helm/mathql/doc/mathql_introduction_textual.tex

   1 \subsection{Textual syntax} \label{Textual}
   2
   3 The syntax of grammatical productions resembles BNF and POSIX notation:
   4
   5 \begin{itemize}
   6
   7 \item
   8 \TT{::=} defines a grammatical production by means of a regular expression.
   9
  10 Regular expressions are made of the following elements
  11 (here \TT{...} is a placeholder):
  12
  13 % \item
  14 % \TT{.} represents any character between U 0020 and U 007F inclusive;
  15
  16 \item
  17 \TT{`...`} represents any character in a character set;
  18
  19 \item
  20 \verb+`^ ...`+ represents any character (U+0020 to U+007E) not in a character
  21 set;
  22
  23 \item
  24 \TT{"..."} represents a string to be matched verbatim;
  25
  26 \item
  27 \GP{...} represents a regular expression defined by a grammatical production;
  28
  29 \item
  30 \TT{... ...} represents a conjunctive regular expression;
  31
  32 \item
  33 \TT{... | ...} represents a disjunctive regular expression;
  34
  35 \item
  36 \TT{[ ... ]?} represents an optional regular expression;
  37
  38 \item
  39 \TT{[ ... ]+} represents a regular expression to be repeated one or more times;
  40
  41 \item
  42 \TT{[ ... ]*} represents a regular expression to be repeated zero or more times;
  43
  44 \item
  45 \TT{[ ... ]} represents a grouped regular expression.
  46
  47 \end{itemize}
  48
  49 \noindent
  50 {\MathQL} Expressions can contain quoted constant strings with the syntax of
  51 \figref {StrTS}.%
  52 \footnote{Note that the first slash of the \GP{path} is not optional as
  53 in {\MathQL}.3.}
  54
  55 \begin{figure}[ht]
  56 \begin{footnotesize} \begin{verbatim}
  57 <dec>     ::= '0 - 9'
  58 <num>     ::= <dec> [ <dec> ]*
  59 <hex>     ::= <dec> | 'A - F' | 'a - f'
  60 <escaped> ::= "u" <hex> <hex> <hex> <hex> | '"' | "\" | "^"
  61 <string>  ::= '"' [ "\" <escaped> "^" | '^ "\^' ]* '"'
  62 <path>    ::= "/" | [ "/" <string> ]+
  63 \end{verbatim} \end{footnotesize}
  64 \vskip-1pc
  65 \caption{Textual syntax of numbers, strings and paths} \label{StrTS}
  66 \end{figure}
  67
  68 \noindent
  69 The meaning of the escaped sequences is shown in \figref{EscTS}
  70 (where $ .... $ is a 4-digit placeholder).
  71
  72 \begin{figure}[ht]
  73 \begin{footnotesize}
  74 \begin{center} \begin{tabular}{|l|l|c|}
  75 \hline {\bf Escape sequence} & {\bf Unicode character} & {\bf Text} \\
  76 \hline \verb+\u....^+        & U+....                  &            \\
  77 \hline \verb+\"^+            & U+0022                  & \verb+"+   \\
  78 \hline \verb+\\^+            & U+005C                  & \verb+\+   \\
  79 \hline \verb+\^^+            & U+005E                  & \verb+^+   \\
  80 \hline
  81 \end{tabular} \end{center}
  82 \end{footnotesize}
  83 \vskip-1pc
  84 \caption{Textual syntax of escaped characters} \label{EscTS}
  85 \end{figure}
  86
  87 {\MathQL} character escaping syntax aims at complying with W3C character model
  88 for the World Wide Web \cite{W3Ca} which recommends a support for standard
  89 Unicode characters (U+0000 to U+FFFF) and escape sequences with start/end
  90 delimiters.
  91 In particular {\MathQL} escape delimiters (backslash and caret) are chosen
  92 among the {\em unwise} characters for URI references (see \cite{URI}) because
  93 URI references are the natural content of constant strings and these
  94 characters should not be so frequent in them.
