Download The data warehouse architecture

F4: DW Architecture and Lifecycle
Erik Perjons, DSV, SU/KTH
[email protected]
The data warehouse architecture
The back room
The front room
Analysis/OLAP
Data warehouse
External sources
Extract
Transform
Load
Operational
source systems
Serve
Data marts
Productt
Time1
Value1
Value11
Product2
Time2
Value2
Value21
Product3
Time3
Value3
Value31
Product4
Time4
Value4
Value41
Query/Reporting
Data mining
Falö aöldf
flaöd aklöd
falö alksdf
Operational source Data staging
systems (RK)
area (RK)
Legacy systems
Back end tools
OLTP/TP systems
Data presentation
area (RK)
”The data warehouse”
Data access tools (RK)
End user applications
Business Intelligence tools
Presentation (OLAP) servers
1
Operational Source Systems
Operational source systems
characteristics:
Operational
source systems
• the source data often in OLTP (Online Transaction Processing)
systems, also called TPS (Transaction Processing Systems)
• high level of performance and availability
• often one-record-at-a time queries
• already occupied by the normal operations of the organisation
OLTP vs. DSS (Decision Support Systems)
OLTP vs. OLAP (Online analytical processing)
Operational Source Systems
More operational source systems
characteristics:
Operational
source systems
• a OLTP system may be reliable and consistent, but there are
often inconsistencies between different OLTP systems
• different types of data format and data structures in
different OLTP systems AND DIFFERENT SEMANTICS
2
Operational Source Systems
Kimball et al´s assumptions (p 7):
Operational
source systems
•Source systems are not queried in the broad
and unexpected ways
•Maintain little historical data
•Each source systems is often a natural
stovepipe application
DW architecture: Data staging area
Analysis/OLAP
Data warehouse
External sources
Operational
source systems
Extract
Transform
Load
Serve
Data marts
Productt
Time1
Value1
Value11
Product2
Time2
Value2
Value21
Product3
Time3
Value3
Value31
Product4
Time4
Value4
Value41
Query/Reporting
Data mining
Falö aöldf
flaöd aklöd
falö alksdf
Operational
source systems
Data staging area Data presentation area Data access tools
3
The Data Staging Area
Often the most complex part in
the architecture, and involves...
•
•
•
•
Extract
Transform
Load
Extraction (E)
Transformation (T)
Load (L)
indexing
ETL-tools can be used
Scripts for extraction, transformation and load are
implemented
Data staging area
Extract
Transform
Load
Extraction
means reading and understanding the source data and
copying the data needed for the data warehouse into
staging area for further manipulation, i.e.
transformation
4
Data staging area
Transformation involves…
Extract
Transform
Load
• data conversion/transformation
(specify transformation rules to convert to a common data format
and common terms/semantics)
• data cleaning/cleansing
– data scrubbing (use domain-specific knowledge (e.g postal
adresses) to check the data)
– data auditing (discover suspicious pattern, discover violation of
stated rules)
• combining data from multiple sources
• assigning warehouse (surrogate) keys
• data aggregation
Data staging area
A debate questions:
Extract
Transform
Load
Should the data in the data staging area be stored in a
3NF relational database and loaded into the presentation
area for querying and reporting?
Kimball (p 8-9): a 3NF relational database in data staging area
requires more time and resources for development, periodic
loading and updating and more capacity of storing the multiple
copies of the data
5
A Real World Example
Flat file
C
DB2Connect
DB2
table(s)
D’
Various source files
Customer
data
F
Customer
data
G
Start
balance
H
Fees
(manually adjusted
to individual
agreements)
I
Staging area for checking, analysing,
cleaning, complementing etc transaction
data
Three star/join schemas
comprising altogether 8 tables
Fact tables:
- transactions (10 attributes)
- fees (7 attributes)
- start balance (4 attributes)
Dimensional tables:
- time (7 attr)
- customer (> 40 attr)
- company (> 90 attr)
- product (13 attr)
- ”Service charged” (2 attr)
SQL, C++ ??
