Workshop “Enhancing educational data quality in heterogeneous learning contexts using Pentaho Data Integration” by Alex Rayón Jerez (www.alexrayon.es). Heterogeneous data integration and quality normalization are sensitive issues to properly exploit learning data. In this hands-on tutorial, we will not only extract learning data from their databases, but also enhance data quality issues (granularities, dimensions, duplications, nulll values, etc.) through the use of Pentaho Data Integration. We will practice with the integration of learning data from technology-rich learning environments (LMS, Social Networks, wiki, etc.). It is required the use of a laptop with Pentaho Data Integration module already installed on it, but it is not required previous knowledge of Pentaho.
El Big Data y Business Intelligence en mi empresa: ¿de qué me sirve?
Enhancing educational data quality in heterogeneous learning contexts using pentaho data integration
1. Enhancing educational data
quality in heterogeneous
learning contexts using
Pentaho Data Integration
Learning Analytics Summer Institute, 2015
Alex Rayón Jerez
@alrayon, alex.rayon@deusto.es
June, 22nd, 2015
2. 2
Table of contents
● Introduction
● Why data quality?
● Data lifecycle
● Data quality framework
● Data quality plan
● ETL approach
● Tools
3. 3
Table of contents
● Introduction
● Why data quality?
● Data lifecycle
● Data quality framework
● Data quality plan
● ETL approach
● Tools
12. 12
Table of contents
● Introduction
● Why data quality?
● Data lifecycle
● Data quality framework
● Data quality plan
● ETL approach
● Tools
13. 13
Why data quality?
Data sources
Today we have so much data
that come in an unstructured
or semi-structured form that
may nonetheless be of value in
understanding more about our
learners
14. 14
Why data quality?
Data sources (II)
“Learning is a complex social activity”
[Siemens2012]
Lots of data
Lots of tools
Humans to make sense
15. 15
Why data quality?
Data sources (III)
● The world of technology has changed
[Eaton2012]
o 80% of the world’s information is unstructured
o Unstructured data are growing at 15 times the rate
of structured information
o Raw computational power is growing at such an
enormous rate that we almost have a supercomputer
in our hands
o Access to information is available to all
16. 16
Why data quality?
Data sources (IV)
Source: http://www.bigdata-startups.com/BigData-startup/understanding-sources-big-data-infographic/
19. 19
Why data quality?
Challenges
● Data is everywhere
● Data is inconsistent
o Records are different in each system
● Performance issues
o Running queries to summarize data for
stipulated long period takes operating
system for task
o Brings the OS on max load
● Data is never all in Data Warehouse
o Excel sheet, acquisition, new application
20. 20
Why data quality?
Challenges (II)
● Data is incomplete
● Certain types of usage data are not logged
● Data are not aggregated following a
didactical perspective
● Users are afraid that they could draw
unsound inferences from some of the data
[Mazza2012]
21. 21
Why data quality?
Development of common language for data exchange
The IEEE defines
interoperability to be:
“The ability of two or more
systems or components to
exchange information and
to use the information that
has been exchanged”
22. 22
Why data quality?
Development of common language for data exchange (II)
● The most difficult challenges with achieving
interoperability are typically found in
establishing common meanings to the data
● Sometimes this is a matter of technical
precision
o But culture – regional, sector-specific, and
institutional – and habitual practices also affect
meaning
23. 23
Why data quality?
Development of common language for data exchange (III)
● Potential benefits
o Efficiency and timeliness
No need for a persona to intervene to re-enter, re-
format or transform data
o Independence
Resilience
o Adaptability
Faster, cheaper and less disruptive to change
o Innovation and market growth
Interoperability combined with modularity makes
it easier to build IT systems that are better
matched to local culture without needing to create
and maintain numerous whole systems
24. 24
Why data quality?
