Data Model for SIPAMER Prototype

collection of metadata, consisting of a set of schema components: element and attribute declarations and complex and simple type definitions. These components are usually created by processing a collection of schema documents, which contain the source language definitions of these components which are organized by namespace: all the named schema components belong to a target namespace, and the target namespace is a property of the schema document as a whole. According to the definition in [12], a schema component is the generic term for the building blocks that comprise the abstract data model of the schema. The xs:schema symbol defines the root element of a schema that contains representations for a collection of components (type definitions and element declarations), which have a common target namespace. There are 13 kinds of component in all as follows:data model of the schema. The xs:schema symbol defines the root element of a schema that contains representations for a collection of components (type definitions and element declarations), which have a common target namespace. There are 13 kinds of component in all as follows:  Simple type definitions a set of constraints of an element with no element children. It is defined as xs:simpleType;  Complex type definitions a set of constraints of an element that contains a sequence of items which conforms to a particular model group. It is defined as xs:complexType;  Attribute declarations an association between a name and a simple type definition, together with occurrence information and a default value. It is defined as xs:attribute;  Element declarations an association of a name with a type definition, either simple or complex, an default value and a set of identity-constraint definitions. It is defined as xs:element;  Attribute group definitions an association between a name and a set of attribute declarations, enabling reuse of the same set in several complex type definitions. It is defined as xs:attributeGroup; 44 Data Model for SIPAMER Prototype  Identity-constraint definitions an association between a name and one of several varieties of identity-constraint related to uniqueness and reference ;  Model group definitions an association between a name and a model group, enabling re-use of the same model group in several complex type definitions ;  Notation declarations an association between a name and an identifier for a notation ;  Annotations information for human and/or mechanical consumers ;  Model groups a constraint in the form of a grammar fragment that applies to lists of element information items. It consists of a list of particles, i.e. element declarations, wildcards and model groups ;  Particles a term in the grammar for element content, consisting of either an element declaration, a wildcard or a model group, together with occurrence constraints ;  Wildcards a special kind of particle which matches element and attribute information items dependent on their namespace name, independently of their local names ;  Attribute Uses an attribute declaration within a complex type definition is embedded within an attribute use, which specifies whether the declaration requires or merely allows its attribute, and whether it has a default or fixed value. For the data types description XSD provides a set of 19 primitive data types (boolean, string, decimal, double, float, anyURI, QName, hexBinary, base64Binary, duration, date, time, dateTime, gYear, gYearMonth, gMonth, gMonthDay, gDay, and NOTATION). Also, new data types can be derived from these primitives by the following methods:  restriction by reducing the set of permitted values ;  list by allowing a sequence of values of the attributes ;  union by allowing a choice of values from several types; For a relational data representation the XSD schema components can be used as it is described in the following table: Table 1 – Relational and XSD components No Relational element XSD component 1 Table Element, complex type 2 Attribute Element, simple type 3 Constraint Restriction, reference For example, in order to specify the structure of the table CENTRALA (centrala_id number primary key, denumire varchar(29), locatie varchar(30)), the XSD schema can be written as follows: Database Systems Journal vol. V, no. 4/2014 45 46 Data Model for SIPAMER Prototype