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Appendix A
Glossary of Terms
An Alphabetical Reference of Common Tango and Internet Terms
action
This is short for Tango action.
Tango Editor has a suite of actions which do many different tasks,
including: getting data from or sending data to a database, invoking
external actions (such as reading and writing files and sending
email), and controlling application file execution. Actions form the
basis of an application file in Tango Editor.
Apple Event
Macintosh only: An Apple Event is
a high-level event that conforms to the Apple Event Interprocess
Messaging Protocol. The Apple Event Manager uses the services of the
Event Manager to send Apple events between applications on the same
computer, between applications on remote computers, or from an
application to itself. For more information, visit:
http://www.apple.com/
application file
Application files are written using Tango
Editor and are composed of one or a series of actions that are
executed by Tango Server. Each action's reaction or response from a
database, server, external program, etc. can be posted in HTML. When
an application file is completed, the results are returned to the
client.
applet
A small Java program that can be embedded
in an HTML page. Applets differ from full-fledged Java applications in
that they are not allowed to access certain resources on the local
computer, such as files and serial devices, and are prohibited from
communicating with most other computers across a network. The current
rule is that an applet can only make an Internet connection to the
computer from which the applet was sent.
ASCII
American Standard Code for
Information Interchange
This is the de facto world-wide standard for
the code numbers used by computers to represent all the upper- and
lower-case Latin letters, numbers, punctuation, and related data.
There are 128 standard ASCII codes each of which can be represented by
a seven-digit binary number.
bandwidth
This is the measure of how much you can
send through a connection, usually measured in bits per second. A full
page of English text is about 16,000 bits. A moderately fast modem can
move about 15,000 bits in one second. Full-motion full-screen video
would require roughly 10,000,000 bits per second, depending on
compression.
baud
In common usage the baud rate of a modem is
how many bits it can send or receive per second. Technically, baud is
the number of times per second that the carrier signal shifts value.
For example, a 1200 bit-per-second modem actually runs at 300 baud,
but it moves 4 bits per baud (4 x 300 = 1200 bits per second).
bit
binary digit
A single digit number in base-2, in other words, either
a one or a zero. The smallest unit of computerized data.
bps
bits per second
A measurement of how fast data is moved from one place
to another. A 28.8K modem can move 28,800 bits per second.
CGI
Common Gateway Interface
A set of rules that describes how a Web server
communicates with another piece of software, often on the same
machine, and how the other piece of software (the "CGI program")
talks to the Web server. Any piece of software can be a CGI program if
it handles input and output according to the CGI standard.
Usually a CGI program is a small program
that takes data from a Web server and does something with it, like
putting the content of a form into an e-mail message, or turning the
data into a database query.
You can often see that a CGI program is
being used when "cgi-bin" appears in a URL.
cgi-bin
The most common name of a directory on a Web
server in which CGI programs are stored.
The "bin" part of "cgi-bin"
is a shorthand for "binary", because once upon a time, most
programs were referred to as "binaries". In real life, most
programs found in cgi-bin directories are text files--scripts that are
executed by binaries located elsewhere on the same machine.
client
A software program that is used to contact
and get data from a server software program on another computer, often
across a network or the Internet. Each client program is designed to
work with one or more specific kinds of server programs, and each
server requires a specific kind of client. A Web browser is a specific
kind of client.
configuration variables
Special values that control aspects of
Tango behavior. System variables affect system wide settings. They
apply to all users of Tango Server.
cookie
The most common meaning of cookie
on the Internet refers to a piece of information sent by a Web server
to a Web browser that the browser software is expected to save and to
send back to the server whenever the browser makes additional requests
from the server.
Depending on the type of cookie used and the
browser's settings, the browser may accept or not accept the cookie,
and may save the cookie for either a short time or a long time.
Cookies might contain login or registration
information, on-line shopping cart information, or user preferences.
When a server receives a request from a
browser that includes a cookie, the server is able to use the
information stored in the cookie. For example, the server might
customize what is sent back to the user, or keep a log of particular
users' requests.
Cookies are usually set to expire after a
predetermined amount of time and are usually saved in memory until the
browser software is closed down, at which time they may be saved to
disk if their expire time has not been reached.
data source
An abstraction or description of the
database that Tango Editor and Tango Server are referencing.
domain name
The unique name that identifies an Internet
site. Domain names always have two or more parts separated by dots.
The part on the left is the most specific, and the part on the right
is the most general. A given machine may have more than one domain
name, but a given domain name points to only one machine. For example,
the domain names
pervasive.com
training.pervasive.com
mail.pervasive.com
can all refer to the same machine, but each
domain name can refer to no more than one machine.
Usually, all of the machines on a given
network have the same thing as the right-hand portion of their domain
names (pervasive.com in the examples above). It is also
possible for a domain name to exist but not be connected to an actual
machine. This is often done so that a group or business can have an
Internet e-mail address without having to establish a real Internet
site. In these cases, some real Internet machine must handle the mail
on behalf of the listed domain name.