Development of common language for data exchange (IV)
● Potential benefits
o Durability of data
Structures and formats change over time
The changes are rarely properly documented
o Aggregation
Data joining might be supported by a common set
of definitions around course structure, combined
with a unified identification scheme
o Sharing
Specially when there are multiple parties involved
28. 28
Why data quality?
Importance
● Data quality emerged as an academic
research theme in the early 90’s
● In large companies, awareness of the
importance of quality is much more recent
● The core of any business process where data
is the main asset
○ Why?
■ Poor decision taking process
■ Time to fix the errors
■ ...
29. 29
Why data quality?
Meaning
● The primary meaning of
data quality is data suitable
for a particular purpose
○ Fitness for use
○ Conformance to requirements
○ A relative term depending on
the customers’ needs
● Therefore the same data can
be evaluated to varying
degrees of quality according
to users’ needs
Fuente:
http://mitiq.mit.edu/iciq/pdf/an%20evaluation%20framework%20for%20dat
a%20quality%20tools.pdf
30. 30
Why data quality?
Meaning (II)
● How well the representation model lines up
with the reality of business processes in the
real world [Agosta2000]
● The different ways in which the project
leader, the end-user or the database
administrator evaluate data integrity
produces a large number of quality
dimensions
31. 31
Why data quality?
Where are problems generated?
Data entry
External data integration
Loading errors
Data migrations
New applications
32. 32
Índice de contenidos
● Introduction
● Why data quality?
● Data lifecycle
● Data quality framework
● Data quality plan
● ETL approach
● Tools
35. 35
Data lifecycle
Knowledge Discovery in Databases (II)
SQL
XML
CSV
...
Data
Management /
Integration
Ciclo /
Proceso
datos
Modelo
datos
Dashboard
Report
API
36. 36
Table of contents
● Introduction
● Why data quality?
● Data lifecycle
● Data quality framework
● Data quality plan
● ETL approach
● Tools
37. 37
Data quality framework
Measuring data quality
● A vast number of bibliographic references
address the definition of criteria for
measuring data quality
● Criteria are usually classified into quality
dimensions
○ [Berti1999]
○ [Huang1998]
○ [Olson2003]
○ [Redman2001]
○ [Wang2006]
39. 39
Data quality framework
Dimensions
● A dimension captures a facet (at a high level)
of the quality
○ Completeness
○ Accuracy
○ Consistency
○ Relevancy
○ Uniqueness
[Goasdoué2007]
40. 40
Data quality framework
Dimensions (II)
QUALITY INDICATORS
Completeness
Accuracy
Consistency
Relevancy
Uniqueness
Do I have all the information?
Is my dataset valid?
Are there conflicts within my data?
Is my data useful?
Do I have repeated information?
41. 41
Data quality framework
Quality factors
Freshness Validity, age, volatility, opportunity,
obsolescence, etc.
Completeness Density, coverage, sufficiency, etc.
Data quantity Volume, data quantity, etc.
Interpretation Traceability, appearance, presentation,
modifiability, etc.
Understanding Clarity, meaning, readability,
comparability, etc.
Concise
representation
Uniqueness, minimality, etc.
Consistent
representation
Format, syntas, alias, semantic, version
control, etc.
42. 42
Data quality framework
Quality metrics
● A metric is the tool that permits us to measure
a quality factor
● We must define
○ The semantic (how it is measured)
■ i.e. amount of null values, time elapsed since the last update
○ The measurement units
■ i.e. response time in ms, GB volume, transaction/seg. quantity
○ The measurement granularity
■ i.e. error quantity in the whole table or in one attribute
■ Usual granularities: cell, triple, attribute, view, table, etc.
43. 43
Data quality framework
Quality methods
● A method is a process that implements a
metric
● It is the responsible of obtaining a set of
measurements (in relation to a metric) for a
given database
● The method implementation is dependant of
the application and of the database structure
o i.e. to measure the time since the last update we can
Use database timestamps
Access to the update logs
Compare versions of the database
44. 44
Data quality framework
Dimensions: 1) Completeness
● Is a concept missing?
