AUTHORING REUSABLE SLIDE PRESENTATIONS

Alberto González Téllez

Dept. of Computer Engineering, Polytechnic University of Valencia, Spain

Keywords: Content reuse, Slides, Docbook, SMIL, XML, XSLT.

Abstract: Slide presentations have become a common method used by lecturers to prepare and deliver teaching

content. The amount of effort invested in authoring this material is usually very high and then it is desirable

to be able to reuse it. Unfortunately commonly used slide editors offer very little reuse capabilities. In this

paper we present a method of authoring teaching slide presentations that has the advantage of being able to

automatically port slide contents into other delivering formats (textbooks, synchronized multimedia

presentations, e-learning platforms, etc). The technique is based on using an XML compliant language with

available tools that are user friendly and free.

1 INTRODUCTION

Slide presentations have become a common method

to make lectures more effective and efficient (Alley,

2005). To produce good slide presentations requires

carefull design and working time (Alley et al.,

2005), in order to avoid countereffects like those

exposed in (Parker, 2001). The amount of effort

invested by lecturers producing their presentations

is, after some years, quite big. But as a result they

find themselves with hundreds of slides packed in

proprietary format. In order to take the maximum

profit from this investment it would be desirable to

be able to automatically reuse this material as much

as posible (several final formats, topic units, exercise

collections, multimedia presentations, etc).

A way to separate content from format is to use

XML compliant markup languages (W3C rec 04,

2004). This need appeared for instance on the web

and this was the reason why the W3C developed

XML specification. A widespread XML language

oriented to book production is Docbook (Docbook,

2006, Walsh, 2003, Stayton, 2005). It was born in

the seventies under the SGML domain with the aim

of being used to document computer products,

particularly the UNIX operating system. Nowadays

Docbook is available in both SGML and XML, and

it is being used as a general documentation tool. A

dialect from Docbook is Slides that is oriented to

slide presentations authoring. Slides markup reuses

some of Docbook content elements and it basically

changes the hierarchical structure. There are also

specific XSLT style sheets (Docbook, 2006) to

generate HTML and printing format from Slides

content.

Besides of being technically feasible to

automatically reuse content it is important to have

productive and easy to use authoring tools. XML

editors tend to be much less friendly than slide

presentation editors because they usually show the

text markup instead of a WYSIWYG preview.

XMLMind XML Editor or XXE (XXE site, 2006)

does not follow this line. This editor is intended to

be used by non technical authors that are interested

in XML capabilities that are not available in

proprietary formats.

The content of the paper is organized as follows:

first we describe briefly Slides markup and style

sheets. Then we propose some authoring and format

generation tools we have found very effective.

Finally we describe two slides reuse applications:

textbooks and multimedia presentations.

2 SLIDE PRESENTATIONS WITH

SLIDES

As stated previously our proposal to author reusable

slides, is based on XML, particularly on the

Docbook dialect Slides. Norman Walsh defined this

language to be used for authoring slide presentation

in a similar style as other proprietary tools.

Slides markup language is specified by a public

DTD and it includes a subset of Docbook content

elements. The hierarchical elements differ from

Docbook to make them suitable for presentations.

366

González Téllez A. (2007).

AUTHORING REUSABLE SLIDE PRESENTATIONS.

In Proceedings of the Third International Conference on Web Information Systems and Technologies - Society, e-Business and e-Government /

e-Learning, pages 366-371

DOI: 10.5220/0001263703660371

 SciTePress

The root element is slides and it has as children:

slidesinfo and a sequence of one or more foilgroup.

The slidesinfo element includes the next element

types:

• Title and subtitle.

• Author information.

• Meta information (release, revision, etc).

Some of slidesinfo elements are generated by

default by the style sheets (i.e. title and author). To

show other elements style sheets customizations is

required [6].

A foilgroup element contains a sequence of one

or more foil elements. A foil element corresponds to

a slide and then can contain a title and a sequence of

one or more content elements.

The set of content elements available inside a foil

is a small subset of content elements defined inside a

section element in Docbook. These content elements

can be classified as:

• Text block and text inline.

• Lists of items (ordered, unordered and

variable)

• Figures and media objects.

• Tables.

• Links (local, external and web).

A speakernotes element is also available to

include lecturer guide notes that are not intended to

appear in the presentation.

When a Slides document is completed it has to be

transformed into presentation format. To accomplish

this there are available XSLT style sheets (Docbook,

2006) to generate chunked HTML and XSL-FO.

This later format can be transformed into WordML,

OpenDocument, PDF or RTF in order to get a final

printed format. Slides style sheets can also be

customized to get a satisfactory presentation format

in combination with CSS.

To apply the style sheets to the slides document

we need an XSLT processor. There are many

publicly available in both native code like libXML

(Libxlst site, 2006) and Java like Saxon (Saxon site,

2006).

