/*
 *  $Id: execute.js,v 1.64 2010/01/13 22:07:54 source Exp $
 *
 *  This file is part of the OpenLink Software Ajax Toolkit (OAT) project.
 *
 *  Copyright (C) 2009 OpenLink Software
 *
 *  See LICENSE file for details.
 *
 */

/*
	iSPARQL query executer & visualizer
*/

window.defaultPrefixes = [
    {"label":'foaf', "uri":'http://xmlns.com/foaf/0.1/'},
    {"label":'owl', "uri":'http://www.w3.org/2002/07/owl#'},
    {"label":'sioct', "uri":'http://rdfs.org/sioc/types#'},
    {"label":'sioc', "uri":'http://rdfs.org/sioc/ns#'},
    {"label":'ibis', "uri":'http://purl.org/ibis#',"hidden":1},
    {"label":'conf', "uri":'http://www.mindswap.org/~golbeck/web/www04photo.owl#'},
    {"label":'scot', "uri":'http://scot-project.org/scot/ns'},
    {"label":'ical', "uri":'http://www.w3.org/2002/12/cal/icaltzd#'},
    {"label":'mo', "uri":'http://purl.org/ontology/mo/'},
    {"label":'annotation', "uri":'http://www.w3.org/2000/10/annotation-ns#'},
    {"label":'rdfs', "uri":'http://www.w3.org/2000/01/rdf-schema#'},
    {"label":'rdf', "uri":'http://www.w3.org/1999/02/22-rdf-syntax-ns#'},
    {"label":'dcterms', "uri":'http://purl.org/dc/terms/'},
    {"label":'dc', "uri":'http://purl.org/dc/elements/1.1/'},
    {"label":'cc', "uri":'http://web.resource.org/cc/'},
    {"label":'geo', "uri":'http://www.w3.org/2003/01/geo/wgs84_pos#'},
    {"label":'rss', "uri":'http://purl.org/rss/1.0/'},
    {"label":'skos', "uri":'http://www.w3.org/2008/05/skos#'},
    {"label":'vs', "uri":'http://www.w3.org/2003/06/sw-vocab-status/ns#'},
    {"label":'opo',"uri":'http://ggg.milanstankovic.org/opo/ns/'},
    {"label":'nco',"uri":'http://www.semanticdesktop.org/ontologies/nco/'},
    {"label":'lsdis',"uri":'http://lsdis.cs.uga.edu/projects/meteor-s/wsdl-s/ontologies/LSDIS_FInance.owl'},
    {"label":'nao',"uri":'http://www.semanticdesktop.org/ontologies/nao/'},
    {"label":'cohere',"uri":'http://cohere.open.ac.uk/ontology/cohere.owl#'},
    {"label":'nfo',"uri":'http://www.semanticdesktop.org/ontologies/nfo/'},
    {"label":'nmo',"uri":'http://www.semanticdesktop.org/ontologies/nmo/'},
    {"label":'nie',"uri":'http://www.semanticdesktop.org/ontologies/nie/'},
    {"label":'nid3',"uri":'http://www.semanticdesktop.org/ontologies/nid3/'},
    {"label":'kuaba',"uri":'http://www.tecweb.inf.puc-rio.br/ontologies/kuaba'},
    {"label":'wot', "uri":'http://xmlns.com/wot/0.1/',"hidden":1},
    {"label":'xhtml', "uri":'http://www.w3.org/1999/xhtml',"hidden":1},
    {"label":'atom', "uri":'http://atomowl.org/ontologies/atomrdf#',"hidden":1},
    {"label":'dataview', "uri":'http://www.w3.org/2003/g/data-view#',"hidden":1},
    {"label":'xsd', "uri":'http://www.w3.org/2001/XMLSchema#',"hidden":1}];

var QueryExec = function(optObj) {
    var self = this;
    
    this.options = {
	showNav:false,
	div:false,
	virtuoso:false,
	executeCallback:false
    };

    for (var p in optObj) { self.options[p] = optObj[p]; }
    
    this.queryOptions = {
	/* ajax */
	onstart:false,
	onend:false,
	onerror:false,		
	endpoint:false,
	query:false,
	backupQuery:false, /* to be executed if original fails */
	defaultGraph:false,
	namedGraphs:[],
	sponge:false,
	maxrows:false
    };
	
    this.cache = [];
    this.cacheIndex = -1;
    this.dom = {};
    this.tab = false;
    this.store = new OAT.RDFStore(false);
    this.mini = false;
    this.miniplnk = false;
    this.mRDFCtr = false;

