<head>
<title>MathQL</title>
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content="text/html; charset=ISO-8859-1">
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<meta name="author" content="Ferruccio Guidi">
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<meta name="description" content="MathQL Home Page">
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<body>
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<h1 align="center">MathQL-1</h1>
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+
<h2 align="center">A query language for RDF metadata</h2>
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<table cellpadding="10" cellspacing="2" border="0" width="95%"
bgcolor="#ffffff">
- <tbody>
- <tr>
- <td valign="top" align="left">
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+ <tbody>
+ <tr>
+ <td valign="top" align="left">
+
<ul>
- <li><a href="index.html">Forward</a><br>
- </li>
+
<li><a href="index.html">Forward</a><br>
+ </li>
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+
</ul>
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+
<ul>
- <li><a href="features.html">Features</a></li>
-
+
<li><a href="features.html">Features</a></li>
+
</ul>
-
+
<ul>
- <li>What's new<br>
- </li>
-
+ <li>What's new<br>
+ </li>
+
+
</ul>
-
+
+
<ul>
- <li><a href="documentation.html">Documentation</a></li>
+
<li><a href="documentation.html">Documentation</a></li>
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+
</ul>
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+
<ul>
- <li><a href="implementation.html">Implementation</a><br>
- </li>
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+
<li><a href="implementation.html">Implementation</a><br>
+ </li>
+
</ul>
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+
<ul>
- <li><a href="authors.html">The authors</a><br>
- </li>
+
<li><a href="authors.html">The authors</a><br>
+ </li>
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</ul>
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<ul>
- <li><a href="links.html">Links</a><br>
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<li><a href="links.html">Links</a><br>
+ </li>
+
</ul>
- <br>
- </td>
- <td valign="top">
-
+ <br>
+ </td>
+ <td valign="top">
+
<div align="right"><b>What's new</b><br>
- <br>
- </div>
- This page reports the newly <a href="implementation.html">implemented</a>
- features of MathQL-1 that are not included in the
ufficial <a
+ <br>
+ </div>
+ This page reports the newly <a href="implementation.html">implemented</a>
+ features of MathQL-1 that are not included in the
official <a
href="documentation.html">documentation</a> yet.<br>
- <br>
- Changes and additions to MathQL-1 operators:<br>
-
+ <br>
+ <hr width="100%" size="2">
+ <div align="center">
+ <h3> Changes and additions to MathQL-1 operators:</h3>
+ </div>
+
<ul>
- <li>The <b>add</b> operator now accepts a syntax extension allowing
-to specify more than one explicit attribute group.</li>
-
+ <li>The <b>add</b> operator now accepts a syntax extension allowing
+ to specify more than one explicit attribute group.</li>
+
</ul>
-
+
<blockquote>The syntax now is:</blockquote>
-
- <blockquote><query> := "add" [ "distr" ]? [ <groups> | <avar>
-] "in" <query><br>
- <groups> := <group> [ ";" <group> ]*<br>
- <group> := <attribute> [ "," <attribute> ]*<br>
- <attribute> := <value> "as" <path><br>
- <br>
- Examples:<br>
- the query <b>add "1" as "a", "2" as "b" in subj "A"</b> gives the result
- <b>"A" attr {"a"="1"; "b"="2"}</b> while<br>
- the query <b>add "1" as "a"; "2" as "b" in subj "A"</b> gives the result
- <b>"A" attr {"a"="1"}, {"b"="2"}</b>.<br>
- </blockquote>
-
- <ul>
- <li>The new <b>align</b> operator takes an integer <i>i</i> (represented
-as a string), a multiple string value <i>v</i> and returns the same <i>v</i>
-where each string with length <i>n < i</i> is prefixed with <i>i - n</i>
-spaces. The syntax of the add operator is:</li>
-
- </ul>
-
+
+ <blockquote><query> := "add" [ "distr" ]? [ <groups> |
+<avar> ] "in" <query><br>
+ <groups> := <group> [ ";" <group> ]*<br>
+ <group> := <attribute> [ "," <attribute> ]*<br>
+ <attribute> := <value> "as" <path><br>
+ <br>
+ Examples:<br>
+ the query <b>add "1" as "a", "2" as "b" in subj "A"</b> gives the result
+ <b>"A" attr {"a"="1"; "b"="2"}</b> while<br>
+ the query <b>add "1" as "a"; "2" as "b" in subj "A"</b> gives the result
+ <b>"A" attr {"a"="1"}, {"b"="2"}</b>.<br>
+ </blockquote>
+
+ <ul>
+ <li>The new <b>align</b> operator takes an integer <i>i</i> (represented
+ as a string), a multiple string value <i>v</i> and returns the same <i>v</i>
+ where each string with length <i>n < i</i> is prefixed with <i>i - n</i>
+ spaces. The syntax of the add operator is:</li>
+
+ </ul>
+
<blockquote><value> := "align" <string> "in" <value><br>
- <br>
- This operators aligns strings containing numbers so that their alphabetic
-order agrees with their numeric order.<br>
- </blockquote>
-
- <ul>
- <li>The <b>intersect</b> operator now intersects the attribute groups
-of the mathing subject strings set-theoretically rather than making their
-"Cartesian product". This semantics reduces the computational costs and makes
-intersection the dual of union.</li>
-
- </ul>
-
- <ul>
- <li>The <b>property</b> operator now accepts more than one <b>isfalse</b>
-clause to increase the complexity of the constraint condition used to filter
-the raw query results. This feature is exploited in the queries produced
-by the <a href="implementation.html">HELM query generator</a>.
