MGI Definitions
Beginning Tag
- Many HTML tags require simply a single -entry tag structure to function.
Others require a tag complex to be opened, then closed, inside which is
contained other information customarily called the body. The portion of
the tag complex that begins the instruction set is called the Beginning
Tag. For example, in the mgiSendMail tag, one is required to have a beginning
tag, a body, and a closing tag. The form taken is:
<mgisendmail>
Body
</mgiSendMail>
- Where <mgiSendmail> is the beginning tag and </mgiSendMail>:
is the ending tag. Note that the ending tag is the same as the beginning
tag with the addition of a slash prepended to the tag name itself.
- Certain MGI tags must have both the beginning and ending tags since
MGI first looks for the beginning tag as an indication where processing
begins and then looks for the ending tag to know where that processing
is supposed to stop.
- Note that the term "Beginning Tag" is different from the
term "Opening Tag". The opening tag is the carat, or"<",
located at the beginning of the HTML tag.
Body
- On tags which require a beginning and ending tag to demark the extent
of what MGI is to process, those tags act against the body of the tag.
The body is the information contained between the beginning and ending
tag and the content of the body varies depending on the function of the
individual MGI tag. Using mgiSendMail as an example, the body would be
placed as follows:
<mgiSendMail>
Body
</mgiSendMail>
- Where Body is the formatting information for the email generated by
mgiSendMail.
Caching
- The formal definition of caching is to take something and hide it away
for future use, i.e., taking a boatload of money and hiding it is a buried
cache, or treasure chest. In the world of computers, a cache is a way of
taking information already requested, holding it is storage, and having
it available for use at a later time. The intended purpose of a cache is
to reduce the load on the number of times the CPU (or the brains of the
computer) needs to grab information from the hard drive (or the place where
information is stored.) That is done since the process of getting information
from the hard drive to the CPU is far slower than if that information is
already in the CPU when you need to do something with it.
- Unfortunately, there is a downside. Any change you make to your files,
either via FTP or through a database manipulation, takes place on the hard
drive. Suppose someone hits your web site home page and that page is taken
from the hard drive and placed in the cache on the CPU. The next time that
person views your home page, the HTML is pulled from the cache. Since there
is no hard drive access on that second request, the page serves much faster
from the cache. But what if you have altered your home page?
- The end user will still pull the page from the cache and not from the
hard drive. But you have made the change on the hard drive. As much as
you would like to show the end user your new home page, they will continue
to get the old page from the cache. Such is why when using MGI, one must
not turn on the cache on the server. Even if there are mechanisms available
for flushing, or clearing, the cache, there will always be a delay. The
upside is that unless the end user is trying to view your page using a
telco connection far faster than the speed at which information can be
retrieved from the hard drive and moved to the CPU, it doesn't slow things
down to not have a cache. And that telco connection needed to produce download
speeds faster than the drive transfer itself does not exist in any great
quantity. Even ADSL and modem connections are slower than the information
is transferred from the drive to the CPU.
- There is another type of caching as well and that is the caching which
occurs at the browser level. When a page is viewed in a browser, many times
the browser itself will cache the information. That way, when the end user
goes back to that same page, it pulls it from their own machine rather
than actually going back to the server to obtain the information requested.
However, what happens if there is information which constantly changes
on that page such as a counter?
- In that case, the end user will not see the page counter increment
since the request never goes to the server for processing. They keep pulling
the cached information from their own computer which, of course, contained
the count as it was when they first loaded the page. There is not much
a designer can do about that type of cache since it is under the full control
of the end user and depends on how they have configured their own personal
browser.
Ending Tag
- Many HTML tags require simply a single-entry tag structure to function.
Others require a tag complex to be opened, then closed, inside of which
is contained other information customarily called the body. The portion
of the tag complex that ends the instruction set is called the Ending Tag.
For example, in the mgiSendMail tag, one is required to have a beginning
tag, a body, and a ending tag. The form taken is:
<mgiSendMail>
Body
</mgiSendMail>
- Where <mgiSendMail> is the beginning tag and </mgiSendMail>:
is the ending tag. Note that the ending tag is the same as the beginning
tag with the addition of a slash prepended to the tag name itself.
