706 ITU‐T's Technical Reports and Specifications Figure 2 – Overall Standard Data layers for Open Data Portal The first layer is raw data layer. According to Elmasru and Navathe and Kent, data can be further classified into three components: structured data, semi‐structured data, and unstructured data. Structured data are those organized in according to a rigid and pre‐defined criteria such as respecting various fields (or attributes) of data, delimiting thes cope, domain (possible values) of data, data type, etc. This is the case, for example, with data involved in tables of relational databases (RDB) used by most institutions. The structured data extractor is responsible for data extraction of data stored on the RDB. An important aspect of data publication on the traditional Web is related to the loss of structure while transforming this data from RDB to open data portals. These data are converted into current web formats, making them unstructured. Semi‐structured data are given in a way one cannot always predict all aspects of a given piece of data. Some of its general attributes can be known and required in advance, others added later depending on circumstances. References are an example of semi‐structured dataset, containing fairly similar items. The semi‐structured data extractor is responsible for data extraction of semi‐structured data on the open data portals. Unstructured data are those for which no scheme isspecified, containing only the content and a means of presenting it. An example is the text on a HTML page. The unstructured data extractor is responsible for data extraction of unstructured data on the open data portals36. ____________________ 36 Please see: http://linkeddata.org/faq RDF Convertor Structure RDB Data Raw Data Extractor Extractor Extractor Semi-Structure Data Unstructure Data RDF Triple Storage Query Processor Semantic Reasoner Semantic Analyzer SparQL Endpoint Query Interface SparQL Query RDF Interconnect the Dataset with other Datasets Data Visualization Social Networks Linked Data Structure Data