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Federated PM and Haze Data Warehouse Project
a sub- project of
(enter your sticker & logo here )
St. Louis Midwest Supersite Project
RPO
Regional Planning Organization
SupSite
EPA Supersites
NARSTO
NARSTO PM
EPA
EPA Division1, Division2, Division2
Me
Me and my dog for our aerosol project
Nov 20, 2001, RBH
PM/Haze Data Flow in Support of AQ Management
FLM
RPO
FLM
RPO
FLM
RPO
Federal Land Managers
Regional Planning Orgs
EPA
EPA
EPA
EPA Regul. & Research
Shared
PM/Haze
Data
SuperSite
NARSTO
Industry
Academic
Other: Private, Academic
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PM and haze data are used for may parts of AQ
management, mostly in form of Reports
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There are numerous organizations in need of data
relevant to PM/Haze
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The variety of pertinent (ambient, emission) data
come from many different sources
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Most interested parties (stakeholders) are both
producers and consumers of PM and haze data
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To produce relevant reports, the data need to be
‘processed’ (integrated, filtered aggregated)
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There is a general willingness to share data but the
resistances to data flow and processing are too high
Scientific and Administrative Rationale for Resource Sharing
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Scientific Rationale:
Regional haze and its precursors have a 1000-10000 km airshed.
(Smoke, Dust, Haze) – Data integration
Substantial fraction of haze originates from natural sources or from out-ofjurisdiction man-made sources
Cross-RPO data and knowledge sharing yields better operational and science
support to AQ management
Management Rationale:
• Haze control within some RPOs cannot yield
• Data sharing saves money and ….
A Strategy for the Federated PM/Haze Data Warehouse
• Negotiate with the data providers ‘open up’ their data servers for limited,
controlled, access in accordance with clear ‘access contract’ with the Federated
Warehouse
• Design an interface to the warehoused datasets that has simple data access and
satisfies the data needs of most integrating users.(oxymoron ????)
• Facilitate the the development of shared value-adding processes (analysis tools,
methods) that refine the raw data to useful knowledge
Three-Tier Federated Data Warehouse Architecture
(Note: In this context, ‘Federated’ differs from ‘Federal’ in the direction of the driving force. Federated meant to indicate
a driving force for sharing from ‘bottom up’ i.e. from the members, not dictated from ‘above’, by the Feds)
1.
Provider Tier: Back-end servers containing heterogeneous data, maintained by the federation members
2.
Proxy Tier: Retrieves designated Provider data and homogenizes it into common, uniform Datasets
3.
User Tier: Accesses the Proxy Server and uses the uniform data for presentation, integration or processing
Federated Data Warehouse
User Tier
Data presentation,
processing
Proxy Tier
Data homogenization,
transformation
Provider Tier
Heterogeneous data in
distributed SQL Servers
Federated Data Warehouse Interactions
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The Provider servers interact only with the Proxy Server in accordance with the Federation Contract
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The contract sets the rules of interaction (accessible data subsets, types of queries)
Strong server security measures enforced, e.g. through Secure Socket layer
The data User interacts only with the generic Proxy Server using flexible Web Services interface
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Generic data queries, applicable to all data in the Warehouse (e.g. data sub-cube by space, time, parameter)
The data query is addressed to the Web Service provided by the Proxy Server
Uniform, self-describing data packages are passed to the user for presentation or further processing
Federated Data Warehouse
Proxy Tier
Provider Tier
Data Homogenization, etc.
Heterogeneous Data
User Tier
Data Consumption
Presentation
SQLDataAdapter1
SQLServer1
Processing
SQLDataAdapter2
SQLServer2
Integration
CustomDataAdapter
LegacyServer
Data Access & Use
Proxy Server
Member Servers
Web Service, Uniform Query & Data
Fire Wall, Federation Contract
Live Demo of the Data Warehouse Prototype
http://capita.wustl.edu/DSViewer/DSviewer.aspx
Currently online data are accessible from the
CIRA (IMPROVE) and CAPITA SQL
servers
Uniform Data Query regardless of the native
schema: Query by parameter, location,
time, method
The hidden DataAdopter
- accepts the uniform query
- accesses the data server
- transforms the original to uniform data
- delivers uniforms DataSets
A rudimentary viewer displays the data in a
table for browsing.
‘Global’ and ‘Local’ AQ Analysis
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AQ data analysis needs to be performed at both global and local levels
The ‘global’ refers to regional national, and global analysis. It establishes the largerscale context.
‘Local’ analysis focuses on the specific and detailed local features
Both global and local analyses are needed for for full understanding.
Global-local interaction (information flow) needs to be established for effective
management.
National and Local AQ Analysis
Data Model
Ray Plante, Virtual Obs
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What’s the difference between Data Models and Metadata? Intertwined
– metadatum: a datum with a name or semantic tag that refers to the data
– data model: a description of the relationships between metadata
• structural & logical relationships between compound objects & their components
• operations that can be performed on them (really -
– framework: the architecture/process used to define metadata/data models that
enables their ready use in applications
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Formalized data modeling process
– encourages community involvement for defining standard models & metadata
– structure enables easy verification, dissemination, & automated use
– “standard” metadata should point directly to components of the “standard”
models
– allow groups to define metadata independent of a “standard” metadata
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Practical Difference?
– data model captures as complete a picture of a concept as possible
– metadata represents the instantiation of portion of the model’s components
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Data access through a data model (Wrapper Classes for each data model)
4D Satellite data
• Satellite data: e.g. SeaWiFS, GOES
– X, Y, Channel, Time
Integration for Global-Local Activities
Global and local activities are both needed – e.g. ‘think global, act local’
‘Global’ and ‘Local’ here refers to relative, not absolute scale
Global Activity
Local Benefit
Global data, tools
=> Improved local productivity
Global data analysis
=> Spatial context; initial analysis
Analysis guidance
=> Standardized analysis, reporting
Local Activity
Global Benefit
Local data, tools
=> Improved global productivity
Local data analysis
=> Elucidate, expand initial analysis
Identify relevant issues
=> Responsive, relevant global work
Data Re-Use and Synergy
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Data producers maintain their own workspace and resources (data, reports, comments).
Part of the resources are shared by creating a common virtual resources.
Web-based integration of the resources can be across several dimensions:
Spatial scale:
Data content:
Local – global data sharing
Combination of data generated internally and externally
Local
Local
User
Shared part of resources
User
Content
Virtual Shared Resources
User
Data, Knowledge
Tools, Methods
Content
User
Global
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Global
User
The main benefits of sharing are data re-use, data complementing and synergy.
