This document provides an overview of data quality standards and their application to open data. It discusses ISO standards for data quality, including ISO 25012 which defines a data quality model. Key data quality characteristics like accuracy, completeness, consistency and understandability are explained. The document also presents two case studies on open data quality: Open Coesione portal data in Italy and public contract data from Italian universities. Various data quality measures defined in ISO 25024 are calculated for the case studies, and findings around areas like traceability, metadata and decentralized vs centralized disclosure are discussed.

1. Data Quality
Standards and Application to Open Data
February 21, 2018 – Brunel University, UK
Marco Torchiano
marco.torchiano@polito.it
Version 1.1.0
© Marco Torchiano, 2018

2. About me
 Marco Torchiano
 Associate Professor, Politecnico di Torino
 Senior Member IEEE
 Faculty Fellow – Nexa Center for Internet
and Society
 Member UNI CT504–Software Engineering
 Contacts:
– mailto:marco.torchiano@polito.it
– http://softeng.polito.it/torchiano/
– Twitter: @mtorchiano
3

3. Current Research Interests
 Mobile UI Automated Testing
 PhD student working on fragility
 (Open)Data Quality
 PhD student working on KB quality
 Software Energy Consumption
 Several collaborations
 Also: MDD, Survey methodology, code
obfuscation, SE education, …
4

4. Acknowledgments
 Antonio Vetrò
 The counterpart for
this line of research
 Many other people
 L.Canova, R.Iemma, F.Iuliano, F.Morando,
C.Orozco Minotas, G.Procaccianti,
R.Rashid
5

5. OPEN DATA QUALITY
7

6. Open Coesione
 portal about the fulfilment of
investments using the 2007-2013
European Cohesion funds
 Interactive Interface
 Downloadable .csv datasets
 ~100 billion Euros are being tracked,
~100K projects
 http://www.opencoesione.gov.it/

7. 9

8. Errors in data
10

9. 43 !
* extraction, transformation, and loading
11

10. Accuracy
12

11. » Refer always to raw data
» If not possible, estimate accuracy on analysis (e.g., about 5% in the example above)
43 !
13

12. Missing data
14

13. 15

14. »Outliers can point to interesting facts
Outliers
16

15. »… or to something which deserves a second look
Outliers
17

16. Valu
e
pcvc= percentage of cells with correct value
18

17. ISO DATA QUALITY
STANDARDS
19

18. ISO - SQuaRE
2503x
Quality
Requirements
2504x
Quality
Evaluation
2501x
Quality Model
2500x
Quality Management
2502x
Quality Measurement
Family of standards
20

19. ISO SQuaRE
 Internal Quality
 Values, formats, relation
 External Quality
 Technological environment
 Quality in Use
 Context of use of the data user
21

20. ISO 25012
Data Quality Model
22
2503x
Quality
Requirements
2504x
Quality
Evaluation
2501x
Quality Model
2500x
Quality Management
2502x
Quality Measurement

21. Roles
 Data Quality evaluator
 Data Producer
 Data Acquirer
 Data User
23

22. Data evaluator
 Defines/adapts a quality model
 Evaluate and act
 Data correction
 Technological adjustments
 Organizational measures
24

23. Model structure
 Characteristic
 Main aspects, e.g., usability
 Sub-Characteristic (optional)
 A detailed aspect of a characteristic, e.g.
Understandability
 Metric
 A set of rules to assign and interpret a
(numerical) evaluation to a specific (sub)-
characteristic
25

24. Characteristics
 Accuracy
 Completeness
 Consistency
 Credibility
 Currentness
 Accessibility
 Compliance
 Confidentiality
 Efficiency
 Precision
 Traceability
 Understandability
 Availability
 Portability
 Recoverability
26

25. Characteristics
 Accuracy
 Correspondence between data and reality
(syntactic and semantic)
 Completeness
 Computer: presence of all necessary
values
 User: how much the data is able to satisfy
the needs
 Consistency
 Absence of contradictions in the data
27

26. Characteristics
 Credibility
 The extent to which data are regarded as
true and credible by users
 Currentness
 the extent to which data is up-to-date
 Accessibility
 The capability of data to be accessed,
particularly by people who need
supporting technology or special
configuration because of some disability
28

