Method of a Structure-Independent Databases Design in
Configurable Information Systems
Yuri I. Rogozov, Alexander S. Sviridov and Alexander N. Belikov
Department of System Analyses and Telecommunications,
Southern Federal University, 1 Engels, Taganrog, Russia
Keywords: Variability of Data, The Method of the Database Design, The Data Model, Structure-Independent Database.
Abstract: We propose a method of developing different structure-independent databases using relational technology.
The method allows depending on the motivation of the developer to obtain various structure independent
databases using relational technology. The requirements that structure-independent database must satisfy
have been formulated. Alternatives of method realization were considered.
1 INTRODUCTION
Nowadays information systems work with complex
data structures with a high degree of variability
(Rogozov Y., Degtyarev A., 2014). Configurable
information systems are one type of such systems
(Rogozov Y., Sviridov A., Belikov A., 2014). Often
we have to design a database (DB) in conditions of
the absence of a priori description of the structure of
stored information. Application of relational
technology in such situation becomes difficult:
variability of the structure of stored information
affects the physical layer of implementation, which
requires redesigning the entire database. As a result,
there are additional costs, both time and financial.
To reduce costs and continue to use relational
technology, some developers and researchers create
a database model with physical layer of
implementation which is independent of the logical
structure (Paley, 2002; Tenzer, 2001; Polishchuk,
Chernykh, 2009).
In this paper, we propose a method that allows
depending on the motivation of the developer to
obtain various structure independent databases using
relational technology. Sequence of steps that leads to
compliance with the identified requirements and
obtaining the physical structure of the database is
defined.
2 REQUIREMENTS FOR THE
METHOD
To formulate the method there has previously been
carried out the analysis of the physical layer
implementation of the relational model and the
Entity-Attribute-Value model, which reveals the
structural requirements to independent databases.
For structure-independent database there is no
need of a priori description of the domain – they are
ready for use, even if they don’t contain any entities
or attributes. A complete separation of the physical
and logical levels of implementation is achieved:
•Logical structure that characterizes user data is
described not by the physical structure of the
database, but by the metadata directly stored in it;
•The physical structure of the database is
unchanged and its creation relational technology can
be used.
Conducted analysis of data models (Kucherov,
S., Rogozov, Y., Sviridov, A., Zhibulis, Y., 2010)
allows us to formulate the requirements that must be
satisfied by structure-independent database,
implemented using relational technologies:
1. The metadata that define the logical structure
of the database is stored directly in the database in
form of data sets in relational tables and make up the
metadata subschema;
2. Data are grouped by type in the tables that
store the attribute values indicating tenancy in a
form of reference to the metadata tables, and make
139
Rogozov Y., Sviridov A. and Belikov A..
Method of a Structure-Independent Databases Design in Configurable Information Systems.
DOI: 10.5220/0005110201390145
In Proceedings of 3rd International Conference on Data Management Technologies and Applications (DATA-2014), pages 139-145
ISBN: 978-989-758-035-2
Copyright
c
2014 SCITEPRESS (Science and Technology Publications, Lda.)
up the appropriate subschema. Name of the field,
that stores the value, is not the name of the attribute;
3. Data structure in the database is represented
by a sparse matrix. Logical data structure is formed
actually, i.e. comprises only entities and attributes,
that are really used in system, and can be
supplemented or changed at any time;
4. Total number of tables in a database on the
physical layer is fixed and depends only on the
number of metadata tables and the types of data and
is independent of the logical structure of data stored.
Limitation of the number of tables in the physical
layer is the key to increase the productivity and
reduce the complexity of database queries and
maintaining the characteristics obtained during its
operation.
These requirements are fulfilled by most of
known models of structure-independent databases
that use relational technology (Paley, 2002; Tenzer,
2001; Polishchuk, Chernykh, 2009), but each model
corresponds to a specific motivation of the
developer.
3 THE METHOD OF
CONSTRUCTING THE
STRUCTURE-INDEPENDENT
DATABASES
Regardless of the motivation of the developer there
is a finite sequence of steps leading to obtain the
necessary set of linked relational tables
corresponding to above requirements. This set of
tables is the physical layer structure-independent
database, and the sequence of steps is a method of
constructing a structure-independent database using
relational technology (Rogozov Y., Sviridov A.,
Kucherov S., 2014).
For the first requirement it is necessary:
1. Determine the set of metadata needed to
describe the logical structure of the database;
2. Identify the metadata structure and implement
it in the form of a set of linked relational tables that
make up the metadata subschema. This step
includes:
•divide of generated metadata set into groups of
tenancy;
•create for each such group a separate relational
table;
•specify the relationships between tables;
To fulfill the second requirement it is necessary:
3. Determine the types of data that will be used
to store the attribute values;
4. Develop data subschema in the form of a
finite set of similar unrelated relational tables needed
to store attribute values. It is advisable to store the
values in the form of triples "entity- attribute-value",
where the first two elements – are links to entries in
the metadata tables. This enables to present the data
structure in form of sparse matrix;
For the final formation of structure-independent
database, you should:
5. Implement the physical structure of the
database.
Performing the third and fourth requirement is a
consequence of implementation of the first two
requirements:
• Presentation of stored data structures in the
form of sparse matrices is implemented by storing
the values in the form of triples (sparse matrix of
instances) and storage of metadata within the
database (sparse matrices of entities and attributes);
• Independence between the physical and logical
levels is implemented by storing metadata in the
database.
Application of the above sequence of steps
precedes the development of user (logical) data
structures (Rogozov Y., Sviridov A., Kucherov S.,
2014), which is performed by the developer-defined
database technology.
4 THE PROOF OF METHOD
Proposed method allows to get different structure-
independent databases using relational technology
depending on the goals of the developer. To prove
this statement, let’s consider the example of
obtaining the already known structure on the basis of
this method.
Example 1. In (Paley,2002) authors describe the
database model, which is the aim of developers to
create a universal relational structure for processing
and storage of quasi-structured data in terms of
object-oriented technology – in the form of classes
and objects. According to the proposed method of
structure-independent database designing to obtain a
model of such structure is as follows:
Stage One. Defining Metadata Sunschema.
Step 1. To store entities and attributes, it is
needed to select the representation format
"Directory". In this case, the implementation of
the entity set
i
eE
is represented by the
following ternary relation (table):
R
E
),,( FEIDE
ER
DATA2014-3rdInternationalConferenceonDataManagementTechnologiesandApplications
140
where
– is a set of unique identifiers, E – is the
original set of entities.
For relationship graph F the following is correct:
,
Where - is the set of identifiers of parent
classes of objects, because of using which hierarchy
is achieved.
Implementation of the attribute set is
presented as ternary relation (table):
where IDA – is the set of unique attribute identifiers,
VL – is the lengths of the attribute values. At the
same time because of the unique identifiers of
classes is also a realization of the relationship.
Step 2. Practical significance of relations exists
only between objects. It is in this context the
relationship
),,( FAEL
should be used. To
convert the relations
),,( FAEL
,
),,( FIER
into the corresponding tables, it is needed to define
the following "References":
1. Directory of objects relations, the realization
:
where – is a set of unique identifiers of objects,
NL – set of link names.
For relationship graph F the following is correct:
Where
and
- are the subsets of the first and
second binding objects, respectively.
2. Directory of objects, the implementation of
relation :
Second Stage. Defining Data Subschema.
Step 3. It is nesessary to determine the range of
acceptable values for the data elements. Since the
model is conceptual, let’s choose one base area –
individual characters and character strings:
1
СС
where C1 – is a set of random character strings of
limited length.
Let’s specify a set N of allowed value area
names:
1
nN
where n1 = “string".
Let’s specify the correspondence, thereby
determining the available data types in the database:
,,
Step 4. Correspondence potency
|
|
1, so it’s
nesessary to create seven identical data tables, which
are an implementation of relationship
),,,( FDAIV
i
t
:
Third Stage. Building Relationships.
Step 5. It’s nesessary to define the sets
,
,
,
,
,
as primary and
foreign keys.
Step 6. Based on this set of tables with primary
keys it’s needed to specify the relations between
tables. Thus, on the basis of the formulated method
we obtained database structure-model that is similar
to an extended relational schema for the
quasistructured data processing, which is described
in the literature (Paley, 2002). Targets of modelers
(Grigoriev, 2001) coincide with those considered in
this example.
Example 2. In the works
(Polishchuk, 2009;
Chernykh, 2011)
authors describe the database model.
The aim of model developers is to create a universal
relational structure for XML-data storing in terms of
object-oriented technology. According to the
proposed method to obtain the structure-independent
database model of such structure we should perform
the following steps:
Stage One. Construction of the Metadata
Subschema.
Step 1. To store entities (in the terminology of
the target – the object classes), we should select the
format for the "Directory." In this case, the
E
IDF )(
1
EF )(
2
E
EE
IDIDIDF
pp
,)(
3
p
E
ID
R
A
),,,,,(
21
FVLAAIDIDA
EAR
R
A
R
L
),,( FIDNLL
OR
O
ID
NLF
)(
1
O
OO
IDIDIDF
112
,)(
O
OO
IDIDIDF
223
,)(
R
R
),(
EOR
IDIDR
1
СС
''строкаN
'',
1
строкаСNCT
),,,,,( FODIDIDIDV
SPR
A
IVR
MethodofaStructure-IndependentDatabasesDesigninConfigurableInformationSystems
141
implementation E
of the entity set
i
eE
is
represented by the following ternary relation (table):
where
– is a set of unique identifiers, E – is the
original set of classes.
