1. Architetture della Informazione Anno accademico Carlo Batini Methodologies for planning the evolution of data architectures 1

2. The data architecture migration problem
DBMS
Global schema
Global schema
DBMS
source
DBMS
source
Global schema
Design of the
optimal architecture ?
source
DBMS
DBMS
Global schema
DBMS
source
Global schema
Global schema
source
source
Technologies
EII
DDBMS
Consolidation
DI architecture
GAV
LAV
DW architecture
EAI
P&Subscribe
Organizational context
Application load
Data quality assessment
Global schema
DBMS
source

3. Consolidation ….. New architecture Old architecture Source 1 Source 2
Source n
…..
Unique DB
New architecture
Old architecture

4. From centralized to distributed
DBMS
Global schema
DBMS
source
Global schema
Network
Local
schema
Local
schema
Local
schema
source
source
source

5. From a cluster of autonomous databases to data integration
Queries
DBMS
Mediator
local schema
local schema
DBMS
Source 2
Global
schema
Source 1
Wrapper
Wrapper
Wrapper
local schema
DBMS
Local
schema
Local
schema
Local
schema
Source 1
Source 2
Source n …
Source n

6. From a cluster of autonomous databases to data warehouse
Queries
local schema
DBMS
Source n
Source 1
Source 2
DW management
system
Global
schema
Integrated
data
Source 1
Source 2
Source n …

7. Two methods
Decision table, based both on organizational issues and on technological issues  This presentation
Optimization problem  Next presentation 5.7.2

8. Organizational issues
1 Autonomy, the degree of independency between the different Data base Administrators in their design choices;
4. Relevance of currency in queries, the need for queries to extract current data;
5. Economic value of integration, relevance for business operational and de- cisional process of having integrated information in input so to produce effective outputs;
6. Volatility of sources, frequency of adding or deleting sources, and frequency of change of source schemas;
8. Management complexity, the effort to be spent in management activities related to databases and hw-sw infrastructures, due to the corresponding complexity of the organizations using the data bases;
9. Costs of heterogeneity, hidden and explicit costs related to business processes that are due to making use of heterogeneous data.

9. Technological issues
2. Relevance of historical data, and consequent need to store periodically new data without deleting the old ones;
3. Query complexity, in terms of number of data and tables visited and number of operators on them, and consequent time complexity in query execution;
7. Relevance of queries w.r.t transactions, relative importance and frequency of queries with respect to changes in data

10. A Decision table (to be extended…)
Decision criteria
Suggested
solution
Autonomy
Relevance of historical data
Query complexity
Relevance of currency in queries
Economic value of integration
Relevance of queries wrt transactions
Volatility
of queries
Management complexity
Costs of heterogeneities -
High
Data
Warehouse
Publish &
Subscribe
Low
Consolidation
Data integration
Wharehouse