● Are there missing values in a column, in a
table?
● Are there missing values?
● Examples
○ Empty postal codes in the 50% of the records
45. 45
Data quality framework
Dimensions: 1) Completeness (II)
● Extensity
o The amount of entities/states of the reality
represented for solving our problem
● Intensity
o The amount of data of each entity/state of the data
model
47. 47
Data quality framework
Dimensions: 1) Completeness (IV)
● Density
o How much information about my entities do I have in
my information system?
o We need to measure the quantity of information and
the gap
o Some interpretations about missing values
They exist but I do not know them
It does not exist
I do not know if they exist
Factors: Completeness
48. 48
Data quality framework
Dimensions: 1) Completeness (V)
● Coverage
o How many entities does my information system
contain?
Closed world: a table contains all the states
Open world: a table contains some of the states
o We need to measure the quantity of of real world data
my information system contain
o Examples
From all my students, ¿how much do I know?
Which percentage of learning activities are registered in my
database?
Factors: Completeness
49. 49
Data quality framework
Dimensions: 1) Completeness (VI)
● Density factor
○ Density ratio: % of no null values
● Coverage factor
○ Coverage ratio: % of data within the data model
● Improvement opportunities
○ Crosschecking or external data acquisition
○ ƒImputation with statistical models
○ ƒStatistical smoothing techniques
Metrics: Completeness
50. 50
Data quality framework
Dimensions: 1) Completeness (VII)
● Completeness applies to values of items and
to columns of a table (no missing values in a
column) or even to an entire table (no missing
tuples in the table)
● Great attention is paid to completeness issues
where they are essential to the correct
execution of data processes
○ For example: the correct aggregation of learning
activities requires the presence of all activitiy lines
51. 51
Data quality framework
Dimensions: 2) Accuracy
● Closeness between a value v and a value v’
considered as the correct representation of
the reality that v aims to portray
● It indicates the lack of errors of the data
● It covers aspects that are intrinsic of the data
and aspects of the representation (format,
accuracy, etc.)
52. 52
Data quality framework
Dimensions: 2) Accuracy (II)
Dimension
Factors
Metrics
ACCURACY
Sintactic RepresentationSemantic
boolean
degrees
deviation
boolean
deviation scale
standard
deviation
granularity
SUMMARY
53. 53
Data quality framework
Dimensions: 2) Accuracy (III)
● Semantic accuracy
o The closeness between a value v and a real value v’
o We need to measure how well are represented real
world states within the information system
o Some problems that may arise
Data that do not correspond to any real world state
● i.e. An student that does not exist
Data that correspond to a wrong real world state
● i.e. Data that does not refer to the proper student
Data with errors in some attributes
● i.e. Data that refer to the correct student but with some wrong
attribute
Factors: Accuracy
54. 54
Data quality framework
Dimensions: 2) Accuracy (IV)
● Syntactic accuracy
o It refers to the closeness that exist between a value v and
the elements of the domain D
o We need to know if v corresponds to a correct value within
D, leaving aside if it corresponds to a real world value
o Some problems that may arise
Value errors: out-of-range values, orthographical
errors, etc .
● i.e. “Smiht” instead of “Smith” for a last name of a student
● i.e. 338 years
Standardization errors:
● i.e. for genre, “0” or “1”, instead of “M” or “F”
● i.e. in a foreign currency instead of €
Factors: Accuracy
55. 55
● Boolean
○ If data satisfies rules or not
● Standard deviation
○ If the accuracy error is within the standard deviation
or not
Metrics: Accuracy
Data quality framework
Dimensions: 2) Accuracy (V)
56. 56
Data quality framework
Dimensions: 2) Accuracy (VI)
Referentials vs.
