Everything about Forward Compatibility totally explained
Forward compatibility (sometimes confused with
extensibility) is the ability of a system to gracefully accept
input intended for later versions of itself.
The behavior expected from an older version of a forward compatible system is to gracefully handle input which is intended for a newer version, by ignoring the unknowns and selecting the known subset of the data that the system is capable of handling. Forward compatibility is harder to achieve than
backward compatibility because a system needs to cope gracefully with an unknown future
data format or requests for unknown future features. Backward compatibility doesn't have this issue because it accepts a known data format.
An example of forward compatibility is a
web browser ignoring the
HTML tags that it doesn't (yet) recognize. It is typical for
forward compatible systems to ignore unknown
data or
application instructions.
Many
application software systems are designed with a robust and self-sufficient
systems architecture so that they can operate adequately even when
input for a more advanced version is entered.
In all cases, when the application system accepts the input data or operating system isn't as expected, it'll produce an
output that will identify the problem accurately for the user.
A code example
Assume that version
v0 of a program expects inputs of the form <t>X</t>, where t is an envelope containing some data X. Version
v1 requires some extra functionality and thus it's also able to accept inputs of the form <s>X</s>, where s is a specialization of t. Now
v0 can't read the input <s>X</s>, since
v0 has no knowledge that s can be treated as t. It would appear that since s is a specialization of t, the new input could have been coded as <t type="s">X</t> where the ‘type’ attribute denotes the specialized nature. This is indeed a better form of the input, but if
v0 wasn’t designed to
gracefully ignore the ‘type’ attribute, this won’t present forward-compatibility either. In fact, the design of
v0 determines its forward compatibility. The choice now is simple: forward compatibility or new functionality?
If the choice is new functionality, then we break forward compatibility. But it's important now to build into
v1 the ability to gracefully treat future inputs we could foresee (for example, ignore attributes, such as "type", that the program doesn't understand).
Further Information
Get more info on 'Forward Compatibility'.
|
External Link Exchanges
Do you know how hard it is to get a link from a large encyclopaedia? Well we're different and will prove it. To get a link from us just add the following HTML to your site on a relevant page:
<a href="http://forward_compatibility.totallyexplained.com">Forward compatibility Totally Explained</a>
Then simply click through this link from your web page. Our crawlers will verify your link, extract the title of your web page and instantly add a link back to it. If you like you can remove the words Totally Explained and embed the link in article text.
As long as your link remains in place, we'll keep our link to you right here. Please play fair - our crawlers are watching. Your site must be closely related to this one's topic. Any kind of spamming, dubious practises or removing the link will result in your link from us being dropped and, potentially, your whole site being banned. |