27. Characteristics
 Regulatory compliance
 The capability of data to adhere to standards,
conventions or regulations in force and similar
rules relating to data quality
 Confidentiality
 The capability of the data to be accessed and
interpreted only by authorized users
 Efficiency
 The capability of data to be processed (accessed,
acquired, updated, etc) and to provide
appropriate levels of performance using the
appropriate amounts and types of resources
under stated conditions
29

28. Characteristics
 Precision
 Capability of the value assigned to an
attribute to provide the degree of
information needed in a stated context of
use
 Traceability
 Presence of attributes providing an audit trail
of access and changes made to data
 Understandability
 The extent to which data can be read and
interpreted by users
30

29. Characteristics
 Availability
 The capability of data to be always
retrievable.
 Recoverability
 The capability to preserve a specified level of
operations and its physical and logical
integrity, even in the event of failure
 Portability
 The capability of data to be moved to
another platform preserving quality
31

30. Inherent System
Dependent
Facts
(Data)
Artefacts
(D+Hw+Sw+Sys)
Accuracy
Completeness
Consistency
Credibility
Currentness
Accessibility
UnderstandabilityHCI
Support
Compliance
Confidentiality
Efficiency
Precision
Traceability
Perspectives
32
Availability
Portability
Recoverability

31. ISO 25024
Measurement of Data Quality
33
2503x
Quality
Requirements
2504x
Quality
Evaluation
2501x
Quality Model
2500x
Quality Management
2502x
Quality Measurement

32. Relationships among standards
ISO/IEC 25010
System and Software
Product Quality
ISO/IEC 25012
Data Quality
composed of
Quality characteristics
Quality sub-characteristics
composed of
Quality Measure
ISO/IEC 25022, 25023, 25024
Measuremen
t function
defines
composed of
Quality Measure Elements
QME
Measuremen
t method
ISO/IEC 25021
Property to quantifyTarget Entity
Source: ISO/IEC 25024 34

33. Data Life Cycle: examples
Data
design
Data
collection
Data
integration
External
data
acquisition
Source: ISO/IEC 25024
Data
processin
g
Presentation
Other use
Data store
Delete
35

34. Data design: target entities
 Architecture
 Contextual schema
 Data models (conceptual, logical,
physical)
 Data dictionary
 Document
36

35. Data design: properties
 Attribute
 Element
 Information
 Metadata
 Vocabulary
37

36. Other stages: target entities
 Data file
 DBMS
 RDBMS
 Form
 Presentation device
38

37. Properties
 Data format
 Data item
 Data value
 Information item
 Information item content
 Data record
39

38. Metrics definition
A) ID: abbreviated code of the quality characteristics +
(I/D)+serial number
b) Name: QM name related to data;
c) Description
d) Measurement function: formula showing how the QMEs
are combined to produce the QM;
e) DLC, Target entities, Properties: DLC includes stages of
the DLC where the data QMEs are applicable, target
entities and properties of target entities;
f) Note: in the note, additional information such as an
acceptable range of values, reference to other standards,
explanations or interpretation or criteria, measurement
method used to obtain the
40

39. ACCURACY (Acc-I-1)
Copyright: ISO/IEC 25024
42

40. CASE STUDIES
Open Government Data
50

41. Open Government Data
OD: open data, data that can be
 Used
 Reused
 Redistributed
 By anyone and with any goal
G: Government produced or commissioned
by a government or an institutional
entity controlled by the government
http://opengovernmentdata.org
51

42. Why OGD ?
 Transparency
 Social and commercial value
 Participation
52

43. Case 1: Open Coesione
 Published data
 Structured
 Open data format
OpenCoesione
Statistical data from municipalities
 Residents
 Weddings
 Commercial activities
60

44. Datasets analyzed
61
Orchestrated disclosure Decentralized disclosure
● Open Coesione
● portal about the
fulfilment of
investments using the
2007-2013 European
Cohesion funds
● 85 billion Euros are
being tracked, 850K
projects
Dataset
Torino
Roma
Milano
Firenze
Bologna
Residents X X X X X
Weddings X X X
Business
Activities
X X X