The goal of the system is to have the benefits of sharing outweigh the costs.
Federated Data Warehouse Features
• Data reside in their respective home environment where it can mature.
‘Uprooted’ data in separated databases are not easily updated, maintained,
enriched.
• Abstract (universal) query/retrieval facilitates integration and comparison
along the key dimensions (space, time, parameter, method)
• The open data query based on Web Services promotes the building of further
value chains: Data Viewers, Data Integration Programs, Automatic Report
Generators etc..
• The data access through the Proxy server protects the data providers and the
data users from security breaches, excessive detail
A.
Citations of:
A. P. Sheth and J. A. Larson.
Federated Database Systems for Managing Distributed, Heterogeneous, and Autonomous Databases .
ACM Computing Surveys, 22(3):183--236, 1990.
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Registering Scientific Information Sources for Semantic.. - Amarnath Gupta Bertram
The general problem of defining a global schema over a set of local schema is not a new problem, see, e.g.
SL90,PS98] In [RR97] a seven step methodology for schema integration based on semantic integrity constraints
is presented; see [Tur99] for a comprehensive treatment of semantic integrity constraints in federated
databases.
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Metadata Management in Federated Multimedia Systems - Mark Roantree School
Please refer to [Pitoura et al. #995, Sheth and Larson, #990] for a complete background on federated databases.
The concept of a federation of databases [Sheth and Larson, #990] is one where heterogeneous databases (or
information systems) can communicate with one another through an interface provided by a common data
model.
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A.
Citations of:
A. P. Sheth and J. A. Larson.
Federated Database Systems for Managing Distributed, Heterogeneous, and Autonomous Databases .
ACM Computing Surveys, 22(3):183--236, 1990.
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Semantic Integration and Querying of Heterogeneous Data - Sources Using Hypergraph
A typical approach for dealing with the heterogeneity of the data sources chooses one model as a common data model [23] and
converts the modeling languages of the data sources into this model.
Supporting Telecom Business Processes by means of - Workflow Management And
Research into federated databases was originally motivated by the problem of legacy systems (see [Brod92, Shet90]) However, we
argue that database federation is a good structuring principle of its own, and as a result it is a useful technology in structuring newly
developed information systems
Discovering and Reconciling Value Conflicts for.. - Fan, Lu, Madnick, Cheung (2001)
this physical connectivity does not automatically lead to the meaningful exchange of information. The quest for this logical
connectivity (more commonly referred to as semantic interoperability [1]) has been an active area of research in the last decade (see
[2] for a recent survey) Traditional approaches to achieving semantic interoperability can be identified as either tightly coupled or
loosely coupled [3] In tightly coupled systems, semantic conflicts are identified and reconciled a ....
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Research Project Application -- MIGI - Metadata Integration And
loosely coupled systems cannot guarantee the same degree of integrity as tightly coupled ones. Integrity control in tightly coupled
federations has been investigated in [CoTu95] Conr96] CoST97] and [Conr97] However, the proposed concepts require an
integration by schema translation [ShLa90] and are not appropriate for operational integration [GaCO90] see below) In [SpCo97] a
wrapper based architecture is defined for a tightly coupled FDBMS. The wrap pers encapsulate the CDBMS integrity control systems
and extend them (if necessary) EventCondition Action rules (ECA rules) as ....
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A FIPA Compliant Agent Platform for Federated Information.. - Panti Penserini Spalazzi
....a uniform access to autonomous and heterogeneous information sources. Furthermore, information sources may be classified as
structured, as for instance relational databases, semi structured, i.e. web pages in HTML source, or de structured (text or images)
The basic components of a FIS are [12] f a common data model that should be flexible enough to represent different kinds of
information from different sources and to cope with missing or wrong information; f a common language that could be used to
submit queries to the integrated system
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VirtuE: Virtual Enterprises for Information Markets - D'Atri, Motro (2001)
.... products) may be considered a specialized form of work ow management [6, 20, 5] Within this area, considerable attention had
been given recently to the application of work ow management techniques to virtual organizations [9, 8] Finally, in the area of data
modeling, federated database models [11, 17, 16, 15] may be considered as predecessors of VirtuE. A federated database provides an
environment in which information may be exchanged among 1 Often the members of such an enterprise reside in the same
geographical area. A notable example is the Saxon region in Germany [4] 3 autonomous o
A.
Citations of:
A. P. Sheth and J. A. Larson.
Federated Database Systems for Managing Distributed, Heterogeneous, and Autonomous Databases .
ACM Computing Surveys, 22(3):183--236, 1990.
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CASE Support for the Development of Federated.. - Thiran, Chougrani.. (2000)
Introduction Federated Information Systems (FIS) [1] provide transparent access to heterogeneous data sources. The development of
FIS involves yielding local schemas, integrating them into one or more schemas, controlling complex mappings and building
architecture components.
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Semantic Query Transformation for the Intelligent
Two strategies have been advocated for the design and implementation of information mediation networks: Global As View (GAV)
and Local As View (LAV) The (GAV) follows the traditional strategy developed for federated databases [12]. The global view is
constructed by several layers of views on the relations exported by the sources. Queries are expressed in terms of the global view and
are evaluated in the conventional way. GAV is the strategy applied by TSIMMIS [7] HERMES [13] and Gestalt [11] for instance.
Integrating Ontologies and Thesauri For Rdf Schema and.. - Amann, Fundulaki, Scholl (1999)
Providing access to heterogeneous and distributed databases through integrated views has been studied from the early 80 s [6] A
large number of papers exist on the integration of distributed databases and [36,46,43] are comprehensive studies on the topic.
However such approaches for data This work was partially supported by the European project C Web (IST1999 13479) The work of
this author was supported by a fellowship from the TMR European Network Chrorochronos. integration are not appropriate
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Model Theoretic Semantics for Information Integration - Ghidini, Serafini (1998)
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Due to the increasing necessity and availability of information from different sources, information integration is becoming one of the
challenging issues in artificial intelligence and computer science. A successful methodology for information integration is that of
federated databases [14]. However, differently form databases (for which there are well established formalisms, see for instance [1] a
completely satisfactory formal treatment of federated databases is still missing (see [16] for a survey of the state of the state of the art) The
goal of this paper is to fill this ....
conventions, and certain operations are performed locally by the databases, without interactions with the other databases. Distribution,
redundancy, partiality, and autonomy generate many problems in the management of a federated database. The most important are:
semantic heterogeneity [14], interschema dependencies [6] query distribution [2, 12] local control over data and processing [5] and
transparency [7] The definition of a formal semantics for federated databases able to cope with these problems is a key point to
understand, specify, and verify the behavior of a federated ....
