3.1 Metadata Classification
Croatian Bureau of Statistics developed its own metadata model called CROMETA based on Reference ModelTM from the MetaNet project of Eurostat. It includes also some specific metadata from CBS and has nine groups or sections of metadata. Metadata objects in each section are closely related, but there are relationships between metadata from different sections.
- Organizational structure - all metadata as regards the statistical office, related organizations, persons working within the organizations and the responsibility of the latter, is kept within this metadata section.
Examples of metadata objects belonging to this section are organization, person and contact person, etc.
- Variables and measurements - this section contains metadata about the variables collected within the frame of the statistical activity, as well as the methods and ways of measuring them. In this section the variables are described from a more general point, regardless of use and implementation in different studies/surveys.
Examples of metadata objects belonging to the section are global variable, object variable, value domain, measure unit, etc.
- Studies and questionnaires - all metadata as regards studies, their versions, general methods for performing them and other, is kept within this metadata section. (Study is a term used for more broad definition of statistical activities, and includes surveys and other activities).
Examples of metadata objects belonging to this section are study, study version, questionnaire, question, interview method, population, coverage type, etc.
- Classifications - this section contains metadata as concerns classifications used in statistical office.
Examples of metadata objects belonging to the section are classification family, classification, classification version, classification item, correspondence table, etc.
- Publications - contains all metadata concerning publishing and dissemination of statistics.
Examples of metadata objects belonging to this section are publication, edition, publication series, etc.
- Processing and validation rules - the Variables and measurements section describes the variables and the way of measuring them independent on implementation in a study/survey, and the Studies and questionnaires section handles all the metadata about studies and their methods. This metadata section could in some sense be described as the instance of variables and measurements put in the context of a study (or study version). E.g. the section contains all metadata as regards the methods for processing the studies, including validation, production process, registers/cubes/tables created etc.
Examples of metadata objects belonging to the section are context variable, data collection, statistical process, rule, matrix, register, cube, table, etc.
- General - general characteristics of metadata objects (which are often metadata objects themselves) are kept within this metadata section. Furthermore there are some metadata objects that are used within all or at least several other metadata sections, and therefore cannot be placed directly in any of them. Also these metadata objects are kept within the General metadata section.
Examples of metadata objects belonging to the section are language, keyword, footnote, status, theme, statistical object type, etc.
- Access and authorization rules - this metadata section stores metadata about who can do what with metadata and the data owned by CBS.
Examples of metadata objects belonging to the section are user group, privilege, access condition, access form, etc.
- History and version handling - metadata has a certain life-cycle as determined by the methods defined by the statistical office. This means that all metadata objects may exists in an indefinite number of versions and that the history management is extremely important in order to keep consistency in metadata and data over time. The main part of the history and version handling is implemented through methods used by other metadata objects, but one example of a metadata object belonging to the section is update information, used for logging all changes made to a metadata object over time.
This classification of metadata could be mapped the other classifications: e.g. navigational metadata as keywords can be found in general section, or quality metadata is included in the section of studies and questionnaires.
3.2 Metadata used/created at each phase
Today metadata management is done at several places, but intention is to create one central metadata repository and use a tool for metadata browsing and maintenance that should cover all the aspects of management. Metadata was first collected to fill the repository in metadata sections of organizational structure, general metadata, studies and measurements. There were several sources of metadata for this initialization: Annual Implementation Plan, database about publications, so-called inventory of metadata that was done before going to developing metadata model, etc.
Then metadata is available for other other applications that are part of statistical data production. The most important consumer of metadata is so-called Survey processor application. This is a metadata-driven application for automatic survey processing.
Survey processor is not only a consumer but also a producer of metadata. Metadata is captured during survey processing because it is the natural place where processing metadata is created. This metadata is immediately stored in the central repository. When a survey is processed, then following metadata is created: populations, questionnaires, questions, context variables, matrix variables, matrices, registers, cubes, tables, etc. This metadata can be easily used in metadata management tool to create new versions for next processing periods.
Data processing is the most important one from all phases of statistical business process where metadata is used and created. Initial metadata about surveys for processing phase are prepared in planning phase, but handled in Annual Implementation Plan that is independent from metadata management tools.
Additionally, some metadata are produced in dissemination phase (on publications). Hopefully more metadata will be collected in other phases of business process as the management tools develop in the future.
3.3 Metadata relevant to other business processes
Metadata sections Organizational structure contains metadata that could be used for management process. This means that persons who are responsible for specific processes are stored as contact persons for them (not only as contact persons regarding the statistical data and publications). Contact person has a role that can be for example head of department.
Section Access and authorization rules contains metadata that provide control over the access and management of statistical processes. User group has certain privileges that allow to group members to access and run specific process on statistical data.