|
A
B
C
D
E
F
G
H
I
J
K
L
M
N
O
P
Q
R
S
T
U
V
W
X
Y
Z
Glossary S
 Safari is Apple Computer's Web browser. It is the default browser in Apple's OS X and is currently only available for that operating system. Safari was developed in-house by Apple and released in 2003.
Safari features tabbed browsing, similar to Firefox and Opera, RSS feed support and integration of Apple's Quicktime multimedia player. Safari also has a search field that uses Google's search engine. Apple's Keychain identify management scheme manages passwords. Other standard features include a pop-up ad blocker, spell check, bookmark management and integration with Apple's iWeb software.
Safari is based upon Apple's Webkit, an application framework based upon two open source frameworks, WebCore and JavascriptCore. The sourcecode for the non-rendering portions of Safari are all available at OpenDarwin.org.
Other Web browsers include Firefox, Internet Explorer, Opera and Mosaic, developed in 1993 and the original code base for Netscape's browser, Lynx.
[more...]
 top
 In computer programming, a script is a program or sequence of instructions that is interpreted or carried out by another program.
[more...]
top
 In cryptography, a private or secret key is an encryption/decryption key known only to the party or parties that exchange secret messages. In traditional secret key cryptography, a key would be shared by the communicators so that each could encrypt and decrypt messages. The risk in this system is that if either party loses the key or it is stolen, the system is broken. A more recent alternative is to use a combination of public and private keys. In this system, a public key is used together with a private key. See public key infrastructure (PKI) for more information.
[more...]
top
 A segment is a defined portion or section of something larger such as a database, geometric object, or network. The term is used in database management, graphics, and communications.
[more...]
top
 In information technology, a server is a computer program that provides services to other computer programs (and their users) in the same or other computers.
[more...]
top
 SLIP is a TCP/IP protocol used for communication between two machines that are previously configured for communication with each other. For example, your Internet server provider may provide you with a SLIP connection so that the provider's server can respond to your requests, pass them on to the Internet, and forward your requested Internet responses back to you. Your dial-up connection to the server is typically on a slower serial line rather than on the parallel or multiplex lines such as a line of the network you are hooking up to.
A better service is provided by the Point-to-Point Protocol (PPP).
[more...]
top
 The SHA (Secure Hash Algorithm) hash functions refer to five FIPS-approved algorithms for computing a condensed digital representation (known as a message digest) that is, to a high degree of probability, unique for a given input data sequence (the message). These algorithms are called “secure” because (in the words of the standard), “for a given algorithm, it is computationally infeasible 1) to find a message that corresponds to a given message digest, or 2) to find two different messages that produce the same message digest. Any change to a message will, with a very high probability, result in a different message digest.”
The five algorithms, denoted SHA-1, SHA-224, SHA-256, SHA-384, and SHA-512, are cryptographic hash functions designed by the National Security Agency (NSA) and published by the NIST as a U. S. government standard. The latter four variants are sometimes collectively referred to as SHA-2.
SHA-1 is employed in several widely used security applications and protocols, including TLS and SSL, PGP, SSH, S/MIME, and IPsec. It was considered to be the successor to MD5, an earlier, widely-used hash function.
The security of SHA-1 has been somewhat compromised by cryptography researchers. Although no attacks have yet been reported on the SHA-2 variants, they are algorithmically similar to SHA-1 and so efforts are underway to develop improved alternative hashing algorithms. Due to recent attacks on the SHA-1, "NIST is initiating an effort to develop one or more additional hash algorithms through a public competition, similar to the development process for the Advanced Encryption Standard (AES)."
[more...]
top
 Smalltalk is a programming language that was designed expressly to support the concepts of object-oriented programming. In the early 1970's, Alan Kay led a team of researchers at Xerox to invent a language that let programmers envision the data objects they intended to manipulate. Unlike C++, Smalltalk was not built on the syntax of a procedural language; it is a "pure" object-oriented language with more rigorously enforced rules than C++, which permits some of the procedural constructs of the C language.
Although Smalltalk may continue to attract a loyal following, Java, a derivative of C++ designed for distributed systems, has become the most prevalent object-oriented language on the Web.
[more...]
top
 A server-side include is a variable value (for example, a file "Last modified" date) that a server can include in an HTML file before it sends it to the requestor. If you're creating a Web page, you can insert an include statement in the HTML file that looks like this:
<!--#echo var="LAST_MODIFIED"-->
and the server will obtain the last-modified date for the file and insert it before the HTML file is sent to requestors.
LAST_MODIFIED is one of several environment variables that an operating system can keep track of and that can be accessible to a server program. The server administrator can make these environment variables usable when the system is set up.