45. Open Coesione

46. Measures
Characteristic Description ISO name
Completeness
Percentage of complete cells Com-I-1 (cell)
Percentage of complete rows Com-I-1 (row)
Accuracy
Percentage of syntactically accurate
cells
Acc-I-1
Traceability
Track of creation Tra-D-2 ( c )
Track of update Tra-D-2 (u)
Currentness
Percentage of current rows Cur-I-2
Delay in publication ~Cur-I-1
Compliance
eGSM compliance Cmp-D-1
five stars open data Cmp-D-1
Understandability
Percentage of columns with metadata Und-I-3
Percentage of columns in
comprehensible format
Und-I-4
63

47. e.GMS
1. Accessibility (mandatory if
appl)
2. Addressee (optional)
3. Aggregation (optional)
4. Audience (optional)
5. Contributor (optional)
6. Coverage (recommended)
7. Creator (mandatory)
8. Date (mandatory)
9. Description (optional)
10. Digital signature (optional)
11. Disposal (optional)
12. Format (optional)
13. Identifier (mandatory if appl)
14. Language (recommended)
15. Location (optional)
16. Mandate (optional)
17. Preservation (optional)
18. Publisher (mandatory if appl)
19. Relation (optional)
20. Rights (optional)
21. Source (optional)
22. Status (optional)
23. Subject (mandatory)
24. Title (mandatory)
25. Type (optional)
UK - e-Governmant Metadata Standard
https://www.oasis-open.org/committees/download.php/7271/eGMS%20version%203.pdf 64

48. Results – Open Coesione
65
0.00 0.20 0.40 0.60 0.80 1.00
Com-I-1 (cell)
Com-I-1 (row)
Acc-I-1
Tra-D-2 ( c )
Tra-D-2 (u)
Cur-I-2
~Cur-I-1
Cmp-D-1
Cmp-D-1
Und-I-3
Und-I-4
Null/zero
values :
domain
uncertain
Track
updates
missing
Missing
metadata
data not
linked

49. 0 0.2 0.4 0.6 0.8 1
Com-I-1 (cell)
Com-I-1 (row)
Acc-I-1
Tra-D-2 ( c )
Tra-D-2 (u)
Cur-I-2
~Cur-I-1
Cmp-D-1
Cmp-D-1
Und-I-3
Und-I-4
Results – Municipality data
66
Discrepancies
of values with
domain
No info on
updates
Missing
metadata

50. Findings
 Disclosure strategy implies different
data quality
 Centralized vs.
 Decentralized
 Traceability is generally lacking
 Proposals to use Sw Conf Mgmt tools
 Metadata is often missing or
incomplete
67

51. Case 2: Public Contracts
 Published data
 Structured
 Open format
Data on public contracts ex Art.37
Decree Transparency + prescriptions
ANAC
68

52. Public contracts
 Decree Transparency (14 march 2013
n.33)
 Public contracts (Art.37 & Art 9.)
 Open Data Publication
 XML Standard Format (ANAC)
 Selected administrations: Italian
universities
69

53. Data Structure
XML
METADATA
DATA
LOTS
PARTICIPANTS
WINNER
70

54. <lotto>
<cig>4421574E47</cig>
<strutturaProponente>
<codiceFiscaleProp>00518460019</codiceFiscaleProp>
<denominazione>Politecnico di Torino</denominazione>
</strutturaProponente>
<oggetto>
Procedura di cottimo fiduciario per affidamento servizio di manutenzione e
assistenza di primo livello stazioni self-service
</oggetto>
<sceltaContraente>08-AFFIDAMENTO IN ECONOMIA - COTTIMO FIDUCIARIO</sceltaContraente>
<partecipanti>
<partecipante>
<codiceFiscale>06267040019</codiceFiscale>
<ragioneSociale>OVER S.A.S. DI VERGNANO CARLO & C.</ragioneSociale>
</partecipante>
</partecipanti>
<aggiudicatari>
<aggiudicatario>
<codiceFiscale>06267040019</codiceFiscale>
<ragioneSociale>OVER S.A.S. DI VERGNANO CARLO & C.</ragioneSociale>
</aggiudicatario>
</aggiudicatari>
<importoAggiudicazione>7500.00</importoAggiudicazione>
<tempiCompletamento>
<dataInizio>2014-09-01</dataInizio>
<dataUltimazione>2014-11-30</dataUltimazione>
</tempiCompletamento>
<importoSommeLiquidate>7500.00</importoSommeLiquidate>
</lotto>
71