    this.init = function() {
	this.dom.result = OAT.Dom.create("div");
	this.dom.request = OAT.Dom.create("div"); 
	this.dom.response = OAT.Dom.create("pre");
	this.dom.query = OAT.Dom.create("pre");
	this.dom.select = OAT.Dom.create("select");
	OAT.Dom.option("Machine-readable","1",this.dom.select);
	OAT.Dom.option("Human-readable","0",this.dom.select);
	
	var tabs1 = ["Result","SPARQL Params","Response","Query"];
	var tabs2 = [self.dom.result,self.dom.request,self.dom.response,self.dom.query];
	self.dom.tab = OAT.Dom.create("div",{padding:"5px",backgroundColor:"#fff"});
	self.dom.ul = OAT.Dom.create("ul",{},"tabres");
	self.tab = new OAT.Tab(self.dom.tab,{dockMode:true,dockElement:self.dom.ul});
	for (var i=0;i<tabs1.length;i++) {
	    var li = OAT.Dom.create("li");
	    self.dom.ul.appendChild(li);
	    li.innerHTML = tabs1[i];
	    self.tab.add(li,tabs2[i]);
	}
	if (self.options.div) { 
	    OAT.Dom.clear(self.options.div);
	    OAT.Dom.append([self.options.div,self.dom.select,OAT.Dom.create("br")]);
	    OAT.Dom.append([self.options.div,self.dom.ul,self.dom.tab]); 
	}
	self.initNav();
	
	OAT.Event.attach(self.dom.select,"change",function(){
	    if (self.cacheIndex > -1) { self.draw(); }
	});
	OAT.Event.attach(self.dom.check,"click",function(){
	    if (self.cacheIndex > -1) { self.draw(); }
	});
    };
	
    this.initNav = function() {
	var ip = OAT.Preferences.imagePath;
	var b = ip+"Blank.gif";
	self.dom.first = OAT.Dom.create("li",{},"nav");
	self.dom.prev = OAT.Dom.create("li",{},"nav");
	self.dom.next = OAT.Dom.create("li",{},"nav");
	self.dom.last = OAT.Dom.create("li",{},"nav");
	self.dom.first.appendChild(OAT.Dom.image(ip+"RDF_first.png",b,16,16));
	self.dom.prev.appendChild(OAT.Dom.image(ip+"RDF_prev.png",b,16,16));
	self.dom.next.appendChild(OAT.Dom.image(ip+"RDF_next.png",b,16,16));
	self.dom.last.appendChild(OAT.Dom.image(ip+"RDF_last.png",b,16,16));
	self.dom.first.title = "First";
	self.dom.prev.title = "Back";
	self.dom.next.title = "Forward";
	self.dom.last.title = "Last";
	OAT.Dom.append([self.dom.ul,self.dom.first,self.dom.prev,self.dom.next,self.dom.last]);
	OAT.Event.attach(self.dom.first,"click",function(){
	    if (self.cacheIndex > 0) { 
		self.cacheIndex = 0;
		self.draw() 
	    }
	});
	OAT.Event.attach(self.dom.prev,"click",function(){
	    if (self.cacheIndex > 0) { 
		self.cacheIndex--;
		self.draw();
	    }
	});
	OAT.Event.attach(self.dom.next,"click",function(){
	    if (self.cacheIndex > -1 && self.cacheIndex < self.cache.length-1) { 
		self.cacheIndex++;
		self.draw();
	    }
	});
	OAT.Event.attach(self.dom.last,"click",function(){
	    if (self.cacheIndex > -1 && self.cacheIndex < self.cache.length-1) { 
		self.cacheIndex = self.cache.length-1;
		self.draw();
	    }
	});
	self.refreshNav();
    };
    
    this.refreshNav = function() {
	var activate = function(elm) {
	    OAT.Style.opacity(elm,1);
	    elm.style.cursor = "pointer";
	}
	var deactivate = function(elm) {
	    OAT.Style.opacity(elm,0.3);
	    elm.style.cursor = "default";
	}
	if (self.cacheIndex > 0) {
	    activate(self.dom.first);
	    activate(self.dom.prev);
	} else {
	    deactivate(self.dom.first);
	    deactivate(self.dom.prev);
	}
	
	if (self.cacheIndex > -1 && self.cacheIndex < self.cache.length-1) {
	    activate(self.dom.next);
	    activate(self.dom.last);
	} else {
	    deactivate(self.dom.next);
	    deactivate(self.dom.last);
	}
    };
	
