RDF use-case

1. Alexey Zakhlestine

   RDF use-case

   Tue August 31 2010 09:55:08 UTC
   So, let's see if we can use current API for real-world stuff.
   vala-code in sections below doesn't need to be complete application. just pieces of relevant code would be enough.
   Let's keep it simple
   
   I will answer with code myself too.
   
   So, here we go:
   
   =-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-
   
   1. Here, I define desired data-structure as a YAML file (looks a bit easier than usual RDF ontologies)
   
   ---
   namespaces:
   -
   uri: http://purl.org/dc/elements/1.1/
   alias: dc
   -
   uri: http://example.com/client/
   alias: client
   
   properties:
   -
   uri: http://purl.org/dc/elements/1.1/title
   db_type: text # can be varchar(1024) for sql
   -
   uri: http://purl.org/dc/elements/1.1/date
   db_type: datetime
   -
   uri: http://purl.org/dc/elements/1.1/language
   db_type: text # can be varchar(50) for sql
   -
   uri: http://example.com/client/book
   db_type: uuid # reference to book. can be char(32) or binary(16) for sql
   
   classes:
   -
   uri: http://example.com/client/book
   fields:
   - http://purl.org/dc/elements/1.1/title
   - http://purl.org/dc/elements/1.1/date
   - http://purl.org/dc/elements/1.1/language
   
   -
   uri: http://example.com/client/movie
   fields:
   - http://purl.org/dc/elements/1.1/title
   - http://purl.org/dc/elements/1.1/date
   - http://purl.org/dc/elements/1.1/language
   - http://example.com/client/book
   ...
   
   
   2. Vala code, for defining namespaces
   
   (place email-replies here)
   
   
   3. Vala code for defining properties
   
   (place email-replies here)
   
   
   4. Vala code for defining classes
   
   (place email-replies here)
   
   
   5. Vala code for creating objects of defined classes
   
   (place email-replies here)
   
   
   =-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-
   
   
   
   
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2. Alexey Zakhlestine

   Re: [midgard-dev] RDF use-case

   Tue August 31 2010 10:55:07 UTC
   On 31.08.2010, at 13:49, Alexey Zakhlestin wrote:
   
   > 2. Vala code, for defining namespaces
   
   var nm = new NamespaceManager; // should it be singleton?
   
   nm.create_uri('http://purl.org/dc/elements/1.1/', 'dc');
   nm.create_uri('http://example.com/client/', 'client');
   
   
   > 3. Vala code for defining properties
   
   var dc_title = new SchemaModelProperty();
   dc_title.namespace = 'dc';
   dc_title.name = 'title';
   dc_title.value_gtype = gchararray;
   
   var dc_date = new SchemaModelProperty();
   dc_date.namespace = 'dc';
   dc_date.name = 'date';
   dc_date.value_gtype = GDateTime; // from http://github.com/chergert/gdatetime
   
   var dc_language = new SchemaModelProperty();
   dc_language.namespace = 'dc';
   dc_language.name = 'language';
   dc_language.value_gtype = gchararray;
   
   var client_book = new SchemaModelProperty();
   client_book.namespace = 'client';
   client_book.name = 'book';
   client_book.value_gtype = ClientBook; // we'll need to define this beforehand
   
   // ====================================================================
   // We need means to store properties definitions at this point without
   // attaching them to classes
   // ====================================================================
   
   
   > 4. Vala code for defining classes
   
   // http://example.com/client/book
   var book_model = new SchemaModel();
   book_model.namespace = 'client';
   book_model.name = 'book';
   
   book_model
   .add_model(dc_title)
   .add_model(dc_date)
   .add_model(dc_language);
   
   // http://example.com/client/movie
   var movie_model = new SchemaModel();
   movie_model.namespace = 'client';
   movie_model.name = 'movie';
   
   movie_model
   .add_model(dc_title)
   .add_model(dc_date)
   .add_model(dc_language)
   .add_model(client_book);
   
   // register in type-system
   var builder = new SchemaBuilder();
   builder.register_model(book_model);
   builder.register_model(movie_model);
   builder.execute();
   