55. Quality Evaluation Framework
Intrinsic
Dimensions
Domain
Dependent
Dimension Measure
Accuracy Percentage of elements
with correct values.
Completeness
Percentage of complete
elements.
Percentage of complete
aggregate elements.
Dimension Measure
Consistency Percentage of lots that
meet the Intrarelational
and Interrelational
Integrity Constraints.
Duplication Number of duplicates.
72

56. Identification of datasets
 First 25 universities of the overall ranking for
the 2014 provided by the newspaper Il Sole 24
Ore.
 Only 12 universities provide summary tables in
XML format.
Total numer of assessed lots: 123702
Average number of published lots:10308,5
 The remaining 13 universities either do not
provide the summary tables or they provide
summary tables but not in XML format.
73

57. CIG
74
The University of Torino
publishes summary tables that
have 100% cig completeness,
that is, the 100% of lots have the
cig element but about 32% of
them are out of domain.
1
0.94
0.9999
0.999
0.67
1
0.99
1
0.998
0.997
0.9998
0.99
1
1
1
1
1
1
1
1
1
1
1
1
0.600.700.800.901.00
UniBo
PoliMi
PoliTo
UniMi
UniTo
UniVe
UniUpo
UniFe
UniMib
UniPv
UniSa
UnivPm
Unique Tender Identifier
A lot of “00000000000”.

58. The element is present for
each lot but it is always
empty.
Choice of
contracting part
75
0.9999
0.998
0.9999
0
1
1
1
0.9991
1
1
1
1
1
1
1
1
1
1
1
0.999
1
1
1
1
0.000.200.400.600.801.00
UniBo
PoliMi
PoliTo
UniMi
UniTo
UniVe
UniUpo
UniFe
UniMib
UniPv
UniSa
UnivPm

59. All the lots published by
University of Milano have a
winner but no information about
the participants.
Fiscal Code
76
1
0.97
0.99
1
1
1
1
1
1
1
1
1
1
1
1
1
0.974
1
1
0.996
1
0.951
0.900.920.940.960.981.00
UniBo
PoliMi
PoliTo
UniMi
UniTo
UniVe
UniUpo
UniFe
UniMib
UniPv
UniSa
UnivPm

60. In 14% of lots the amount paid is
greater than the awarded amount.
Amount paid
vs. Total paid
78
0.87
0.97
0.96
0.9999
0.998
0.99
0.999
0.93
0.995
0.9999
0.98
0.98
0.800.850.900.951.00
UniBo
PoliMi
PoliTo
UniMi
UniTo
UniVe
UniUpo
UniFe
UniMib
UniPv
UniSa
UnivPm
PayedlessorequaltoAwarded

61. Final considerations
 ISO standard provides several
predefined measures
 Must be adapted to the case at hand
 Can be aggregated in different ways
 Possibility to define new measures
 ISO standard is intended for
structured data
 What about semantic knowledge bases?
79

62. References
 ISO/IEC 25012:2008, Software engineering — Software
product Quality Requirements and Evaluation (SQuaRE) —
Data quality model
 ISO 25024:2015, Software engineering — Software product
Quality Requirements and Evaluation (SQuaRE) —
Measurement of data quality
 Vetrò, Antonio; Canova, Lorenzo; Torchiano, Marco; Orozco
Minotas, Camilo; Iemma, Raimondo; Morando, Federico “Open
Data Quality Measurement Framework: Definition and
Application to Open Government Data”GOVERNMENT
INFORMATION QUARTERLY, Vol.33, pp.325-337, ISSN:0740-
624X
 Torchiano, Marco; Vetro', Antonio; Iuliano, Francesca
“Preserving the Benefits of Open Government Data by
Measuring and Improving Their Quality: An Empirical Study” in
IEEE 41st Annual Computer Software and Applications
Conference (COMPSAC 2017)
80