MEDIATION FRAMEWORK FOR ENTERPRISE
INFORMATION SYSTEM INFRASTRUCTURES:
Application-driven Approach
Leonid Kalinichenko, Dmitry Briukhov, Dmitry Martynov, Nikolay Skvortsov and Sergey Stupnikov
Institute of Informatics Problems, Russian Academy of Science, Vavilov Street,44-2, Moscow, Russian Federation
Keywords: Mediator, canonical models, application-driven approach, ontology, refinement, information sources,
registration, query rewriting, semantic identification and integration of sources.
Abstract: This position paper provides a short summary of results obtained so far on an application-driven approach
for mediation-based EIS development. This approach has significant advantages over the conventional,
information source driven approach. Basic methods for the application-driven approach are discussed
including synthesis methods of canonical information models, unifying languages of various kinds of
heterogeneous information sources in one extensible model, methods of identification of sources relevant to
an application and their registration at the mediator applying GLAV techniques as well as ontological
contexts reconciliation methods. Methodology of EIS application development according to the approach is
briefly discussed emphasizing importance of a mediator consolidation phase by the respective community,
application problem formulations in canonical model and their rewriting into the requests to the registered
information sources. The technique presented is planned to be used in various EIS and information systems.
1 INTRODUCTION
One of the widely spread views of Enterprise
Information Systems (EIS) is considering them as
infrastructures provided for collecting information
and services from across the entire enterprise thus
giving all its workers complete and transparent
access to information. Diverse forms of enterprise
inter- and intra-organizational models were
developed (such as, virtual corporation, extended
enterprise). A basic issue for modeling of such
distributed business activities, their collaboration is
that there are many types of elements to be modeled
in an enterprise, and many perspectives and contexts
in which those definitions would be “viewed.” Often
such elements can be implemented as legacy
applications. Advanced enterprise modeling
approaches share the fundamental strategy of
integrating at the model level - taking fragments of
information within the enterprise and placing them
in a larger context. What model is to be taken and
how a proper context is to be formed and
implemented are the basic issues that are discussed
in this paper.
The following concerns will be touched during
these discussions. Various applications are to be
supported by EIS, each of them working in its own,
specific context (probably, overlapping with
contexts of other applications) that should be
semantically supported. Heterogeneous information
sources of various kinds (data sources, service
sources, process sources, ontological sources)
relevant to EIS are to be used in a specific context of
an application. Many of such sources are
autonomous and evolve with time. A set of sources
relevant to a specific EIS may be changed quite
rapidly. The technologies applied for relevant
sources are also rapidly evolving. Therefore
justifiable identification of relevant to EIS sources,
reaching semantic integration of various kinds of
them in contexts of appropriate applications, making
EIS stable in the rapidly evolving world constitute
serious challenges. New methods and tools for EIS
application development over multiple distributed
collections of data and services are required.
We emphasize two principally different
approaches to the problem of integrated
representation of multiple information sources for an
EIS: 1) moving from sources to problems (an
integrated schema of multiple sources is created
independently of specific applications) and 2)
moving from an application to sources (a description
of an application subject domain (in terms of
concepts, data structures, functions, processes) is
246
Kalinichenko L., Briukhov D., Martynov D., Skvortsov N. and Stupnikov S. (2007).
MEDIATION FRAMEWORK FOR ENTERPRISE INFORMATION SYSTEM INFRASTRUCTURES: - Application-driven Approach.
In Proceedings of the Ninth International Conference on Enterprise Information Systems - DISI, pages 246-251
DOI: 10.5220/0002407202460251
Copyright
c
 SciTePress

created, in which sources relevant to the application
are mapped). The first approach driven by
information sources is not scalable with respect to
the number of sources, does not make semantic
integration of sources in a context of specific
application possible, does not lead to justifiable
identification of relevant to EIS sources, does not
provide for enhancing of EIS stability w.r.t.
evolution of the relevant to EIS sources. These
deficiencies are inherent to the Global as View
(GAV) approach studied elsewhere (Ullman, 1997),
(Halevy, 2001). GAV might be used as a basic
technique for the information sources driven
approach.
The second approach (application-driven)
assumes creation of subject mediator that supports
an interaction between an application and sources on
the basis of the application domain definition
(description of the mediator). Subject mediator
approach (new technology) has obvious advantages
over the approach driven by specific information
sources. Some of the results of our research and
experimental work oriented on application-driven,
subject mediation development for various kinds of
information systems are summarized in this paper.
2 APPLICATION-DRIVEN
APPROACH METHODS
The method for synthesis of the mediator canonical
information model as the common language for
semantic mapping of various source models into it
as well as methods for identification of information
sources relevant to a mediator and their registration
at
the mediator are discussed in this section.
