Document Formats

While most of the documents you view within your WWW browser are like this one, containing links and formatting, the bulk of the document collection within the NASA - OLMSA Research Opportunities is stored as downloadable documents. The user either downloads one of these documents or tries to view it within his or her WWW browser or with the aid of an external viewer.

Since there are different utilities available to the different classes of users (Mac, PC and UNIX), we have stored most of the documents within the NASA - OLMSA Research Opportunities in multiple formats. There is a standard suite of formats that we have attempted to store for the bulk of the document collection, including text, PostScript, RTF, and PDF. There are pros and cons associated with each of these formats, but as a group they provide a well rounded offering.

Also, there will be times when not all of these formats are available. Only PostScript and Acrobat formats will be available when the creating application is only able to output PostScript. RTF format will only be available if the creating application was Microsoft Word.

Portable Document Format (PDF)

Adobe Systems, Inc., the developers of PostScript, have attempted to address some of the problems inherent with cross platform document exchange with their PDF format. This is the format that is associated with a family of products that they have recently released under the name Acrobat. More information and a free copy of the Reader are available from Adobe Systems.

A PDF file is similar to a PostScript file in that it is platform independent and contains information that allows for the scaling of the fonts and objects in the file. There are additional features, however, that aid in the exchange of documents.

PDF files store metrics and information about the fonts used to create the file without including the fonts themselves. If a receiver of a PDF file does not have a font on his system which was used in the original document, the Acrobat software (along with the bundled Adobe Type Manager (ATM) package), simulates the absent fonts with a special Multiple Master font from Adobe. There are two Multiple Master fonts with characteristics that allow them to be used to simulate almost any typeface.

PDF files are also stored and transmitted as compressed files, and may contain various navigational enhancements to the original file (like bookmarks and links) to aid viewing. Sections of a PDF file can be cut out and pasted into other applications, and simple searches can be performed on the textual content of the file.

Adobe has made the PDF an open format by publishing a PDF reference that can be used by third party developers who wish to incorporate the PDF file structure into their own applications.

While there are other Acrobat products, a user needs only the Acrobat Reader to view PDF files.

Rich Text Format (RTF)

RTF is a format that can be imported into a variety of platforms. Microsoft Word for Windows and Microsoft Word for the Macintosh can both import and export the RTF format. A Macintosh MS Word user, for instance, can save a document directly out of Word into RTF format (rather than the native Mac format). A PC version of Word will then automatically convert the RTF format when the document is opened.

For a further understanding of the nature of RTF, the following introductory paragraphs from the Rich-Text Format Specification v 1.2 are offered:

The rich-text format (RTF) standard is a method of encoding formatted text and graphics for easy transfer between applications. Currently, users depend on special translation software to move word-processing documents between different MS-DOS, Windows, OS/2 applications, and Apple Macintosh applications.

The RTF standard provides a format for text and graphics interchange that can be used with different output devices, operating environments, and operating systems. RTF uses the ANSI, PC-8, Macintosh, or IBM PC character set to control the representation and formatting of a document, both on the screen and in print. With the RTF standard, documents created under different operating systems and with different software applications can be transferred among those operating systems and applications.

MS Word, RTF and Graphics:

Revisions of MS Word

Import of RTF into MS Word

  • Almost all graphics will be lost to users of Word for Windows 2.0.

    Text Format

    Text is limited to the 7-bit ASCII representations. While this is certainly a big limitation, text documents have a place in this system.

    Since text is universally viewable, it is required to accommodate users who access the NASA - OLMSA Research Opportunities from alphanumeric terminals. All graphics and table formatting are lost, but the text content of the document remains intact.

    Additionally, users may want to quickly view the text form of a document to make sure that it is of interest to them. After this viewing, they can take the time required to download and/or convert the document in a more usable format like RTF.

    PostScript Format

    PostScript is the page description language developed by Adobe that is generally used for printing to PostScript printers. PostScript files on the NASA - OLMSA Research Opportunities may be downloaded and printed if desired.

    For UNIX and PC users, there is also the option to view these PostScript files on the screen through the use of Ghostscript and Ghostview. Ghostview allows the printing of only specific pages from the original file.

    Although PostScript provides a standard for page description, not all printers or applications adhere to that standard. There are also Level One and Level Two PostScript documents, and unavoidable problems that occur when the receiving platform does not have the fonts that were available to the creating application.

    For the record, we will be creating our PostScript files as Level One documents using the Adobe PS Driver.

    NASA / OLMSA Research Opportunities
    E-Mail: peer1@hq.nasa.gov