1. Peter Fox Data Science – ITEC/CSCI/ERTH Week 3, September 13, 2011
Data formats, metadata standards, conventions, reading and writing data and information
Peter Fox
Data Science – ITEC/CSCI/ERTH
Week 3, September 13, 2011

2. Contents Assignment on data collection plan Reading from last week
Data formats
Metadata standards, conventions,
Reading and writing data and information (embedded)
Next week (collecting data)

3. Data Formats We will cover some (not all) ASCII, UTF-8, ISO 8859-1
Self-describing formats
Table-driven
Markup languages and other web-based
Database
Graphs
Unstructured

4. ASCII American Standard Code for Information Interchange
Table of characters
ISO (aka ISO Latin 1) is a superset of ASCII – used on the web to represent ‘non-ASCII’ characters

5. Example – good or bad?
MONTHLY.PLT and MONTHLY

6. Example – good or bad?

7. Example – good or bad?
SW48-T0271.asc

8. Example – good or bad?
SW48-T0271.asc

9. EBCDIC Extended Binary-Coded Decimal Interchange Code IBM
7-bit, 8-bit, 9-bit
If someone mentions this just RUN away
Seriously, it is okay to convert

10. Making ASCII more useful
Delimited: CSV or tab or (gulp) ASCII space
Improves parsing
How to handle special characters?
How to handle ambiguous delimiters?
Templates
Encoding strings, e.g.
‘f7.4, c32, i8,f5.3,e9.4’

11. Reading and writing ASCII
Text editor (vi, emacs, wordpad)
Dangers exist in applications that add hidden formatting, i.e. characters
Even cr, lf (two ASCII characters, non-printable) can often cause major reading and interoperability problems
Procedural languages (e.g. C)
Interpreted languages (e.g. Perl)
Data structures are utilized (e.g. typed arrays, often multidimensional) to provide logical organization to data that is read in, or in preparation for writing it out

12. Data in applications
Increasing trend in storing data in application files, e.g. Excel, .mat (Matlab), .sav (IDL), …
What advantages?
Ready to use
Data structures are provided
What problems?
Data structures may not match the underlying data representation (model), i.e. information and data may be lost (e.g. float instead of double)
Format versions
Interoperability – can it be read by another app?

13. FreeForm
10+ years ago there was an attempt to provide a templated (almost table driven) approach
Good homework assignment when you are bored – find out why it was created and what happened to it

14. Spreadsheets
E.g. Excel – import data, Save As csv

15. Documentation?

16. CDF
Common Data Format
The Common Data Format (CDF) is a self-describing data format for the storage and manipulation of scalar and multidimensional data in a platform- and discipline-independent fashion
Although CDF has its own internal self describing format, it consists of more than just a data format. CDF is a scientific data management package (known as the "CDF Library") which allows programmers and application developers to manage and manipulate scalar, vector, and multi-dimensional data arrays

17. CDFML
The CDF office realized that scientific progress is often impeded by the lack of, or excessive multiplicity of, available standards for data formats and structures and/or data format translators. In a bid to facilitate and promote data sharing with other data formats, the CDF office has decided to adopt Extensible Markup Language (XML) as a basis for establishing interoperability with other scientific data formats and created CDF Markup Language (CDFML) to describe CDF data and metadata.

18. netCDF Network Common Data Format (and API)
Self describing – what does this mean?
Variables, dimensions, types, attributes, coordinates
nc_dump
nc_open
nc_inquire
nc_dim
nc_varget/ put
nc_attget/ put

20. NcML
NcML is an XML representation of netCDF metadata, (approximately) the header information one gets from a netCDF file with the "ncdump -h" command.
NcML is similar to the netCDF CDL (network Common data form Description Language), except, of course, it uses XML syntax.
NetCDF-Java library support -