<br>
- </li>
-
+ This operators aligns strings containing numbers so that their alphabetic
+ order agrees with their numeric order.<br>
+ </blockquote>
+
+ <ul>
+ <li>The <b>intersect</b> operator now intersects the attribute
+groups of the matching subject strings set-theoretically rather than making
+their "Cartesian product". This semantics reduces the computational costs
+and makes intersection the dual of union.</li>
+
</ul>
- </td>
- </tr>
-
- </tbody>
+
+ <ul>
+ <li>The <b>property</b> operator now accepts more than one <b>isfalse</b>
+ clause to increase the complexity of the constraint condition used to filter
+ the raw query results. This feature is exploited in the queries produced
+by the <a href="implementation.html">HELM query generator</a>.</li>
+
+ </ul>
+ <br>
+ <hr width="100%" size="2">
+ <div align="center">
+ <h3>The PostgreSQL database map:</h3>
+ </div>
+The <b>PostgreSQL database map</b> is a file describing how the MathQL-1
+interpreter must interact with the underlying PostgreSQL database, when it
+is run in Postgres mode. Currently this file contains the following information:<br>
+ <ul>
+ <li>the <i>database connection string</i> to be used when the interpreter
+opens a connection with the database;</li>
+ </ul>
+ <ul>
+ <li>the <i>map</i> describing the correspondence between the metadata
+access paths used by the <i>property</i> operator and the fields of the database
+tables.</li>
+ </ul>
+The format of the file is textual and line oriented, but a corresponding
+XML syntax will be provided soon.<br>
+The first line must contain the database connection string and the subsequent
+lines contain the map with the following syntax:<br>
+ <ul>
+ <li>blank lines: ignored (used for separation);</li>
+ </ul>
+ <ul>
+ <li>lines starting with a # followed by a space: ignored (used for
+comments);<br>
+ </li>
+ </ul>
+ <ul>
+ <li><table_name> <field_name> "<-"
+[ <path_component> ]*<br>
+ </li>
+ </ul>
+ <blockquote>the information about the metadata denoted by the given
+path is found in the given field of the given table in the database. For
+example the line:<br>
+ <br>
+refobj h_occurrence <- refObj h:occurrence<br>
+ <br>
+tells that the metadata denoted by the path <b>/"refObj"/"h:occurrence"</b>
+is found in the field "h_occurrence" of the table "refobj" in the database,
+while:<br>
+ <br>
+refobj source <-<br>
+ <br>
+tells that the metadata denoted by the path <b>/</b> is found in the field
+"source" of the table "refobj" in the database;<br>
+ </blockquote>
+ <ul>
+ <li><table_name> <field_name> "<+"
+[ <path_component> ]*<br>
+ </li>
+ </ul>
+ <blockquote>same as the previous but defines a default table and field
+for the given path. This is used to force the interpreter to query a particular
+table when the information denoted by a path can be found in more than one
+table and field. For example:<br>
+ <br>
+objectname source <+<br>
+refobj source <-<br>
+refrel source <-<br>
+refsort source <-<br>
+ <br>
+tells that the metadata denoted by the path <b>/</b> is found in the "source"
+field of the "objectname", "refobj", "refrel" and "refsort" tables, and that
+the first choice is preferred;<br>
+ </blockquote>
+ <ul>
+ <li><table_name> "<-" [ <path_component> ]*</li>
+ </ul>
+ <blockquote>the given path denotes a structured metadata whose components
+are found in the fields of the given table. For example:<br>
+ <br>
+refobj <- refObj<br>
+ <br>
+tells that the path <b>/"refObj"</b> denotes a structured metadata whose
+components are found in the fields of the table "refobj"; <br>
+ </blockquote>
+ <ul>
+ <li><table_name> "<+" [ <path_component> ]*</li>
+ </ul>
+ <blockquote>same as the previous but tells that this is a default correspondence;
+ <br>
+ </blockquote>
+ <ul>
+ <li><virtual_table_name> "->" <concrete_table_name></li>
+ </ul>
+ <blockquote>defines a correspondence between a virtual table name an
+a concrete table name. All the <table_name> entries represent virtual
+table names that are mapped to concrete table names using the identity function
+unless a particular mapping is defined for them using the above construction.
+This mechanism allows to define several set of metadata on the same database
+table as in:<br>
+ <br>
+refobj source
+ <-<br>
+refobj h_occurrence <-
+ refObj h:occurrence<br>
+backpointer source
+ <- backPointer h:occurrence<br>
+backpointer h_occurrence <-<br>
+backpointer
+ -> refobj<br>
+ </blockquote>
+ <blockquote>which defines four path accessing two virtual tables ("refobj"
+and "backpointer") and then maps these tables in a single concrete table;<br>
+ </blockquote>
+ <ul>
+ <li>"->" <br>
+ </li>
+ </ul>
+ <blockquote>a line like this must end the map file. <br>
+ </blockquote>
+Here you can find the <a
+ href="http://www.cs.unibo.it/cgi-bin/cvsweb/helm/mathql_db_map.txt">current
+version of PostgreSQL database map for HELM</a>.<br>
+ <br>
+ <b>How does the interpreter use the map?</b> The map file is read during
+the interpreter initialization process from the file pointed by the MATHQL_DB_MAP
+environment variable and is used during the execution of each <i>property</i>
+operation in the issued queries.When executing a <i>property</i> operation,
+the interpreter uses the map to find the smallest set of database tables
+containing the information required by the given access paths and then queries
+these tables to obtain the wanted information. <br>
+ </td>
+ </tr>
+
+ </tbody>
</table>
- <br>
- <br>
+ <br>
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projects / helm.git / blobdiff