added attribute.tex

.gitattributes

@@ -28,6 +28,7 @@ doc/cdi_cman.pdf -text
 doc/cdi_fman.pdf -text
 doc/tex/FUNCTIONS -text
 doc/tex/Modules -text
+doc/tex/attribute.tex -text
 doc/tex/bib.tex -text
 doc/tex/c_examples.tex -text
 doc/tex/c_grid.tex -text

doc/tex/attribute.tex

+Attributes may be associated with each variable to specify non
+CDI standard properties. CDI standard properties as code, name,
+units, and missing value are directly associated with each variable by
+the corresponding CDI function (e.g. {\htmlref{\tt vlistDefVarName}{vlistDefVarName}}).
+An attribute has a variable to which it is assigned, a name, a type,
+a length, and a sequence of one or more values.
+The attributes have to be defined after the variable is created and 
+before the variable list is associated with a stream.
+
+It is also possible to have attributes that are not associated with any variable.
+These are called global attributes and are identified by using CDI\_GLOBAL as a 
+variable pseudo-ID. Global attributes are usually related to the dataset as a whole.
+
+CDI supports attributes with tree different data types. The data types
+are defined by the following predefined constants:
+
+\vspace*{3mm}
+\hspace*{8mm}\begin{minipage}{15cm}
+\begin{deflist}{{\large\tt DATATYPE\_TXT \ \ }}
+\item[{\large\tt DATATYPE\_INT}]     Integer attribute
+\item[{\large\tt DATATYPE\_FLT}]     Floating point attribute
+\item[{\large\tt DATATYPE\_TXT}]     Text attribute
+\end{deflist}
+\end{minipage}