•
A.
Citations of:
A. P. Sheth and J. A. Larson.
Federated Database Systems for Managing Distributed, Heterogeneous, and Autonomous Databases .
ACM Computing Surveys, 22(3):183--236, 1990.
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CASE Support for the Development of Federated.. - Thiran, Chougrani.. (2000)
Introduction Federated Information Systems (FIS) [1] provide transparent access to heterogeneous data sources. The development of
FIS involves yielding local schemas, integrating them into one or more schemas, controlling complex mappings and building
architecture components.
•
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Semantic Query Transformation for the Intelligent
Two strategies have been advocated for the design and implementation of information mediation networks: Global As View (GAV)
and Local As View (LAV) The (GAV) follows the traditional strategy developed for federated databases [12]. The global view is
constructed by several layers of views on the relations exported by the sources. Queries are expressed in terms of the global view and
are evaluated in the conventional way. GAV is the strategy applied by TSIMMIS [7] HERMES [13] and Gestalt [11] for instance.
Integrating Ontologies and Thesauri For Rdf Schema and.. - Amann, Fundulaki, Scholl (1999)
Providing access to heterogeneous and distributed databases through integrated views has been studied from the early 80 s [6] A
large number of papers exist on the integration of distributed databases and [36,46,43] are comprehensive studies on the topic.
However such approaches for data This work was partially supported by the European project C Web (IST1999 13479) The work of
this author was supported by a fellowship from the TMR European Network Chrorochronos. integration are not appropriate
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Model Theoretic Semantics for Information Integration - Ghidini, Serafini (1998)
•
Due to the increasing necessity and availability of information from different sources, information integration is becoming one of the
challenging issues in artificial intelligence and computer science. A successful methodology for information integration is that of
federated databases [14]. However, differently form databases (for which there are well established formalisms, see for instance [1] a
completely satisfactory formal treatment of federated databases is still missing (see [16] for a survey of the state of the state of the art) The
goal of this paper is to fill this ....
conventions, and certain operations are performed locally by the databases, without interactions with the other databases. Distribution,
redundancy, partiality, and autonomy generate many problems in the management of a federated database. The most important are:
semantic heterogeneity [14], interschema dependencies [6] query distribution [2, 12] local control over data and processing [5] and
transparency [7] The definition of a formal semantics for federated databases able to cope with these problems is a key point to
understand, specify, and verify the behavior of a federated ....
•
A.
Citations of:
A. P. Sheth and J. A. Larson.
Federated Database Systems for Managing Distributed, Heterogeneous, and Autonomous Databases .
ACM Computing Surveys, 22(3):183--236, 1990.
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Providing Security and Interoperation of Heterogeneous Systems - Dawson, Qian, al. (1998)
First initiated within the context of federated architectures [20], interoperation proposals have been more recently developed with
reference to mediator based architectures [23] Unlike federated databases, approaches A preliminary version of this paper appeared
under the title Secure Interoperation of Heterogeneous Systems: A Mediator Based Approach, in ....
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Event Storage and Federation using ODMG - Alexis (2000)
Event Federation Federating event systems involves schema federation [16] and object translation
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Interoperability between a Distributed System and a.. - Adriana Danes Franois
....information that is stored within different systems, to make programs that create or manipulate information cooperate (i.e. invoke
each other to retrieve data or perform services) Interoperability has been particulary studied in the area of database systems.
Federated database systems [1] [2] and multidatabases [3] are examples of interoperability
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Myriad: Design and Implementation of a Federated Database.. - Ee-Peng Lim San-Yih (1995) (5 citations) (Correct) ....integration
tool, as shown in the previous section, has being designed and implemented to assist the Myriad DBAs in generating a global schema
mapping Loosely coupled vs. Tightly coupled FDBSs The Myriad integration framework demonstrates the merits of both loosely and
tightly coupled FDBS[28]. In a loosely coupled FDBS, the federation DBAs do not attempt to integrate export relations from different
local databases. Federation users can freely use the data manipulation operations provided by the FDBS to integrate data from
export relations in a manner that best suits their precise ....
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Schema Integration and View Derivation by Resolving.. - Schmitt, Saake (1996) (1 citation) (Correct) ....data management systems
is commonly used. As a rule, applications for specific needs continue to be based on such systems. More recent applications often
require access to distributed databases but their implementation fails due to heterogeneity. Federated database management systems
(FDBMS, cf. [20]) are designed to solve this problem. An FDBS offers a homogeneous integrated schema. There exist transformations
from the integrated schema to the local schemata. In the first step of the integration process the data model heterogeneity can be
resolved by transforming the local schemata into the ....
DataFoundry: Information Management for Scientific Data - Critchlow, Fidelis.. (2000) (Correct) ....language. Unless every
potential user is intimately familiar with the detailed workings of each connected data source, this is not a desirable approach. When
providing a resource to a broad community, it is critical to provide a consistent interface to the data. To this end, federated databases
[14] define an integrated schema over the subset of available data that is interesting to the federation as a whole. This global schema
represents a virtual database, combining data from each participating source to form a single, consistent representation. Queries
posed over a federated database are ....
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An Architecture to Support Interoperability of Autonomous.. - Zisman, Kramer (1996) (Correct) ....Various architectures and
methodologies have been proposed in the literature addressing the problem of manipulating and accessing heterogeneous databases.
Some of these architectures use a global schema integrating the databases [1, 6, 16, 17] Other architectures avoid the use of a global
schema [3, 5, 7, 8, 10, 11, 12, 13, 15] making the databases interoperable. Based on the existing architectures we propose an approach
to the problem of interoperating with a large number of autonomous heterogeneous databases. The architecture aims to permit users
A.
Citations of:
A. P. Sheth and J. A. Larson.
Federated Database Systems for Managing Distributed, Heterogeneous, and Autonomous Databases .
ACM Computing Surveys, 22(3):183--236, 1990.
•
An Architecture to Support Interoperability of Autonomous.. - Zisman, Kramer (1996) (Correct) ....Various architectures and
methodologies have been proposed in the literature addressing the problem of manipulating and accessing heterogeneous databases.