2.1 Synthesis of Canonical Information
Models
The present period of IT development is
characterized by the process of explosive growth of
various information representation models. This
development takes place in frame of specific
distributed infrastructures (such as OMG
architectures (in particular, the model driven
architecture (MDA)), SemanticWeb and Web
service architectures, digital library architectures as
collective memories of information in various
subject domains, architectures of the information
Grid), as well as in the standards of languages and
data models (such as, for example, ODMG, SQL,
UML, XML and RDF stacks of data models),
process models and workflow models, semantic
models (including ontological models and models of
metadata), models of digital repositories of data and
knowledge in particular domains.
This process is accompanied by another trend —
intensive development of based on such models
information components and services. This growth
causes the accelerating need for integration in
various applications of components and services
represented in heterogeneous models, as well as
their reuse and composition implementing new
information systems. The more variety of applied
models we meet in various components and services,
the more complex become problems of their
integration and composition. Research and
development of adequate methods for manipulation
of various information models are required.
The basis of these methods is constituted by the
concept of a canonical information model serving as
the common language, ”Esperanto”, for adequate
uniform expression of semantics of various
information models surrounding us. To prove that a
definition in one language can be substituted with a
definition in another one, formal specification
facilities and commutative model mapping methods
are provided. Initially ideas of mapping structured
data models and canonical model construction for
them were developed. The basic definitions of
equivalence of database states, database schemas
and data models were introduced to preserve
operations and information while constructing of
mappings of various structured data models into the
canonical one (Kalinichenko, 1990). According to
this approach, each data model was defined by
syntax and semantics of two languages – data
definition language (DDL) and data manipulation
language (DML). The main principle of mapping of
an arbitrary source data model into the target one
(the canonical model) constituted the principle of
commutative data model mapping. According to it,
preserving of operations and information of a source
data model while mapping it into the canonical one
could be reached under the condition, that the
diagram of DDL (schemas) mapping and the
diagram of DML (operators) mapping are
commutative. At that time in the process of data
model mappings construction the denotational
semantics were used as a formalism (metamodel),
allowing to prove a commutativity of the diagrams
mentioned (Kalinichenko, 1990).
Later, for the object data models, the method of
data model mapping and canonical models
constructions was modified as follows. As a
formalism (metamodel) of the method the Abstract
Machine Notation (AMN) (Abrial, 1996) was used
instead of the denotational semantics. It allowed to
define the model-theoretic specifications in the first
order logics and to prove the fact of specification
refinement. Instead of equivalence of respective
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Application-driven Approach
247

specifications, it became possible to reason on their
refinement (Kalinichenko, 1997). It is said that
specification A refines specification D, if it is
possible to use A instead of D so that the user of D
does not notice this substitution. Existence of B-
technology for AMN (Abrial, 1992) provides for
conducting proofs of commutativity of model
mappings semi-automatically.
The main principle of canonical model synthesis
is that its extensibility is required for semantic
integration and information interoperability in
heterogeneous environment, including various
models. A kernel of the canonical model is fixed.
For each specific information model M of the
environment an extension of the kernel is defined so
that this extension together with the kernel is refined
by M. Such refining transformation of models
should be provably correct. The canonical model for
the environment is synthesized as the union of
extensions, constructed for models M of the
environment. The source schema refines the
canonical model schema. The refinement of the
schema mapping is formally checked. Another
existing methods (e.g., used in Clio project (Haas,
2005)) supporting generation of mappings (queries)
between source and target schemas are applicable to
limited class of structured data models and do not
allow to create an application specifications
providing for registration of various kinds of
relevant sources (including objects, services,
processes). On the contrary, our canonical data
model synthesis method provides a seminal role for
synthesis of canonical models for various kinds of
source information models including process models
(Kalinichenko, 2005), service models (Stupnikov,
2006), ontological models (Kalinichenko, 2002).
Canonical model synthesis method we applied
recently to the process models, required for
describing application activities of enterprises
(Kalinichenko, 2005). While mapping processes for
synthesis of their canonical model, it is required to
preserve the semantics of concurrency. A possibility
of interpretation of concurrent process events in
logics, and specifically, in the AMN has been
discovered recently. Algorithms of process
specifications mappings into AMN were constructed
(Butler, 2000) (Stupnikov, 2002). This approach
allows to construct provable refinements of process
specifications, applying the B-technology.
Simultaneously classification of the diversity of
workflow models by means of workflow patterns
has been obtained (Aalst, 2003). Due to these
findings, the possibility of creation of a canonical
process model kernel and construction of its
extensions, refined by various workflow patterns,
became possible. Finally we showed how to
synthesize the canonical process model
(Kalinichenko, 2005).
Similarly, to work with ontologies of different
sources a unified representation of ontologies is
required. Again, it is provided by a canonical
ontological model that includes a kernel and its
extensions for every specific ontological model used
in the information sources. Extensions are developed
so that the ontological model of a source should
serve as a refinement of an extended canonical
ontological model of the mediator.