2.1 Theory and Exercises

Contents in slides can be classified as theory and

exercises. In order to be able to clearly distinguish

and manage both types of elements it is convenient

to be able to identify them. This can be

accomplished with the next slides markup

customization:

o The role attribute of foil elements is restricted

to the values: theory, exercise.

o Inside a foil, with its role attribute set to

“exercise”, enunciate elements are marked

setting its role attribute to “enunciate”. This

has to be done only to direct foil descendants.

With this simple customization we can easily

separate theory from exercises. Applications of this

capability are for example: publishing an exercise

book, create an exercise repository, etc. In order to

make exercises more effective solutions can be

filtered when the presentation format is generated.

3 AUTHORING TOOLS

The slides DTD and XSLT style sheets are the

technical basement of the proposal. In order to make

it attractive to final users it is required the

availability of user friendly tools that hide as much

as possible XML related details.

The tools required are an editor and a format

generator. After looking for sometime among the

many available free and commercial products we

have chosen XXE editor (XXE site, 2006) and XFC

XSL utility (XFC site, 2006). They are commercial

products from XMLMind but there is a free license

for both tools that offers enough functionality to

fulfill our requirements.

3.1 Proposed Editor

XXE stands for XMLMind XML Editor, it is Java

written general purpose and friendly XML editor.

XXE is specially customized to Docbook, Slides and

XHTML. There are two views of document content,

one shows the XML tree structure and the other is a

pseudo WISYWIG view, based on CSS, that is

proven to be very comfortable and productive. This

friendlier preview is shown in figure 1.

The application has the common main menu and

two toolbars. The one below the main menu gives

quick access to the most common operations. Below

the quick access toolbar there is the navigating

toolbar that permits quick location of:

• XIncluded elements.

• Elements in the document element subtree

of the active element.

• Sibling elements and ancestor/descendant

elements.

The main panel is divided into the editor panel

and the tools panel. This later panel permits:

• Attribute setting.

• Spell checking.

• Searching and replacing.

AUTHORING REUSABLE SLIDE PRESENTATIONS

367

• Selecting especial characters.

• Locating validity errors.

Figure 1: WISYWIG like preview in XXE.

There are two license modalities for XXE:

standard and professional. The standard edition is

free and it has been artificially limited in

functionality. The most relevant features not

available are:

• Schema based validation.

• Documents can not be saved to FTP and

WebDAV servers.

• It could not be deployed using Java Web

Start.

• XSL-FO plug-ins do not work inside XXE.

None of these missing features is relevant for the

proposed application because we use DTD

validation, our content files are stored in the local

file system and we generate format from another

application. Then standard edition is the sensible

choice.

3.2 Proposed Format Generator

The tool we propose to generate presentation format

is XFC (XMLMind Format Converter) XSL utility.

It is also written in Java and it has a free personal

license.

XFC is in fact an XSL-FO processor that

generates WordML, OpenDocument and RTF. The

XSL utility also allows generating other formats like

HTML and PDF. It includes also Saxon XSLT

processor and FOP converter from XSL-FO to PDF.

XFC XSL utility is customized to generate

HTML, chunked HTML and printing formats from

Docbook and Slides documents. The corresponding

XSLT style sheets are included in the distribution.

The transformation process is described in figure 2.

The tool is completely customizable the only

restriction is that Saxon can not be replaced. New

transformations can be defined by setting the style

sheet, defining its parameter values, passing the

transformation output to a external program (i.e. an

XSL-FO processor or a script) and setting an output

format viewer (i.e. web client, PDF viewer, etc).

Figure 2: Format generation with XFC XSL utility.

3.3 Collaborative Authoring

Docbook and Slides documents are plaintext, this

allows to use concurrent versioning systems like

CVS to collaborative authoring teaching material.

We use a CVS server on Linux and the java client

SmartCVS which is very user friendly and free for

non commercial use.

4 SLIDES REUSE EXAMPLES

Next we are going to describe two interesting

applications of the proposal capability of flexible

reuse. First we will port slides content into textbook

by means of transforming slide presentations into

Docbook. The second application consists of

including slides content into synchronized

multimedia presentations based on SMIL (W3C rec

13, 2005).

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4.1 Reusing Slides Into Textbook

When a lecturer begins with a subject he or she

needs to write a sketch of content in slide format

normally based on preexisting information sources.

In this first approach we propose to use Slides

language as the source.

From the Slides source a chunked HTML format

can be generated directly just applying Slides HTML

style sheets. A printed format, more convenient for

students can be obtained translating Slides to

Docbook and then applying Docbook XSL-FO

styles sheets and an XSL-FO processor to get final

printable format. The XSLT style sheet required to

convert Slides to Docbook is very simple because it

has to change only the document structure. We can

also take advantage of the role attribute that is

always present in Slides and Docbook elements and

does not have predefined values.

Figure 3: Slides to textbook conversion.