Some of these architectures use a global schema integrating the databases [1, 6, 16, 17] Other architectures avoid the use of a global
schema [3, 5, 7, 8, 10, 11, 12, 13, 15] making the databases interoperable. Based on the existing architectures we propose an approach
to the problem of interoperating with a large number of autonomous heterogeneous databases. The architecture aims to permit users
of different databases to access local data and data from other ....
Knowledge-Based Integration of Neuroscience Data Sources - Gupta, Ludäscher, Martone (2000) (1 citation) (Correct) .... system is
underway; first experiments with a preliminary (centralized, non distributed) prototype have proven the viability of the approach
[KIN00] We like to emphasize that the integration problem we address is different from the problems addressed in database
federation (or multidatabases) SL90, BE96, PS98] There a huge body of work has dealt with issues like schema integration, resolving
conflicts and mismatches (structural, extensional, naming, etc. global query processing in the presence of local autonomy etc. Those
heterogeneities are between different representations of ....
Extending OLAP Querying To External Object Databases - Pedersen, Shoshani, Gu, Jensen (2000) (Correct) ....For example, the
complex data structures tend to make it hard to formulate correct queries that aggregate the data in the ODB. Also, ODB systems are
optimized to perform more general types of queries, so the performance for aggregate queries is usually not satisfactory. Federated
database systems [22] support the logical integration of autonomous database systems, without affecting the functioning of the
individual autonomous database systems. When integrating data from databases based on different data models, the traditional
approach has been to map all data into one common data model and ....
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Version Propagation in Federated Database Systems - Schönhoff, Strässler, Dittrich (Correct) ....application workspaces local user
local schema local workspaces schema FDBMS CDMS 1 CDMS 2 Figure 2. Overview of an FDBS with version management 2. 2
Federated Database Systems with Version Management Figure 2 depicts the coarse architecture of a tightly coupled database
federation [SL90] with version management as it was realised in the IDEE project. Labels in boldface font are elements specific for a
versioned federation. So far isolated systems (comprising applications, their data stores and possibly a separate version management
system) are now called the component data ....
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AMOS - An Architecture for Active Mediators - Fahl, Risch, Sköld (1993) (10 citations) (Correct) ....are implemented with two
kinds of AMOS servers; Translation AMOS (TAMOS) servers and Integration AMOS (IAMOS) servers (see figure 2) We will
initially concentrate on access to heterogeneous data sources, not updates. There is a lot of current research on heterogeneous
database systems [She90]. The usual way to deal with data model heterogeneity is to map the schemas of the data sources to schemas
in a common data model (CDM) Most previous research use a relational CDM. This is inadequate if there are data sources with a
data model that is semantically richer than the relational ....
....define object views [Abi91] in terms of combinations of data from other AMOS servers and from local data and views. To access
the data sources it is not necessary to use a IAMOS server. Queries can be put directly against TAMOS servers using the multi
database language. Using the terminology from [She90], our architecture can be seen as a combination of a Loosely Coupled
Federated DBS and a Tightly Coupled Federated DBS (with multiple federations) Thus, the same OO multi database query language
is used for local queries, multi database queries, and for defining multi database object views. One ...
A.
Citations of:
A. P. Sheth and J. A. Larson.
Federated Database Systems for Managing Distributed, Heterogeneous, and Autonomous Databases .
ACM Computing Surveys, 22(3):183--236, 1990.
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Strategies for the Conceptual Design of Federated.. - Busse, Kutsche, Leser (2000) (Correct) ....customer s interest is to obtain an
integrated access to the information resources as a global information system, see Fig. 1. We call such a system a federated
information system (FIS) 3] Federated information systems in our understanding differ from federated database systems as described
in [15] in the fact that information resources are not restricted to database systems, but may include also other kinds of information
provision. Figure 1: Architecture of Tightly Coupled FIS The meanwhile classical work of Sheth and Larson ( 15] defines a reference
schema architecture for tightly ....
....differ from federated database systems as described in [15] in the fact that information resources are not restricted to database
systems, but may include also other kinds of information provision. Figure 1: Architecture of Tightly Coupled FIS The meanwhile
classical work of Sheth and Larson ([15]) defines a reference schema architecture for tightly coupled federated database systems
which use a global schema for integration. 1 They distinguish five different schema layers: The local conceptual schemas of the
information resources are translated into the common data model (CDM) to form ....
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A KIF Mediator for Multiple F-logic Object Databases - Louiqa Raschid Mar'ia (1996) (Correct) .... may be classified as follows:
those advocating a unified global schema [1, 2, 9, 17, 18] those requiring the use of a higher order language or logic or a meta model
[28, 3, 7, 15, 20, 21] and those advocating a federated approach or a mapping approach based on a canonical representation [4, 8, 9,
19, 22, 24, 25, 26, 27]. We will compare our research with these projects in section 6. Mediators resolve conflicts so that data from
multiple information sources can be integrated. The KIF Mediator has knowledge about the semantics of the multiple object
databases in the KIF formalism and can reason about the ....
Ontologies and Knowledge Sharing in Urban GIS - Fonseca, Egenhofer, Davis.. (2000) (1 citation) (Correct) .... Borges Computer,
Environment and Urban Systems (in press) been characterized as an integration tool, GIS interoperability is far from being fully
operational (Vckovski et al. 1999) Literature shows many proposals for integration of data, ranging from federated databases with
schema integration (Sheth and Larson 1990) and the use of object orientation (Kent 1994; Papakonstantinou et al. 1995) to mediators
(Wiederhold 1991) and ontologies (Wiederhold 1994; Guarino 1998) Sheth (1999) considers that the new generation of information
systems should be able to solve semantic heterogeneity to make use of the ....
Semantic Relations: The key to integrating and query.. - Rishe, Athauda, Yuan.. (2000) (1 citation) (Correct) ....automobiles, and
entertainment. Access to such heterogeneous multiple data sources in collective manner has created a need to investigate the older
research issues such as semantic heterogeneity with more vigor, interest and emphasis. Early research on multi databases [1]
federated databases [11] and heterogeneous database systems [4] 5] 10] has resulted in different architectures for accessing multiple
heterogeneous data sources. A main focus has been dealing with structural heterogeneity between data models and entities of schemas
[1] 6] 7] 11] A plethora of approaches and innovative ....
....on multi databases [1] federated databases [11] and heterogeneous database systems [4] 5] 10] has resulted in different
architectures for accessing multiple heterogeneous data sources. A main focus has been dealing with structural heterogeneity between
data models and entities of schemas [1] 6] 7][11]. A plethora of approaches and innovative techniques has been proposed and
implemented. However, problem of resolving semantic heterogeneity still evades requiring further research. For resolving semantic
heterogeneity, techniques have been proposed to identify semantically related attributes and ....