A Web file that contains server-side include statements (such as the "echo" statement above) is usually defined by the administrator to be a file with an "." suffix. You can think of a server-side include as a limited form of common gateway interface application. In fact, the CGI is not used. The server simply searches the server-side include file for CGI environment variables, and inserts the variable information in the places in the file where the "include" statements have been inserted.
When creating a Web site, a good idea is to ask your server administrator which environment variables can be used and whether the administrator can arrange to set the server up so that these can be handled. The administrator may be able to help you add the appropriate "include" statements to your HTML file.
[more...]
top
 A servlet is a small program that runs on a server. The term was coined in the context of the Java applet, a small program that is sent as a separate file along with a Web (HTML) page. Java applets, usually intended for running on a client, can result in such services as performing a calculation for a user or positioning an image based on user interaction.
Some programs, often those that access databases based on user input, need to be on the server. Typically, these have been implemented using a Common Gateway Interface (CGI) application. However, with a Java running in the server, such programs can be implemented with the Java programming language. The advantage of a Java servlet on servers with lots of traffic is that they can execute more quickly than CGI applications. Rather than causing a separate program process to be created, each user request is invoked as a thread in a single daemon process, meaning that the amount of system overhead for each request is slight.
Instead of a URL that designates the name of a CGI application (in a "cgi-bin" subdirectory), a request in a form on a Web HTML page that results in a Java servlet getting called would call a URL that looks like this:
http://www.whatis.com:8080/servlet/gotoUrl?http://www.someplace.com
The "8080" port number in the URL means the request is intended directly for the Web server itself. The "servlet" would indicate to the Web server that a servlet was being requested.
Add-on modules allow Java servlets to run in Netscape Enterprise, Microsoft Internet Information Server (IIS), and Apache servers.
[more...]
top
 Shell is a Unix term for the interactive user interface with an Operating system. The shell is the layer of programming that understands and executes the commands a user enters. In some systems, the shell is called a command interpreter. A shell usually implies an interface with a command syntax (think of the DOS operating system and its "C:>" prompts and user commands such as "dir" and "edit").
[more...]
top
 In Windows NT and 2000 operating systems, the security identifier (SID) is a unique alphanumeric character string that identifies each operating system and each user in a network of NT/2000 systems.
[more...]
top
 A smart card is a plastic card about the size of a credit card, with an embedded microchip that can be loaded with data, used for Cell phone calling, electronic cash payments, and other applications, and then periodically refreshed for additional use. Currently or soon, you may be able to use a smart card to:
- Dial a connection on a Cell phone and be charged on a per-call basis
- Establish your identity when logging on to an Internet access provider or to an online bank
- Pay for parking at parking meters or to get on subways, trains, or buses
- Give hospitals or doctors personal data without filling out a form
- Make small purchases at electronic stores on the Web (a kind of cybercash)
- Buy gasoline at a gasoline station
Over a billion smart cards are already in use. Currently, Europe is the region where they are most used. Ovum, a research firm, predicts that 2.7 billion smart cards will be shipped annually by 2003. Another study forecasts a $26.5 billion market for recharging smart cards by 2005. Compaq and Hewlett-Packard are reportedly working on keyboards that include smart card slots that can be read like bank credit cards. The hardware for making the cards and the devices that can read them is currently made principally by Bull, Gemplus, and Schlumberger.
[more...]
top
 SMS (Short Message Service) is a service for sending messages of up to 160 characters (224 characters if using a 5-bit mode) to mobile phones that use Global System for Mobile (GSM) communication. GSM and SMS service is primarily available in Europe. SMS is similar to paging. However, SMS messages do not require the mobile phone to be active and within range and will be held for a number of days until the phone is active and within range. SMS messages are transmitted within the same cell or to anyone with roaming service capability. They can also be sent to digital phones from a Web site equipped with PC Link or from one digital phone to another. Typical uses of SMS include:
- Notifying a mobile phone owner of a voice-mail message
- Notifying a salesperson of an inquiry and contact to call
- Notifying a doctor of a patient with an emergency problem
- Notifying a service person of the time and place of their next call
- Notifying a driver of the address of the next pickup
An SMS gateway is a Web site that lets you enter an SMS message to someone within the cell served by that gateway or that acts as an international gateway for users with roaming capability.
SMS for Authentication is considered insecure and unreliable.
[more...]
top
 SMTP (Simple Mail Transfer Protocol) is a TCP/IP protocol used in sending and receiving e-mail. However, since it is limited in its ability to queue messages at the receiving end, it is usually used with one of two other protocols, POP3 or IMAP, that let the user save messages in a server mailbox and download them periodically from the server. In other words, users typically use a program that uses SMTP for sending e-mail and either POP3 or IMAP for receiving e-mail. On Unix-based systems, sendmail is the most widely-used SMTP server for e-mail. A commercial package, Sendmail, includes a POP3 server. Microsoft Exchange includes an SMTP server and can also be set up to include POP3 support.