Some cleansing
and scrubbing
may be needed
here
DB2
Preliminary
target DW
E
+aggregation
(new program)
DB2
Final
target DW
E’
E complemented with some
aggregated tables
DW architecture: Data presentation area
Analysis/OLAP
Data warehouse
External sources
Operational
source systems
Extract
Transform
Load
Serve
Data marts
Productt
Time1
Value1
Value11
Product2
Time2
Value2
Value21
Product3
Time3
Value3
Value31
Product4
Time4
Value4
Value41
Query/Reporting
Data mining
Falö aöldf
flaöd aklöd
falö alksdf
Operational
source systems
Data staging area Data presentation area Data access tools
6
Data presentation area
Data warehouse
OLAP
servers
Data marts
•
•
•
•
What is OLAP?
Dimensional modelling vs. 3 NF modelling
Data Marts
ROLAP/MOLAP servers
What is OLAP?
• Acronym for “On-line analytical processing”
• A decision support system (DSS) that support ad-hoc querying, i.e.
enables managers and analysts to interactively manipulate data. The
idea is to allow the users to easy and quickly manipulate and visualise
the data through multidimensional views, i.e. different perspectives.
Service
quarter
e
fic
of
Quarter
Facts
Office
product
Kimball: Dimensional modelling
7
Dimensional modelling
Service Dimension
Service
Key Service
group
S1
Local call Group A
S2
Intern. call Group A
S3
SMS
Group B
S4
WAP
Group C
1
0..*
Time Dimension
Date/
Key
991011
991012
C210
C210
C212
C213
C214
S1
S3
S2
S1
S4
F11
F11
F13
F13
F13
991011
991011
991011
991011
991012
0..*
Office
Sundsvall
Sundsvall
Kista
1
Year
99
99
Number
of calls
3
1
1
1
1
0..*
Customer Dimension
Sales Dimension
Seller
Anders C
Lisa B
Janis B
Sum
25:00
05:00
89:00
12:00
08:00
Quarter
4 - 99
4 - 99
1
Fact table - Transactions
0..*
Key
F11
F12
F13
Month
9910
9910
Key
C210
C211
C212
C213
C214
1
Customer
Anna N
Lars S
Erik P
Danny B
Åsa S
Address
Stockholm
Malmö
Rättvik
Stockholm
Stockholm
Region
Stockholm
Skåne
Dalarna
Stockholm
Stockholm
Income
group
B
B
C
A
A
Dimensional modelling
Service Dimension
Service
Key Service
group
S1
Local call Group A
S2
Intern. call Group A
S3
SMS
Group B
S4
WAP
Group C
Time Dimension
Date/
Key
991011
991012
S1
S3
S2
S1
S4
F11
F11
F13
F13
F13
991011
991011
991011
991011
991012
Sum
25:00
05:00
89:00
12:00
08:00
Number
of calls
3
1
1
1
1
Σ=37:00
Key
F11
F12
F13
Seller
Anders C
Lisa B
Janis B
Office
Sundsvall
Sundsvall
Kista
Quarter
4 - 99
4 - 99
Year
99
99
Fact table - Transactions
C210
C210
C212
C213
C214
Sales Dimension
Month
9910
9910
Query:
For how much
did customers in Sthlm
use service “Local call”
in october 1999?
Customer Dimension
Key
C210
C211
C212
C213
C214
Customer
Anna N
Lars S
Erik P
Danny B
Åsa S
Address
Stockholm
Malmö
Rättvik
Stockholm
Stockholm
Region
Stockholm
Skåne
Dalarna
Stockholm
Stockholm
Income
group
B
B
C
A
A
8
3 NF modelling vs. Dimensional modelling
Key difference between 3NF and Dimensional modelling:
- the degree of normalisation
3 NF modelling
- a logical design technique to eliminate data redundancy to keep
consistency and storage efficiency, and makes transaction simple
and deterministic
- ER models for enterprise are usually complex, e.g. they often
have hundreds, or even thousands, of entities/tables
Dimensional modelling
- a logical design technique that present data in a intuitive, i.e.
