Codificación actual: «una orquesta de instrumentos discordantes»

As can be seen from Figure 29, Brusilovsky separates Adaptive Hypermedia techniques into the two major categories, ‘Adaptive Presentation’ and ‘Adaptive Navigation Support’.

FIGURE 29 - BRUSILOVSKY'S TAXONOMY OF ADAPTATION TECHNIQUES

With the exception of Adaptive Multimedia Presentation, Natural Language Adaptation and Map Adaptation, the whole of Brusilovsky’s taxonomy can be implemented in the ADE delivery engine using the LAG adaptation language as will be shown below.

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6.13.1.1Adaptive Presentation

6.13.1.1.1Adaptive Multimedia Presentation

This refers to the adaptation of multimedia (generally video or audio) before or during presentation to the end-user and involves a complex authoring process [101], hence falling outside of the scope of this work.

While the necessary data to control multimedia presentation can be stored in elements as defined by the LAOS framework, this technique requires support from all aspects of the authoring and delivery process for Adaptive Hypermedia, including authoring tools, adaptation languages and delivery engines.

Currently this technique for adaptation is not directly supported by the LAG adaptation language or by the ADE delivery engine. However, it would be possible to sequence multimedia files (delivered embedded within HTML) in an adaptive manner using ADE (with associated authoring in MOT). Similarly it would be theoretically possible to allow ADE to deliver XML content (such as SMIL [102]) to describe multimedia.

6.13.1.1.2Adaptive Text Presentation

The ‘Adaptive Text Presentation’ subcategory is one of the largest in Brusilovsky’s taxonomy and its further category ‘Canned text adaptation’ has been the focus of significant research as a result. Knutov et.al. later expanded ‘Canned Text Adaptation’ and made it one of their three major categories [16] (see section

160 6.13.2.1 for a detailed comparison of both Brusilovsky and Knutov’s taxonomies to LAG and LAOS).

The additional subcategory of ‘Natural language adaptation’ currently has not been fully implemented in Adaptive Hypermedia research thus far, and therefore it is difficult to classify and compare how this can be implemented at present. More importantly, it is not clear how something which would rely on machine learning (and thus sub-symbolic) would be expressible in an external adaptation language (which is equivalent to a rule-based system, and thus symbolic), so for the time being, such adaptation is not relevant for the adaptation language development research.

6.13.1.1.3Adaptation of Modality

Adaptation of modality refers to high-level content adaptation, where an AHS has a choice of different versions of the content (typically multimedia). Examples of this could be where a choice of content alternatives is based on learning style [103], abilities [104] or network conditions [61]. The latter example is from Case Study 1, presented in section 7.3.1 of this thesis, and is an excellent example of how the Domain Model and Goal and Constraints Model in LAOS can provide for storage of alternative types of content with relevant meta-data, to allow an adaptation language (LAG in the case study) to select the relevant alternative, using contextual information from the delivery engine.

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6.13.1.2Adaptive Navigation Support

6.13.1.2.1Direct Guidance

‘Direct Guidance’ refers to specific recommendations to the user as to the next suitable topic to view. Most current AH systems currently support this through the presentation of a “Next Page” recommendation [28] [24]. The ADE delivery engine includes this, and through the use of LAG it is possible to specifically adapt the link shown (as described in section 6.6).

6.13.1.2.2Adaptive Link Sorting

This subsection refers to the order in which the navigational links are displayed to the user. This is primarily the domain of the adaptation language, by setting the ‘order’ variable for concepts/links, which allows the delivery engine to present the desired order to the end user. Both content and navigational sorting are supported by ADE and the LAG language (as described in section 6.5.3).

6.13.1.2.3Adaptive Link Hiding

Link hiding is categorised into three types:

 Link Hiding: this refers to the display of a working link, but without any external indication (such as underlined and blue in a web browser) that the text is a working link. The end-user sees text that is indistinguishable from normal text but that can be clicked on to access another page in the course.

162  Link Disabling: a step further than link hiding, this refers to replacing the link

with text. The end-user sees just normal text that is not clickable.

 Link Removal: this means removing both the link and the anchor text completely.

The efficient updating of variables from the link within the presentation model, achievable within LAOS-based systems, can be used to flag the required presentation mode to the delivery engine. This is exemplified in ADE and LAG in section 6.6.

6.13.1.2.4Adaptive Link Annotation

This is the annotation of links within the navigational elements and can be achieved in the LAG adaptation language by setting variables in the LAOS Presentation Model that can be interpreted by the ADE delivery engine and presented appropriately (see section 6.6).

For example, addition of an image to a link in the navigation element can be achieved using the following syntax in LAG 5.0:

PM.ToDo.GM.Concept.altText = “<img

src=’highlight.jpg’/>” + GM.Concept.title

6.13.1.2.5Adaptive Link Generation

This is further sub-categorised by Knutov et. al. [16], and therefore will be discussed in section 6.13.2.3.1 below.

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6.13.1.2.6Map Adaptation

Navigational links can be displayed in a graphical presentation (similar to an image map in HTML [105]) which can then be adapted [106]. This type of adaptation is currently complex to author content for and therefore it falls outside of the scope of the research in this thesis, which aimed to improve upon authoring for adaptive hypermedia content and simplify the creation of adaptation specifications that can be created by the non-technical adaptation specification author.

However, it is within the capability of the LAOS model to support Map Adaptation based on meta-data about the map being stored in the domain and goal models.