SMTP usually is implemented to operate over Internet port 25. An alternative to SMTP that is widely used in Europe is X.400. Many mail servers now support Extended Simple Mail Transfer Protocol (ESMTP), which allows multimedia files to be delivered as e-mail.
[more...]
top
 SOAP (Simple Object Access Protocol) is a way for a program running in one kind of Operating system (such as Windows 2000) to communicate with a progam in the same or another kind of an operating system (such as Linux) by using the World Wide Web's Hypertext Transfer Protocol (HTTP) and its Extensible Markup Language (XML) as the mechanisms for information exchange. Since Web protocols are installed and available for use by all major operating system platforms, HTTP and XML provide an already at-hand solution to the problem of how programs running under different operating systems in a network can communicate with each other. SOAP specifies exactly how to encode an HTTP header and an XML file so that a program in one computer can call a program in another computer and pass it information. It also specifies how the called program can return a response.
SOAP was developed by Microsoft, DevelopMentor, and Userland Software and has been proposed as a standard interface to the Internet Engineering Task Force (IETF). It is somewhat similar to the Internet Inter-ORB Protocol (IIOP), a protocol that is part of the Common Object Request Broker Architecture (CORBA). Sun Microsystems' Remote Method Invocation (RMI) is a similar client/server interprogram protocol between programs written in Java.
An advantage of SOAP is that program calls are much more likely to get through firewall servers that screen out requests other than those for known applications (through the designated port mechanism). Since HTTP requests are usually allowed through firewalls, programs using SOAP to communicate can be sure that they can communicate with programs anywhere.
[more...]
top
 Software, consisting of programs, enables a computer to perform specific tasks, as opposed to its physical components (hardware) which can only do the tasks they are mechanically designed for. The term includes application software such as word processors which perform productive tasks for users, system software such as operating systems, which interface with hardware to run the necessary services for user-interfaces and applications, and middleware which controls and co-ordinates distributed systems.
[more...]
top
 Solaris is the computer Operating system that Sun Microsystems provides for its family of Scalable Processor Architecture-based processors as well as for Intel-based processors. Sun has historically dominated the large Unix workstation market. As the Internet grew in the early 1990s, Sun's SPARC/Solaris systems became the most widely installed servers for Web sites. Sun emphasizes the system's availability (meaning it seldom crashes), its large number of features, and its Internet-oriented design. Sun advertises that its latest version, the Solaris 8 Operating Environment, is "the leading UNIX environment" today.
[more...]
top
 A term extended from print publishing to online media, a style sheet is a definition of a document's appearance in terms of such elements as:
- The default typeface, size, and color for headings and body text
- How front matter (preface, figure list, title page, and so forth) should look
- How all or individual sections should be laid out in terms of space (for example, two newspaper columns, one column with headings having hanging heads, and so forth).
- Line spacing, margin widths on all sides, spacing between headings, and so forth
- How many heading levels should be included in any automatically generated Table of Contents
- Any boilerplate content that is to be included on certain pages (for example, copyright statements)
Typically, a style sheet is specified at the beginning of an electronic document, either by embedding it or linking to it. This style sheet applies to the entire document. As necessary, specific elements of the overall style sheet can be overridden by special coding that applies to a given section of the document.
For Web pages, a style sheet performs a similar function, allowing the designer to ensure an underlying consistency across a site's pages. The style elements can be specified once for the entire document by either imbedding the style rules in the document heading or cross-referring (linking to or importing) a separate style sheet. A browser may allow the user to override some or all of the style sheet attributes.
A cascading style sheet is a style sheet that anticipates that other style sheets will either fill in or override the overall style sheet. This provides the designer the advantage of being able to rely on the basic style sheet when desired and overriding it when desired. The filling in or overriding can occur on a succession of "cascading" levels of style sheets. For example, one style sheet could be created and linked to from every Web page of a Web site as the overall style sheet. For any portion of a page that included a certain kind of content such as a catalog of products, another style sheet that amends the basic style sheet could be linked to. And within the span of that style sheet, yet another style sheet could be specified as applying to a particular type of product display.
When creating Web pages, the use of style sheets is now recommended by the World Wide Web Consortium. The latest version of the Hypertext Markup Language, HTML 4.0, while continuing to support older tags, indicates which ones should be replaced by the use of style sheet specifications. The Web's Cascading Style Sheets, level 1 (CSSL1) is a recommendation for cascading style sheets that has been developed by a working group of the World Wide Web Consortium (W3C).
[more...]
top
 SMP (symmetric multiprocessing) is the processing of programs by multiple processors that share a common Operating system and memory. In symmetric (or "tightly coupled") multiprocessing, the processors share memory and the I/O bus or data path. A single copy of the Operating system is in charge of all the processors. SMP, also known as a "shared everything" system, does not usually exceed 16 processors.
[more...]
| 