Dictionaries
Verify semantic accuracy Verify syntactic accuracy
<key, value> pair List of valid values for a given domain
The key represents an element or a state of the
real world
A value represents an attribute of that element
57. 57
Data quality framework
Dimensions: 2) Accuracy (VII)
● It is often connected to precision, reliability
and veracity
○ In the case of a phone number, for instance, precision
and accuracy are equivalent
● In practice, despite the attention given to
completeness, accuracy is often a poorly
reported criterion since it is difficult to
measure and often leads to high repair costs
● This is due to the fact that accuracy control and
improvement requires external reference
data
58. 58
Data quality framework
Dimensions: 2) Accuracy (VIII)
● In practice, this comes down to comparing
actual data to a true counterpart (for
example by using a survey)
● The high costs of such tasks leads to less
ambitious verifications such as consistency
controls (for example French personal phone
numbers must begin with: 01, 02, 03, 04, 05)
or based on likelihood (disproportional ratios
of men versus women)
59. 59
Data quality framework
Dimensions: 3) Consistency
● Data are consistent if they respect a set of
constraints
● Data must satisfy some semantic rules
○ Integrity rules
■ All the database instances must satisfy properties
○ User rules
■ Not implemented in the database, but needed for
any given application
● Improvement opportunities
○ Definition of a control strategy
○ Comparison with another, apparently more reliable,
60. 60
Data quality framework
Dimensions: 3) Consistency (II)
● A consistency factor is based on a rule, for
example, a business rule such as “town address
must belong to the set of French towns” or
“invoicing must correspond to electric power
consumption”
○ Consistency can be viewed as a sub-dimension of
accuracy
● This dimension is essential in practice as
much as there are many opportunities to
control data consistency
61. 61
Data quality framework
Dimensions: 3) Consistency (III)
● Consistency can not be measured directly
○ It is defined by a set of constraints
● Instead, we often measure the percentage of
data which satisfy the set of constraints (and
therefore deduce rate of suspect data)
● Consistency only gives indirect proof of
accuracy
● In the context of data quality tools, address
normalisation and data profiling processes use
consistency and likelihood controls
63. 63
Data quality framework
Dimensions: 3) Consistency (V)
Factors: Consistency
● Domain integrity
o Rule satisfaction over the content of an attribute
i.e. age of the student must be between 0 and 120 years
● Intra-relation integrity
o Rule satisfaction within attributes of the same table
Functional dependencies
Value dependencies
Conditional expressions
● Inter-relation integrity
o Rule satisfaction among attributes of different tables
Inclusion dependencies (foreign key, referential integrity,
64. 64
Data quality framework
Dimensions: 3) Consistency (VI)
Metrics: Consistency
● Boolean
o If data satisfies rules or not
o Granularity could be the cell or a set of cells
● Aggregation
o Integrity ratio: % of data that satisfy the rules
o Since it can exist a variety of rules for a same
relationship (or group of relations), in general, we
build a weighted sum of the results after measuring
those rules
65. 65
Data quality framework
Dimensions: 4) Relevancy
● Is the data useful for the task at hand?
● Relevancy corresponds to the usefulness of
the data
○ Database users usually access huge volumes of data
● Among all this information, it is often difficult
to identify that which is useful
○ In addition, the available data is not always adapted to
user requirements
○ For this reason users can have the impression of poor
relevancy, leading to loss of interest in the data(base)
66. 66
Data quality framework
Dimensions: 4) Relevancy (II)
● Relevancy is very important because it plays a
crucial part in the acceptance of a data
source
● This dimension, usually evaluated by rate of
data usage, is not directly measurable by the
quality tools
67. 67
Data quality framework
Dimensions: 4) Relevancy (III)
● It indicates how updated is the data
o Are they current enough for our needs?
o Are they updated or obsolete?
o Do we have the most recent data?
o Do we update the data?
● It has a temporary perspective
o When were those data created/updated?
o When did we check those data?
69. 69
Data quality framework
Dimensions: 4) Relevancy (V)
Factors: Relevancy
● Present
o Are in force the data of my information system?
A data model is a view of the entities and states of a given
reality in a given moment
i.e.