- Certain MGI tags must have both the beginning and ending tags since
MGI first looks for the beginning tag as an indication where processing
begins and then looks for the ending tag to know where that processing
is supposed to stop.
- Note that the term "Ending Tag" is different from the term
"Close Tag". The close tag is the carat, or">",
located at the end of the HTML tag.
File Extension
- A file extension is the text that appears after the file name itself.
In the example:
image.jpg
- "image" is the file name and "jpg" is the extension.
The file name and extension are always separated by a period.The extension
is used for more than simply telling the user what type of file they are
looking at; it is also important in telling the computer what type of file
it is serving and what to do with that file during the process of serving
it. MGI will process all MGI tags on a given page only if the web server
tells it to. And the server differentiates which files to pass onto MGI
through the use of file extensions. Since MGI only processes when contained
in HTML code, there is no need to send image files with extensions such
as .jpg or .gif through MGI; there is nothing to process. Nor are files
with extensions like .txt or .hqx processed through MGI. What is processed
are files that contain HTML. Those files generally end in .htm or .html.
But one can configure the server to process custom file extensions as well.
For instance, suppose you have a text file that is being used a a caption
for an image on an HTML page and that text file is not only being included
in the HTML page with an mgiFileInclude tag, but it also contains MGI tags
embedded in the text file itself? You would not want to configure the server
to process .txt files thought MGI since .txt files are generally just downloaded
to the end user or displayed in the browser without any HTML coding. You
might want to construct a new file extension, in this case perhaps .caption,
that is processed through MGI before being served out. The extension, .mgi,
is already built into the server when MGI is installed. One must manually
configure .html and .htm to process through MGI. And one must also manually
configure any custom extensions in the server as well.
- Once a file extension is configured to have MGI process it, then all
files with that extension will be processed through MGI. But anytime you
wish to discontinue having MGI process a particular extension, simply remove
that configuration from the server's preferences.
FTP (File Transfer Protocol)
- An internet client-server protocol to transfer files between computers.
Parameter
- Many MGI tags have required and optional parameters with which the
designer can customize the function of the tag. For example, the mgiCounter
tag is constructed as follows:
<mgiCounter name="index" display="yes" increment="yes">
- In this example, the parameter of Name is required, while Display and
Increment are optional. Display and Increment are optional because they
do not have to be specified for the tag to function; in this case, Display
defaults to yes and Increment defaults to Yes. In other words, even if
you do not specify the parameters, they still have a value, though you
can override those defaults by changing the parameter value to something
other than the default value.
- A parameter, whether required or optional, always requires a value
which always appears in quotes and after an equal sign, separating the
parameter name from its value.
- In each MGI tag, the various parameters are always separated by a single
space.
Parameter Value
- For any required or optional parameter in MGI, each of those parameters
are indicated by a value. In the example of the mgiCounter tag:
<mgiCounter name="index" display="yes" increment="yes">
- The parameter values are "index", "yes", and "yes"
respectively for the parameters, name, display, and increment. A parameter
value is always contained in quotation marks and is separated from the
parameter name by an equal sign.
-
Parsed (Parsing)
- Parsing is synonymous with processing. When MGI parses a tag, it looks
at the tag, determines what the tag is supposed to do, processes that tag
according to the rules of MGI, and returns HTML code which is then displayed
in the browser.
Tag
- A tag is an instruction to MGI to perform an action. In MGI, as with
all of HTML, a tag is comprised of an open tag character, or"<",
the text which defines the tag, and a close tag, or ">" In
the example of mgiCounter, <mgiCounter>, the open tag character (<)
is followed by the name of the tag, "mgiCounter", and end with
a close tag character (>).
- Tags often have required and optional parameters which are defined
between the actual tag name and the ending tag character. For example,
the mgiCounter tag has several parameters:
<mgiCounter name="index" display="yes" increment="yes">
- As in that example, tag parameters are separated by a space, include
an equal sign after the parameter name, and have the value of the parameter
contained in quotation marks.
Text Editor
- A program that displays a document as ASCII text.
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