bases. First is a tool to modify the content, called editor. Users log in to the editor and can modify the databases according to their privileges. Content can be added, changed, previewed, and deleted.

The second application is for the students of the material. The application presents exercises to the user and allows solving them. It displays the feedback coded in the exercises and can also display an overview of the students strengths and weaknesses according to the course's topics.

Technical overview

The applications are web based, meaning that they are used with a web browser. Also they are client - server applications, since the client uses the server's data bases. Overview of the system is pictured below:

1. Client side

Clients use the applications with a web browser. The web browser needs the IBM TechExplorer plug-in for displaying material written with TeX.

2. Server side

In the server side servlets are used as to handle the user interface and user's actions. Standard xml libraries are used to work with xml data. All applications are written in the Java programming language.

3. Interfaces

As the data structures and the applications should be flexible, there is an interface between them. This allows the changing of the implementation of the data base without changing the applications as long as the interface does not change. Also the applications can change without affecting the data base definitions. These interfaces are coded using the Java language.
 

Installing the HLS system

HLS system is a web application that is installed into a directory structure in a java enabled web server. The preferred server is Apache Tomcat 4. HLS system should be rooted at a directory called hls. The direcoty structure is following:

editor

the starting point for editor application

mathapp

the starting point for the student application

css

contains css stylesheets defining a common style for the web pages

dtds

contains all the dtds defining the xml data structures

js

contains javascripts used in populating topic lists in problem and exercise input forms

jsp

contains java server page files used in the user interface layer of the application

lib

contains jsp tag libraries and other libraries used

WEB-INF/classes

contains servlet class files

WEB-INF/lib

contains java class libraries

WEB-INF/src

contains java source files

xjs

contains jaxb definitions for xml bindings into java objects

xml

contains the databases in xml format

xsl

contains xsl stylesheets for transforming xml data into html pages

Current status