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Date: Tue, 16 Nov 2010 13:54:14 +0000
Message-ID: <AANLkTik_mUdq1A2oWvqxrnKnDGgoR5An47tPmK5hHXZE@mail.gmail.com>
To: "guilhermeblanco@gmail.com" <guilhermeblanco@gmail.com>
Cc: PHP internals <internals@lists.php.net>
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Subject: Re: [PHP-DEV] PHP 5.4 - Meta attribute (aka. Annotations) support discussion
From: petercowburn@gmail.com (Peter Cowburn)

On 15 November 2010 17:07, guilhermeblanco@gmail.com
<guilhermeblanco@gmail.com> wrote:
> Hi folks,
>
> I'll start a series of topics (in this thread) about meta attribute
> (aka. Annotations) discussion.
> So as soon as we agree on each topic I'll open another point to be discus=
sed.
> Only when we reach some consensus I'll open another topic discussion.
> I suggest to have a poll for each topic, so we can do some democratic
> internals decision. I'd reduce the scope of voters to only people with
> PHP karma.
>
> The first topic to be defined is: Does PHP need meta attribute support?
>
> Any language is built at the top of syntax, words, semantics and context.
> We cannot define it as a language if we don't have these 4 parts well
> fit together.
> For a simple sentence like: I am all ears, we can easily identify these p=
arts.
> But the real meaning of this sentence (context) is only achieved with
> another part of the language: signifier-significate.
> A signifier is an atomic form, material element, visible, sensitive.
> A significate is an idea, semantic content, conceptual element, not
> sensitive perceptive.
>
> This important part is only reminded when we get back to semantics,
> specifically when talking about idiomatic expressions, a metaphor in
> our sample. The meaning will only work if we have the context, a known
> information. Our sentence would mean that spoker person only have
> ears, while the true meaning is that he/she is paying attention.
> A computer language doesn't differ from a language by any means. We
> have tokens (words), a syntax, semantic. But the lack of
> contextualization brings a hole on language and how your application
> should behave. This behavior can be achieved by many different ways;
> the simplest way is known as meta information.
>
> Considering you have a lack of idiomatic expressions knowledge of
> someone that is reading. He'd think person only have ears, but if you
> meta notify him that it is a metaphor, he'd try to find a different
> meaning. Example: (Metaphor) I am all ears.
>
> Now that we find how meta-information can benefit languages, it is
> time to understand how meta-information can benefit a computer
> language.
>
> A good example is define a Service that validates Domain Objects.
> Imagining a scenario where you have a User class that holds email and
> password. Email and password fields must be validated, for example,
> email as an email and password with at least 6 chars. A generic
> validation service could not have the User validation hardcoded inside
> the service, so the solution would be an external factor that explains
> to service how to validate the DO. One of the possible implementations
> would be a UserValidator class that contains validation rules for each
> field. This external factor is a good sample of meta-information. But
> how would a meta attribute would solve this situation?
> A Service could simple retrieve the validation instructions by
> Reflecting the class which instance is going to be validated.
> Basically, to validate a Domain Object, it is simply required to add
> validation rules on desired attributes. Example:
>
> class User {
> =A0 =A0<Email Meta Information>
> =A0 =A0protected $email;
>
> =A0 =A0<At least 6 chars Meta Information>
> =A0 =A0protected $password;
> }
>
> *NOTE*: Please understand that this do not enter in any implementation
> details. It is not time (yet) to talk baout docblock, new syntax, etc.
> Scope now is simpler than that.
>
> Now that is possible to see how meta attribute support could benefit a
> language, I compiled a simple list of known projects and how can they
> benefit of meta support:
> - phpUnit Providing meta functionality for test cases, examples:
> @dataProvider for test data iteration, @expectedException for catching
> exceptions, etc.
> - Doctrine For Object-Relational mapping, examples: @Entity,
> @OneToOne, @Id, etc.
> - Zend Framework Server classes Used to automate mappings for XML-RPC,
> SOAP, etc.
> - FLOW3 for dependency injection and validation
> - Symfony2 for validation and routing rules
> - Others: Validation, Functional Behavior injection (which could take
> advantage of Traits), etc.
>
>
> Poll will be opened for voting for 7 days (1 week) starting from now.
> Poll will be closed next Monday at 5pm GMT.
> Question: Does PHP need meta attribute support?
>

+1 on this poll.

> Happy voting!
>
> --
> Guilherme Blanco
> Mobile: +55 (16) 9215-8480
> MSN: guilhermeblanco@hotmail.com
> S=E3o Paulo - SP/Brazil
>
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