    this.isNew = function(opts) {
	if (self.cacheIndex == -1) { return true; }
	var cache = self.cache[self.cacheIndex];
	return (cache.opts.query != opts.query || cache.opts.endpoint != opts.endpoint || cache.opts.defaultGraph != opts.defaultGraph);
    };
	
    this.buildRequest = function(opts) {
	var paramsObj = {};
	
	paramsObj["format"] = "application/rdf+xml";
	if (opts.defaultGraph && !opts.query.match(/from *</i)) { paramsObj["default-graph-uri"] = opts.defaultGraph; }
	if (opts.maxrows && opts.query && !opts.query.match(/limit *[0-9].*/i)) { paramsObj["maxrows"] = opts.maxrows; }
	if (opts.sponge && self.options.virtuoso) { paramsObj["should-sponge"] = opts.sponge; }
	
	var pragmas = [];

	if (opts.pragmas) { 
	    for (var i=0;i<opts.pragmas.length;i++) {
		var pragma = opts.pragmas[i];
		var name = pragma[0];
		var values = pragma[1];
		for(var j=0;j<values.length;j++) { pragmas.push(name+" "+values[j]); }
	    }
	}
	
	paramsObj["query"] = pragmas.join('\n') + '\n' + opts.query;
	
	var arr = [];
	for (var p in paramsObj) {
	    arr.push(p+"="+encodeURIComponent(paramsObj[p]));
	}
	if (opts.namedGraphs) {
	    for (var i=0;i<opts.namedGraphs.length;i++) {
		arr.push("named-graph-uri="+encodeURIComponent(opts.namedGraphs[i]));
	    }
	}

	if (opts.endpoint.match(/^http/i)) {
	    var req = "url=" + encodeURIComponent(opts.endpoint + "?" + arr.join ("&"));
	    opts.endpoint = "/proxy";
	    return req;
	}

	return arr.join("&");
    };
	
    this.addResponse = function(request,opts,wasError,data) { /* something arrived. maybe cache and visualize */
	if (OAT.AnchorData.window) { OAT.AnchorData.window.close(); }
	if (self.isNew(opts) || (self.cache[self.cacheIndex].wasError && !wasError)) {
	    var cache = {
		opts:opts,
		wasError:wasError,
		request:request,
		data:data
	    }
	    self.cache.push(cache);
	    self.cacheIndex = self.cache.length - 1;
	}
	self.draw();
    };

    this.makeMiniRDFPlinkURI = function (caller,msg,o) {
	var item = self.cache[self.cacheIndex];
	var opts = item.opts;
	var request = item.request;
	var plnk = self.miniplnk;

	var nloca = document.location;

	var xparm = "?query=" + encodeURIComponent(opts.query);

	if (opts.endpoint)
	    xparm = xparm + "&endpoint="  + opts.endpoint;
        xparm = xparm + "&resultview=" + self.mini.options.tabs[o.tabIndex][0];
	xparm += "&maxrows=" + (opts.maxrows ? opts.maxrows : "");

	plnk.target = "_blank";
	plnk.href= nloca.protocol + "//" + nloca.host + "/isparql/view/" + xparm;
	
    }

    this.parseTabIndex = function (rvVal, tabs) {
	for (var i=0;i < tabs.length;i++) {
	    if (rvVal == tabs[i][0]) return i;
	}
	return 0;
    };

    this.drawTable = function() {
	OAT.Dom.clear(self.dom.result);
	
	var entCount = 0;
	var entities = {};
	var q = self.cache[self.cacheIndex].opts.query.replace(/[\r\n]/g," ");
	var where = q.match(/where *{(.*)}/i);
	if (where) {
	    var regs = where[1].match(/<[^>]+>/g);
	    if (regs) for (var i=0;i<regs.length;i++) {
		var entity = regs[i].substring(1,regs[i].length-1);
		if (!(entity in entities)) { 
		    entities[entity] = 1; 
		    entCount++;
		}
	    }
	}
	