easier to navigate for the user
- allow high performance access/queries (the complexity of 3NF
models overwhelms the database systems optimizer, which means
bad performance)
[Kimball et al, p 10-11]
- aims at model decision support data
Data presentation area – Data marts
Kimball et al (p.10-12 and 396)
“we refer to the presentation area as a series of integrated
data marts”
“a data mart is a flexible set of data, ideally based on the
most atomic (granular) data possible to extract from
operational source, and presented in a symmetric
(dimensional) model that is resilient when faced with
unexpected user queries”
“in its most simplistic form a data mart represent data from
a single business process” (business process=purchase
order, store inventory and so on)
9
Data marts
Service
Quarter
Calls
Service
Quarter
Office
Subscription
orders
Office
Service
Quarter
Calls
Office
Subscription
orders
The data warehouse bus architecture
A data mart
A data mart
Orders
ction
Produ
Dimensions
Time
Sales Rep
Customer
Promotion
Product
Plant
Distr. Center
[Kimball et al, p 78-79]
10
Data marts
• A dimensional model for a large data warehouse
consists of between 10 and 25 similar-looking data
marts. Each data marts will have 5 to 15 dimensional
tables.
The Data marts
Kimball et al’s strong opinions (p.10-12)
• all data in the presentation area should be presented,
stored and accesses in dimensional models
• the data marts must contain detailed, atomic data (it
is unacceptable that the detailed data should be
locked up in 3 NF models for drill-down)
• the data marts dimensions should be conformed for
drill-across techniques, which tie the data marts
together in the data warehouse bus architecture
11
The Data marts
More about data marts:
• far smaller data volumes, fewer data sources
• easier data cleaning process, faster roll-out
• allows a “piecemeal” approach to some of the enormous
integration problems involved in creating an enterprise
wide data model, but complex integration in the long
term
Dependent vs. Independent Data marts
Independent Data marts
Data warehouse
Dependent Data marts
Data warehouse
12
The presentation/OLAP servers
Extended Relational DBMS (ROLAP servers)
–
–
–
–
data stored in RDB
star-join schemas
support SQL extensions
index structures
Data warehouse
OLAP
servers
Data marts
Multidimensional DBMS (MOLAP servers)
–
–
–
–
data stored in arrays (n-dimensional array)
direct access to array data structure
excellent indexing properties
poor storage utilisation, especially when the data is sparse.
More about presentation servers
What is characteristics regarding data warehouse,
according to Chaudhiri&Dayal :
• Index structures (bit map indexes, join indexes)
• SQL extensions (operators like Cube, Crossjoin)
•
Materialised views (pre-aggregations)
13
DW architechture: Metadata repository
Monitoring & Administration
Metadata
repository
OLAP
servers
Data warehouse
External sources
Operational
source systems
Extract
Transform
Load
Refresh
Serve
Analysis
Productt
Time1
Value1
Value11
Product2
Time2
Value2
Value21
Product3
Time3
Value3
Value31
Product4
Time4
Value4
Value41
Query/Reporting
Data mining
Data marts
Operational
source systems
Falö aöldf
flaöd aklöd
falö alksdf
Data staging area Data presentation area Data access tools
What is metadata?
“Data about data”/”Information about data”
Main functions are to give...
• data definitions
• the origin of data
• the structure of data
• rules for the selection and transfer of data
• qualitative and quantitative data about data
Contained in metadata repository Æ
14
The metadata repository
An integrated complete source of metadata
• is at the heart of the data warehouse architecture
• supports the information needs of...
– system developers
– data administrators
– system administrators
– users
– applications on the data warehouse
• very complex data structure
• must contain full version history
• must always be up to date
Metadata life cycle activities
• Collection
• identify and capture metadata in a central
repository
• Maintenance
• establish processes to synchronise metadata with
the changing data structure
• Deployment
• provide metadata to users in the right form and
with the right tools
15
Different types of metadata
• Administrative metadata
(includes all information necessary for setting up and using a DW,
e.g. Information about source databases, dw schemas,
dimensions, hierachies, predefined queries, physical
organisation, rules and script for extraction, transformation
and load, back-end and front end tools)
• Business metadata
(business terms and definitions, ownership of data)
• Operational metadata
(information collected during the operations of the DW, e. g.
