Terminology¶
Catalog¶
In the Data Agency, this is the module that hosts the service to index, search, update, and delete entries in several indexes.
More information is available in the section describing the catalog.
Content Type¶
A media type is an identifier for file formats on the Internet.
application/atom+xml
It indicates the format of the representation of the metadata of the datasets.
Most of the content types will represent the metadata as a list of entries such as the Atom format.
Index¶
An index is a collection of entries in the Catalog that most of the time describe a dataset. For example, there is an index for Sentinel-1 data, another index for Landsat-8 data, and yet another index for your own data. An index is identified by a name (that must be all lowercase) and this name is used to refer to the index when performing indexing, search, update, and delete operations against the entries in it. Index names are unique in the cluster where they are hosted.
Type¶
Within an index, the entries are defined by one type. A type is a logical category/partition of your index whose semantics is defined according to a metadata model. In general, a type is defined for entries that have a set of common properties. One of the common type is Geo&Time that specifies spatial and temporal properties for an entry.
Entry¶
An entry is the basic object indexed in the catalog. Each entry has a unique identifier in an index. The other properties are specific to the Type that structures the entry.
Note
A set of one or more entries is always represented in a feed (e.g. Atom).
Collection¶
A collection is a reference to an abstract set of entries sharing one or more properties. A collection typically references a series in an index in the catalog or a data package in the portal.
Storage¶
In the Data Agency, this is the module that hosts the service to upload, download and delete data in the repositories.
More information is available in the section describing the storage.
Repository¶
This is the storage unit for uploading and downloading data files to/from the Storage. As per the indices, there is a repository for Sentinel-1 data, another index for Landsat-8 data, and yet another index for your own data. A repository is identified by a name (that must be all lowercase) and this name is used to refer to the repository when performing upload, download and delete operations against the data files in it. Repository names are unique in the cluster where they are hosted.
There are 3 types of repositories:
- Local repository: It is a storage unit where data are located on the Data Cluster. this is the usual type of repository for users, groups or community laboratories,
- Remote repository: It acts as a proxy for another third-party data source and abstract the access to this source as a repository,
- Virtual repository: This is an aggregation of any types of repository in a single one.
Dataset¶
A datset is a set of one or more data files in a repository. Each dataset is stored in a directory on the repository and are organised as in a file system.
Index and Repository Relationship¶
Indices and repositories names are usually linked, they are associated. The entries indexed in sentinel1 index describe the data stored in sentinel1 repository. There is usually one Entry describing a Dataset.
Data Cluster¶
A data cluster is a collection of one or more nodes (servers) that together brings an instance of the data agency and holds your entire documents and data. It provides federated indexing and search capabilities across all nodes. A cluster is identified by its host name. The prime data cluster is data.terradue.com and all the tools uses it by default.