2. An overview of SDMX(What is SDMX? Part I)

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Edward CookEurostatUnit B5: “Central data and metadata services”

SDMX Basics course, 27-29 October 2015

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• A model to describe statistical data and

metadata

• A standard for automated communication from machine to machine

• A technology supporting standardised IT tools

What is SDMX?

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for which statisticians agree to use common descriptions and guidelines

driven by these common descriptors for all to reuse

developed as wide-ranging open source software

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• The SDMX Information model:

What is the information model underlying the data and metadata exchange between the partners?

• Content-oriented guidelines:

How to increase the interoperability and statistical harmonisation?

• IT Architecture for Data Exchange:

How to exchange the data?

Presentation of SDMX

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THE INFORMATION MODEL

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The Information Model:

… is a representation of concepts, relationships, constraints, rules and operations.

… is a formal way to:- express and design information needs- communicate with IT people- give specifications to reporting agents- document the system- drive the software

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What things does SDMX need to model?

• Statistical data• Through descriptor concepts. These concepts can be

further classified into dimensions, attributes and measures.

• Metadata• Structural metadata (such as concept names etc.)• Reference (or explanatory) metadata

• Data exchange processes 6

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Modelling statistical data in SDMX

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Key SDMX object concerning data:

Data Structure Definition (DSD)

• Identification of dimensions, attributes and measures

• Use of common codelists

• Integration into concept schemes

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Modelling reference metadata in SDMX

So much descriptive information. It needs to be expressed in a common, standard way.

Quality descriptions

Process descriptions

Methodological descriptions

Administrative descriptions

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The standard way is the Metadata Structure Definition (MSD)

A Metadata Structure Definition describes how metadata sets, containing reference metadata are organised.

In particular, it defines:- which metadata are being exchanged; - how these concepts relate to each other;- how they are represented (free text or coded values);- with which object types (agencies, data flows, data

providers, subsets of data flows, or others) they are associated.

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Modelling reference metadata in SDMX

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THE CONTENT-ORIENTED GUIDELINES

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Content-oriented guidelines

• The content-oriented guidelines are a set of recommendations within the scope of the SDMX standard in order to produce maximum interoperability.

• The SDMX standards:- provide essential support to statisticians;- maximise the amount of information through to

users;- allow an automation of the process;- allow web-service queries.

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There are three main areas in the content-oriented guidelines:

1. Statistical subject-matter domains.

2. Cross-domain concepts (and code lists).

3. A Metadata Common Vocabulary.

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Statistical subject-matter domains

• Statistical subject matter domains is a high level classification of statistical areas.

• They refer to statistical activities that have common characteristics with respect to variables, concepts and methodologies for data collection.

• Examples: price statistics, national accounts, environment statistics or education statistics.

• It is intended to cover the universe of official statistics.

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Functions of the classification of statistical domains.

• A standard against which domain lists of national and international organisations can be mapped to facilitate the exchange of data and metadata.

• Provides an identifier for registering and searching statistical data on SDMX registries.

• Navigation aide for the identification and organisation of corresponding domain groups.

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Cross-domain concepts

• They are a list of statistical concepts, related to statistical processes and data quality.

• The list is based on the concepts used by the contributing international organisations.

• The concepts can be used at the data side as well as at the metadata side.

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Examples of cross-domain concept

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Examples of cross-domain concept

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• A cross-domain concept may have a code list as presentation.

• This means that the concept might take a limited set of possible values enumerated in its corresponding code list.

• The code lists associated with cross-domain concepts are called cross-domain code lists.

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• Code lists have a general description, a list of codes, their description and annotations that provide additional information on the codes.

• Examples of cross-domain concepts and code list:• FREQ and its associated code list CL_FREQ.• SEX and its associated code list CL_SEX.

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Metadata Common Vocabulary

• The Metadata Common Vocabulary (MCV) is a vocabulary that recommends a common terminology to be used in order to facilitate communication and understanding

• The MCV is closely linked to the cross-domain concepts as it also contains all these concepts, stating their definitions and context descriptions.

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Metadata common vocabulary

• The MCV covers a selected range of metadata concepts:• General metadata concepts.• Metadata terms decribing statistical

methodologies and data quality.• Terms referring specifically to data and metadata

exchange.

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Examples of Metadata Common Vocabulary

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Examples of Metadata Common Vocabulary

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IT Architecture for data exchange

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• Standard formats for the exchange of data and metadata.• SDMX-EDI• SDMX-ML

• Architectures for data exchange:• Push• Pull• Data-hub

• SDMX Tools

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Push mode

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Pull mode

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Data Hub

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SDMX tools

• Eurostat tools at our SDMX Info Space https://webgate.ec.europa.eu/fpfis/mwikis/sdmx/index.php/Main_Page• SDMX Registry (a central repository for storing and sharing

SDMX artefacts). • SDMX Data Structure Wizard (used to create, edit and test

SDMX artefacts).• SDMX Converter (converts data files between SDMX formats

and other file formats). • SDMX Reference Infrastructure (SDMX-RI) (set of tools

that allows to connect your IT systems to the SDMX world). • SDMX Mapping Assistant (mapping and transcoding of the

contents of an existing database to SDMX data structures).

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SDMX toolsOther tools available in the community (

www.sdmxtools.org)

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Questions?