Domain Name Server (DNS)
A machine on the Internet that converts ("resolves")
domain names to IP address numbers.
e-mail
Messages, usually text, sent from one person
to another via computer. The "e" is for "electronic".
firewall
A combination of hardware and software that
separates a LAN into two or more parts for security purposes.
gateway
A hardware or software setup that translates
between two dissimilar protocols. For example, Prodigy has a gateway
that translates between its internal, proprietary e-mail format and
Internet e-mail format. Another meaning of gateway is to describe any
mechanism for providing access to another system, for example, AOL
might be called a gateway to the Internet.
hit
A single request from a Web browser for a
single item from a Web server; thus for a Web browser to display a
page that contains three graphics, four hits would occur at the
server--one for the HTML page, and one for each of the three graphics.
Hits are often used as a rough measure of
load on a server, such as the server gets 300,000 hits per month.
Because each hit can represent anything from a request for a tiny
document (or even a request for a missing document) all the way to a
request that requires some significant extra processing (such as a
complex search request), the actual load on a machine from one hit is
almost impossible to define.
home page
The Web page that your browser is set to
use when it starts up, or the main Web page for a business,
organization, person, or simply the main page out of a collection of
Web pages.
host
Any computer on a network that is a
repository for services available to other computers on the network.
It is quite common to have one host machine provide several services,
such as WWW and Usenet (Netnews).
HTML
HyperText Markup Language
The coding language used to create hypertext documents
for use on the World Wide Web. HTML looks a lot like old-fashioned
typesetting code, where you surround a block of text with codes that
indicate how it should appear. Additionally, in HTML you can specify
that a block of text, or a word, is linked to another file on the
Internet. HTML files are meant to be viewed using a World Wide Web
client program, such as Netscape Navigator or Microsoft Internet
Explorer.
HTTP
HyperText Transfer Protocol
The protocol for moving hypertext files across the
Internet. Requires a HTTP client program on one end, and an HTTP
server program on the other end. HTTP is the most important protocol
used in the World Wide Web.
hypertext
Generally, any text that contains links to
other documents--words or phrases in the document that can be chosen
by a reader and that cause another document to be retrieved and
displayed.
Internet
The vast collection of interconnected
networks that all use the TCP/IP protocols and that evolved from the
ARPANET of the late sixties and early seventies.
intranet
A private network inside a company or
organization that uses the same kinds of software that you would find
on the public Internet, but that is only for internal use.
As the Internet has become more popular
many of the tools used on the Internet are being used in private
networks, for example, many companies have Web servers that are
available only to employees.
ISDN
Integrated Services Digital
Network
A way to move more data over existing regular phone
lines. It can provide speeds of roughly 128,000 bits per second over
regular phone lines. In practice, most people will be limited to
56,000 or 64,000 bits per second.
IP number
Internet Protocol Number
A unique number consisting of four parts separated by
dots, such as 207.107.95.106. Every machine that is on the
Internet has a unique IP number--if a machine does not have an IP
number, it is not really on the Internet. Most machines also have one
or more domain names that are easier for people to remember.
Java
Java is a network-oriented programming
language invented by Sun Microsystems that is specifically designed
for writing programs that can be safely downloaded to your computer
through the Internet and immediately run without fear of viruses or
other harm to your computer or files. Using small Java programs
(called applets), Web pages can include functions such as
animations, calculators, and other fancy tricks.
Java bean
A component technology for Java that lets
developers create reusable software objects. These objects can be
shared. A database vendor can create a Java bean to support its
software, and other developers can easily drop the bean into their own
projects.
Java class
In Java, a type that defines the
implementation of a particular kind of object. A class definition
defines instance and class variables and methods, as well as
specifying the interfaces the class implements and the immediate
superclass of the class. If the superclass is not explicitly
specified, the superclass will implicitly be Object.
LAN
Local Area Network
A computer network limited to the immediate area,
usually the same building or floor of a building.
meta tag
The basic component of a tag language
unique to Tango Server. Meta tags communicate with Tango Server in the
same way that HTML communicates with a Web server.
MIME
Multipurpose Internet Mail
Extensions
A standard for attaching non-text files to standard
Internet mail messages. Non-text files include graphics, spreadsheets,
formatted word-processor documents, sound files, and most other files.
An e-mail program is said to be MIME
Compliant if it can both send and receive files using the MIME
standard.
When non-text files are sent using the MIME
standard they are converted (encoded) into text--although the
resulting text is not readable.
Generally speaking, the MIME standard is a
way of specifying both the type of file being sent (for example, a
Quicktime video file), and the method that should be used to turn it
back into its original form.
Besides e-mail software, the MIME standard
is also universally used by Web Servers to identify the files they are
sending to Web clients. In this way, new file formats can be
accommodated simply by updating the browsers' list of pairs of
MIME-types and appropriate software for handling each type.
network
Any time you connect two or more computers
together so that they can share resources, you have a computer
network. Connect two or more networks together and you have an
internet.
