id: asdf://asdf-format.org/core/manifests/core-1.1.0
extension_uri: asdf://asdf-format.org/core/extensions/core-1.1.0
title: Core extension 1.1.0
description: Tags for ASDF core objects.
asdf_standard_requirement: 1.1.0
tags:
- tag_uri: tag:stsci.edu:asdf/core/asdf-1.0.0
  schema_uri: http://stsci.edu/schemas/asdf/core/asdf-1.0.0
  title: Top-level schema for every ASDF file.
  description: This schema contains the top-level attributes for every ASDF file.
- tag_uri: tag:stsci.edu:asdf/core/column-1.0.0
  schema_uri: http://stsci.edu/schemas/asdf/core/column-1.0.0
  title: A column in a table.
  description: |-
    Each column contains a name and an array of data, and an optional description
    and unit.
- tag_uri: tag:stsci.edu:asdf/core/complex-1.0.0
  schema_uri: http://stsci.edu/schemas/asdf/core/complex-1.0.0
  title: Complex number value.
  description: |-
    Represents a complex number matching the following EBNF grammar

    ```
      dot           = "."
      plus-or-minus = "+" | "-"
      digit         = "0" | "1" | "2" | "3" | "4" | "5" | "6" | "7" | "8" | "9"
      sign          = "" | plus-or-minus
      suffix        = "J" | "j" | "I" | "i"
      inf           = "inf" | "INF"
      nan           = "nan" | "NAN"
      number        = digits | dot digits | digits dot digits
      sci-suffix    = "e" | "E"
      scientific    = number sci-suffix sign digits
      real          = sign number | sign scientific
      imag          = number suffix | scientific suffix
      complex       = real | sign imag | real plus-or-minus imag
    ```

    Though `J`, `j`, `I` and `i` must be supported on reading, it is
    recommended to use `i` on writing.

    For historical reasons, it is necessary to accept as valid complex numbers
    that are surrounded by parenthesis.
- tag_uri: tag:stsci.edu:asdf/core/constant-1.0.0
  schema_uri: http://stsci.edu/schemas/asdf/core/constant-1.0.0
  title: Specify that a value is a constant.
  description: Used as a utility to indicate that value is a literal constant.
- tag_uri: tag:stsci.edu:asdf/core/history_entry-1.0.0
  schema_uri: http://stsci.edu/schemas/asdf/core/history_entry-1.0.0
  title: An entry in the file history.
  description: |-
    A record of an operation that has been performed
    upon a file.
- tag_uri: tag:stsci.edu:asdf/core/ndarray-1.0.0
  schema_uri: http://stsci.edu/schemas/asdf/core/ndarray-1.0.0
  title: An *n*-dimensional array.
  description: |-
    There are two ways to store the data in an ndarray.

    - Inline in the tree: This is recommended only for small arrays.  In
      this case, the entire ``ndarray`` tag may be a nested list, in
      which case the type of the array is inferred from the content.
      (See the rules for type inference in the ``inline-data``
      definition below.)  The inline data may also be given in the
      ``data`` property, in which case it is possible to explicitly
      specify the ``datatype`` and other properties.

    - External to the tree: The data comes from a [block](ref:block)
      within the same ASDF file or an external ASDF file referenced by a
      URI.
- tag_uri: tag:stsci.edu:asdf/core/software-1.0.0
  schema_uri: http://stsci.edu/schemas/asdf/core/software-1.0.0
  title: Describes a software package.
  description: General-purpose description of a software package.
- tag_uri: tag:stsci.edu:asdf/core/table-1.0.0
  schema_uri: http://stsci.edu/schemas/asdf/core/table-1.0.0
  title: A table.
  description: |-
    A table is represented as a list of columns, where each entry is a
    [column](ref:core/column-1.0.0)
    object, containing the data and some additional information.

    The data itself may be stored inline as text, or in binary in either
    row- or column-major order by use of the `strides` property on the
    individual column arrays.

    Each column in the table must have the same first (slowest moving)
    dimension.
- tag_uri: tag:stsci.edu:asdf/fits/fits-1.0.0
  schema_uri: http://stsci.edu/schemas/asdf/fits/fits-1.0.0
  title: A FITS file inside of an ASDF file.
  description: |-
    This schema is useful for distributing ASDF files that can
    automatically be converted to FITS files by specifying the exact
    content of the resulting FITS file.