usage statistics, error reports)
DW architecture: End user applications
Monitoring & Administration
Metadata
repository
OLAP
servers
Data warehouse
External sources
Operational DBs
Extract
Transform
Load
Refresh
Serve
Analysis
Productt
Time1
Value1
Value11
Product2
Time2
Value2
Value21
Product3
Time3
Value3
Value31
Product4
Time4
Value4
Value41
Query/Reporting
Data mining
Data marts
Operational
source systems
Falö aöldf
flaöd aklöd
falö alksdf
Data staging area Data presentation area Data access tools
16
End user applications
Analysis
Productt
Time1
Value1
Value11
Product2
Time2
Value2
Value21
Product3
Time3
Value3
Value31
Product4
Time4
Value4
Value41
Query/Reporting
• OLAP tools, BI apps, DSS
• Query/Reporting tools
• Data mining
Data mining
Falö aöldf
flaöd aklöd
falö alksdf
Spreadsheet output of OLAP tool
product
product group
mounth
quarter
Column headers
(join constraints)
Product Group
Group A
Group A
Group B
Group B
office
region
Column header
(application constraint)
Region
ABC
XYZ
ABC
XYZ
Answer set representing
focal event
First Quarter - 1997
1245
34534
45543
34533
Row headers
17
Graphical output of OLAP tool
Functionalities of OLAP tools
• Drill-down - decreasing the level of aggregation
• Drill-up/Roll-up/Consolidation - increasing the level of aggregation
• Drill-across - move between different star-join schemas using
conformed dimensions and joins
• Slicing and dicing – ability to look at the database from different
views, e.g. one slice shows all sales of product type within regions,
another slice shows all sales by sales channel within each product
type
• Pivoting - e.g. change columns to rows, rows to columns
• Ranking - sorting
“Think of an OLAP data structure as a Rubik´s Cube of data that users
can twist and twirl in different ways to work through what-if an
what-happend scenarios”
[Lee Thé]
18
Business Intelligence (BI) apps
Strategic
Who: strategic leaders
What: formulate strategy and monitor corporate performance
Examples: Balance scorecard, Strategic Planning
Operational
Who: operational managers
What: execution of strategy againts objectives
Examples: Budgeting, Sales forcasting
Analytical
Who: analysts, knowledge worker, controller
What: ad-hoc analysis
Examples: Financial and Sales Analysis, Customer Segmentation,
Clickstream analysis
Problems of Data Warehousing
• Complexity of integration
– Hidden problems with source systems
– Data homogenisation
– Underestimation of resources for data loading
• Required data not captured
• High maintenance
• Long duration projects
• Why not integrating the legacy applications
(OLTP systems) instead?
19
Operational Data Store (ODS)
No singel universal defintion...
ODS definition 1: Implemented to deliver operational reporting,
especially when neither the legacy nor the modern OLTP systems
provide adequate operational reports – fixed queries and for tactical
decision making
ODS definition 2: Built to support real-time interactions, especially
in Customer Relationsship Management applications – the tradtional
data warehouse typically is not in a position to support the demand
for near-real-time data
OMG’s standards
Meta Object Facility (MOF)
M3 layer
M2 layer
Meta
metamodel
Metamodel
UML Metamodel CWM Metamodel
M1 layer
M0 layer
Model
Instances
Helen
Nagy
Invoice
no 34
20
Common Warehouse Metamodel (CWM)
Data
Source
Analysis
Data Mart
Reporting
Data
Source
Operational
Data Store
ETL
Data
Warehouse
Data Mart
Visualization
Data Mart
Data Mining
Data
Source
The collection of metamodels by CWM can be
used to model the whole data warehousing
environment i.e from data sources to end use
analysis, and data warehouse management
Common Warehouse Metamodel
• Common Warehouse Metamodel (CWM) is a
language specifically design to model data
warehousing and data mining applications, i.e.
integrating data warehousing and business
analysis (business intelligence) tools
• CWM has a lot in common with the UML metamodel
but has a number of special metamodels
(metaclasses), e.g modelling relational databases,
multidimensional databases, OLAP, schema
transformations, XML
[Kleppe et al, p.139-140 (2003)]
21
Why
metamodelling?
