1 Peter Fox Data Science – ITEC/CSCI/ERTH Week 4, September 23, 2009 Data formats, metadata standards, conventions, reading and writing data and information

Key Points Regarding Flu Epidemics Wash your hands often, especially after shaking hands with others (use hand disinfectants if there is no access to soap and water). Avoid close contact with people who are sick Cover your mouth and nose with a tissue when coughing or sneezing. If you don't have a tissue, use the inside of your elbow. Do not touch your eyes, nose, or mouth, especially after contact with shared keyboards, microscopes, instruments, or other people. STAY HOME-If you have flu-like symptoms (i.e., fever (100 degrees F [37.8 decrees C] or higher, cough, sore throat, runny or stuffy nose, body aches, headache, chills, fatigue). For more information

Contents Review assignment and data collection exercise Data formats Metadata standards, conventions, Reading and writing data and information (embedded) Next week (presenting your data) 3

Data Formats We will cover some (not all) –ASCII, UTF-8, ISO –Self-describing formats –Table-driven –Markup languages and other web-based –Database –Graphs –Unstructured 4

ASCII American Standard Code for Information Interchange mlhttp:// ml Table of characters e.asp e.asp ISO (aka ISO Latin 1) is a superset of ASCII – used on the web to represent ‘non- ASCII’ characters 5

Example – good or bad? 6

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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 19

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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 - java/index.html java/index.html 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. 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. 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 des/OperationalCodes.htmlhttp:// des/OperationalCodes.html 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 Schema Editor Library Tutorial Application API - IDL 34

CSML 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(" "); for (Record record : cov.getRange()) { // Each Record is a row in the table out.print(" "); for (String memberName : rangeType.getMemberNames()) { // Each member represents a different Phenomenon and // is a column in the table. out.print(" " + record.getValue(memberName) + " "); } out.println(" "); } out.println(" "); 36

RDF - Resource Description Frameworkhttp:// 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

DC Type Vocabulary - Sect. 7 Collection Dataset Event Image InteractiveResource MovingImage PhysicalObject Service Software Sound StillImage 40

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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 43

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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: time.htmlhttp:// time.html In XML encodings, see xsd:datetime – – 47

ISO 19xxx idec.cat/geoportal/eng/familiaiso.htmlhttp:// 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. 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. 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

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 standard-names/ 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 df_profile.htmlhttp://ferret.wrc.noaa.gov/noaa_coop/coop_c df_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 mission_profiles/docs/mission2.gifhttp://eospso.gsfc.nasa.gov/eos_homepage/ mission_profiles/docs/mission2.gif 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

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Wire protocols Data Access Protocol ( –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 UML and tools…. 60

ISO 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

Presenting your data ~10 min each Split over two weeks but all need to be prepared to present next week 4-5 slides MAX Present –The goal, and the mode of collection –How data was acquired –Physical and logical organization –Other ‘management’ aspects –Metadata and documentation collected/ stored –Some data in some form 63

What is next Assignment 2 on the wiki later today Assignment 1 grades will be sent to you tomorrow Next week (Presenting your data) Reading (none required this week) 64