21. HDF5
HDF5 is a data model, library, and file format for storing and managing data. It supports an unlimited variety of datatypes, and is designed for flexible and efficient I/O and for high volume and complex data.
HDF5 is portable and is extensible, allowing applications to evolve in their use of HDF5.
The HDF5 Technology suite includes tools and applications for managing, manipulating, viewing, and analyzing data in the HDF5 format.
VERY complex API

22. HDF4
At its lowest level, HDF is a physical file format for storing scientific data
At its highest level, HDF is a collection of utilities and applications for manipulating, viewing, and analyzing data in HDF files
Between these levels, HDF is a software library that provides high-level APIs and a low-level data interface

23. HDFEOS A variant of HDF for the Earth Observing System (EOS)
More under metadata later

24. HDFEOS Profiles over time

25. Common Data Model
Coming v 1.0 combines netCDF and HDF into one model, and API
Uses the underlying HDF format representation
Simplifies access

26. FITS
FITS stands for `Flexible Image Transport System' and is the standard astronomical data format endorsed by both NASA and the IAU.
FITS is much more than an image format (such as JPG or GIF) and is primarily designed to store scientific data sets consisting of multi-dimensional arrays (1-D spectra, 2-D images or 3-D data cubes) and 2-dimensional tables containing rows and columns of data.
Many APIs

27. TIFF/GeoTIFF Tagged Image File Format 24-bit support
GeoTIFF is a public domain metadata standard which allows georeferencing information to be embedded within a TIFF file.
The potential additional information includes projections, coordinate systems, ellipsoids, datums, and everything else necessary to establish the exact spatial reference for the file.
The GeoTIFF format is fully compliant with TIFF 6.0, so software incapable of reading and interpreting the specialized metadata will still be able to open a GeoTIFF file.
From wikipedia pages

28. RDBMS (in one slide)
A Relational database management system (RDBMS) is a database management system (DBMS) that is based on the relational model as introduced by E. F. Codd.
Most popular commercial and open source databases currently in use are based on the relational model.
A short definition of an RDBMS may be a DBMS in which data is stored in the form of tables and the relationship among the data is also stored in the form of tables.
From wikipedia
mysql

29. BUFR
Binary Universal Form for the Representation of meteorological data (BUFR) is a binary data format maintained by the World Meteorological Organization
The latest version is BUFR Edition 4
BUFR Edition 3 is also considered current for operational use

30. BUFR structure
A BUFR message is composed of six sections, numbered zero through five.
Sections 0, 1 and 5 contain static metadata, mostly for message identification.
Section 2 is optional; if used, it may contain arbitrary data in any form wished for by the creator of the message (this is only advisable for local use).
Section 3 contains a sequence of so-called descriptors that define the form and contents of the BUFR data product.
Section 4 is a bit-stream containing the message's core data and meta-data values as laid out by Section 3.The product description contained in Section 3 can be made sophisticated and non-trivial by the use of replication and/or operator descriptors.

31. GriB
GRIB (GRIdded Binary) is a mathematically concise data format commonly used in meteorology to store historical and forecast weather data
Significant amount of software available
See wikipedia page for more details

32. ESML
is an interchange technology that enables data (both structural and semantic) interoperability with applications without enforcing a standard format within the Earth science community.
Users can write external files using ESML schema to describe the structure of the data file.
Applications can utilize the ESML Library to parse this description file and decode the data format.
Software developers can build data format independent scientific applications utilizing the ESML technology.
Semantic tags can be added to the ESML files by linking different domain ontologies to provide a complete machine understandable data description.
ESML description file allows the development of intelligent applications that can now understand and "use" the data.

