Pengantar Data Warehouse dan OLAP

Agenda

•Pengertian data warehouse•Model data multidimensi•Operasi-operasi dalam OLAP•Arsitektur data warehouse•Kegunaan data warehouse

Apa itu Data Warehousing?

• Data warehouse adalah koleksi dari data yang subject-oriented, terintegrasi, time-variant, dan nonvolatile, dalam mendukung proses pembuatan keputusan.

• Sering diintegrasikan dengan berbagai sistem aplikasi untuk mendukung pemrosesan informasi dan analisis data dengan menyediakan platform untuk historical data.

• Data warehousing: proses konstruksi dan penggunaan data warehouse.

Data warehouse -- subject oriented

• Data warehouse diorganisasikan di seputar subjek-subjek utama seperti customer, produk, sales.

• Fokus pada pemodelan dan analisis data untuk pembuatan keputusan, bukan pada operasi harian atau pemrosesan transaksi.

• Menyediakan sebuah tinjauan sederhana dan ringkas seputar subjek tertentu dengan tidak mengikutsertakan data yang tidak berguna dalam proses pembuatan keputusan.

Data warehouse -- terintegrasi

• Dikonstruksi dengan mengintegrasikan banyak sumber data yang heterogen. – relational database, flat file, on-line

transaction record

• Teknik data cleaning dan data integration digunakan– Untuk menjamin konsistensi dalam konvensi-

konvensi penamaan, struktur pengkodean, ukuran-ukuran atribut dll diantara sumber data yang berbeda. • Contoh: Hotel price: currency, tax, breakfast

covered, dll.– Data dikonversi ketika dipindahkan ke

warehouse.

Data Warehouse—Time Variant

• Data disimpan untuk menyediakan informasi dari perspektif historical, contoh 5-10 tahun yang lalu.

• Struktur kunci dalam data warehouse– Mengandung sebuah elemen waktu, baik

secara ekspisit atau secara implisit.

– Tetapi kunci dari data operasional bisa mengandung elemen waktu atau tidak.

Data Warehouse — Non-Volatile

• Data warehouse adalah penyimpanan data yang terpisah secara fisik yang ditransformasikan dari lingkungan operasional.

• Data warehouse tidak memerlukan pemrosesan transaksi, recovery dan mekanisme kontrol konkurensi.

• Biasanya hanya memerlukan dua operasi dalam pengaksesan data, yaitu initial loading of data dan access of data.

OLAP (on-line analitical processing)

• OLAP adalah operasi basis data untuk mendapatkan data dalam bentuk kesimpulan dengan menggunakan agregasi sebagai mekanisme utama.

• Ada 3 tipe:– Relational OLAP (ROLAP):– Multidimensional OLAP (MOLAP) – Hybrid OLAP (HOLAP) membagi data antara

tabel relasional dan tempat penyimpanan khusus.

Data Warehouse vs. Operational DBMS

• OLTP (on-line transaction processing)– Major task of traditional relational DBMS

– Day-to-day operations: purchasing, inventory, banking, manufacturing, payroll, registration, accounting, etc.

• OLAP (on-line analytical processing)– Major task of data warehouse system

– Data analysis and decision making

• Distinct features (OLTP vs. OLAP):– User and system orientation: customer vs. market

– Data contents: current, detailed vs. historical, consolidated

– Database design: ER + application vs. star + subject

– View: current, local vs. evolutionary, integrated

– Access patterns: update vs. read-only but complex queries

Dari tabel dan spreadsheet ke Kubus Data

• Data warehouse didasarkan pada model data multidimensional, dimana data dipandang dalam bentuk kubus data

• Kubus data, seperti sales, memungkinkan data dipandang dan dimodelkan dalam banyak dimensi

– Tabel dimensi, seperti item (item_name, brand, type), or time(day, week, month, quarter, year)

– Tabel fakta mengandung measures (seperti dollars_sold) dan merupakan kunci untuk setiap tabel-tabel dimensi terkait.

• n-D base cube dinamakan base cuboid. 0-D cuboid merupakan cuboid pada level paling tinggi, yang menampung ringkasan data dalan level paling tinggi, dinamakan apex cuboid. Lattice dari cuboid-cuboid membentuk sebuah data cube.

Cube: A Lattice of Cuboids

all

time item location supplier

time,item time,location

time,supplier

item,location

item,supplier

location,supplier

time,item,location

time,item,supplier

time,location,supplier

item,location,supplier

time, item, location, supplier

0-D(apex) cuboid

1-D cuboids

2-D cuboids

3-D cuboids

4-D(base) cuboid

Pemodelan Konseptual Data Warehouse

• Star schema: Sebuah tabel fakta di tengah-tengah dihubungkan dengan sekumpulan tabel-tabel dimensi.

• Snowflake schema: perbaikan dari skema star ketika hirarki dimensional dinormalisasi ke dalam sekumpulan tabel-tabel dimensi yang lebih kecil

• Fact constellations: Beberapa tabel fakta dihubungkan ke tabel-tabel dimensi yang sama, dipandang sebagai kumpulan dari skema star, sehingga dinamakan skema galaksi atau fact constellation.

Hirarki Konsep: Dimensi (Lokasi)

all

Europe North_America

MexicoCanadaSpainGermany

Vancouver

M. WindL. Chan

...

......

... ...