   > 5. Vala code for creating objects of defined classes
   
   var book = SchemaBuilder.factory("http://example.com/client/book") as SchemaObject;
   book.set_property_value('dc:title', 'Do Androids Dream of Electric Sheep?');
   book.set_property_value('dc:date', '1968');
   book.set_property_value('dc:language', 'en_EN');
   
   var movie = SchemaBuilder.factory("http://example.com/client/movie") as SchemaObject;
   movie.set_property_value('dc:title', 'Blade_Runner');
   movie.set_property_value('dc:date', '1982-06-25');
   movie.set_property_value('dc:language', 'en_EN');
   movie.set_property_value('client:book', book);
   
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3. Piotr Pokora

   Re: [midgard-dev] RDF use-case

   Tue August 31 2010 10:55:10 UTC
   > namespaces:
   > -
   > uri: http://purl.org/dc/elements/1.1/
   > alias: dc
   > -
   > uri: http://example.com/client/
   > alias: client
   >
   > properties:
   > -
   > uri: http://purl.org/dc/elements/1.1/title
   > db_type: text # can be varchar(1024) for sql
   > -
   > uri: http://purl.org/dc/elements/1.1/date
   > db_type: datetime
   > -
   > uri: http://purl.org/dc/elements/1.1/language
   > db_type: text # can be varchar(50) for sql
   > -
   > uri: http://example.com/client/book
   > db_type: uuid # reference to book. can be char(32) or binary(16) for sql
   >
   > classes:
   > -
   > uri: http://example.com/client/book
   > fields:
   > - http://purl.org/dc/elements/1.1/title
   > - http://purl.org/dc/elements/1.1/date
   > - http://purl.org/dc/elements/1.1/language
   >
   > -
   > uri: http://example.com/client/movie
   > fields:
   > - http://purl.org/dc/elements/1.1/title
   > - http://purl.org/dc/elements/1.1/date
   > - http://purl.org/dc/elements/1.1/language
   > - http://example.com/client/book
   > ...
   >
   >
   > 2. Vala code, for defining namespaces
   
   With NamespaceManager in *current* shape:
   
   NamespaceManager nsm = NamespaceManager ();
   nsm.create_uri ("http://purl.org/dc/elements/1.1/", "dc");
   nsm.create_uri ("http://example.com/client/", "client");
   nsm.create_uri ("uri: http://purl.org/dc/elements/1.1/title", "title");
   
   Latter case clearly shows there's additional reference needed.
   
   > 3. Vala code for defining properties
   >
   
   SchemaModelProperty title_p = SchemaModelProperty ("title", "string",
   "", "The title");
   SchemaModelProperty date_p = SchemaModelProperty ("date", "datetime",
   "0000-01-01 00:00:00", "Date");
   SchemaModelProperty language_p = SchemaModelProperty ("language",
   "string", "", "Languge");
   
   > 4. Vala code for defining classes
   
   SchemaModel book_model = SchemaModel ("Book");
   SchemaModel movie_model = SchemaModel ("Movie");
   
   book_model.add_model (title_p).add_model (date_p).add_model (language_p);
   
   movie_model.add_model(title_p).add_model (date_p).add_model
   (language_p).add_model (book_model);
   
   SchemaBuilder schema_builder = SchemaBuilder ();
   
   try {
   schema_builder.register_model (book_model);
   schema_builder.register_model (movie_model);
   schema_builder.execute ();
   } catch () { }
   
   >
   > 5. Vala code for creating objects of defined classes
   
   StorageModelManager model_manager = storage.get_model_manager();
   
   StorageModel book_storage_model = model_manager.create_storage_model
   (book_model, "books_table");
   StorageModel movie_storage_model = model_manager.create_storage_model
   (movie_model, "movies_table");
   
   StorageModelProperty title_storage = StorageModelProperty (title_p,
   "title_field");
   StorageModelProperty date_storage = StorageModelProperty (date_p,
   "date_field");
   StorageModelProperty lang_storage = StorageModelProperty (language_p,
   "lang_field");
   
   book_storage_model.add_model (title_storage).add_model
   (date_storage).add_model (lang_storage);
   
   StorageModelProperty book_storage = StorageModelProperty (book_model,
   "book_field");
   
   movie_storage_model.add_model (title_storage).add_model
   (date_storage).add_model (lang_storage).add_model (book_storage);
   
   model_manager.add_model (book_storage_model).add_model
   (book_model).add_model (movie_storage_model).add_model (movie_model);
   
   try {
   model_manager.prepare_create ();
   model_manager.execute ();
   } catch () {}
   