33. ESML Earth Science Markup Language http://esml.itsc.uah.edu/ Schema
Editor
Library
Tutorial
Application API - IDL

34. CSML http://csml.badc.rl.ac.uk/ Climate Science Markup Language
CSML is a standards-based data model and GML (Geography Markup Language) application schema for atmospheric and oceanographic data with associated software tools developed at the Rutherford Appleton Laboratory.
Java library at:

35. CSML Java code ProfileCoverage cov = ...;
PrintStream out = ...; // e.g. System.out
RecordType rangeType = cov.getRangeType();
out.println("<table>");
for (Record record : cov.getRange()) {
// Each Record is a row in the table
out.print("<tr>");
for (String memberName : rangeType.getMemberNames()) {
// Each member represents a different Phenomenon and
// is a column in the table.
out.print("<td>" + record.getValue(memberName) + "</td>"); }
out.println("</tr>");
out.println("</table>");
If you are generating an HTML table or CSV file from a ProfileCoverage that contains measurements of many phenomena at each vertical coordinate value, you will probably want to access the Coverage's collection of Records as follows:

36. RDF http://www.w3.org/RDF/ - Resource Description Framework
Read the introduction and overview
Graph representation and encoding
RDF the model and RDF/XML
Many tools, and very good language support
Becoming the foundation of ‘data on the web’, see

37. Metadata formats Fall into three categories
Unstructured and disconnected
With the data
‘Close’ to the data
See the ASCII example and contrast this with the netCDF example
Structure around metadata is very important
Vocabulary (constraints) are also very useful
We dream of contextual metadata…

38. Dublin Core
DCMI is an open organization engaged in the development of interoperable online metadata standards that support a broad range of purposes and business models.
ISO Standard of February 2003
ANSI/NISO Standard Z of May 2007
IETF RFC 5013 of August 2007
Metadata element set -
Metadata terms -

39. DC Type Vocabulary - Sect. 7
Collection
Dataset
Event
Image
InteractiveResource
MovingImage
PhysicalObject
Service
Software
Sound
StillImage
DCMI vo

40. Dcmi vocabulary model from http://dublincore

41. METS
The METS schema is a standard for encoding descriptive, administrative, and structural metadata regarding objects within a digital library, expressed using the XML schema language of the World Wide Web Consortium. The standard is maintained in the Network Development and MARC Standards Office of the Library of Congress, and is being developed as an initiative of the Digital Library Federation.

42. METS example

45. METS example profile

46. Time ISO 8601 specifies numeric representations of date and time.
helps to avoid confusion in international communication due to different national notations
increases the portability of computer user interfaces
Good read:
In XML encodings, see xsd:datetime

47. ISO 19xxx http://www.geoportal-idec.cat/geoportal/eng/familiaiso.html
Is a family of standards *yes real ones*
Covers
Geospatial
Features
Many more
How to read and write?

48. Spatial representation
ISO 19115:2003 defines the schema required for describing geographic information and services
It provides information about the identification, the extent, the quality, the spatial and temporal schema, spatial reference, and distribution of digital geographic data
ISO 19115:2003 is applicable to:
the cataloguing of datasets, clearinghouse activities, and the full description of datasets
geographic datasets, dataset series, and individual geographic features and feature properties.
From

49. Spatial representation
ISO 19115:2003 defines
mandatory and conditional metadata sections, metadata entities, and metadata elements
the minimum set of metadata required to serve the full range of metadata applications (data discovery, determining data fitness for use, data access, data transfer, and use of digital data)
optional metadata elements - to allow for a more extensive standard description of geographic data, if required
a method for extending metadata to fit specialized needs.
Though ISO 19115:2003 is applicable to digital data, its principles can be extended to many other forms of geographic data such as maps, charts, and textual documents as well as non-geographic data.
From

50. Spatial representation
ISO :2009 extends the existing geographic metadata standard by defining the schema required for describing imagery and gridded data
It provides information about the properties of the measuring equipment used to acquire the data, the geometry of the measuring process employed by the equipment, and the production process used to digitize the raw data
This extension deals with metadata needed to describe the derivation of geographic information from raw data, including the properties of the measuring system, and the numerical methods and computational procedures used in the derivation
The metadata required to address coverage data in general is addressed sufficiently in the general part of ISO

51. netCDF+CF
netCDF – good but there are NO required attributes or controlled vocabularies
In the atmospheric sciences, a group formed to developed COARDS –
And then CF – the climate and forecast conventions
The conventions define metadata that provide a definitive description of what the data in each variable represents, and the spatial and temporal properties of the data. This enables users of data from different sources to decide which quantities are comparable, and facilitates building applications with powerful extraction, regridding, and display capabilities.