A.
Citations of:
A. P. Sheth and J. A. Larson.
Federated Database Systems for Managing Distributed, Heterogeneous, and Autonomous Databases .
ACM Computing Surveys, 22(3):183--236, 1990.
•
Ontologies and Knowledge Sharing in Urban GIS - Fonseca, Egenhofer, Davis.. (2000) (1 citation) (Correct) .... Borges Computer, Environment and
Urban Systems (in press) been characterized as an integration tool, GIS interoperability is far from being fully operational (Vckovski et al. 1999) Literature
shows many proposals for integration of data, ranging from federated databases with schema integration (Sheth and Larson 1990) and the use of object
orientation (Kent 1994; Papakonstantinou et al. 1995) to mediators (Wiederhold 1991) and ontologies (Wiederhold 1994; Guarino 1998) Sheth (1999)
considers that the new generation of information systems should be able to solve semantic heterogeneity to make use of the ....
Smart Supply Web: An Application of Web-based Data and.. - Hull, Kumar, Simeon (2000) (Correct) ....schema and data in the same framework. XML
provides the flexibility required by information manipulation in a Web environment, as opposed to more relational or object oriented models. For this
reason, mediation systems based on XML [14, 6, 4] are preferred over traditional relational middleware [19, 11, 15, 13], in order to deal with such
heterogenous, unstructured data. In this paper, we use the Y A T System [6, 16, 5] as a backbone to support information integration and access in an e
commerce environment. The Y A T System provides a number of services dedicated to mediation of Web data: Fast ....
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Considering Integrity Constraints During Federated Database .. - Conrad, Schmitt, Türker (1998) (Correct) ....of the data management systems is
commonly used. As a rule, applications for specific needs continue to be based on such systems. More recent applications often require access to the
distributed databases but their implementation fails due to heterogeneity. Federated database systems [SL90] are designed to overcome this problem by
integrating data of legacy database systems only virtually. That is, only the local schemata are integrated to a federated schema. Global applications can
retrieve and update federated data through the federated schema. The main task during the design ....
•
Semantic Integration of Heterogeneous Information Sources.. - Thomas Adams James (2000) (Correct) ....databases. We also wanted to explore how some
of the field data, once integrated, could be used to aid decision makers such as planners, schedulers, training personnel, and reliability engineers. This
problem can be conceptualized as a federation of heterogeneous and autonomous database systems [SHET90], which do not share a common global data
schema [LITW90] We decided to investigate the feasibility of using knowledge based techniques to address this problem in order to achieve the following
objectives: semantic integration of data from the various databases without the use of a global data ....
•
Flexible Generation of Global Integrated Schemata using GIM - Schmitt, Saake (Correct) ....continue to be based on such systems. More recent
applications often require access to the distributed databases but their implementation fails due to heterogeneity. Federated database management systems
(FDBMS) are designed to overcome this problem. FDBMSs are explained in greater detail in [SL90] An FDBS offers at least one homogeneous integrated
schema. There exist transformations to the local schemata. In the first step of the integration the data model heterogeneity is overcome by transforming the
local schemata into a canonical data model. In the second step schematic heterogeneity ....
•
A Model for Query Decomposition and Answer Construction in.. - al. (1998) (1 citation) (Correct) .... such databases and has focused on distributed
databases (Williams and Hu, 1992; Bell P1: GRN Journal of Intelligent Information Systems KL587 01 Mackinnon May 8, 1998 10:54 70 MACKINNON,
MARWICK AND WILLIAMS and Grimson, 1992) multidatabases (Litwin and Roussopoulos, 1990) federated databases (Sheth and Larsen, 1990), view
integration (Hayne and Ram, 1986) schema integration (Batini et al. 1986) and interoperability (Brodie, 1992) Brodie describes interoperability as the
ability to interact effectively to achieve shared goals, e.g. a joint activity. The main purpose of such integrated access is to enable ....
....databases to be queried as if they were a single homogeneous distributed database. The more autonomous the databases in the system, the greater the
problems of interoperability and semantic heterogeneity and, hence, the greater the problems in managing an integrated query across the databases. Sheth
and Larsen (1990) identify four forms of autonomy: design, communication, execution and association, each of which must remain inviolate to preserve the
autonomy of the databases in any integrated system. However, Colomb and Orlowska (1993) argue that in general semantic heterogeneity is not resolvable
without ....
A.
Citations of:
A. P. Sheth and J. A. Larson.
Federated Database Systems for Managing Distributed, Heterogeneous, and Autonomous Databases .
•
ACM Computing Surveys, 22(3):183--236, 1990.
Efficient Maintenance of Materialized Mediated Views - Lu, Moerkotte, Schü.. (1995) (17 citations) (Correct) ....the different sources on a semantic level
by providing an integrated view spanning these sources. Traditional research on view or schema integration, and interoperability of databases concentrates
on integrating databases, possibly with different underlying schemata or even data models [16, 29, 33, 36]. The basic idea often is to aim for a global
integrating schema or view whose definition mediates between different databases. Only lately, investigations started to integrate other sources of data
available. The most prominent example of such a source is the file. Lately, it was proposed to ....
A Graphical Data Flow Language for Retrieval, Analysis, and.. - Sait Dogru Vijay (Correct) ....databases by viewing them as a single piece. Each database
may contain incompatible data models (e.g. some relational, some non relational) use different retrieval languages, or store conflicting information.
Researchers in federated databases have proposed ways to overcome these difficulties [25, 26, 27]. We are currently exploring the possibility of using DFQL
as the user interface for a federated database. DFQL can also be adapted to work with traditional, schema intensive databases with the help of an additional
tool to browse the database schema or to constrain query construction based on ....
•
Integration of Disparate Information Sources: A Short.. - Lee, Bressan, Goh.. (1999) (Correct) ....and semantic query optimization techniques. 4.1 Views
Views can be defined in essentially twoways. The world view or Gestalt schema can be defined as a global view of the federation of sources from which in
their turn, users views are defined. The fivelayer architecture of Sheth and Larson [45] constitutes a guideline for the schematic integration from this
perspective. This approach acknowledges the fact that the data is stored (primarily managed) by the sources and that the world and users view are
composed of virtual relation (i.e. relations defined in intension) Query processing ....
