MongoDB stores data (documents in MongoDB terms) in collections organized in databases (so the structure has two levels). There is one special database admin for user information, permissions and passwords. Some query operations can span collections in the same database, but usually not collections across databases.

Therefore polyDB uses just two databases inside a MongoDB instance: Data is stored in collections inside the database polyDB. Users and permissions are stored in admin.

In the MongoDB instance the polyDB uses just one database and organizes everything in collections within this database.

In polyDB objects are stored in polyDB collections, and these collections can be organized in (nested) sections. For each data collection there is an accompanying collection containing meta information on the data. The name of the MongoDB collection is composed from the collection and the chain of sections the collection is in. A family of objects collection organized in the subsection sub of section section is stored in the MongoDB collection section.sub.collection. The meta information is in _collectionInfo.section.sub.collection.

For example, the family of smooth reflexive polytopes is in the collection SmoothReflexive in the subsection Lattice of the section Polytopes. In terms of MongoDB, the dtaa is stored in the in the MongoDB collection Polytopes.Lattice.SmoothReflexive of the database polyDB, and the meta information is in _collectionInfo.Polytopes.Lattice.SmoothReflexive in the same database.

Any documentation for the sections and collections are in the collections _collectionInformation.section.sub.collection and _sectionInfo.section, _sectionInfo.section.sub etc.

Data in the data collection is described by two documents in the meta collection:

• a document for meta information. This document should have the following entries
  • description: A short description of the data, only for internal use, this will not be displayed.
  • maintainer: Maintainer of the data in polyDB, will be added to documents in the collection
  • creator: Name of person creating the data, will be added to documents in the collection
  • contributor: Name of the person who prepared the data for inclusion onto polyDB, will be added to documents in the collection
  • fields: A list of data fields contained in a document in the collection. This can be used to produce a list of data that can be queried from the collection.
  • polydb_version: the version of polyDB used to store the data
  • packages: Here software packages can store additional information they need to access the data
• a json schema: A json schema that completely describes the data. Each document in the collection should verify against this schema. MongoDB comes with its own internal schema verification methods. However, in polyDB we do not use this as it is based on an old draft of the schema language and has modifications from the standard. The schema is stored in a schema document with the three entries
  • section: the section of the collection the schema applies to
  • collection: the collection the schema applies to
  • schema: The actual json schema. Both json schemas and MongoDB use $ as a special character. We need to replace this in the schema for stroring as this would lead to conflicts otherwise. In polyDb we use __ (two underscores) for this.

The MongoDB _id of the info document is info.<polydb version> and of the schema document schema.<polydb version>, where <polydb version. is the polydb version number for which the two documents apply.