Hierarchies in a multidimensional model: From conceptual modeling to logical representation

Document-Oriented Data Warehouses: Complex Hierarchies and Summarizability

“…For each element having multiple parents, a parent composed from the fusion of its parents is created and inserted between the two. The last algorithm Makeonto is used to manage onto hierarchies [11] In similar work based on the solution from Pederson, Mansmann and Scholl [10] present a visual tool OLAP which allows for normalizing, browsing and visualizing the different levels of a hierarchy . In their graphic structure, each level of the hierarchy is modeled by a directory.…”

“…In the second solution of normalization, the principle is to separate the correct hierarchies from the hierarchies susceptible to cause aggregate calculation errors. In this context, [11] propose to put the non-strict hierarchies in the new tables, called joint tables also called separated tables by Malinowski and Zimanyi [11]. In 2008, Mazon and al, proposed a conceptual model normalized UML, separating the different associations [13].…”

“…A hierarchy is said to be non-covering if a dimension value can have no direct upper parent [11,15]. The complex hierarchies cause summarizability issues [13,10] i.e.…”

“…A hierarchy is said to be non-strict when a child of a given level can have more than a parent of the superior level [11,15].…”

“…we cannot drill-down or roll-up in data. Several solutions have been proposed for summarizability issues, but these solutions are adapted to the relational model [6,7,8,11,18] With these solutions, it is necessary to alter original schemas and to override attribute values to act as arrays. NoSQL systems have interesting features that can useful for dealing with complex hierarchies.…”