openstack
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murano-specs
Code Issues Proposed changes

Add more details to metadata spec problem description 

Change-Id: Ida539ad330ed7a1ad9fa3a0fe9b89c2886396eee
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Valerii Kovalchuk 2016-07-29 18:43:07 +03:00
parent 9a810b91aa
commit 20d054ca0d
1 changed files with 20 additions and 5 deletions
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25
specs/mitaka/muranopl-metadata.rst
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@ -20,10 +20,25 @@ Problem description
===================
With time and development of the language new challenges arrived and MuranoPL
need to be extended with new keywords for new features. Metadata will be used
to store new information about various MuranoPL entities which can be needed
in the future. With this new feature MuranoPL will become more flexible and
go away from the "new keyword for new feature" rule.
need to be extended with new keywords for new features. For example, it may
be needed to mark some method as the one that serves special purpose to
distinguish it from other methods in the program workflow. Let's say one
wants to obtain the list of all methods within the class and choose only
methods that can be called by the unprivileged user. The one way to do
it is to introduce a new possible value for the `Usage` attribute, something
like `Usage: Non-admin`. Another way is to introduce even new keyword. The
problem is that every application developer may need to attach different kinds
of such information depending on the needs of their apps, and the range of
these needs can be endless. With the current approach, every new sort of
additional information requires modification of the core MuranoPL language
code.
In order to solve this problem, metadata will be used to store new
information about various MuranoPL entities. With this new feature MuranoPL
will become more flexible and go away from the "new keyword for new feature"
rule. All the developer will need to do is to define his own kind of data he
wants to apply to the elements of his application (in the form of the custom
MuranoPL class) and use it.
Proposed change
===============
@ -34,7 +49,7 @@ that control how and where instances of that meta-class can be attached.
To distinguish meta-classes from regular classes new class-level attribute
will be introduced called `Usage`. When `Usage` is `Class` (which is a default)
the rest of markup is interpreted as a class. Usage `Meta` is used ot define
the rest of markup is interpreted as a class. Usage `Meta` is used to define
meta-class.
In addition to Usage the following attributes are available for meta-classes: