Pieces of a didactical content are typically referred with the term ‘‘learning object’’ (LO). Different definitions of LO are available; probably, the most representative one has been provided by the IEEE Learning Technology Stan-dards Committee, which describes it as ‘‘any entity, digital or non-digital, that may be used for learning, education or training’’ (IEEE 2007). We can then define a content package as a set of LOs coupled with a document which identifies the association among LOs and possible sequencing rules, which allow to organize the whole didactical content. From a technological point of view, a standard description of the content structure is required to guarantee that contents will be interoperable across different e-learning systems.
The Shareable Content Object Reference Model (SCORM) is a de-facto standard, through which it is possible to define learning resources, called Sharable Content Objects (SCOs). SCOs can be presented in any SCORM-compliant system and are composed of one or more ‘‘assets’’ or resources (e.g., digital media, Web pages, etc.) (ADL 2004). An XML document is associated to the whole learning content, referred as the ‘‘manifest’’, which contains meta-data, navigation or structural description and the locations of each resource. Metadata are defined through IEEE Learning Object Metadata (LOM). LOM is a data model that describes LOs and similar digital resources in order to facilitate their reusability, interoperability and to aid discoverability (IEEE LTSC 2002).
The main specifications of SCORM are the following: (i) the Content Aggregation Model (CAM), which defines the content structure and provides metadata, (ii) the Run-Time Environment (RTE), which delivers real-time information about learner actions and (iii) the Sequencing and Navigation (SN), which describes possible paths through learning contents.
It is worth noting that SCORM is strongly based on the use of client-side scripting technologies, which seem to break Web Content Accessibility Guide-lines 1.0 (W3C 1999) and some international laws related to Web accessibility. However, two considerations are in order: first, at the moment it is not practi-cally possible to leave out SCORM due to its wide use in e-learning systems and second, main current assistive technologies are consistent with the most com-mon client-side scripting technologies; hence, SCORM compliance does not represent a crucial barrier to e-learning accessibility.