Notes:
The XCEDE schema provides an extensive metadata hierarchy for
describing and documenting research and clinical studies. The
schema organizes information into five general hierarchical levels:
•a complete project
•studies within a project
•subjects involved in the studies
•visits for each of the subjects
•the full description of the subject's participation during each
visit
Each of these sub-schemas is composed of information relevant to
that aspect of an experiment and can be stored in separate XML
files or spliced into one large file allowing for the XML data to
be stored in a hierarchical directory structure along with the
primary data. Each sub-schema also allows for the storage of data
provenance information allowing for a traceable record of
processing and/or changes to the underlying data. Additionally, the
sub-schemas contain support for derived statistical data in the
form of human imaging activation maps and simple statistical value
lists.
XCEDE was originally designed in the context of neuroimaging
studies and complements the Biomedical Informatics Research Network
(BIRN) Human Imaging Database, an extensible database and intuitive
web-based user interface for the management, discovery, retrieval,
and analysis of clinical and brain imaging data. This close
coupling allows for an interchangeable source-sink relationship
between the database and the XML files, which can be used for the
import/export of data to/from the database, the standardized
transport and interchange of experimental data, the local storage
of experimental information within data collections, and human and
machine readable description of the actual data.
The core XCEDE schema supports several major extensible components:
•A flexible experimental hierarchy: As illustrated in the above,
the XCEDE experiment hierarchy consists of several levels (project,
subject, visit, study, episode and acquisition) representing
divisions of experiment data at various granularities. Elements at
each level contain level-specific "info" elements, whose schema
types may be derived to store experiment-specific or data
modality-specific metadata. The linking mechanism between levels is
flexible enough to support the omission of levels if the schema
user finds them unnecessary.
•Experimental protocols: Specifications for order, number and time
of experimental components (e.g. assessments within a clinical
interview, scans within a scanning session, visits within a
project) are supported using a generic protocol element.
•Event data: XCEDE has elements to support time-interval-annotated
metadata such as behavioral stimulus/response data, per-timepoint
QA metrics, etc.
•Data provenance: The complete history of a processing stream can
be stored and propagated using provenance elements provided by the
XCEDE schema.
•Plus: application-specific file and analysis lists (catalogs),
interfaces to binary data, arbitrary user and application
annotations, derived data, and more.
Changes:
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