In XML technology, the structure of any classes
can be described by the corresponding XSD- scheme
(Veselov, 2000)
. Therefore, the directory
includes
the implementation
of attribute set, which is a set
of XSD-class schemas. Such representation of the
class also describes the implementation
of the set
of classes attributes
),,( FAES
, where the
relationships of each class with attributes are stored
in the XSD-scheme.
Step 2. There are two kinds of relationships in
this approach: classes links and object links.
Therefore, for relation
),,( FAEL
let’s define two
implementations:
1. Directory of class relations L
implementation of relationship
),,( FAEL
:
where - is the set of unique identifiers of
classes links, NL – set of link names.
For relationship graph F the following is correct:
where
and
- are the subsets of the first and
second linked classes, respectively.
2. Directory of object links, the implementation
of relation
),,( FAEL
:
Where
– is a set of unique object identifiers, NL
- set of link names.
For relationship graph F the following is correct:
where
and
- are the subsets of the first and
second linked objects, respectively.
Implementation
of relation
),,( FAES
in
the context of this goal is considered in the next
stage.
Second Stage. Defining the Data Subschema.
Step 3. Let us determine the range of admissible
values for data elements. Since the model focuses on
data storage in XML, we will use the same range of
permissible values:
where C1 – is a set of random character strings of
limited length (because support for XML data type
does not exist in all DBMS).
Specify a set N of range of admissible values
names :
where n1 = «BLOB».
Let us specify the line
),,( FNCT
, thereby
determining the available data types in the database:
,,
Step 4. Correspondence potency
|
|
1, so it’s
nesessary to create one data table, which is an
implementation
of relationship
),,,( FDAIV
i
t
and implementation
of relationship
),,( FAEL
:
Third Stage. Building the Relationships.
Step 5. It’s necessary to define the sets
С
,
and
as primary and foreign keys.
Step 6. Based on this set of tables with primary
keys it’s needed to specify the relations between
tables. Thus, on the basis of the formulated method
we obtained model of database structure that is
similar to the model data storage using XML-
scheme, which is described in the literature
(Polishchuk, Chernykh, 2009).
In order to prove the applicability of the
proposed in this paper method for solving a wide
range of problems of flexible database design, let’s
consider the example of creating the new SIBD on
its base.
),,,( FAEIDE
RCR
),,,( FIDNLIDL
C
L
R
C
R
C
R
C
L
ID
R
C
L
IDF )(
1
NLF )(
2
C
CC
IDIDIDF
113
,)(
C
CC
IDIDIDF
224
,)(
),,( FIDIDL
O
L
R
O
R
C
O
OO
IDIDIDF
111
,)(
O
OO
IDIDIDF
222
,)(
R
C
L
IDF )(
3
1
СС
1
nN
1
СС
'' BLOBN
'',
1
BLOBСNCT
),,,(, FDIDIDVR
CORR
R
C
L
ID
DATA2014-3rdInternationalConferenceonDataManagementTechnologiesandApplications
142
5 DEVELOPMENT OF SIDB
MODEL
Let’s construct a model of structure-independent
database that store relational data structures with a
high degree of variability (Kutcherov, 2010;
Rogozov, 2008). This model is called SIDB.
According to the proposed method of designing
structure-independent database model the process of
obtaining such structure consists of three stages.
Stage One. Defining Metadata Subschema.
Step 1. To store entities and attributes, it is
needed to select the representation format
"Directory". It is necessary to bring into standard set
i
eE
a number of additions that will determine
the implementation of the directory:
1. Hierarchy. Will be used to simplify the
navigation in the SIDB logical structure, to store
data models of different domains within a SIDB
instance and to separate entities and attributes.
Hierarchy is defined on the basis of the set of unique
directory entries identifiers ID
SPR
.
2. Synonyms will be used to store the artificial
primary keys that have semantic charge. Synonyms
are determined by the set Y.
3. Brief descriptions will be used to simplify the
understanding of stored data structure and each of its
elements. Descriptions are determined by the set H.
4. Logical deletion identifier. In the field of
flexible data structures one of the most important
features is the possibility to recover from errors.
Identifiers are determined by the boolean set O.
5. Data Types will be used to specify the type of
value stored in one way or another attribute. Data
types are determined by the projection of the second
element of the attributes set
},{
kj
taA
.
Thus, the implementation of the entity set
i
eE
and attributes set is represented with
the help of hierarchical directory – relationship
(table):
For relationship graph F the following is correct:
– names of all entities and
attributes.
,
,
– hierarchy of
attributes and entities.
Where – is a subset of the identifiers of all
entities and attributes, that are parental for one or
more records.
– determining
record belonging (is that entity or attribute),
where – is a subset of the identifiers of all
entities that are directories. This approach allows to
organize a set of logical directories within a single
physical.