A special attention is paid to exercises. We

implement exercises in Docbook by means of

qandaentry elements. Originally this element was

defined to write FAQ collections but it is very well

suited to exercises also. Qandaentry elements are

wrapped in qandaset elements. On the other side

qandaentry elements have as children one question

element and one or several answer elements.

Then the conversion from Slides to Docbook is

performed in the next way:

o Slides root slides is converted to Docbook

root chapter.

o Slides foilgroup elements are converted to

Docbook section elements.

o Slides foil elements with its role attribute set

to “theory” are converted to Docbook

simplesect elements.

o Slides foil elements with its role attribute set

to “exercise” are folded in a qandaset element

and converted to Docbook qandaentry

elements:

• Foil children with attribute role set to

“enunciate” are folded inside a question

element.

• Other foil children are folded inside an

answer element.

The conversion process is shown graphically in

figure 3.

When the authored material has reached a critical

mass then the source can be changed to Docbook

Focus now will not be on the presentation summary

but on producing a complete textbook. From that

moment the Slides document will be generated from

the Docbook document by means of custom XSLT

style sheets. The Slides document content will be a

subset of Docbook content and the lecturer has to be

able to define this subset. Content selection will

follow the next criteria:

• Text selected from:

o Inline marked text (i.e. emphasis).

o <literallayout> elements

o <programlisting> elements.

• Tables.

• Media as block and inline elements.

Common block text elements (i.e. paragraphs) are

filtered in such a way that only inline marked text is

selected. The most common inline text element is

<emphasis>. Also block elements inside a literal

layout or program listing elements are included in

the Slides document.

Tables content and media elements are not

filtered as they are supposed to be relevant in the

presentation format.

As before exercises are specially considered. The

textbook can be used as exercises repository then a

mechanism is required to select what exercises will

be included in the presentation format (i.e. as

examples), this can be accomplished by using the

role attribute of qandaentry elements. Selected

exercises will generate a foil element according to

the previously described design.

XLST style sheets required to perform Slides to

Docbook and Docbook to Slides conversions are

available at (Slides2Docbook site, 2006) and

Docbook2Slides site, 2006), respectively.

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369

4.2 Porting Slides to Multimedia

Presentations

In order to keep the student attention alive it is

convenient to make class presentations as much

dynamic as possible. A way to achieve this is to

combine several media elements, not only text and

graphics, into a timeline. An open XML standard

designed specifically with this goal in mind is SMIL

that stands for Synchronized Multimedia Integration

Language.

There are several SMIL clients (RealPlayer,

Ambulant, QuickTime, etc) and authoring tools

(LimSee2, GoLive, GiNS, etc). The fact that SMIL

is a compliant XML language allows other

alternatives to create SMIL presentations: a plain

text editor or automatic generation through XSLT.

The later alternative is particularly attractive in our

case because we can use as input to the XSLT

transformation our slides documents.

Slides language is capable of including media

objects. An example is to add to every foil element

an audio stream file that will expand the slide

content. Other audio and video object can be added

in order to make the presentation more attractive.

All the previous objects have to be located in the

screen and scheduled in time. SMIL allows to define

a layout on the screen, decomposing it into regions,

and to schedule media objects in time in sequence

and/or in parallel.

In spite of SMIL being a standard, there are many

details that have to be considered to produce SMIL

presentations: the way text is included and

formatted, the media formats supported, the types of

linking mechanisms, etc. This means that a

particular client has to be selected in order to

guaranty that everything will work. We choose

RealPlayer because it is a widely spread client and it

has a considerable SMIL 2.0 support (Real

Networks, 2004). Other interesting features of this

client are: it is free, it is multiplatform and it has

complementary authoring tools also free and

multiplatform like RealProducer Basic.

An institution that has choosen SMIL as their

presentation tool is INRIA (Institut National de

Recherche en Informatique et en Automatique) in

Grenoble, France. Their interest in SMIL is proven

by the fact that they have developed an open source

SMIL authoring tool called Limsee. A good example

of the SMIL capabilities can be seen at the INRIA

presentations site (INRIA, 2006)

5 CONCLUSIONS AND FUTURE

WORK

We have proposed a method to author teaching slide

presentations based on XML, particularly on the

Slides language. Our experience using this method

has shown that losing some user friendly features,

present in more conventional slide editors, is paid

off by the ability of reusing content. In the context of

teaching topics at graduate level and above, this

benefit is particularly relevant.

An important aspect of the proposed method is

the authoring tools, particularly the XXE editor that

has proven to be very productive to non XML

experts.

As present and future work we are developping

Docbook and Slides customizations, at markup and

style sheets levels (González, 2006), in order to

better fulfill teaching material authoring

requirements. We also are working on porting Slides

document to SMIL as much automatically as

possible using RealPlayer as the target client.

Other interesting areas for future development

will try to take advantage of other XML related

capabilities like content repository management

(Dhraief, 2001) and to port content to e-learning

platforms (González, 2005, Mengod, 2006).

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