•
Interoperability in Large-scale Distributed Information.. - Liu, Yan, Özsu (Correct) ....[Aea91] or SQL M in the UniSQL M system [Kea93] Although the
enforcement of a single global schema through data integration yields full transparency for uniform access, component databases have much restricted
autonomy, scalability and their evolution becomes difficult. The federated approach [SL90] improves the autonomy and the flexibility (composability) of
multidatabase management by relying on multiple import schemas and the customized integration at various multidatabase levels. However, the integration
of component schemas at each multidatabase level is enforced by the system. The ....
....and Mediator based information delivery paradigm. The former contributes to the interoperability research in terms of techniques for resolution of
semantic heterogeneity and techniques for distributed query optimization in tightly coupled and somewhat closed distributed environments [She91, SL90]
The later contributes to the interoperability research in terms of techniques for handling both structured data sources and semistructured or unstructured
data sources, and techniques for providing scalable and adaptable data delivery services in loosely coupled and open distributed ....
•
A Generic Integration Architecture for Cooperative.. - John Mylopoulos (1996) (7 citations) (Correct) ....approach. Both system types seek to support
global updates, while preserving site autonomy. Distributed databases [7] unlike global information systems, do not have a full autonomy of their data.
Issues in structuring heterogeneous databases are discussed in [4] and others. Federated databases [28] can be implemented based on several architectures.
For example, federated databases can be implemented using loosely coupled systems, where the responsibility for understanding the semantics of the global
system is transferred to the user. Federated databases can also be implemented using tightly ....
A.
Citations of:
A. P. Sheth and J. A. Larson.
Federated Database Systems for Managing Distributed, Heterogeneous, and Autonomous Databases .
•
•
ACM Computing Surveys, 22(3):183--236, 1990.
Heterogeneous Active Agents - Eiter, al. (1998) (23 citations) (Correct) ....In this paragraph, we merely explain the relationship between code call
conditions and existing work on data and software integration. For example, there have been several efforts to integrate multiple relational DBMSs [29, 81]
and relational DBMSs, object oriented DBMSs and or file systems [39, 63, 95]. However, to date, the semantics of mediators that take actions has not been
explored. The work in this paper builds upon mediation efforts reported upon in our HERMES effort described previously in [19, 74, 74, 100, 76] The
Stanford TSIMMIS project [22] effort aimed at integrating a wide ....
Organising Knowledge of a Federated Database System to.. - Karunaratna, Gray.. (1998) (1 citation) (Correct) .... supports operations on multiple
databases (possibly autonomous and heterogeneous) is usually referred to as a multidatabase system [BHP92, KS91, Lit88, PBE96] There are two popular
system architectures for multidatabases: tightly coupled federation and loosely coupled federation [CHS91, KS93, SL90] In a tightly coupled federation,
data is accessed using a global schema(s) created and managed by a federated database administrator(s) In a looselycoupled federation it is the user s
responsibility to create and maintain the federation s integration regime. They may access data either by
Interoperability for Digital Libraries: Problems and.. - Paepcke, Chang.. (Correct) ....For example, the modeling cell in the information management
column represents basic technologies for organizing information in such a way that it can be shared with other parts of a system, even if those follow
different information structure conventions. Early federated database systems [11], for instance, created global database schemas to help smooth over
syntactic differences. Translators would convert data field specifications to local conventions at the target components. For example, a global schema for a
set of business directory databases might specify that the names of firms ....
•
Federating Process-Centered Environments: the Oz Experience - Israel Ben-Shaul (1997) (Correct) ....is analogous to distributed database systems, where
there is transparent access to distributed data, while the independent choice of SDE end is comparable to a collection of independent databases. The
database community has also delineated an intermediate range, often termed federated databases [64, 58]. Federated databases generally permit a high
degree of autonomy with respect to one or both of two criteria, schema and system: local components of a single database system with intrinsic federation
glue may devise and administer their own schema independently (known as a homogeneous federation) ....
•
Designing a Global Information Resource for Molecular Biology - Leser (1999) (Correct) ....today is the WWW, where interfaces can vary greatly: from
simple HTML or ASCII pages and tables, through different levels of WWW fill out forms to full query language access provided through a text entry field.
3 Conventional approaches to database integration, such as federated databases ([12]) expect the sources to be full fledged database management systems.
They assume the existence of an export schema in a standard data model and a conventional query language. These assumptions do not hold in our setting.
Access is in general not granted through a query language. For instance, ....
....and translates requests into source specific queries, method calls, HTTP requests etc. In our system the interface between a wrapper and the mediator is
a, though possibly very restricted, relational query interface. Each wrapper has an export schema; however, in contrast to federated databases ([12]) the
wrapper can answer only certain, pre defined queries. A mediator holds a federated schema which models all concepts of the intended domain, which does
not necessarily contain each source schema completely. Given a user query the mediator tries to find a sequence of queries against wrappers ....
•
Concurrency Control in Federated Databases: A Dynamic Approach - San-Yih Hwang (1993) (2 citations) (Correct) ....query languages, and transaction
management mechanisms. Autonomy dictates that a participating local DBMS should not be modified by the FDBS, and a local DBMS has the right to
decide the types of internal information provided to the FDBS and execute queries and transactions according its own rule [Shet90]. Due to autonomy, there
are two types of transactions in the entire FDBS environment, namely local transactions and global transactions. A local transaction, which accesses data
controlled by a single DBMS, is submitted to and executed by a local DBMS without the control of the FDBS. A global ....
A.
Citations of:
A. P. Sheth and J. A. Larson.
Federated Database Systems for Managing Distributed, Heterogeneous, and Autonomous Databases .
•
•
ACM Computing Surveys, 22(3):183--236, 1990.
A Meta-Wrapper for Scaling up to Multiple Autonomous.. - Vidal, Raschid, Gruser (1998) (8 citations) (Correct) ....meta wrapper identifies alternate
sources for the query. A meta wrapper cost model is then used to select among alternate relevant sources and choose the best plan. 1. Introduction The
problem of providing access to data from heterogeneous databases or legacy servers, has been studied extensively [2, 3, 9, 22, 25, 26, 28]. Architectures
based on wrappers and mediators [31] and a common model and schema have been proposed in [1, 13, 8, 9, 20, 23, 29] In this architecture, wrappers handle
query processing on individual sources. The mediator solves the task of capability based rewriting (CBR) to determine the ....
geoPOM: A Heterogeneous Geoscientific Persistent Object.. - Nittel, Muntz, Mesrobian (1997) (1 citation) (Correct) ....repositories. Starting in the mid
eighties, most of the work focussed on integrating relational DBMS through multidatabase languages, and multidatabase systems with varying degrees of
coupling between data repositories and the integrating system, as well as, the autonomy of the data repositories ([26, 4]) In recent years, approaches have
been developed which leverage the benefits introduced by the object oriented programming paradigm (powerful data modeling, new implementation
strategies for problems in heterogeneous DBMS transaction management, etc. A good overview of the work in this area ....
