Identity
IP focuses on the concept of identity. Since most programming languages
represent the source code as plain text, objects are defined by names, and their uniqueness has to be inferred by the compiler.
For example, the same symbolic name may be used to name different variables, procedures, or even types. In code that spans
several pages - or, for globally visible names, multiple files - it can become very difficult to tell what symbol refers to what actual object. If a name is changed, the code where it is used must carefully be
examined.
In an IP system, on the other hand, all definitions not only assign symbolic names, but
also unique private identifiers to objects. This means that in the IP development
environment, every time you refer to a variable or procedure, it's not just a name - you're actually linking back to the original
defined entity. The major advantage of this is that if you rename a definition, all of the references to that entity in your
program are changed automatically. This also means that if you use the same name for unique definitions in different namespaces
(eg. ".to_string()"), you won't rename the wrong references as is sometimes the case with Search/Replace in current editors.
This feature also makes it easy to have multi-language versions of your program. You can have a set of English names for all
your definitions as well as a set of Japanese names which can be swapped in at will.
Having a unique identity for every defined object in the program also makes it easy to perform automated refactoring tasks, as
well as simplifying code checkins in versioning systems. For example, in current code
collaboration systems (i.e. CVS, SVN), when two programmers commit
changes that conflict (i.e. if one programmer renames a function while another changes one of the lines in that function), the
versioning system will think that one programmer created a new function while another modified an old function. In an IP
versioning system, it will know that one programmer merely changed a name while another changed the code.
Levels of detail
IP systems also offer several levels of detail, allowing the programmer to "zoom in" or out. In the example above, the
programmer could zoom out to get a level that would say something like:
<<print the numbers 1 to 10>>
Thus IP systems are self-documenting to a large degree, allowing the programmer to
keep a good high-level picture of the program as a whole.
Similar works
There are projects that exploit similar ideas to create code with higher level of abstraction. Among them are:
