Web words

Abstract

Graphical and friendly it may be, but the web is also burdened with some heavy-duty jargon (http://www.ccil.org/jargon/jargon_toc.html). So what does it all mean? To help you find your way, The spider has prepared a glossary of terms — some basic, some less so. Web servers (http://guide-p.infoseek.com/DB?tis=1378&tid=556&db=110&sv=IS&lk=frames&col=WWW): The programs which send out web pages across the Internet. Most run on UNIX (http://www.research.microsoft.com/research/analysts/daniel/UNIX-haters.html) machines, but there are also servers for Windows and Mac. Setting up UNIX Web servers requires considerable expertise, but on the Mac even a non-technical user can quickly get a web server up and running. Browsers: The programs which interpret pages of HTML and display them to the user. Many different browsers exist, but increasingly, web pages are specifically designed with two browsers in mind: Netscape Navigator (http://home.netscape.com/comprod/products/navigator/index.html) and Microsoft Internet Explorer (). Versions of Netscape Navigator since 2.0 support many extra features, such as ‘plug-in’ (http://home.netscape.com/comprod/products/navigator/version_2.0/plugins/index.html) helper applications, integrated e-mail and news reading, and Sun Microsystems’ all-singing, all-dancing programming language Java (http://Java.sun.com/allabout.html) (which will feature in a future article) and its offshoot mini-applications. HTML: Hypertext markup language (HTML) is the language in which web pages are written. It has been adapted and extended greatly during its short history. In the early days, the standard (http://www.w3.org/pub/WWW/#Specification) was agreed on by a scientific committee, but now its development is increasingly commercially driven: Netscape HTML (http://home.netscape.com/assist/net_sites/html_extensions.html) is the de facto standard, and if you use a non-Netscape browser, you may have problems with many sites. URL: A Uniform Resource Locator (URL) (http://wombat.doc.ic.ac.uk/cgi-bin/foldoc?Uniform+Resource+Locator) is the standard ‘address’ given to a resource such as an HTML page or an image on the web (for example, http://BioMedNet.com/ for the site that houses Current Biology). URLs are used for linking between pages, and you can also access a page directly by typing its URL into your browser. Cache (http://wombat.doc.ic.ac.uk/cgi-bin/foldoc?query=Cache): A local copy of recently accessed information that offers quicker access than the original source of that information (which may be on another continent). Most browsers use Caches to store web pages — typically a small, fast, memory Cache, and a larger, slower, disk Cache. The size of the Caches can usually be configured by the user. Proxy server (http://wombat.doc.ic.ac.uk/cgi-bin/foldoc?proxy+server): A big, central, disk Cache. If your browser is set to use a Proxy server, then when you access a URL the browser passes the request on to the proxy. If the proxy already has a copy of the file for that URL, it quickly connects to the web server concerned to check that the file is still valid, and if so passes its own copy of the file on to your browser. Proxy servers are very useful when accessing sites on the other side of the Atlantic, for example. They take care of static HTML pages (see below) and images, so only dynamic HTML pages need to be sent over slow links. Static and dynamic HTML pages: Files of HTML which the web server passes to the browser can be static or dynamic. Static pages pass unchanged, and once they have been downloaded, they can be kept by a Cache or local Proxy server and so retrieved much more quickly. Dynamic pages are created by the web server in response to a request from a browser, so they can be customized to suit the user (for example, by displaying different information depending on the country), and can contain information retrieved in response to a query. GIFs and JPEGs: Images embedded in HTML pages must be either GIFs (http://wombat.doc.ic.ac.uk/cgi-bin/foldoc?Graphics+Interchange+Format) or JPEGs (http://wombat.doc.ic.ac.uk/cgi-bin/foldoc?query=JPEG). GIFs have (at most) 256 colours and are best used for diagrams or computer-generated artwork. JPEGs have smaller file sizes for photographic images and an unlimited range of colours. Both are bitmap file formats: the images are represented as pixels. For many purposes, especially printing, this is inferior to the alternative vector graphic representation. Hence the increasing popularity of PDF. PDF: Portable document format (PDF), as used by Adobe’s Acrobat program (http://www.adobe.com/Acrobat/readstep.html), is an alternative to HTML. PDF files can be easily created from documents by printing them as Postscript files and converting them to PDF using Adobe’s Acrobat Distiller. Adobe Acrobat Reader, which displays PDF files, is available free from Adobe’s web site. Advantages of PDF are retention of fonts, special characters, vector graphics, and layout information. Disadvantages are the comparative difficulty of including external links, the files are more like static pages than dynamic ones, and (for now) (http://www.adobe.com/Amber) they must be downloaded in their entirety before viewing. E-mail: [email protected] This online version of The spider’s web contains additional cross-references not present in the printed version. HTML. Beginners guide to HTML PDF. Adobe Acrobat Java. Experimental biological uses of Java Experimental biological uses of Java Other reference resources. Acronyms Computing Dictionary Dictionary of Cell Biology