Mercurial > hg > ltpda
diff m-toolbox/html_help/help/ug/repo_retrieve.html @ 0:f0afece42f48
Import.
| author | Daniele Nicolodi <nicolodi@science.unitn.it> |
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| date | Wed, 23 Nov 2011 19:22:13 +0100 |
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--- /dev/null Thu Jan 01 00:00:00 1970 +0000 +++ b/m-toolbox/html_help/help/ug/repo_retrieve.html Wed Nov 23 19:22:13 2011 +0100 @@ -0,0 +1,143 @@ +<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" + "http://www.w3.org/TR/1999/REC-html401-19991224/loose.dtd"> + +<html lang="en"> +<head> + <meta name="generator" content= + "HTML Tidy for Mac OS X (vers 1st December 2004), see www.w3.org"> + <meta http-equiv="Content-Type" content= + "text/html; charset=us-ascii"> + + <title>Retrieving LTPDA objects from a repository (LTPDA Toolbox)</title> + <link rel="stylesheet" href="docstyle.css" type="text/css"> + <meta name="generator" content="DocBook XSL Stylesheets V1.52.2"> + <meta name="description" content= + "Presents an overview of the features, system requirements, and starting the toolbox."> + </head> + +<body> + <a name="top_of_page" id="top_of_page"></a> + + <p style="font-size:1px;"> </p> + + <table class="nav" summary="Navigation aid" border="0" width= + "100%" cellpadding="0" cellspacing="0"> + <tr> + <td valign="baseline"><b>LTPDA Toolbox</b></td><td><a href="../helptoc.html">contents</a></td> + + <td valign="baseline" align="right"><a href= + "repo_explore.html"><img src="b_prev.gif" border="0" align= + "bottom" alt="Exploring an LTPDA Repository"></a> <a href= + "repo_gui.html"><img src="b_next.gif" border="0" align= + "bottom" alt="Using the LTPDA Repository GUI"></a></td> + </tr> + </table> + + <h1 class="title"><a name="f3-12899" id="f3-12899"></a>Retrieving LTPDA objects from a repository</h1> + <hr> + + <p> + <p> + Objects can be retrieved from the repository either by specifying an object ID or a collection ID. The LTPDA + Toolbox provides class construtors to retrieve objects. In additon, to retrieve a collection of objects, the <tt>collection</tt> class + can be used. +</p> +<br> +<h2>The retrieval process</h2> +<p> + When an object is retrieved, the following steps are taken: + <ol> + <li>The object type for the requested ID is retrieved from the <tt>objmeta</tt> table</li> + <li>A call is made to the appropriate class constructor</li> + <li>The class constructor retrieves the XML string from the objs table</li> + <li>The XML string is then converted into an XML Xdoc object</li> + <li>The Xdoc object is then parsed to recreate the desired object</li> + </ol> +</p> + +<br> +<h2>Retrieving objects</h2> + +<p> + To retrieve an object, you must know its object ID, or the ID of the collection that contains that object. If you don't know the + class of the object, you can use the <tt>collection</tt> class as a container, as follows: + <div class="fragment"><pre> + >> a = collection(plist('hostname', 'localhost', 'database', 'ltpda_test', 'id', 1)) + + ** Connection status: + LWB: Disconnected from localhost/ltpda_test as hewitson + ---- collection 1 ---- + name: none + num objs: 1 + 01: ao | New Block/tsdataNdata=[10x1], fs=1, nsecs=10, t0=1970-01-01 00:00:00.000 + description: + UUID: 9ec7a613-9442-4451-9b40-af18f4afea00 + ---------------------- + </pre></div> +</p> +<p> + If you already know the class of the object (for example, <tt>ao</tt>), you can directly call the class constructor method: + <div class="fragment"><pre> + <span class="comment">% Define the hostname and database</span> + hostname = <span class="string">'localhost'</span>; + database = <span class="string">'ltpda_test'</span>; + + <span class="comment">% Retrieve the object</span> + q = ao(plist(<span class="string">'hostname'</span>, hostname, <span class="string">'database'</span>, dbname, <span class="string">'ID'</span>, 12)); + </pre></div> +</p> + +<br> +<p> + Multiple objects can be retrieved simultaneously by giving a list of object IDs. For example + <div class="fragment"><pre> + >> a = ao(plist('hostname', 'localhost', 'database', 'ltpda_test', 'id', [1 2 3])) + </pre></div> +</p> +<br> +<h2>Retrieving object collections</h2> +<p> + Collections of objects can be retrieved by specifying the collection ID. The following script retrieves a collection: + <div class="fragment"><pre> + >> a = collection(plist('hostname', 'localhost', 'database', 'ltpda_test', 'cid', 1)) + </pre></div> + The output is a <tt>collection</tt> object containing the objects retrieved. +</p> + +<h2>Retrieving binary objects</h2> +<p>The retrieval process may be speeded up by taking advantage of the fact that the objects are stored in the databases also in binary form. +This can be achieved by using the parameter 'binary', that will build the object from the corresponding binary representation, if +stored in the database. + <div class="fragment"><pre> + <span class="comment">% Retrieve the collection</span> + q = ao(plist(<span class="string">'hostname'</span>, hostname, <span class="string">'database'</span>, dbname, <span class="string">'ID'</span>, 12, <span class="string">'binary'</span>, <span class="string">'yes'</span>)); + </pre></div> + If the binary representation is not in the database, the object will be built from the xml one. +</p> + + </p> + + <br> + <br> + <table class="nav" summary="Navigation aid" border="0" width= + "100%" cellpadding="0" cellspacing="0"> + <tr valign="top"> + <td align="left" width="20"><a href="repo_explore.html"><img src= + "b_prev.gif" border="0" align="bottom" alt= + "Exploring an LTPDA Repository"></a> </td> + + <td align="left">Exploring an LTPDA Repository</td> + + <td> </td> + + <td align="right">Using the LTPDA Repository GUI</td> + + <td align="right" width="20"><a href= + "repo_gui.html"><img src="b_next.gif" border="0" align= + "bottom" alt="Using the LTPDA Repository GUI"></a></td> + </tr> + </table><br> + + <p class="copy">©LTP Team</p> +</body> +</html>