# Smart System for the Retrieval of Digital Educational Content
## 2 Related Work
### Standards for the Learning Object Paradigm  
E-learning standards still have much room for improvement and development. More time is needed before standards become generalized and consolidated, enabling greater interoperability, reusability, manageability, accessibility, durability, scalability and reliability. In the case of LO, metadata describe the characteristics of educational content items by means of labels in order to guarantee technical interoperability. Labels enhance the usefulness of the LO, making it easier to reuse items by facilitating their storage, retrieval, localization, and exchange. Moreover, labels make it possible to quickly recognize the characteristics of the content items stored in the repositories. Nevertheless, the metadata are not useful if users do not use metadata standards or use them incorrectly. The adequate use of standards is essential to establish standardized norms for these descriptors and to achieve interoperability between content items. It is evident that the LO paradigm has contributed to the emergence of many technological perspectives on the reuse of learning content. Beyond the standard metadata formats of the previously listed LOs, there are a large number of other standards that facilitate the management and communication of platforms and their integration into more complex models. There exist several standards proposing conceptual models for the aggregation of learning resources, such as the Resource Aggregation Model for Learning, Education, and Training (RAMLET) [19]. It aims to facilitate interoperability by providing an ontology that allows in the mapping of existing aggregation formats [20; 21]. Many are the challenges that have emerged during the innovation and development processes, such as including adaptive mechanisms in the use of LOs [22], semantic web services [23], and developing complex services [24]. These challenges are yet to be overcome. For now, the problems that impede the interoperability of educational content can be divided into three main groups:  
1. The biggest problem is the LOR's tight structure, which prevents external management from becoming flexible and powerful. These features are essential if we are to ensure interoperable systems and easy access to dispersed and heterogeneous sources. This tight structure also impedes external users from managing resources. This tight structure also impedes comprehensive user management according to user interests in line with other users in the same context. Furthermore, the LOR's search interface does not display accurate and reliable LO information because it cannot retrieve data from the Deep Web. 2. Another problem is that the internal logic of the majority of LORs is not understandable to the applications that access them. Most of them need some intermediate abstraction layer, such as web services or related technologies. The extraction of LOs is, therefore, a complicated and slow process that sometimes requires the user to intervene manually. The systems that include a middleware layer also encounter problems, such as high response times, unavailable LORs, erroneous results, etc. 3. The following group of problems is directly related to the absence of automatic mechanisms that would control the quality of the labels and of the contents, according to technical, semantic and syntactic aspects of the LOs, ensuring the correct specification of these LOs in any of the metadata schemes that describe them. This improvement would provide simple channels for the user to access all possible resources. On many occasions, the same contents may have different metadata, depending on the repository in which the search is performed. Beyond the problems associated with the LORs, there are some additional problems directly related to the specification of LOs. Standard metadata labeling must accurately define the educational resource, however, current mechanisms do not establish a minimum number of characteristics that an LO must have in order to be used within a particular educational context.