Data formats

The Research Software Directory (Netherlands eScience center (n.d.)) was developed as a tool to find existing open source software/code that can be used during research.  

Data formats are often indicated by their MIME type. MIME stands for Multipart (Multipurpose) Internet Mail Extension. A more modern name for this is media type, but MIME type is still more established. MIME provides the operating system with information on how to handle a file.

A MIME type is written down as two indications separated by a slash (MIME type/subtype). Example: text/plain is the MIME type for plain text.

Many people recognise data formats by their extension. These are usually the three or four letters after the last point in the file name. For example, a movie on your computer has the extension .avi. The corresponding MIME type is video/msvideo. If the .avi movie is on a website, the URL doesn't have to end in .avi even when it is in fact an .avi. And an extension doesn't always have to be correct, for example when the file has been renamed. Someone might alter a file extension to .CH1 for 'chapter 1'. Also, several types of formats can use the same extension, for example .mid is used for a MIDI sound file as well as for the geographical map file Mapinfo Interchange Drawing. 

The advantage of using MIME types is that they are located in the 'http header' of a web page (which is invisible to the user), so the operating system knows with which program to open a clicked file.

MIME types in 4TU.Centre for Research Data

If you go to  4TU.ResearchData (n.d.), you will see MIME types in the left column (look in the left column under the heading Data format and click on 'more'). Application means that the file is related to a certain type of application or program. Strictly speaking, applications are data formats that are read by a particular application.

• application/pdf
  When exchanging programs, the layout of documents can sometimes be lost or shifted. To prevent this, applications exist that provide a universal view of the document. An example is a PDF document (Portable Document Format). This is an open and universal file format for the electronic exchange of documents in which the layout is retained.
• application/vnd.google-earth.kml +xml
  The geographical data for the above MIME types are encoded in such a way that they are readable in a so-called earth browser such as Google Earth, Google Maps, and Google Maps on your mobile. The indication '+xml' indicates that this is an xml file. You can view the content of these files with a regular text editor.
• application/gml+xml 
  GML stands for Geographic Markup Language: a standard way of describing geographical information. Geographical data describe the world in spatial terms, simply in plain text. It is a language that is independent of any form of visualisation of that data. In an earth browser the data is visualised. The indication '+xml' indicates an xml file. You can view the content of these files with a regular text editor.
• application/x-java-archive 
  A dataset associated with this MIME type is related to the Java programming language. "Archive" means that it is a container format to pack files and directories, such as zip.
• application/octet-stream 
  In this case, there is a general type of binary data that is not further defined. It is a residual category for all datasets for which it is not clear what it is or for which there is simply no separate MIME type.

 
The text formats plain, html and xml:

• text/plain means that the file consists of text. Often this is simply text without formatting, but any file that can be read with a text editor (such as notepad) is basically text/plain. However, you can sometimes give a more specific MIME type, such as text/xml or text/csv. In such a case, more specific is always better, because it gives more information.
• text/html (HyperText Markup Language) is a format that indicates what the information will look like on a website. You can use code to indicate what the text should look like: for example, printed or italic. This formatting is not present in plain text.
• text/xml (or application/xml). In XML (eXtensible Markup Language) you do not specify the format, but you can provide information about the content of the file, for example by adding metadata such as <title> for a title and <creator> for the person who created the document.
  Note that xml uses two different MIME types. This is not uncommon. Sometimes a text-based datatype uses application/... and not text/... because it is not meant to be viewed in a text editor, although it is possible.

Numerical data: 

• application/x-matlab data is an example of numerical data: Matlab is an advanced scientific calculator.
• HDF5 (application/x-hdf5) and NetCDF (application/x-netcdf) are both data formats that are frequently used to store large amounts of numerical data.