● Student data (address, email addresses, etc.)
● Grades (exercises, courses, etc.)
We need to measure the difference between existing data and
valid data
70. 70
Data quality framework
Dimensions: 4) Relevancy (VI)
Factors: Relevancy
● Opportunity
o Are in force the data of my information system?
How updated are my data for the task we have
The data we have in our information system can be recently
updated but no relevant for the task in force for having
arrived late
i.e.
● Activity improvement obtained after having finished the
course
● Teaching method improvement after having finished the
course
We need to measure the moment of opportunity of our data
71. 71
Data quality framework
Dimensions: 4) Relevancy (VII)
Factors: Relevancy
● Volatility
o How unstable are my data?
It characterizes the frequency within my data changes over
time
It is an intrinsic characteristic of the nature of data
i.e.
● Born date has 0 volatility
● Average degree has high volatility
We need to measure the time interval within data are still
valid
72. 72
Data quality framework
Dimensions: 4) Relevancy (VIII)
Metrics: Relevancy
● Present
o Temporary: query moment - first modification without
update in the database
o Boolean: data is updated or not
● Opportunity
o On time: if it is updated and arrived on time for the
task in force
● Volatility
o Frequency: how often changes happen
73. 73
Data quality framework
Dimensions: 5) Uniqueness
● It indicates the duplicity levels of the data
o The duplicity happens when a same entity is
represented two or more times in the information
system
o A same entity can be identified under different ways
i.e. A teacher is identified by his/her email address; a student
is identified by the enrollment id. But some students could in
the future become teachers.
o A same entity can be two times represented due to
errors on the key
i.e. an id badly digitalized
o A same entity can be repeated with different keys
i.e. A teacher is identified by email address; but can have
more than one
75. 75
Data quality framework
Dimensions: 5) Uniqueness (III)
Factors: Uniqueness
● No-duplicity
o There is duplicity if the same entity appears repeated
Key values and attributes match (or are nulls in some triples)
● No-contradiction
o There is contradiction if the same entity appears
repeated with different values
Key values could be the same or not
There are some differences in the values of some attributes
(not null)
76. 76
Data quality framework
Dimensions: 5) Uniqueness (IV)
Metrics: Uniqueness
● Boolean
o If the data is duplicated or not
o If the data has contradictions or not
o Granularity could be from the cell or from a given set
of cells
● Aggregations
o No-duplication ratio: % of data that are not duplicated
o No-contradiction ratio: % of data that are not
duplicated with contradictions
77. 77
Table of contents
● Introduction
● Why data quality?
● Data lifecycle
● Data quality framework
● Data quality plan
● ETL approach
● Tools
79. 79
Data quality plan
1) Data profiling
● It permits to locate, measure, monitorize and
report data quality problems
● It is a project itself
● Two types
o Structure
Position
Format
o Content
80. 80
Data quality plan
1) Data profiling (II)
● Structure profiling
o It consists on the data analysis without considering its
meaning
o Semi-automatic and massive
o Column profiling
81. 81
Data quality plan
1) Data profiling (III)
● Structure profiling
o Dependency profiling
o Redundancy profiling
Referential integrity
Foreign keys
82. 82
Data quality plan
1) Data profiling (IV)
● Structure profiling
o Example: for a given student
Name
● How much students do have name and last name?
● % of syntactic errors? (badly written)
● Consistency between the name and the sex?
Contact phone number
● Pattern recognition: 999 999 999 - 999.999.999, etc.
● Length
● Strange characters: . , -
etc.
83. 83
Data quality plan
1) Data profiling (V)
● Content profiling
o It analyses in depth the data and its meaning
o It is specific for each field
o It is realized in combination with dictionaries, specific
components of data treatment, etc.