....of geoPOM is to provide highperformance geoscientific data management for heterogeneous spatial repositories. Two main architectural decisions were
made to achieve this goal: first, the elimination of a set of indirections which are known from the classical architecture of heterogeneous systems ([26]) and
second, the empowerment of users to choose several optimization parameters. A full blown heterogeneous geoscientific persistent object system is a very
complex software system; several assumption were made to make the problem more tractable. First, the state of a geoPOM object is always ....
•
Metadata-Based Middleware for Integrating.. - Kapsammer, Wagner.. (1998) (Correct) ....for horizontal integration at the data level in terms of different
relational and objectoriented databases, possibly located at different sites. Thus, the transparency supported by IRO DB refers to both, distribution and
heterogeneity. IRO DB falls into the category of federated database systems [13] that hide local databases and simulate the users that they work with one
instead of multiple possibly heterogeneous databases. However, IRO DB realizes not only appropriate middleware services for accessing distributed and
heterogeneous data, but rather the middleware provides full database ....
•
Interoperability and Workflow: Multi-Agency Databases - Müller, Frank (Correct) ....of a FDBS are heterogeneity and autonomy. Autonomy dictates that
a LDBMS participating in a FDBS should not be modified by the FDBS and has the right to decide which types of internal information can be provided to
the FDBS and to execute queries and transactions according to its own rules [8]. Due to autonomy there are two types of transactions in the entire FDBS.
These are local transactions within a LDBMS and global transactions. Local transactions are executed by the LDBMS without the control of the FDBS. A
global transaction, which accesses data in more than one LDBMS, is ....
•
Meta-Data Based Mediator Generation - Critchlow, Ganesh, Musick (1998) (2 citations) (Correct) ....are also included. 3. The DataFoundry architecture
The goal of DataFoundry is to provide integrated access to multiple, evolving, domain databases through a consistent interface. To facilitate this, we have
chosen an architecture that combines the advantages of tightlycoupled federated databases [18] with those of data warehouses [12] Federated databases
provide a global schema for the underlying source databases, each of which retain control and management of their data. Queries posed against the global
schema are translated into individual queries against the source databases, and their ....
•
Change Management in Heterogeneous Semistructured Databases .. - Sudarshan Chawathe (Correct) ....interest in the subject of storing and querying
heterogeneous and semistructured data. Heterogeneous data is characterized by a high degree of autonomy, an absence of a common data model, an
absence of standard database control facilities (such as transactions) and differing modes of access [SL90] Heterogeneous and other Web accessible data
frequently is semistructured, meaning that the data may be irregular or incomplete [Abi97, AQM 96, BDHS96] In addition to offering access to large
amounts of heterogeneous and semistructured information, the Web allows this information to change ....
Agents for Information Gathering - Knoblock, Ambite (1997) (21 citations) (Correct) ....efficiently access the desired information. We are focusing on the
problems of how to organize, manipulate, and learn about large quantities of data. Research in databases has also focused on building integrated or
A.
Citations of:
A. P. Sheth and J. A. Larson.
Federated Database Systems for Managing Distributed, Heterogeneous, and Autonomous Databases .
•
•
ACM Computing Surveys, 22(3):183--236, 1990.
A Meta-Wrapper for Scaling up to Multiple Autonomous.. - Vidal, Raschid, Gruser (1998) (8 citations) (Correct) ....meta wrapper identifies alternate
sources for the query. A meta wrapper cost model is then used to select among alternate relevant sources and choose the best plan. 1. Introduction The
problem of providing access to data from heterogeneous databases or legacy servers, has been studied extensively [2, 3, 9, 22, 25, 26, 28]. Architectures
based on wrappers and mediators [31] and a common model and schema have been proposed in [1, 13, 8, 9, 20, 23, 29] In this architecture, wrappers handle
query processing on individual sources. The mediator solves the task of capability based rewriting (CBR) to determine the ....
geoPOM: A Heterogeneous Geoscientific Persistent Object.. - Nittel, Muntz, Mesrobian (1997) (1 citation) (Correct) ....repositories. Starting in the mid
eighties, most of the work focussed on integrating relational DBMS through multidatabase languages, and multidatabase systems with varying degrees of
coupling between data repositories and the integrating system, as well as, the autonomy of the data repositories ([26, 4]) In recent years, approaches have
been developed which leverage the benefits introduced by the object oriented programming paradigm (powerful data modeling, new implementation
strategies for problems in heterogeneous DBMS transaction management, etc. A good overview of the work in this area ....
....of geoPOM is to provide highperformance geoscientific data management for heterogeneous spatial repositories. Two main architectural decisions were
made to achieve this goal: first, the elimination of a set of indirections which are known from the classical architecture of heterogeneous systems ([26]) and
second, the empowerment of users to choose several optimization parameters. A full blown heterogeneous geoscientific persistent object system is a very
complex software system; several assumption were made to make the problem more tractable. First, the state of a geoPOM object is always ....
•
Metadata-Based Middleware for Integrating.. - Kapsammer, Wagner.. (1998) (Correct) ....for horizontal integration at the data level in terms of different
relational and objectoriented databases, possibly located at different sites. Thus, the transparency supported by IRO DB refers to both, distribution and
heterogeneity. IRO DB falls into the category of federated database systems [13] that hide local databases and simulate the users that they work with one
instead of multiple possibly heterogeneous databases. However, IRO DB realizes not only appropriate middleware services for accessing distributed and
heterogeneous data, but rather the middleware provides full database ....
•
Interoperability and Workflow: Multi-Agency Databases - Müller, Frank (Correct) ....of a FDBS are heterogeneity and autonomy. Autonomy dictates that
a LDBMS participating in a FDBS should not be modified by the FDBS and has the right to decide which types of internal information can be provided to
the FDBS and to execute queries and transactions according to its own rules [8]. Due to autonomy there are two types of transactions in the entire FDBS.
These are local transactions within a LDBMS and global transactions. Local transactions are executed by the LDBMS without the control of the FDBS. A
global transaction, which accesses data in more than one LDBMS, is ....
