Databases Reference
In-Depth Information
CHAPTER 8
Organizing Data with References, Types,
and Dimension Scales
Your files aren't just a collection of groups, datasets, and attributes. Some of the best
features in HDF5 are those that help you to express relationships between pieces of your
data.
Maybe one of your datasets provides the
x
-axis for another, and you'd like to express
that in a way your colleagues can easily figure out. Maybe you want to record which
regions of a particular dataset are of interest for further processing. Or maybe you just
want to store a bunch of links to datasets and groups in the file, without having to worry
about getting all the paths right.
This chapter covers three of the most useful constructs in HDF5 for linking your various
objects together into a scientifically useful whole. References, the HDF5 “pointer” type,
are a great way to store links to objects as data. Named types let you enforce type con‐
sistency across datasets. And Dimension Scales, an HDF5 standard, let you attach phys‐
ically meaningful axes to your data in a way third-party programs can understand.
Let's get started with the simplest relational widget in HDF5: object references.
Object References
We've already seen how links in a group serve to locate objects. But there's another
mechanism that can do this, and crucially, this kind can be stored as data in things like
attributes and datasets.
Creating and Resolving References
Let's create a simple file with a couple of groups and a dataset:
