The IEEE-LOM standard for describing metadata may be incomplete in some contexts and, on the other hand, describing not widely used metadata. To solve the problem of its incompleteness, there are some extensions of the IEEE-LOM standard, such as the extension defined by Customized Learning Experience Online (CLEO) (Barrett et al., 2003). CLEO's contributions to IEEE-LOM are:

• Additional vocabularies to improve the aggregation level (general category);
• Alternative vocabulary for the learning resource type (educational category) and purpose (classification category);
• New elements for the educational category.