6.9.2 Relationship between objects (if these objects are not pronouns)
In other languages, like German, Russian, Turkish, etc. the relationship between the objects is established through the declension (something that exists in Italian and in English only in the case of the pronouns). To establish the relationship between the different objects of a sentence through declensions means that the form of the word changes. In Italian for instance the direct object feminine singular is la, but the indirect object is le.
Le do il libro. / I give her the book. La vedo.
/ I see her.
If the object is a noun the relationships between the objects are established through prepositions, in English as well as in Italian.
nominative => not marked at all
La donna è felice.
The woman is happy.
genitive => marked with the preposition di (of)
La porta della casa è aperta.
The door of the house is open.
dative => marked with the preposition a (to)
Do il libro ai bambini.
I give the book to children.
accusative => not marked, function is established through the position in the sentence *
Vediamo le case.
We see the house.
* As you can see the nominative is not marked. The function of this two cases is cleared through the position in the sentence. If you change the position, the meaning changes.
The dog sees the horse.
The horse sees the dog.
Perhaps that sounds trivial, but it is not trivial at all. In other languages the direct object is marked as well, through declension or through preposition and in this case you can change the position without changing the meaning. That happens for instance in german.
Other examples (nominative)
Carla non vuole mangiare la sua pizza.
Carla doesn' t want to eat her Pizza today.
Roberto è stanco oggi.
Roberto is tired today.
Tutti vogliono essere ricchi, ma nessuno vuole lavorare.
Everybody wants to be rich, but nobody wants to work.
Mia nonna abita a Parigi.
My grandmother lives in Paris.
Io sono contento del mio lavoro.
I am happy with my work.
Hanno comprato un litro di latte.
They bought one liter of milk.