    Not all kinds of data in FITS are directly representable in ASDF.
    For example, applying an offset and scale to the data using the
    `BZERO` and `BSCALE` keywords.  In these cases, it will not be
    possible to store the data in the native format from FITS and also
    be accessible in its proper form in the ASDF file.

    Only image and binary table extensions are supported.
- tag_uri: tag:stsci.edu:asdf/time/time-1.1.0
  schema_uri: http://stsci.edu/schemas/asdf/time/time-1.1.0
  title: Represents an instance in time.
  description: |-
    A "time" is a single instant in time.  It may explicitly specify the
    way time is represented (the "format") and the "scale" which
    specifies the offset and scaling relation of the unit of time.

    Specific emphasis is placed on supporting time scales (e.g. UTC,
    TAI, UT1, TDB) and time representations (e.g. JD, MJD, ISO 8601)
    that are used in astronomy and required to calculate, e.g., sidereal
    times and barycentric corrections.

    Times may be represented as one of the following:

    - an object, with explicit `value`, and optional `format`, `scale`
      and `location`.

    - a string, in which case the format is guessed from across
      the unambiguous options (`iso`, `byear`, `jyear`, `yday`), and the
      scale is hardcoded to `UTC`.

    In either case, a single time tag may be used to represent an
    n-dimensional array of times, using either an `ndarray` tag or
    inline as (possibly nested) YAML lists.  If YAML lists, the same
    format must be used for all time values.

    The precision of the numeric formats should only be assumed to be as
    good as an IEEE-754 double precision (float64) value.  If
    higher-precision is required, the `iso` or `yday` format should be
    used.
- tag_uri: tag:stsci.edu:asdf/unit/defunit-1.0.0
  schema_uri: http://stsci.edu/schemas/asdf/unit/defunit-1.0.0
  title: Define a new physical unit.
  description: |-
    Defines a new unit.  It can be used to either:

    - Define a new base unit.

    - Create a new unit name that is a equivalent to a given unit.

    The new unit must be defined before any unit tags that use it.
- tag_uri: tag:stsci.edu:asdf/unit/quantity-1.1.0
  schema_uri: http://stsci.edu/schemas/asdf/unit/quantity-1.1.0
  title: Represents a Quantity object from astropy
  description: |-
    A Quantity object represents a value that has some unit
    associated with the number.
- tag_uri: tag:stsci.edu:asdf/unit/unit-1.0.0
  schema_uri: http://stsci.edu/schemas/asdf/unit/unit-1.0.0
  title: Physical unit.
  description: |-
    This represents a physical unit, in [VOUnit syntax, Version 1.0](http://www.ivoa.net/documents/VOUnits/index.html).
    Where units are not explicitly tagged, they are assumed to be in VOUnit syntax.
- tag_uri: tag:stsci.edu:asdf/wcs/celestial_frame-1.1.0
  schema_uri: http://stsci.edu/schemas/asdf/wcs/celestial_frame-1.1.0
  title: Represents a celestial frame.
  description: Represents a celestial frame.
- tag_uri: tag:stsci.edu:asdf/wcs/composite_frame-1.1.0
  schema_uri: http://stsci.edu/schemas/asdf/wcs/composite_frame-1.1.0
  title: Represents a set of frames.
  description: Represents a set of frames.
- tag_uri: tag:stsci.edu:asdf/wcs/icrs_coord-1.1.0
  schema_uri: http://stsci.edu/schemas/asdf/wcs/icrs_coord-1.1.0
  title: Represents an ICRS coordinate object from astropy
  description: This object represents the right ascension (RA) and declination of
    an ICRS coordinate or frame. The astropy ICRS class contains additional fields
    that may be useful to add here in the future.
- tag_uri: tag:stsci.edu:asdf/wcs/spectral_frame-1.1.0
  schema_uri: http://stsci.edu/schemas/asdf/wcs/spectral_frame-1.1.0
  title: Represents a spectral frame.
  description: Represents a spectral frame.
- tag_uri: tag:stsci.edu:asdf/wcs/step-1.1.0
  schema_uri: http://stsci.edu/schemas/asdf/wcs/step-1.1.0
  title: Describes a single step of a WCS transform pipeline.
  description: Describes a single step of a WCS transform pipeline.
- tag_uri: tag:stsci.edu:asdf/wcs/wcs-1.0.0
  schema_uri: http://stsci.edu/schemas/asdf/wcs/wcs-1.0.0
  title: A system for describing generalized world coordinate transformations.
  description: ASDF WCS is a way of specifying transformations (usually from detector
    space to world coordinate space and back) by using the transformations in the
    `transform-schema` module.