Event
consists of
Meta
metamodel
level or
Reference
model
consists of
Precedes
Transformation
State
Succedes
Precedes/
Succedes
Precedes
Function
State
Activity
Event
Metamodel
level
Precedes
Succedes
Succedes
Order
recieved
Model
level
Capture
ordered items
Capture
ordered items
Ordered item
[captured]
Ordered item
captured
Check material
on stock
Check material
on stock
Material on stock
[checked]
X
Material is
not on stock
Material is
on stock
[Rosemann, Green, 2002]
CWM packages
Management
Warehouse Process
Analysis
Transformation
Resource
Relational
Foundation
Object
Model
Business
Information
Core
Warehouse Operation
OLAP
Record
Data Types
Information
Visualization
Data Mining
Expressions
Behavioral
Business
Nomenclature
Multi-Dimensional
XML
Keys and
Indexes
Type Mapping
Relationships
Software
Deployment
Instance
Packages/Metamodels
22
CWM packages layers
• Object layer - base metamodels/packages, which are
(re)used by the other metamodels/packages
• Foundation layer - extends the object layer with
services required which are (re)used by the other
metamodels/packages, e.g “unique key” in the Key
Indexes metamodel/package is used by relational
databases, OO-databases and record-oriented
• Resource layer - defines metamodels/packages for
various types of data resouces
• Analysis layer - analysis-oriented metadata
• Management layer - describing the data warehousing
process as a whole
[Poole et al, p.36-40 (2002)]
CWM packages relations
Core package
Element
ModelElement
Namespace
re
atu
rFe
Feature
sifie
Expression
s
Cla
StructuralFeature
Classifier
ProcedureExpression
Class
Attribute
Relational package
Datatype package
ColumnSet
NamedColumnSet
Table
Column
QueryExpression
QueryColumnSet
View
23
CWM classifyer equality
Object
Package
Classifier
(Klass)
Feature
(Attribut)
Relational
Schema
Table
Column
Record
Record
file
RecordDef
Field
Multi
Dimensional
Schema
Dimenson
Dimension
ed Objct
Element
Type
Attribute
XML
Schema
More about CWM
Tool Y
Metamodel
Common
Representation
Tool X
Metamodel
Tool Z
Metamodel
<<metamodels>>
CWM Packages
24
Business Dimensional Lifecycle
Technical
Technical
Architecture
Architecture
Design
Design
Product
Product
Selection
Selection &
&
Installation
Installation
Business
Business
Project
Project
Planning
Planning
Requirement
Requirement
Dimensional
Dimensional
Modeling
Modeling
Physical
Physical
Design
Design
Data
Data Staging
Staging
Design
Design &
&
Development
Development
Deployment
Deployment
Definition
Definition
End-User
End-User
Application
Application
Specification
Specification
Maintenance
Maintenance
and
and
Growth
Growth
End-User
End-User
Application
Application
Development
Development
Project
Project Management
Management
The Data Warehouse Architecture
Framework
Level of
detail
Data
ARCHITECTURE AREA
Back room
Front room
Infrastructure
Info needed
for better decisions
Enterprise models
How get,
transform,
make available
data
Major business
issues.
How measure
How analyse
HW/SW
capabilities
needed vs what
we have
Architecture
models and
documents
Focal events,
facts, dimensions
Dimensional
models
Capabilities
needed to get and
transform data
Major data stores
User’s needs
Major classes of
analyses
Priorities
Where is data
coming from
Calc and storage
reqs
Detailed
models and
specs
Logical and
physical models
Domains,
derivation rules
Standards, prods
to provide
capabilities
How hook together
Report layouts,
derivation
For whom, when
How interact with
capabilities
System utilties,
calls, APIs ...
Implementation
DB, indexes
backup ...
Write extracts,
loads
Automate process
Implement report
and analysis env
Build rpt
Train users
Install, test infrastructure. Connect
sourcesto targets
to desktop
Business
reqs and
audit
25