/*	var h = OAT.Dom.create("h3");
	h.innerHTML = "This page is about:";
	
	if (entCount) {
	    var ul = OAT.Dom.create("ul");
	    for (var p in entities) {
		var li = OAT.Dom.create("li");
		ul.appendChild(li);
		li.innerHTML = p;
	    }
	    OAT.Dom.append([self.dom.result,ul]);
	}
*/	
	var item = self.cache[self.cacheIndex];
	var opts = item.opts;
	var request = item.request;
	
	var execURIa = OAT.Dom.create ("a");
	execURIa.innerHTML = "Execute Permalink";
	var nloca = document.location;

	var xparm = "?query=" + encodeURIComponent(opts.query) + "&endpoint="  + opts.endpoint;
	xparm += "&maxrows=" + (opts.maxrows ? opts.maxrows : "");
	xparm += "&default-graph-uri=" + (opts.defaultGraph ? opts.defaultGraph : "");

	execURIa.href = nloca.protocol + "//" + nloca.host + "/isparql/view/" + xparm;
	
	execURIa.target = "_blank";
	
	OAT.Dom.append([self.dom.result,execURIa]);
	
	var root = self.store.data.all[0];
	var ns_var = "http://www.w3.org/2005/sparql-results#resultVariable";
	var ns_var2 = "http://www.w3.org/2005/sparql-results#variable";
	var ns_sol = "http://www.w3.org/2005/sparql-results#solution";
	var ns_bind = "http://www.w3.org/2005/sparql-results#binding";
	var ns_val = "http://www.w3.org/2005/sparql-results#value";
	if (!ns_sol in root.preds) { return; }
		
	var grid = new OAT.Grid(self.dom.result);
	var header = root.preds[ns_var];
	if (self.dom.select.value == "1") {
	    var map = {
		"hasValue":"Range",
		"isValueOf":"Domain",
		"property":"Property"
	    }
	    for (var i=0;i<header.length;i++) {
		if (header[i] in map) { header[i] = map[header[i]]; } 
	    }
	}
	grid.createHeader(header);
	
	if (!(ns_sol in root.preds)) { return; }
	var solutions = root.preds[ns_sol];
	
	for (var i=0;i<solutions.length;i++) {
	    var row = [];
	    var simplified_row = [];
	    for (var j=0;j<header.length;j++) { 
		row.push(""); 
		simplified_row.push(""); 
	    }
			
	    var sol = solutions[i];
	    if (!(ns_bind in sol.preds)) { continue; }
	    var bindings = sol.preds[ns_bind];
	    for (var j=0;j<bindings.length;j++) {
		var val = bindings[j].preds[ns_val][0];
		var v = bindings[j].preds[ns_var2][0];
		var index = header.find(v);
		row[index] = val;
		simplified_row[index] = self.simplifyPrefix(val);
		
		if (self.dom.select.value == "0") {
		    var value = simplified_row[index];
		    
		    if (!value) value = "";
		    
		    var simple = self.store.simplify(value);
		    simplified_row[index] = simple;
		}
	    }
			
	    grid.createRow(simplified_row);
	    for (var j=0;j<row.length;j++) {
		var val = row[j];
		if (val.match(/^(http|urn|doi)/i)) { /* a++ */
		    var a = OAT.Dom.create("a");
		    a.innerHTML = simplified_row[j];
		    a.href = "#";
		    var v = grid.rows[grid.rows.length-1].cells[j].value;
		    OAT.Dom.clear(v);
		    OAT.Dom.append([v,a]);
		    self.processLink(a,val);
		}
	    }
	}
    };

    this.makeErrorMsg = function (data) {
	var msg;
	var r = data.match(/Error (..[0-9]{3})/);
	if (r) {
	    msg="<h3>SPARQL Processor Error ("+ r[1] + ")</h3>\n"
	    if (r[1] == "HT404")
		msg += "<p>Resource not found<br/>Check your query and try again</p>";
	}
	else if (data.match(/Error HTCLI/)) {
	    msg = "<h3>Proxy connection error</h3><p>The proxy could not connect to the endpoint ";
	    msg += "<span class=\"endpoint_url\">" + self.cache[self.cacheIndex].opts.endpoint;
	    msg += "</span>. Please try again later.</p>";
	}
	msg += "<p>See Response tab for full response from SPARQL endpoint.</p>"
	return msg;
    };

    this.makeErrorResp = function (data) {
	var txt = OAT.Xml.serializeXmlDoc(data);
	if (txt.length == 0) 
	    txt = data;
	txt = "<pre>"+txt+"</pre>";
	return txt;
    };

    this.draw = function() {
	var item = self.cache[self.cacheIndex];
	var opts = item.opts;
	var request = item.request;
	var wasError = item.wasError;
	var data = item.data;
	
	if (self.options.executeCallback) { self.options.executeCallback(item); }
	
	OAT.Dom.clear(self.dom.request);
	var r = decodeURIComponent(request);
	var parts = r.split("&");
	var req = OAT.Dom.create("pre");
	OAT.Dom.append([self.dom.request,req]);
	
	for (var i=0;i<parts.length;i++) { req.innerHTML += OAT.Xml.escape(parts[i])+"\n"; }
	