84. 84
Data quality plan
2) Data cleansing
● We implement a reliable methodology of
data quality
○ Normalization
○ Deduplication
○ Standardization
● It permits:
○ Determine and separate a field elements relocating it
in its proper field
○ Format standardization
○ Fix errors within the data
○ Data enriching
85. 85
Data quality plan
2) Data cleansing (II)
● The data is normalized so that there is a
common unit of measure for items in a class
○ For example: feet, inches, meters, etc. are
all converted to one unit of measure
○ Adecuación de un dato a un formato
esperado
○ Ejemplo: NIF
■ 123456789
■ 0123456789B
86. 86
Data quality plan
2) Data cleansing (III)
● Or it contains duplicate records/items and
may have missing or incomplete descriptions
● Fixes misspellings, abbreviations, and errors
● The values are also standardized so that the
name of each attribute is consistent
● For example: inch, in., and the symbol “ are all
shown as inch
87. 87
Data quality plan
3) Data enriching
● Enrichment of data with more attributes,
images, and specifications
● We add some data that did not exist before
88. 88
Data quality plan
4) Data matching
● It is used to:
o Duplicate detection → unicity
o Establish a relationship between two data sources that
did not have linking fields before
o Identify a same entity within different sources that
provide different observations
● Two types
o Deterministic
By identifying the same code (A = A) or by relation of codes
(A = B)
o Probabilistic
A = B in a given % over assessed distances and lengths
89. 89
Data quality plan
4) Data matching (II)
● Data consolidation
o It usually consists on the fusion of two or more
records in the same
o It has been traditionally used for duplicate detection
o It is based on business rules
Record survival
Best record
Best attribute of a given record
o The result is called Golden Record
90. 90
Table of contents
● Introduction
● Why data quality?
● Data lifecycle
● Data quality framework
● Data quality plan
● ETL approach
● Tools
91. 91
ETL approach
Definition and characteristics
● An ETL tool is a tool that
o Extracts data from various data sources (usually
legacy data)
o Transforms data
from → being optimized for transaction
to → being optimized for reporting and analysis
synchronizes the data coming from different
databases
data cleanses to remove errors
o Loads data into a data warehouse
92. 92
ETL approach
Why do I need it?
● ETL tools save time and money when
developing a data warehouse by removing
the need for hand-coding
● It is very difficult for database administrators
to connect between different brands of
databases without using an external tool
● In the event that databases are altered or new
databases need to be integrated, a lot of hand-
coded work needs to be completely redone
94. 94
ETL approach
Kettle (II)
● It uses an innovative meta-driven approach
● It has a very easy-to-use GUI
● Strong community of 13,500 registered
users
● It uses a stand-alone Java engine that
process the tasks for moving data between
many different databases and files
98. 98
ETL approach
Kettle (VI)
● Datawarehouse and datamart loads
● Data integration
● Data cleansing
● Data migration
● Data export
● etc.
99. 99
ETL approach
Transformations
● String and Date Manipulation
● Data Validation / Business Rules
● Lookup / Join
● Calculation, Statistics
● Cryptography
● Decisions, Flow control
● Scripting
● etc.
100. 100
ETL approach
What is good for?
● Mirroring data from master to slave
● Syncing two data sources
● Processing data retrieved from multiple
sources and pushed to multiple
destinations
● Loading data to RDBMS
● Datamart / Datawarehouse
o Dimension lookup/update step
● Graphical manipulation of data
101. 101
Table of contents
● Introduction
● Why data quality?
● Data lifecycle
● Data quality framework
● Data quality plan
● ETL approach
● Tools
103. 103
Tools (II)
Interactive Data Transformation Tools (IDTs)
1. Pentaho Data Integration: Kettle PDI
2. Talend Open Studio
3. DataCleaner
4. Talend Data Quality
5. Google Refine
6. Data Wrangler
7. Potter's Wheel ABC
104. 104
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106. Enhancing educational data
quality in heterogeneous
learning contexts using
Pentaho Data Integration
Learning Analytics Summer Institute, 2015
Alex Rayón Jerez
@alrayon, alex.rayon@deusto.es
June, 22nd, 2015