Attribute Convention for Data Discovery 1-2 Working
Version and Status
This version is designated as Version 1.2 beta.
This page is under development with updated definitions.
Introduction
This page consolidates ongoing work seeking to improve the definitions in the Attribute Convention for Data Discovery (ACDD).
The first 3 sections represent the terms in the corresponding sections of the ACDD.
Modifications relative to the original text may be seen with the history mechanism of this wiki. The original definitions are marked with the Summary keyword Original Definitions.
Process
The edits will be made in this page by anyone in the community who wishes to contribute, and discussed in greater depth in the Discussion page, if necessary. (The discussion page can also be used as an archive of changes on this page, if desired.)
Once there is some consensus about one or a group of definitions, they can be migrated to the primary document and the version number of that document incremented.
Working Definitions
Highly Recommended
- title
- A short phrase or sentence describing the dataset.
- summary
- A paragraph describing the dataset, analogous to an abstract for a paper.
- keywords
- A comma-separated list of key words and/or phrases. Keywords may be common words or phrases, terms from a controlled vocabulary, or URIs for terms from a controlled vocabulary (see keyword_vocabulary below).
Recommended
- id
- An identifier for the data set, provided by and unique within its naming authority. The combination of the "naming authority" and the "id" should be globally unique, but the id can be globally unique by itself also. IDs can be URLs, URNs, DOIs, meaningful text strings, a local key, or any other unique string of characters. The id should not include blanks.
- naming_authority
- The organization that provides the initial id (see above) for the dataset. The naming authority should be uniquely specified by this attribute.
- keywords_vocabulary
- If you are using a controlled vocabulary for the words/phrases in your "keywords" attribute, the unique name or identifier of the vocabulary from which keywords are taken. If more than one keyword vocabulary is used, each may be presented with a prefix (e.g., "CF:NetCDF COARDS Climate and Forecast Standard Names") and a following comma, so that keywords may optionally be prefixed with the controlled vocabulary key.
- cdm_data_type
- The organization of the data, as understood by THREDDS (a [1]THREDDS "dataType"]). One of Grid, Image, Station, Swath, and Trajectory. For points, profiles, and time series (described in this NODC guidance, use Station; for Trajectory Time Series, use Trajectory.
- history
- Describes the processes/transformations used to create this data. A simple description includes one line per process, listing the sources for each process; a more complete description can be provided using the ISO Lineage model, expressed per ISO 19139.
- comment
- Miscellaneous information about the data, not captured elsewhere.
- date_modified
- The date on which this dataset (as seen by users or captured in a file) was last changed.
- creator_person
- The name of the person principally responsible for originating this data.
- creator_person_info
- Additional information for the person principally responsible for the data in the file; can include any information as vcard, ISO 19139, or free text (vcard or ISO 19139 is recommended).
- creator_institution
- The institution that produced the data; should uniquely identify the institution.
- creator_institution_info
- Additional information for the institution that produced the data; can include any information as ISO 19139 or free text.
- creator_project
- The scientific project that produced the data; should uniquely identify the project.
- creator_project_info
- Additional information for the institution that produced the data; can include any information as ISO 19139 or free text.
- publisher_institution
- The institution that published the data; should uniquely identify the institution.
- publisher_institution_info
- Additional information for the institution that published the data; can include any information as ISO 19139 or free text.
- publisher_project
- The scientific project that published the data; should uniquely identify the project.
- publisher_project_info
- Additional information for the institution that published the data; can include any information as ISO 19139 or free text.
- processing_level
- A textual description of the processing (or quality control) level of the data.
- acknowledgement
- A place to acknowledge various type of support for the project that produced this data.
- geospatial_bounds
- Describes geospatial extent using any of the geometric objects (2D or 3D) supported by the Well-Known Text (WKT) format.
- geospatial_lat_min
- Describes a simple lower latitude limit; may be part of a bounding box or cube. Geospatial_lat_min specifies the southernmost latitude covered by the dataset.
- geospatial_lat_max
- Describes a simple upper latitude limit; may be part of a bounding box or cube. Geospatial_lat_max specifies the northernmost latitude covered by the dataset.
- geospatial_lon_min
- Describes a simple longitude limit; may be part of a bounding box or cube. Geospatial_lon_min specifies the westernmost longitude covered by the dataset. Cases where geospatial_lon_min is greater than geospatial_lon_max indicate the bounding box extends from geospatial_lon_max, through the longitude range discontinuity meridian (either the antimeridian for -180:180 values, or Prime Meridian for 0:360 values), to geospatial_lon_min.