Step 2. It is necessary to transform relationships
),,( FAES
,
),,( FAEL
,
),,( FIER
into
the corresponding tables. Relationshipsare defined
on the same sets. Let’s define them in a single
directory:
Object relations directory, realization
of the
relationship
),,( FAEL
:
where – is the set of unique identifiers of
relations.
For relationship graph F the following is correct:
– A subset of
the unique identifiers of the parent entities.
– A subset of
unique identifiers of the attributes.
– A subset of
the unique identifiers of the child entities.
– Identifier of a logical links deletion.
In order to identify the entity instances that are
stored in a hierarchical directory, it is needed to
define the following implementation of
relationship
),,( FIER
:
where – set of instances unique identifiers.
Second Stage. Defining Data Subschema.
Step 3. It is nesessary to determine the range of
acceptable values for the data elements. Let’s define
R
E
R
A
)),(,,,),(,,(,
21
FAOHYAEIDEA
SPRRR
SPR
IDF )(
1
)()(
12
AEF
HF
)(
3
YF
)(
4
OF )(
5
SPR
SPRSPR
IDIDIDF
116
,)(
SPR
ID
1
SPR
SPRSPR
IDIDIDF
227
,)(
SPR
ID
2
),,,(,
,
FOIDIDLS
SPRLSRR
RR
RR
LS
ID
,
RR
LS
IDF
,
1
)(
SPR
SPR
E
SPR
E
IDIDIDF
11
,)(
2
SPR
SPR
A
SPR
A
IDIDIDF ,)(
3
SPR
SPR
E
SPR
E
IDIDIDF
22
,)(
4
OF
)(
5
R
R
),,( OIDIDR
I
SPR
E
R
I
ID
MethodofaStructure-IndependentDatabasesDesigninConfigurableInformationSystems
143
five basic range of acceptable values that are most
commonly used today in the relational database:
1. Random character strings of limited length –
C
1
;
2. Numeric values – C
2
;
3. Temporary markers – C
3
;
4. Random text strings of great length – C
4
;
5. Large binary files – C
5
;
6. Enumerable discrete values.
Furthermore, in relational databases relations
between entities are used (for description of the
logical database model) along with relations
between instances of the entities (for description of
the data stored). Therefore, we introduce another
range of acceptable values – pointers at entity
instances (C
7
).
Specification of the set N of names of acceptable
values range:
1. String – n
1
;
2. Number – n
2
;
3. Date / Time – n
3
;
4. Text Document – n
4
;
5. Binary file – n
5
;
6. Enumerated value – n
6
;
7. Entity reference – n
7
;
Step 4. Correspondence potency
),,( FNCT
:
|
|
7 , so it’s nesessary to create seven identical
data tables, which are an implementation of
relationship
),,,( FDAIV
k
t
:
In addition, for storage of enumerated attributes
it should be entered the appropriate directory of
valid values, that is the following relationship:
where D
D
– is an appropriate domain of acceptable
values of the enumerations. In this case, domain set
D, where the implementation relationship is
defined, will comprise a variety of unique identifiers
of enumerated values.
Third Stage. Building Relationships.
Step 5. It’s nesessary to define the sets
and as primary and
foreign keys.
Step 6. Based on this set of tables with primary
keys it’s needed to specify the relations between
tables. Thus we’ll obtain SIDB logical model (Fig.
1).
Figure 1: Logical model of SIDB.
6 CONCLUSIONS
The method proposed in this paper allows to build
structure-independent databases using relational
technology which has the following advantages:
• Limitation of the structural complexity of
database queries by fixing the amount of relational
tables at physical layer;
• Increasing of data processing operation speed.
Relational technology is originally designed for
static data structures and has rich set of productivity
tools;
• Flexibility. There is no relationship between
physical and logical database levels, implemented
with the proposed method, allowing maximum
flexibility;
• Low maintenance costs. There is no need to
hold highly skilled professionals engaged in support
of the physical layer performance, and that saves
time and money.
As a result of applying the proposed in this
article method there may be obtained a variety of
different structure-independent databases. The
implementation of each step of the method depends
71
,...,
ССС
71
,..., nnN
),,,,,( FODIDIDIDV
SPR
A
IVR
),,,,( FODIDIDV
DAVD
D
R
V
RR
VILSSPR
и
IDIDIDID ,,,
,
D
V
I
D
DATA2014-3rdInternationalConferenceonDataManagementTechnologiesandApplications
144
on the motivation of the developer and is not limited
by discussed in this article examples.
ACKNOWLEDGEMENTS
The research is performed within the government
mandate № 0110021005901621. Theme № 213.01-
11/2014-17 "Development of methods for data
warehouse creation in configurable information
systems and mechanisms for their implementation".
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