source: canSAS2012/docs/source/framework.rst @ 267

Last change on this file since 267 was 267, checked in by prjemian, 9 years ago

re-arrange and add to SAS basics

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Structure of the canSAS2012 data format

Goals

Description

Absolute minimum requirement for analysis of SAS data

Absolute minimum requirement for analysis of SAS data .

Minimum content recommended for reduced SAS data

Minimum content recommended for reduced SAS data.

Terms

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.. index:: ! SASroot
        groups; SASroot
SASroot:

derived from original 1D format, attributes have changed

Caution!

needs full write-up

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.. index:: ! SASentry
        groups; SASentry
SASentry:

derived from original 1D format, content and attributes have changed

Caution!

needs full write-up

SASentry groups have several attributes:

@name:

Text that describes this group. Must conform to the naming standard <naming standard> and must be unique within a SASentry group. Such as:

@name="sasentry01"
@version:

Describes the version of the canSAS standard used to write this data. This must be a text (not numerical) representation. Such as:

@version="1.0"
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.. index:: ! SASdata
        groups; SASdata
SASdata:

different use from original 1D format, refers to a single reduced data set that can be represented thus (such as from one detector)

SASdata groups have several attributes:

@name:

Text that describes this group. Must be unique within a SASentry group. Such as:

@name="sasdata01"
@I_axes:

Comma-separated list that describes the names of the data objects that correspond to the indices of the I data object. Such as:

@I_axes="Temperature,Time,Pressure,Q,Q"
@Q_indices:

Array that describes which indices (of the I data object) are used to reference the Q data object. The items in this array use zero-based indexing. Such as:

@Q_indices=1,3,4

which indicates that Q requires three indices from the I data object: one for time and two for Q position.

@Mask_indices:

Array that describes which indices (of the I data object) are used to reference the Mask data object. The items in this array use zero-based indexing. Such as:

@Mask_indices=3,4

which indicates that Q requires two indices from the I data object for Q position.

To indicate the dependency relationships of other varied parameters, use attributes similar to @Mask_indices (such as @Temperature_indices or @Pressure_indices).

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.. index:: ! data objects

Data Objects

Storage container [1] with numerical data for analysis or any kind of metadata. All data objects have attributes, some required, some optional. The name chosen for each data object must adhere to the naming standard described below.

@size:

(required for numerical arrays) Number of items in this data object. If the array is multi-dimensional, then the length of each index is reported individually, separated by commas. Such as:

size="100,512"

describes a 2-D array of 100 rows and 512 columns. Some implementations (such as HDF5 which uses shape) may provide native versions of the size. Use the native capability, when present.

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.. index:: !units
        Unidata UDunits
        UDunits
@units:(required for all numerical objects) Engineering units of this data object. Use the Unidata UDunits [2] specification as this is compatible with various community standards.
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.. index:: !uncertainty
@uncertainty:(optional for numerical arrays) Name of the data object (in this SASdata group) that provides the uncertainty to be used for data analysis.

Naming Standard

The names for data objects should follow a standard convention that starts with a letter (upper or lower case) and then letters, numbers, and "_". The length of the name is limited to no more than 63 characters (imposed by the rule HDF5 for names).

This standard convention may be described by the regular expression:

[A-Za-z][\\w_]*
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.. index:: ! uncertainty; supplemental

Supplementary Uncertainty Data

A special case discussed at canSAS2012.

Requires a named subdirectory below SASdata to contain the supplementary data. The name of the subdirectory is given in an attribute of the data object.

Contents:

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.. toctree::
   :maxdepth: 2
   metadata

Footnotes

[1]Such as an array or scalar or text. HDF5 calls this a dataset, Not a folder or a group or an object that contain other objects.
[2]

The :index:`UDunits` specification also includes instructions for derived units.

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