Implementing operations to navigate semantic star schemas

Abstract

In the last years, lots of work have been devoted to multidimensional modeling, star shape schemas and OLAP operations. However, "drill-across" has not captured as much attention as other operations. This operation allows to change the subject of analysis keeping the same analysis space we were using to analyze another subject. It is assumed that this can be done if both subjects share exactly the same analysis dimensions. In this paper, besides the implementation of an algebraic set of operations on a RDBMS, we are going to show when and how we can change the subject of analysis in the presence of semantic relationships, even if the analysis dimensions do not exactly coincide.

: a multidimensional conceptual model extending UML

“…Thus, by having candidate Bases and this operation, the most appropriate representation of data can be selected in every situation. The implementation of this set of operations on a Relational DBMS has already been studied and published in [28].…”

“…Moreover, they are not presentation oriented like those in [27]. The implementation on a Relational DBMS of the set of operations presented in this section has already been studied and published in [28].…”

Extending OCL for OLAP querying on conceptual multidimensional models of data warehouses

“…3, it is important to note that even the metadata that describe facts and dimensions have no logical counterparts to be stored in a database. 1 Conceptual models may be decomposed into two layers, one of which contains a kind of metadata: the upper layer provides the visual notation that is rendered in diagrams (e.g., see Fig. 2) whereas the lower layer provides the concepts through which to multidimensionally model the data warehouse storage or database schema (domain model shown in Fig.…”

“…In order to provide compatibility with current developments, this mapping between OCL and SQL should be stated. In [1], the OLAP algebra that is stated as the state-of-the-art backbone in [39] is translated into SQL, thus, proving that relational model expressiveness is at least equal to the expressiveness achieved by OLAP models. In [8], while OCL translation into SQL is stated, whereas OCL and relational calculus are compared in [25].…”

“…1) rendered in SQL. This translation is carried out by means of the mappings discussed in [1]. Let us use the SQL templates employed for querying both kinds of logical configurations as an example: …”