- geospatial_lon_max
- Describes a simple longitude limit; may be part of a bounding box or cube. Geospatial_lon_max specifies the easternmost longitude covered by the dataset. Cases where geospatial_lon_min is greater than geospatial_lon_max indicate the bounding box extends from geospatial_lon_max, through the longitude range discontinuity meridian (either the antimeridian for -180:180 values, or Prime Meridian for 0:360 values), to geospatial_lon_min.
- geospatial_vertical_min
- Describes a numerically smaller vertical limit; may be part of a bounding box or cube. If geospatial_vertical_positive is up ('altitude' orientation), the geospatial_vertical_min attribute specifies the location closest to the earth's center covered by the dataset. If geospatial_vertical_positive is down ('depth' orientation), the geospatial_vertical_min attribute specifies the location furthest from the earth's center covered by the dataset.
- geospatial_vertical_max
- Describes a numerically larger vertical limit; may be part of a bounding box or cube. If geospatial_vertical_positive is up ('altitude' orientation), the geospatial_vertical_min attribute specifies the location furthest from the earth's center covered by the dataset. If geospatial_vertical_positive is down ('depth' orientation), the geospatial_vertical_min attribute specifies the location closest to the earth's center covered by the dataset.
- geospatial_vertical_positive
- One of 'up' or 'down'. If up, vertical values are interpreted as 'altitude', with negative values corresponding to below the reference datum (e.g., under water). If down, vertical values are interpreted as 'depth, positive values correspond to below the reference datum.
- time_coverage_start
- Describes the time of the first data point in the data set. ISO8601 format recommended.
- time_coverage_end
- Describes the time of the last data point in the data set. ISO8601 format recommended.
- time_coverage_duration
- Describes the duration of the data set. ISO8601 duration format recommended.
- time_coverage_resolution
- Describes the time period between each value in the data set.
- standard_name_vocabulary
- The unique name or identifier of the controlled vocabulary from which variable standard names are taken. If more than one controlled vocabulary is used, each may be presented with a prefix (e.g., "CF:NetCDF COARDS Climate and Forecast Standard Names") and a following comma, so that standard names may optionally be prefixed with the controlled vocabulary key.
- license
- Provide the URL to a standard or specific license, describe any restrictions to data access and distribution, or enter "Freely Distributed" or "None".
Suggested
- contributor_info
- The name and role of any individuals or institutions that contributed to the creation of this data. May be presented as free text, or in a format compatible with ISO 19139.
- date_created
- The first date on which this dataset was published (this value never changes after first set of data is released the first time).
- geospatial_lat_units
- Units for the latitude axis. These are presumed to be "degree_north"; other options from udunits may be specified instead.
- geospatial_lat_resolution
- Information about the resolution of the latitude. (Format is not prescribed.)
- geospatial_lon_units
- Units for the longitude axis. These are presumed to be "degree_east"; other options from udunits may be specified instead.
- geospatial_lon_resolution
- Information about the resolution of the longitude. (Format is not prescribed.)
- geospatial_vertical_units
- Units for the vertical axis. These are presumed to be "meter" (of depth); other options from udunits may be specified. Note that the common oceanographic practice of using pressure for a vertical coordinate, while not strictly a depth, can be specified using the unit bar.
- geospatial_vertical_resolution
- Further refinement of the geospatial bounding box can be provided by using these units and resolution attributes.
- converage_content_type
- Information about the content of the variable, valid values are image, thematicClassification, physicalMeasurement, auxiliaryInformation, qualityInformation, referenceInformation, modelResult, coordinate.
Issues for Discussion
The following terms were omitted from the previous version. We should determine if this is intentional and if so, we should determine if there is an equivalent concept.
- Metadata_Link
- See http://wiki.esipfed.org/index.php/Attribute_Convention_for_Data_Discovery_%28ACDD%29#Metadata_Link for definition. Also, we should determine our position on case sensitivity i.e. if we keep Metadata_Link, can we change the capitalization?
- Metadata_Convention
- While this term is not present in the table it is in the examples section. It is being used in practice (e.g. IOOS glider convention draft, and OceanSITES). In practice the following usage is observed: <attribute name="Metadata_Conventions" value="Unidata Dataset Discovery v1.0"/>. TODO: Determine if we will standardize the definition and usage. If we standardize usage, we should determine a recommended way of referring to ACDD and move past the Unidata reference.
Mappings ACDD to other metadata dialects
http://wiki.esipfed.org/index.php/Attribute_Convention_for_Data_Discovery_%28ACDD%29_Mappings
Recommended Order of Precedence
http://wiki.esipfed.org/index.php/Attribute_Convention_for_Data_Discovery_%28ACDD%29_Precedence