  95
  96 Query expressions can contain variables for {\av}'s (production \GP{avar})
  97 and variables for {\av} sets, {\ie} for query results (production \GP{svar})
  98 according to the syntax of \figref{VarTS}.%
  99 \footnote{This syntax resembles the one of programming languages identifiers.}
 100
 101 \begin{figure}[ht]
 102 \begin{footnotesize} \begin{verbatim}
 103 <alpha> ::= [ 'A - Z' | 'a - z' | `_` ]+
 104 <id>    ::= <alpha> [ <alpha> | <dec> ]*
 105 <avar>  ::= "@" <id>
 106 <svar>  ::= "$" <id>
 107 \end{verbatim}\end{footnotesize} %$
 108 \vskip-1pc
 109 \caption{Textual syntax of variables} \label{VarTS}
 110 \end{figure}
 111
 112 \noindent
 113 The syntax of query expressions (production \GP{query}) is described in
 114 \figref{QueryTS}.
 115
 116 \begin{figure}[ht]
 117 \begin{footnotesize} \begin{verbatim}
 118 <qualifier> ::= [ "inverse" ]? [ "sub" | "super" ]? <path>
 119 <main>      ::= [ "main" <path> ]?
 120 <cons>      ::= <path> [ "in" | "match" ] <query>
 121 <istrue>    ::= [ "istrue" <cons> [ "," <cons> ]* ]?
 122 <isfalses>  ::= [ "isfalse" <cons> [ "," <cons> ]* ]*
 123 <exp>       ::= <path> [ "as" <path> ]?
 124 <sec>       ::= [ "attr" <exp> [ "," <exp> ]* ]?
 125 <opt_args>  ::= <main> <istrue> <isfalses> <sec>
 126 <source>    ::= [ "pattern" ]? <query>
 127 <paths>     ::= [ <path> [ "," <path> ]* ]?
 128 <query>     ::= "(" <query> ")" | <string> | "[" <xavs> "]"
 129             |   "property" <qualifier> <opt_args> "of" <source>
 130             |   "let" <svar> "=" <query> "in" <query>
 131             |   <query> ";;" <query> | <svar> | <avar>
 132             |   "ex" <query> | <avar> "." <path>
 133             |   "add" [ "distr" ]? [ <xgroups> | <avar> ] "in" <query>
 134             |   "for" <avar> "in" <query> [ "sup" | "inf" ] <query>
 135             |   "while" <query> [ "sup" | "inf" ] <query>
 136             |   <path> "{" <paths> "}" "{" <queries> "}"
 137             |   "gen" <path> [ "{" <queries> "}" | "in" <query> ]
 138 <queries>   ::= [ <query> [ "," <query> ]* ]?
 139 <xattr>     ::= <path> "=" <query>
 140 <xgroup>    ::= "{" <xattr> [ ";" <xattr> ]* "}"
 141 <xgroups>   ::= <xgroup> [ "," <xgroup> ]*
 142 <xav>       ::= <string> [ "attr" <xgroups> ]?
 143 <xavs>      ::= [ <xav> [ ";" <xav> ]* ]?
 144 \end{verbatim} \end{footnotesize}
 145 \vskip-1pc
 146 \caption{Textual syntax of queries} \label{QueryTS}
 147 \end{figure}
 148
 149 \noindent
 150 The syntax of result expressions (production \GP{avs}) is described in
 151 \figref{ResultTS}.
 152
 153 \begin{figure}[ht]
 154 \begin{footnotesize} \begin{verbatim}
 155 <attr>  ::= <path> "=" <string> | "{" <string> [ "," <string> ]* "}"
 156 <group> ::= "{" <attr> [ ";" <attr> ]* "}"
 157 <av>    ::= <string> [ "attr" <group> [ "," <group> ]* ]?
 158 <avs>   ::= [ <av> [ ";" <av> ]* ]?
 159 \end{verbatim} \end{footnotesize}
 160 \vskip-1pc
 161 \caption{Textual syntax of results} \label{ResultTS}
 162 \end{figure}
 163
 164 The textual syntax of the language extension provided by the basic library
 165 is in \figref{BasicTS}.
 166
 167 \begin{figure}[ht]
 168 \begin{footnotesize} \begin{verbatim}
 169 <query> ::= "empty" | "false" | "true"
 170         |   "not" <query>
 171         |   <query> [ "and" | "or" | "xor"| "sub" | "meet" | "eq" | "le"| "lt" ] <query>
 172         |   <query> [ "union" | "intersect" ] <query> | { <queries> }
 173         |   "if" <query> "then" <query> "else" <query>
 174         |   "select" <avar> "from" <query> "where" <query>
 175 \end{verbatim} \end{footnotesize}
 176 \vskip-1pc
 177 \caption{Textual syntax of basic extension} \label{BasicTS}
 178 \end{figure}
 179