   SchemaObject book = schema_builder.factory ("Book");
   book.set_property_value ("http://purl.org/dc/elements/1.1/title", "The
   true story of the movie");
   
   ContentManager cm = storage.get_content_manager();
   cm.create (book);
   
   SchemaObject movie = schema_builder.factory ("Movie");
   book.set_property_value ("http://purl.org/dc/elements/1.1/title", "The
   great movie");
   book.set_property_value ("http://example.com/client/book", book);
   
   cm.create (movie);
   
   Piotras
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4. Piotr Pokora

   Re: [midgard-dev] RDF use-case

   Tue August 31 2010 11:15:05 UTC
   >> 2. Vala code, for defining namespaces
   >
   > var nm = new NamespaceManager; // should it be singleton?
   
   Yes. If we associate it with StorageManager:
   
   * singleton
   * lazy initialization
   
   >> 3. Vala code for defining properties
   >
   > dc_title.name = 'title';
   > dc_title.value_gtype = gchararray;
   
   I added typename and g_type.
   For typename, you can declare just 'string' which is common in every
   language, while gchararray is GType system specific.
   g_type let us tune schema vs storage models creation. For example
   datetime values which must be string ones in some DBMS.
   
   > // ====================================================================
   > // We need means to store properties definitions at this point without
   > // attaching them to classes
   > // ====================================================================
   
   Proposal?
   
   >
   >> 4. Vala code for defining classes
   >
   > // http://example.com/client/book
   > var book_model = new SchemaModel();
   > book_model.namespace = 'client';
   
   If class namespace is needed, please update Model interface.
   
   Piotras
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5. Alexey Zakhlestine

   Re: [midgard-dev] RDF use-case

   Tue August 31 2010 12:05:07 UTC
   On 31.08.2010, at 15:09, Piotr Pokora wrote:
   
   >>> 2. Vala code, for defining namespaces
   >>
   >> var nm = new NamespaceManager; // should it be singleton?
   >
   > Yes. If we associate it with StorageManager:
   >
   > * singleton
   > * lazy initialization
   
   well… the problem is, that NamespaceManager is not a property of storage
   though, NamespaceManager can (should?) use StorageManager as the backend
   
   Maybe it should be associated with ModelManager, instead?:
   
   var storage = new StorageManager(new Config());
   storage.open();
   
   var nm = storage.model_manager.namespace_manager;
   
   >
   >>> 3. Vala code for defining properties
   >>
   >> dc_title.name = 'title';
   >> dc_title.value_gtype = gchararray;
   >
   > I added typename and g_type.
   > For typename, you can declare just 'string' which is common in every
   > language, while gchararray is GType system specific.
   > g_type let us tune schema vs storage models creation. For example
   > datetime values which must be string ones in some DBMS.
   
   ok. will post updated vala-example in a moment
   
   
   >>> 4. Vala code for defining classes
   >>
   >> // http://example.com/client/book
   >> var book_model = new SchemaModel();
   >> book_model.namespace = 'client';
   >
   > If class namespace is needed, please update Model interface.
   
   done
   
   
   
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6. Alexey Zakhlestine

   Re: [midgard-dev] RDF use-case

   Tue August 31 2010 12:30:06 UTC
   [[ 2-nd edition ]]
   
   2. Vala code, for defining namespaces
   
   var storage = new StorageManager(new Config());
   storage.open();
   
   var nm = storage.model_manager.namespace_manager;
   
   nm.create_uri('http://purl.org/dc/elements/1.1/', 'dc');
   nm.create_uri('http://example.com/client/', 'client');
   
   
   3. Vala code for defining properties
   
   var dc_title = new SchemaModelProperty();
   dc_title.namespace = 'dc';
   dc_title.name = 'title';
   dc_title.value_typename = 'string';
   
   var dc_date = new SchemaModelProperty();
   dc_date.namespace = 'dc';
   dc_date.name = 'date';
   dc_date.value_typename = 'DateTime'; // from http://github.com/chergert/gdatetime
   
   var dc_language = new SchemaModelProperty();
   dc_language.namespace = 'dc';
   dc_language.name = 'language';
   dc_language.value_typename = 'string';
   
   var client_book = new SchemaModelProperty();
   client_book.namespace = 'client';
   client_book.name = 'book';
   client_book.value_typename = 'client:book'; // we'll need to define this beforehand
   
