Module meta 

This module defines all the traits and types used by rustronomy to enable cross-format metadata. Crates in the rustronomy can translate these types into format-specific representations. This way, metadata can be transferred from one storage format to another.

A quick overview of the rustronomy metadata system

The rustronomy metadata system is built from two fundamental traits:

• MetaTag is implemented by types that specify metadata
• MetaContainer is implemented by types that contain metadata.

In addition to the “typed” metadata constructed from rust types implementing the MetaTag trait, rustronomy also supports “untyped” (or “stringly-typed”) metadata consisting of simple String (key, value) pairs. MetaContainer has methods for interacting with both.

Strongly-typed metadata vs stringly-typed metadata

The most important distinction between the typed metadata and the simple (key, value) string pairs is how rustronomy crates implementing specific storage formats are expected to handle them:

• Strongly typed metadata tags are to be encoded into a format-specific representation that conveys their meaning in a machine-readable manner, if this is supported by the specific format.
• Stringly typed metadata key-value pairs are to be interpreted as simple key-value pairs. As an example, the metadata struct Author is encoded by rustronomy-fits using the FITS AUTHOR keyword, whereas a string metadata entry with the key "Author" wouldn’t be parsed in any special way.

Furthermore, if a key-value string pair were to conflict with a strongly typed metadata entry, storage format implementations may ignore the conflicting string entry: strongly-typed entries take precedence over stringly-typed ones.

built-in metadata tags

In addition to these two traits, a bunch of pre-made types that implement the MetaTag trait can be found in the tags module, all of which are transferable between data storage formats.

The strongly-typed metadata system is in principle user-extendable. You can implement MetaTag for you own custom metadata tags, but there is no guarantee that these tags will be respected or parsed properly by implementations (since they are most likely not aware of your custom data type).

Modules

tags

This module contains all pre-defined strongly typed tags supported by rustronomy.

Macros

impl_meta_container

Traits

MetaContainer

Core trait that is implemented by all containers of rustronomy metadata types.

MetaTag

Core trait that must be implemented by all structs representing metadata.

MetaTagClone

This trait is a hack to enable cloning Box<dyn MetaTag> objects.