...

all

region

office

country

TorontoFrankfurtcity

Tampilan datawarehouse dan hirarki

Specification of hierarchies

• Schema hierarchyday < {month <

quarter; week} < year

• Set_grouping hierarchy{1..10} < inexpensive

Data Multidimensional

• Sales volume sebagai fungsi dari product, month, dan region

Pro

duct

Regio

n

Month

Dimension: Product, Location, TimeHierarchical summarization paths

Industry Region Year

Category Country Quarter

Product City Month Week

Office Day

Cuboid yang terkait dengan kubus

all

product date country

product,date product,country date, country

product, date, country

0-D(apex) cuboid

1-D cuboids

2-D cuboids

3-D(base) cuboid

Browsing kubus data

• Visualization• OLAP capabilities• Interactive manipulation

Operasi-operasi OLAP

• Roll up (drill-up): summarize data

– by climbing up hierarchy or by dimension reduction

• Drill down (roll down): reverse of roll-up

– from higher level summary to lower level summary or detailed data, or introducing new dimensions

• Slice and dice:

– project and select

• Pivot (rotate):

– reorient the cube, visualization, 3D to series of 2D planes.

• Other operations

– drill across: involving (across) more than one fact table

– drill through: through the bottom level of the cube to its back-end relational tables (using SQL)

Ilustrasi

• Ilustrasi untuk operasi-operasi pada data multidimensi.

Rancangan Data Warehouse: Business Analysis Framework

• Four views regarding the design of a data warehouse – Top-down view

• allows selection of the relevant information necessary for the data warehouse

– Data source view• exposes the information being captured, stored, and

managed by operational systems

– Data warehouse view• consists of fact tables and dimension tables

– Business query view • sees the perspectives of data in the warehouse from

the view of end-user

Proses Perancangan Data Warehouse

• Top-down, bottom-up approaches or a combination of both– Top-down: Starts with overall design and planning (mature)– Bottom-up: Starts with experiments and prototypes (rapid)

• From software engineering point of view– Waterfall: structured and systematic analysis at each step

before proceeding to the next– Spiral: rapid generation of increasingly functional systems,

short turn around time, quick turn around

• Typical data warehouse design process– Choose a business process to model, e.g., orders,

invoices, etc.– Choose the grain (atomic level of data) of the business

process– Choose the dimensions that will apply to each fact table

record– Choose the measure that will populate each fact table

record

Data Warehouse Back-End Tools and Utilities

• Data extraction:– get data from multiple, heterogeneous, and external

sources• Data cleaning:

– detect errors in the data and rectify them when possible

• Data transformation:– convert data from legacy or host format to warehouse

format• Load:

– sort, summarize, consolidate, compute views, check integrity, and build indicies and partitions

• Refresh– propagate the updates from the data sources to the

warehouse

Three Data Warehouse Models

• Enterprise warehouse– collects all of the information about subjects spanning the

entire organization

• Data Mart– a subset of corporate-wide data that is of value to a

specific groups of users. Its scope is confined to specific, selected groups, such as marketing data mart

• Independent vs. dependent (directly from warehouse) data mart

• Virtual warehouse– A set of views over operational databases– Only some of the possible summary views may be

materialized

Data Warehouse Development: A Recommended Approach

Define a high-level corporate data model

Data Mart

Data Mart

Distributed Data Marts

Multi-Tier Data Warehouse

Enterprise Data Warehouse

Model refinementModel refinement

OLAP Server Architectures

• Relational OLAP (ROLAP) – Use relational or extended-relational DBMS to store and

manage warehouse data and OLAP middle ware to support missing pieces

– Include optimization of DBMS backend, implementation of aggregation navigation logic, and additional tools and services

– greater scalability

• Multidimensional OLAP (MOLAP) – Array-based multidimensional storage engine (sparse matrix

techniques)– fast indexing to pre-computed summarized data

• Hybrid OLAP (HOLAP)– User flexibility, e.g., low level: relational, high-level: array

• Specialized SQL servers– specialized support for SQL queries over star/snowflake

schemas

Data Warehouse Usage

• Three kinds of data warehouse applications– Information processing

• supports querying, basic statistical analysis, and reporting using crosstabs, tables, charts and graphs

– Analytical processing

• multidimensional analysis of data warehouse data

• supports basic OLAP operations, slice-dice, drilling, pivoting

– Data mining

• knowledge discovery from hidden patterns

• supports associations, constructing analytical models, performing classification and prediction, and presenting the mining results using visualization tools.

• Differences among the three tasks

From On-Line Analytical Processing to On Line Analytical Mining (OLAM)

• Why online analytical mining?– High quality of data in data warehouses

• DW contains integrated, consistent, cleaned data– Available information processing structure surrounding

data warehouses

• ODBC, OLEDB, Web accessing, service facilities, reporting and OLAP tools

– OLAP-based exploratory data analysis

• mining with drilling, dicing, pivoting, etc.– On-line selection of data mining functions

• integration and swapping of multiple mining functions, algorithms, and tasks.

• Architecture of OLAM

An OLAM Architecture

Data Warehouse

Meta Data

MDDB

OLAMEngine

OLAPEngine

User GUI API

Data Cube API

Database API

Data cleaning

Data integration

Layer3

OLAP/OLAM

Layer2

MDDB

Layer1

Data Repository

Layer4

User Interface

Filtering&Integration Filtering

Databases

Mining query Mining result

Referensi

• Data Mining: Concepts and Techniques 3rd Ed Jiawei Han, Micheline Kamber and, Jian Pei 2012

• Introduction to Data Mining by Tan, Steinbach, Kumar, 2004

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