   // ====================================================================
   // We need means to store properties definitions at this point without
   // attaching them to classes
   // ====================================================================
   
   
   4. Vala code for defining classes
   
   // http://example.com/client/book
   var book_model = new SchemaModel();
   book_model.namespace = 'client';
   book_model.name = 'book';
   
   book_model
   .add_model(dc_title)
   .add_model(dc_date)
   .add_model(dc_language);
   
   // http://example.com/client/movie
   var movie_model = new SchemaModel();
   movie_model.namespace = 'client';
   movie_model.name = 'movie';
   
   movie_model
   .add_model(dc_title)
   .add_model(dc_date)
   .add_model(dc_language)
   .add_model(client_book);
   
   // register in type-system
   var builder = new SchemaBuilder();
   builder.register_model(book_model);
   builder.register_model(movie_model);
   builder.execute();
   
   5. Vala code for creating objects of defined classes
   
   var book = SchemaBuilder.factory("http://example.com/client/book") as SchemaObject;
   book.set_property_value('dc:title', 'Do Androids Dream of Electric Sheep?');
   book.set_property_value('dc:date', '1968');
   book.set_property_value('dc:language', 'en_EN');
   
   var movie = SchemaBuilder.factory("http://example.com/client/movie") as SchemaObject;
   movie.set_property_value('dc:title', 'Blade_Runner');
   movie.set_property_value('dc:date', '1982-06-25');
   movie.set_property_value('dc:language', 'en_EN');
   movie.set_property_value('client:book', book);
   
   
   
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7. Piotr Pokora

   Re: [midgard-dev] RDF use-case

   Tue August 31 2010 13:50:06 UTC
   >>> var nm = new NamespaceManager; // should it be singleton?
   >>
   >> Yes. If we associate it with StorageManager:
   >>
   >> * singleton
   >> * lazy initialization
   >
   > well… the problem is, that NamespaceManager is not a property of storage
   > though, NamespaceManager can (should?) use StorageManager as the backend
   >
   > Maybe it should be associated with ModelManager, instead?:
   >
   > var storage = new StorageManager(new Config());
   > storage.open();
   >
   > var nm = storage.model_manager.namespace_manager;
   
   Why it can not associated with StorageManager which creates all storage
   related classes? To be consistent with Query, Model, Transaction and
   Profiler, Namespace manager should be created with StorageManager.
   
   On the other hand, if we would like to ModelManager to create Namespace
   one, why do not make Namespace manager yet another model?
   
   Latter makes ModelManager implementation a bit difficult, and the first
   one forces us to clarify StorageManager family relations I mentioned few
   mails earlier.
   
   Piotras
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8. Alexey Zakhlestine

   Re: [midgard-dev] RDF use-case

   Tue August 31 2010 14:45:06 UTC
   On 31.08.2010, at 17:46, Piotr Pokora wrote:
   
   > Why it can not associated with StorageManager which creates all storage
   > related classes? To be consistent with Query, Model, Transaction and
   > Profiler, Namespace manager should be created with StorageManager.
   
   I don't like it either way.
   
   NamespaceManager is not related to StorageManager at all.
   NamespaceManager is the property of the whole runtime context and is active on the level of SchemaModels
   
   Application developer can use aliased property-names/class-names, but internally system operates using full namespaced names.
   And when queries are prepared for StorageManager these names are mapped to SQL field names or whatever current storage requires.
   
   So, we can have several StorageManagers but only one NamespaceManager.
   
   
   Now, that I think of it, other option is, to implement NamespaceManager on application level.
   It's quite easy to do and NamespaceManager doesn't provide any vital functionality. It is there only to make things easier for app-developers
   
   
   
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9. Piotr Pokora

   Re: [midgard-dev] RDF use-case

   Tue August 31 2010 15:00:06 UTC
   > Application developer can use aliased property-names/class-names, but internally system operates using full namespaced names.
   > And when queries are prepared for StorageManager these names are mapped to SQL field names or whatever current storage requires.
   >
   > So, we can have several StorageManagers but only one NamespaceManager.
   
   Agree.
   
   > Now, that I think of it, other option is, to implement NamespaceManager on application level.
   > It's quite easy to do and NamespaceManager doesn't provide any vital functionality. It is there only to make things easier for app-developers
   
   It could be a wrapper for particular SchemaObject class.
   
   Piotras
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