\section{Characterization of Sumerian}


\begin{figure}[htb]
\begin{center}
\includegraphics{../../images/sumerian_cuneiform.png}
\caption{Example of Sumerian cuneiform}
\label{fig:cuneiform}
\end{center}
\end{figure}



The Sumerian language is generally regarded as a language isolate in linguistics. No languages related to it have so far been convincingly identified, although many of its grammatical features are attested in other living languages outside of the Indo-European family to which English belongs.

In its orthographic form, Sumerian is encoded in cuneiform script, as depicted in Figure \ref{fig:cuneiform}, which shows an example of 120 compartments of cuneiform script written by an expert scribe. Note that this example is much clearer and more beautiful than standard scripts because it describes the gifts from highly placed persons to a priestess. 

Originally, cuneiform was logographic in nature, and a sign represented a content word (a thing or an action). It gradually developed into a combined system, where the same set of signs could be used to represent logograms and phonograms or syllabograms. In texts of the period we concentrate on, i.e. late third and early second millennium B.C., logograms were used to write content words and the base (root) of a word, while phonograms were used to write bound morphemes and loan words. In transliterated form, i.e. signs represented in the Roman alphabet with a few additions, these logograms and syllabograms are separated by a dash, as in 
{\tt nam-lugal} (kingship), where the base root {\tt lugal} (king) is combined with a derivational affix that changes the word into an abstract entity.

Another characteristic feature of Sumerian is the large number of homophones (words with the same sound structure but different meanings) - or perhaps pseudo-homophones, since there might have been differences in pronunciation (such as tone) that we do not know about. The different homophones (or, more precisely, the different cuneiform signs that denote them) are marked with different numbers by convention. For example: {\tt du} = "to go", {\tt du3} = "to build".

In terms of language typology, Sumerian is agglutinative. Word roots have grammatical elements glued on before or after them to build up complex grammatical forms. Many words (msotly verbs) consist of a root form (possibly reduplicated) and a chain of more or less clearly distinguishable and separable affixes or clitics. Nouns may have affix chains before as well as after the root. Overall, slightly less than 100 clitics have been postulated. Many of these clitics have allomorphs, depending on properties of the morphological context, such as progressive or regressive assimilation phenomena for vocals and consonants. On top of this, the null morpheme can occur as an allomorphic variant of a number of clitics. Overall, if we take all morphological rules into account, this leads to a huge number of possible interpretations.

Sumerian distinguishes the grammatical genders animate and inanimate, as do Polish, Russian, and some Native American languages, such as Navajo. There are also a large number of cases - nominative, ergative, genitive, dative, locative, comitative, equative ("as, like"), terminative ("to"), and  ablative ("from"). The case markers for nouns convey information about case and animacy, e.g.:
\begin{itemize}
\item {\tt -ak} (genitive)
\item {\tt -da} (comitative)
\item {\tt -e} (animate ergative)
\item {\tt -ra} (animate dative/directive)
\item {\tt -a} (inanimate locative/directive)
\item {\tt -e} (inanimate dative)
\item {\tt -ta} (inanimate ablative)
\end{itemize}

Many of these clitics have allomorphic representations. For example, the genitive clitic 'ak' can be written by means of, amongst others, the following variants: 
\begin{itemize}
\item {\tt a} in final position:
{\tt dumu lugala} 	the son ({\tt dumu}) of the king ({\tt lugal-ak})

\item	{\tt Ca-kV}
In this case, {\tt ak} bridges two syllabograms, where 'C' stands for consonant and 'V' for vocal:
{\tt an}	sky
{\tt an-na-ke4}		of the sky ({\tt an-ak-e4})
\end{itemize}

In order to approach the linguistic complexity of Sumerian in a constructive way, we have created an incrementally complex automatic analysis module, starting with a slot based lookup and adding increasingly complex combinatorial constraints.

