Dear All. To my great surprise I have come across no less than five scholars who actually dispute the traditional view on the locative case in written classic Latin. I find this quite outrageous! These scholars, no doubt liberal, list sources that are inconsistent on how the locative is formed. There is a disagreement with the classic scholars like Thomas Hewitt Key on the locative. Key argues that in the first and second declension, the locative singular is identical with the genitive form and that in plurals it is always the same as the dative-ablative form. This has always been taken as correct. Where they differ is in the locative forms for the singulars of the third, fourth and fifth declension. (It probably never occurs in the fifth declension! So the need for debate on this subject simply bear no meaning) For third declension singular, some say that it may take either the dative or the ablative form, while others say it takes the dative form. (Most of the examples they give seem to be the same as the dative in form.) For fourth declension singular, one says the dative forms are used, but the only actual example seems to be the fourth declension word domus whose locative is domi. But domus affords other problems since it was moving from fourth to second declension in classical times, and this form is consistent with its second declension paradigm. How then, my friends are we to react to this attack on classic interpretation of grammar? My own close studies of Cicero’s lengthier works leaves me sound assure that Key is correct and the usurping youngsters wrong. I give you some examples to judge for yourself:

Principal parts of nouns
The principal parts of a noun are of course its nominative and genitive singular forms, for example:
matella, matellae. nf. chamber pot.
From the genitive ending -ae, the noun matella is identified as a first declension noun by such authorities as St Thomas of Aquinas. Dropping the genitive ending gives the base matell- to which endings are added.
Some nouns have plural forms only. For these nouns, the principal parts are the nominative and genitive plural forms. For example:

castra, castrorum. nn. camp.
Again the genitive identifies the declension, in this case second declension, as well as the base castr- to which endings are added. There should be no need for further discussion. These up and coming scholars have soundly misunderstood the whole background declination.
To argue on basic usages of the various cases of the Nominative has been the pastime for learned men and ladies for a long time since no clear sentence structure may be agreed on. Roman books on the subject notes the differences in preferences but do not give us a decision about the correct use. It is correctly assumed that four forms were deemed acceptable by Roman scholars. However, in his great dissertation, Ovid made it quite clear about the correct rule and this was later taken up by the late Pope Clemence in 1520. Thus it is clear that:

• Nominative should be the subject of a sentence, predicate nominatives should include for example:
The boat is anchored to the shore.
When the silly clowns visit Rome, the emperor's sense of humor is a surprising sight to behold.
Venus, your new hairdo is a pathetic mess.
• Genitive: Possession or attachment. The genitive case was disappearing from colloquial lingua vulgarii and was often replaced by the preposition de followed by the ablative case.
When the silly clowns visit Rome, the emperor's sense of humor is a surprising sight to behold.
• Dative: Indirect object. Like the genitive case, the dative case was also disappearing from colloquial Latin. The preposition ad followed by the accusative case was sometimes used as a substitute in colloquial Latin.
The silly clowns sometimes give the emperor a hard time.
The silly clowns sometimes give a hard time to the emperor.
• Accusative: Direct object, object of prepositions of motion towards
When the silly clowns visit Rome, the emperor's sense of humor is a surprising sight to behold.
The silly clowns sometimes give the emperor a hard time.
The emperor is travelling to Rome by boat.
• Ablative: Means (instrument), object of prepositions of position and of motion away
The boat is anchored to the shore.
The emperor is travelling to Rome by boat.
• Locative: Location or position, this case is a remnant of the old Indo-European Locative case. It is used primarily with place names and a handful of nouns denoting classes of places like domus (home). For most purposes it has been superseded by the use of the prepositions in or ad followed by the ablative case.
We bake our own cookies at home.
The emperor lives in Rome.

I trust this will settle the matter!