52. CF standard names
E.g. air_pressure_at_cloud_base (def: cloud_base refers to the base of the lowest cloud, units: Pa)
Used in netCDF attribute fields

53. COARDS http://ferret.wrc.noaa.gov/noaa_coop/coop_cdf_profile.html
Cooperative Ocean/Atmosphere Research Data Service
For example, if an oceanographic netCDF file encodes the depth of the surface as 0 and the depth of 1000 meters as 1000 then the axis would use attributes as follows:
axis_name:units="meters"; 
axis_name:positive="down";
If, on the other hand, the depth of 1000 meters were represented as then the value of the positive attribute would have been "up". If the units attribute value is a valid pressure unit the default value of the positive attribute is "down”.

54. HDFEOS
This was an effort to add a profile/ convention for NASA use of HDF in the EOS mission
A lot of custom library software was built to use it (e.g. the IDL HDFEOS library)

55. More markup languages
GML - Geography Markup Language – developed as a way to standardize geographic representations (to facilitate interoperability) ISO 19136:2007
Stores data and metadata
Because it focuses on coordinates, is important as representing structural elements, such as points, lines, polygons used in a specific discipline
Features application schema to represent roads, rivers, etc.
Is stored statically as well as generated dynamically

56. Markup languages
KML – Keyhole Markup Language – developed as an interlingua for a specific application, i.e. Google Earth
Currently stores data and metadata
XML tag and nesting provides for embedding structure and associations between metadata and data
Uses other markup languages, e.g. GML
Currently, KML 2.2 utilizes certain geometry elements derived from GML These elements include point, line string, linear ring, and polygon.
Can contain links (external) to other content
Increasingly is now generated dynamically rather than being a storage format
KMZ – compressed version of KML

57. KML model

58. Wire protocols Data Access Protocol (www.opendap.org)
Devised as a superset protocol/ data structure so that any data format could be translated into it, serialized and transported over a network (and de-serialized)
At present (except caching) data is not stored in DAP ‘format’
We’ll cover this in more detail in a later class

59. What to do when none exist?
ISO 19109
UML and tools….

60. ISO 19109
ISO 19109:2005(E) defines rules for creating and documenting application schemas, including principles for the definition of features
Its scope includes the following
conceptual modeling of features and their properties from a universe of discourse
definition of application schemas
use of the conceptual schema language for application schemas
transition from the concepts in the conceptual model to the data types in the application schema
integration of standardized schemas from other ISO geographic information standards with the application schema.

61. Summary and discussion
What is in common about the data and metadata formats?
Many choices for both – what are the key criteria for choosing?
Read and write capability
Faithful representation of structure of data
Accurate representation of metadata with no (or minimal) loss of information

62. What is next Assignment 2 on the web today Assignment 1 due today
Next week (Collecting data)
Reading
Data formats: netCDF
Metadata resources
METS
OAI-PMH Protocol for Metadata Harvesting
Climate and Forecast (CF) conventions

63. Practical details for week 4
The preparation for collection is Assignment 1 which is the theoretical exercise, we aim to provide feedback on this before week 4
Week 4 will be to see how much of this translates into practice
Ground rules
Come with two data collection options
No one off collections, i.e. must be something you could repeat
This is an individual exercise, we will compare notes in class afterwards

64. Practical details for week 4 (ctd)
A write up will be required, details in Assignment 2
No analysis is required
Sources??
Images
Sound
Existing devices, sensors
Others?

65. Hosting data Access to a computer to place data?
http
ftp ?
Another option: a few machines hosted by x.tw.rpi.edu