After analysis of various ontological models the
kernel of canonical ontological model has been
identified as a subset of the object model with
logical capabilities (Kalinichenko, 1995)
(Kalinichenko, 2002). This kernel has been defined
as a subset of the general mediator canonical model
kernel mentioned above. This subset includes:

concepts defined as abstract data types (ADT);
 type invariants expressing concept constraints;
 generic ontological metaclasses, instances of
which are ADTs defining concepts;
 verbal definitions of concepts applying
metaframes annotating types expressing
concepts.
One of the popular ontological models, OWL DL
has been mapped into the ontological canonical
model and respective definition of the canonical
model kernel extension has been defined
(Kalinichenko, 2002). Correctness proof of such
extensions is provided by AMN tools to justify
refinement of the extension by the source
ontological model.
During practical synthesis of canonical
information models it is advisable to produce
reversible language mappings that will be suitable
for the process of heterogeneous sources registration
in the mediator as well as for the run time support
when wrappers (adapters) should interpret
operations of the canonical level in terms of the
source model language. Taking into account the
labor intensive character of development of the
required mappings (compilers) it is reasonable to
apply specific Meta Environment facilities providing
for declarative specification of compilers and
generating them according to such specifications
(Brand, 2002). It is such meta approach that is used
in frame of our project.
Using of extensible canonical models with
formal semantics and possibilities of proof of the
fact of their refinement by source models provides
for systematic consideration of EIS application
development issues in the environment of multiple
heterogeneous distributed information sources and
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for development of respective basic methods and
facilities. Some of them are considered further.
2.2 Identification of Relevant
Information Sources and their
Registration in Mediator
Definition of a subject mediator and registration of
information sources in mediator is based on our
experience of compositional development of
information systems (Briukhov, 2001). Registration
of sources is a process of purposeful specification
transformation including decomposition of mediator
specifications into consistent fragments, search
among specifications of relevant sources of data
types treating as candidates for refining by them of
the mediator specification types, construction of
expressions defining source classes as composition
of the mediator classes. For such manipulation a
specification composition calculus has been
developed (Kalinichenko, 1999). A principle of type
specification decomposition into a set of
specification reducts serving as the basic units of
reuse and composition has been declared. An
operation of identification of the most common
reduct of source type and mediator type
specifications has been introduced. Type lattice and
type algebra have also been defined. Important point
in this scheme consists in implementation of the type
refinement proof applying logical model of the
mediator and source type specifications in AMN.
Our work on compositional calculus emphasizes
complete type specifications and expressiveness
sacrificing tractability in complex cases. Such
decision is motivated by orientation of the modeling
facilities on type refinement and composition. The
benefits we get include rigorous way of
identification of common fragments of source and
mediator type specifications leading to justifiable
mapping of source type into mediator type.
Investigation oriented on simpler data types
considered functions as components modeled with
relations and refinement ordering of functions (Mili,
1997). But this is too restrictive for our purposes.
A process of registration of heterogeneous
information sources in a subject mediator is based
on GLAV that combines two approaches - Local As
View (LAV) and Global As View (GAV).
According to LAV the schemas of sources being
registered are considered as materialized views over
virtual classes of a mediator. GAV views provide for
reconciliation of various conflicts between source
and mediator specifications and provide rules for
transformation of a query results from source into
mediator representation. Such registration technique
provides for stability of EIS application specification
during any modifications of specific information
sources and of their actual presence (removing,
addition new ones, etc.) as well as for scalability of
mediators w.r.t. the number of sources registered in
them.
Identification of sources relevant to a mediator
(that precedes the registration) is based on three
models: metadata model, characterizing source
capabilities represented in external registries,
canonical ontological model, providing for
definition of application domain concepts, and
canonical model providing for definition of structure
and behavior of application and information source
objects. Reasoning in canonical models is based on
the semantics of the canonical model and facilities
for proof of refinement. Reasoning in the metadata
model is a heuristic one based on nonfunctional
requirements to the sources needed in application
(e.g., indexes of data quality in sources). For the
design, the mediator and sources specifications are
given uniformly in canonical model, though in
process of design a transformation into such model
from another specification language (e.g., from
UML) might be required.
Complicated problem of registration consists in
reconciliation of contexts of an EIS application and
specific sources. Ontological definitions annotate
elements of application specification (a mediator)
and of source specifications given in a form of types,
classes, processes. A similarity of concepts is
established in two steps: first, by means of verbal
ontologies, and then by establishing refinement
relationship of concepts as abstract data types. Thus
the conformity of the concepts is verified.
Depending on complexity of specifications such
verification can be provided automatically or
interactively. In the simple cases the verification can
be reduced to justifying of concept subsumption in
description logics applying practically such systems
as FaCT or Pellet.
