Database Reference
In-Depth Information
organization. A data mart is designed according
to a specific model, namely the multidimensional
model that highlights the axes of data analyses.
Data marts are often derived from subsets of a
data warehouse data, though in the bottom-up data
warehouse design methodology the data ware-
house is created from the union of data marts.
Document Type Definition (DTD): A DTD
defines the tags and attributes that can be used in
an XML document. It indicates which tags can
appear within other tags. XML documents are
described using a subset of DTD which imposes a
number of restrictions on the document's structure,
as required per the XML standard.
DTD Simplification: The simplification of
a DTD removes empty elements, replaces each
reference to an ENTITY type with the text cor-
responding to that entity, and then it removes the
corresponding ENTITY declaration, and apply
Flattening, Reduction and Grouping transforma-
tions.
eXtensible Markup Language (XML): XML
is a general-purpose specification for creating
custom markup languages. It is classified as an
extensible language because it allows the user to
define the mark-up elements. The main purpose
of XML is to aid information systems in sharing
data, especially via the Internet.
Model Integration: Model integration produc-
es a single model that combines two or more input
models. The produced model can be represented
in the same definitional formalism as the input
models (or in one of the definitional formalisms
used by the heterogeneous input models). The
expression of the new model must be formally
correct within the definitional formalism used.
Relational Data Model: The relational data
model was introduced by E.F. Codd in 1970. It
is particularly well suited for modeling business
data. In this model, data are organized in tables.
The set of names of the columns is called the
“schema” of the table. The relational model is
the model in most common use today.
Star Schema: The star schema (sometimes
referenced as star join schema) is the simplest
model of multidimensional schema. The star
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