NNTP
Network News Transport Protocol
The protocol used by client and server software to carry
Usenet postings back and forth over a TCP/IP network. If you are using
any of the more common software such as Netscape Navigator, Nuntius,
Internet Explorer, or others to participate in newsgroups then you are
benefiting from an NNTP connection.
ODBC
Open Database Connectivity
A standard set by Microsoft that allows applications to
communicate with a variety of databases from different vendors. An
ODBC client application talks to the ODBC driver manager, which in
turn talks to a database driver for a specific type of database.
plug-in
A (usually small) piece of software that
adds features to a larger piece of software. A common example of a
plug-in is for the Netscape Navigator browser and Web server. The idea
behind plug-ins is that a small piece of software is loaded into
memory by the larger program, adding a new feature, and that users
need only install the few plug-ins that they need, out of a much
larger pool of possibilities. Plug-ins are usually created by people
other than the publishers of the software the plug-in works with.
PPP
Point to Point Protocol
Most well known as a protocol that allows a computer to
use a regular telephone line and a modem to make TCP/IP connections
and connect to the Internet.
security certificate
Information (often stored as a text file)
that is used by the SSL protocol to establish a secure connection.
Security certificates contain information
about who it belongs to, who it was issued by, a unique serial number
or other unique identification, valid dates, and an encrypted
fingerprint that can be used to verify the contents of the
certificate.
For an SSL connection to be created, both
sides must have a valid Security Certificate.
scope
In Tango, refers to an characteristic of
variables that determines where they are valid: in local, user,
cookie, domain, or system scope. See Chapter 7 for details.
In Java, a characteristic of an identifier
that determines where the identifier can be used. Most identifiers in
Java have either class or local scope. Instance and class variables
and methods have class scope; they can be used outside the class and
its subclasses only by prefixing them with an instance of the class or
(for class variables and methods) with the class name. All other
variables are declared within methods and have local scope; they can
be used only within the enclosing block.
server
A computer, or a software package, that
provides a specific kind of service to client software running on
other computers. The term can refer to a particular piece of software,
such as a Web server, or to the machine on which the software is
running. A single server machine could have several different server
software packages running on it, thus providing many different servers
to clients on the network.
SMTP
Simple Mail Transport Protocol
The main protocol used to send mail on the Internet.
SMTP consists of a set of rules for how a program sending mail and a
program receiving mail should interact.
Almost all Internet mail is sent and
received by clients and servers using SMTP, thus if one wanted to set
up an e-mail server on the Internet one would look for e-mail server
software that supports SMTP.
SQL
Structured Query Language
A specialized programming language for sending queries to
databases. Most industrial-strength relational databases and many
smaller database applications are addressed using SQL. Each specific
application will have its own version of SQL implementing features
unique to that application, but all SQL-capable databases support a
common subset of SQL.
SSL
Secure Sockets Layer
A protocol designed by Netscape to enable encrypted,
authenticated communications across the Internet.
SSL is used mostly (but not exclusively) in
communications between Web browsers and Web servers. URLs that begin
with "https" indicate that an SSL connection will be used.
SSL provides three important things:
privacy, authentication, and message integrity.
In an SSL connection each side of the
connection must have a Security Certificate, which each side's
software sends to the other. Each side then encrypts what it sends
using information from both its own and the other side's Certificate,
ensuring that only the intended recipient can decrypt it, and that the
other side can be sure the data came from the place it claims to have
come from, and that the message has not been tampered with.
Tango CGI
The CGI that links Tango Server and your
Web server. Not necessary if you use one of the Web server plug-ins.
Tango Server
Executes and servers up the application
files by which clients can interact with HTML pages to perform a
variety of tasks; for example, querying the data source.
TCP/IP
Transmission Control
Protocol/Internet Protocol
This is the suite of protocols that defines the
Internet. Originally designed for the UNIX operating system, TCP/IP
software is now available for every major kind of computer operating
system. To be truly on the Internet, your computer must have TCP/IP
software.
UNIX
A computer operating system (the basic
software running on a computer, underneath things like word processors
and spreadsheets). UNIX is designed to be used by many people at the
same time (it is multi-user) and has TCP/IP built-in. It is the most
common operating system for servers on the Internet.
URL
Uniform Resource Locator
A standard way to give the address of any resource on
the Internet, most commonly used for the World Wide Web (WWW). Here is
an example of a URL:
http://www.pervasive.com/
The most common way to use a HTTP-type URL
is to enter it into a Web browser program, such as Netscape Navigator
or Microsoft Internet Explorer.
WWW
World Wide Web
The universe of hypertext servers (HTTP servers) on the
Internet, which are the servers that send encoded markup text (HTML)
pages when requested by client Web browsers. HTML pages often link to
graphics, sound files, and many other different kinds of file formats.
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