The techniques listed are used as a basis for the
tool prototype for identification and registration of
information sources in mediator. In this process
ontological specifications are used for identification
of mediator classes semantically relevant to a source
class. The maximal subset of a mediator class
specification semantically relevant to a source class
is identified as the most common fragment (reduct)
of specifications of respective instance types given
for these classes (Kalinichenko,1999). Concretizing
types reconciling the conflicts (of values, structures,
behaviors) are defined so that an instance type of the
mediator class would be refined by an instance type
of the source class. The main registration result is a
GLAV expression defining how a source class is
determined as a composition of the mediator classes.
In process of sources evolution a specification of
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Application-driven Approach
249

mediator remains stable, only such expressions need
to be modified. The tool supporting techniques of
registration of sources in mediator includes:
 facilities identifying relevant information
sources by metadata;
 facilities for reaching consensus of ontological
contexts of information sources being
registered and of the mediator;
 facilities for automation of the heterogeneous
information sources registration in the
mediator based on the GLAV approach;
 metainformation repository storing
specifications of mediators, information
sources and the results of registration.
It is important to note that in the infrastructure
considered the EIS application-driven mediators are
treated as information sources in their turn. They are
provided with meta-definitions and become elements
of registries making possible to construct
applications as composition of other applications
developed also as mediators.
3 APPLICATION
DEVELOPMENT
METHODOLOGY
3.1 Application-driven Mediator
Specification
Application specification for EIS includes definition
of terminology and concepts of the subject domain
of the application. They are expressed by the
respective dictionaries (thesauri) and ontological
definitions in the canonical model. Application
definitions include also specifications of object
classes corresponding to the application subject
domain, specification of instance types of these
classes and of their methods defining behavior of the
objects, specification of processes characteristic for
the application. On the early stages of design the
specifications mentioned can be expressed by means
of various specification languages (e.g., by UML).
However, it is assumed that finally such
specifications (including ontological ones) are
mapped into the canonical model specifications
having formal semantics. It is worth of remark that
application-driven specifications are formulated
independently of specific pre-existing information
sources. The result of this specification activity
fulfilled by a community interested in the specific
EIS application constitutes the mediator
specification created as the result of reaching a
consensus in such community. The mediator
specification activity is called the mediator
consolidation phase.
3.2 Methods and Facilities for
Application Problems Formulation
and Solution
General approach consists in problem formulation in
terms of subject mediator specifications and
transformation of this formulation into set of tasks
(queries) to the real information sources registered at
the mediator. Such transformation in the database
theory is known as view based query rewriting
(information sources are treated as materialized
views over virtual classes of the mediator) (Halevy,
2001). This is complicated problem having various
(usually limited) solutions applicable to specific data
models. In context of the current work rewriting
techniques applying inverse rules are used (Halevy,
2001)(Wang, 2002). The respective algorithms are
characterized by conceptual clarity, modularity,
capability of producing maximally contained queries
in time polynomial w.r.t. the size of query and view
specifications. Our contribution consists in a method
of the mediator programs rewriting applying the
inverse rule technique in a typed object environment
(Kalinichenko, 2004). The method is based on the
use of refinement relationship between mediator
data types and source data types helping to get
containment of the rewritten queries in the original
mediator level queries expressed in canonical model.
It is important to note that a combination of LAV
and GAV approaches is supported during rewriting
queries as GLAV.
4 CONCLUSIONS
Thus, the basic principles of application-driven EIS
development over multiple heterogeneous
information sources are the following:
1. independence of application (mediator)
specification of the existing information
sources;
2. definition of an application mediator as a result
of consolidation effort of the respective
community;
3. emphasizing semantic canonical definitions for
the mediator specification;
4. independence of user interfaces of the sources
registered at the mediator: application users
should be only conscious of definition of the
application domain (definition of mediator);
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5. independence of publication of the newly
developed information sources of the
mediators (as a result of such publication,
actions can be initiated on registration of such
sources in respective mediators);
6. three stage identification of information sources
relevant to mediator providing 1) source
relevance to nonfunctional requirements
expressed by metadata, 2) source ontological
relevance, 3) source structural and behavioral
relevance;
7. semantic integration of relevant heterogeneous
information sources in canonical mediator
specification;
8. integrated access to the information sources
registered at mediator applying the canonical
model and query rewriting system;
9. recursive structure of mediators: each mediator
can be registered as a new information source.
Such mediator capability makes possible
integration of different applications that is
specifically important for virtual organizations
development.
Principles numbered as 1 – 8 define advantages
of application-driven approach over information
source-driven approach for mediation-based EIS
development.
The approach presented is being implemented
and applied to systems in e-science (e.g., virtual
observatories) and is planned for administrative EIS
for the city of Moscow and for life-long learning.
The work reported was partially supported by the
RFBR grants 06-07-08072 and 06-07-89188.
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Application-driven Approach
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