•
Meta-Data Based Mediator Generation - Critchlow, Ganesh, Musick (1998) (2 citations) (Correct) ....are also included. 3. The DataFoundry architecture
The goal of DataFoundry is to provide integrated access to multiple, evolving, domain databases through a consistent interface. To facilitate this, we have
chosen an architecture that combines the advantages of tightlycoupled federated databases [18] with those of data warehouses [12] Federated databases
provide a global schema for the underlying source databases, each of which retain control and management of their data. Queries posed against the global
schema are translated into individual queries against the source databases, and their ....
•
Change Management in Heterogeneous Semistructured Databases .. - Sudarshan Chawathe (Correct) ....interest in the subject of storing and querying
heterogeneous and semistructured data. Heterogeneous data is characterized by a high degree of autonomy, an absence of a common data model, an
absence of standard database control facilities (such as transactions) and differing modes of access [SL90] Heterogeneous and other Web accessible data
frequently is semistructured, meaning that the data may be irregular or incomplete [Abi97, AQM 96, BDHS96] In addition to offering access to large
amounts of heterogeneous and semistructured information, the Web allows this information to change ....
Agents for Information Gathering - Knoblock, Ambite (1997) (21 citations) (Correct) ....efficiently access the desired information. We are focusing on the
problems of how to organize, manipulate, and learn about large quantities of data. Research in databases has also focused on building integrated or
A.
Citations of:
A. P. Sheth and J. A. Larson.
Federated Database Systems for Managing Distributed, Heterogeneous, and Autonomous Databases .
•
ACM Computing Surveys, 22(3):183--236, 1990.
Distributed Knowledge Networks - Vasant Honavar (1998) (Correct) ....to be able to provide seamless access to data that is distributed over multiple
relatively autonomous databases, as well as data that is heterogeneous in form and or content. Approaches to processing heterogeneous data sources can be
broadly classified into two categories: multidatabase systems [10] and mediator based systems [11] The multidatabase systems [10] apply traditional
database techniques to bridge the mismatch between the underlying data sources. Our work has approached this task using object oriented views [12] which
exploits the underlying object structure for incorporating the ....
....over multiple relatively autonomous databases, as well as data that is heterogeneous in form and or content. Approaches to processing heterogeneous data
sources can be broadly classified into two categories: multidatabase systems [10] and mediator based systems [11] The multidatabase systems [10] apply
traditional database techniques to bridge the mismatch between the underlying data sources. Our work has approached this task using object oriented
views [12] which exploits the underlying object structure for incorporating the rich semantics of the common data types. It creates a uniform ....
•
A Meta-Wrapper for Scaling up to Multiple Autonomous.. - Vidal, Raschid, Gruser (1998) (8 citations) (Correct) ....meta wrapper identifies alternate
sources for the query. A meta wrapper cost model is then used to select among alternate relevant sources and choose the best plan. 1 Introduction The
problem of providing access to data from heterogeneous databases or legacy servers, has been studied extensively [2, 3, 10, 22, 28, 27, 31]. Architectures
based on wrappers and mediators [37] and a common model and schema have been proposed in [1, 6, 8, 9, 10, 19, 24, 34] In this architecture, wrappers
handle query processing on individual sources. The mediator solves the task of capability based rewriting (CBR) to determine the ....
•
Information Integration: Conceptual Modeling and.. - Calvanese, De.. (1998) (23 citations) (Correct) ....information. However, performing updates on the
integrated data requires changing the data in the sources. Hence a tight coordination between the sources and the integration system and among the
different sources is needed. Such form of integration is typically of interest to federated databases [32, 18]. Recently a looser approach to integration has
emerged, where the autonomy of the sources is a basic requirement, and the integration system is seen as a client of the sources which cannot interfere with
their operation. Hence, performing updates on the integrated data is not of concern and the ....
•
....different and independent from the organizations managing the single sources [33] In this paper we concentrate on read only integration. Information
integration can be either virtual or materialized. In the first case, the integration system acts as an interface between the user and the sources [32, 24], and is
typical of multi databases, distributed databases, and more generally open systems. In virtual integration query answering is generally costly, because it
requires accessing the sources. In the second case, the system maintains a replicated view of the data at the sources [19, 25] and is ....
Extending the Schema Architecture of Federated Database Systems .. - Hasselbring (Correct) ....is a central issue. The purpose of this paper is to study
some problems and solutions of propagation of information updates across heterogeneous subsystems within hospitals. The general structure of our
presented architecture is based on the reference architecture for federated database systems [SL90] and adapted to the specific demands on integration of
replicated information. This architecture is the basis for algorithms that restore the integrity of replicated information when changes occur. The current
state of the art in connecting subsystems within hospitals through communication ....
....in Section 3. 3 A federated software architecture for integrity maintenance of replicated information A database system (DBS) consists of a database
management system and one or more databases that it manages. In a federated DBS, both global applications and local applications are supported [SL90]
The local applications remain autonomous, but must restrict their autonomy to some extent to participate in the federation. Global applications can access
multiple local DBSs through the federation layer. The federation layer can also control global integrity constraints such as data value ....
•
An Approach to the Integration of File Based Systems into.. - Höding (1996) (1 citation) (Correct) ....uniform access to data from different databases
allows a comfortable and uniform representation of the information. There are different approaches to integrate the different heterogeneous local systems.
We believe, the most suitable approach is the use of a federated database system (FDBS) HM85, SL90] An FDBS provides a uniform and transparent access
to federated data by means of a global interface. For that a special software layer, called the federated database management system, is added to the
Federated Information Systems:Concepts, Terminology and Architectures
Susanne Busse, Ralf-Detlef Kutsche, Ulf Leser, Herbert Weber
Technische Universität Berlin, Fachbereich 13 Informatik
Computergestützte InformationssystemeCIS
Einsteinufer 17, D- 10587 Berlin
Email: {sbusse,rkutsche,leser}@cs.tu-berlin.de
• Dvoy Services offer a homogeneous, read-only access mechanism
to a dynamically changing collection of heterogeneous, autonomous
and distributed information sources.
• Data access uses a global multidimensional schema consisting of
spatial, temporal and parameter dimensions, suitable for data
browsing and online analytical processing, OLAP. The limited query
capabilities yield slices through the spatio-temporal data cubes.
• The main software components of Dvoy are wrappers, which
encapsulate sources and remove technical heterogeneity, and
mediators, which resolve the logical heterogeneity.
• Wrapper classes are available for geo-spatial (incl. satellite) images,
SQL servers, text files,etc. The mediator classes are implemented as
web services for uniform data access, transformation and portrayal.