	OAT.Dom.clear(self.dom.query);
	
	var a = OAT.Dom.create("a");
	a.innerHTML = "Query Permalink";
	var xparm = "?query=" + encodeURIComponent(opts.query) + "&endpoint=" + opts.endpoint;
	xparm += "&maxrows=" + (opts.maxrows ? opts.maxrows : "");
	xparm += "&default-graph-uri=" + (opts.defaultGraph ? opts.defaultGraph : "");
	a.href = document.location.protocol + '//' + document.location.host + '/isparql/' + xparm;
	a.target = "_blank";
	
	var q = OAT.Dom.create("pre");
	q.innerHTML = OAT.Xml.escape(opts.query);
	
	OAT.Dom.append([self.dom.query,a,q]);

	if (wasError && !data.match(/Error SR171/)) { // Timeout SR171 means there may be data to display
	    /* trap http codes */
	    self.dom.result.innerHTML = self.makeErrorMsg (data);
	    self.dom.response.innerHTML = self.makeErrorResp (data);
	    self.tab.go(0); // buggy JS in FireFox...
	    self.refreshNav();
	    return;
	} else {
	    var txt = OAT.Xml.serializeXmlDoc(data);
	    txt = OAT.Xml.escape(txt);
	    self.dom.response.innerHTML = txt;

	    if (opts.query.match(/describe/i) || opts.query.match(/construct/i)) {
		/* rdf mini */
		var lastIndex = 0;
		var tabs = [
		    ["navigator","Navigator"],
		    ["browser","Raw Triples",{removeNS:true}],
		    ["triples","Grid View",{}],
		    ["svg","SVG Graph",{}],
		    ["images","Images",{}],
		    ["map","Yahoo Map",{provider:OAT.MapData.TYPE_Y, 
					markerMode:OAT.RDFTabsData.MARKER_MODE_AUTO,
					clickPopup:true,
					hoverPopup:false}] 
		];
		
		if(self.mini) {
		    lastIndex = self.mini.select.selectedIndex;
		    OAT.Dom.clear (self.dom.result);
		    OAT.Dom.append ([self.dom.result, self.miniplnk, self.mRDFCtr]);
		}
		else { 
		    lastIndex = self.parseTabIndex (opts.resultView, tabs);
		    self.miniplnk = OAT.Dom.create ("a");
		    self.miniplnk.innerHTML = "Permalink";
		    self.mRDFCtr = OAT.Dom.create ("div");
		    self.mRDFCtr.id = "mini_rdf_ctr";
		    OAT.Dom.clear (self.dom.result);
		    OAT.Dom.append ([self.dom.result, self.miniplnk, self.mRDFCtr]);
		    self.mini = new OAT.RDFMini(self.mRDFCtr,{tabs:tabs,
							      showSearch:false});
		}
		self.tab.go(0); // got to do here or maps won't resize properly.
		self.mini.processLink = self.processLink;
		self.mini.store.addXmlDoc(data);
		self.mini.select.selectedIndex = lastIndex;
		self.mini.redraw();
		self.makeMiniRDFPlinkURI (false,false,{tabIndex:lastIndex});
		OAT.MSG.attach (self.mini, OAT.MSG.RDFMINI_VIEW_CHANGED, self.makeMiniRDFPlinkURI);
	    } else {
		/* own table */
		self.store.clear();
		self.store.addXmlDoc(data);
		self.drawTable();
	    }
	}
	self.tab.go(0);
	self.refreshNav();
    };
    
    this.simplifyPrefix = function(str) {
	var plist = window.defaultPrefixes;
	var s = str;
	if (!s) { return; }
	if (s.charAt(0) == "<") { s = s.substring(1,s.length-1); }
	
	for (var i=0;i<plist.length;i++) {
	    var prefix = plist[i];
	    if (s.substring(0,prefix.uri.length) == prefix.uri) {
		return prefix.label + ":" + s.substring(prefix.uri.length); 
	    }
	}
	return s;
    };
	
    this.processLink = function(domNode,href) {
	var dereferenceRef = function(event) {
	    OAT.Event.prevent(event);
	    
	    var cache = self.cache[self.cacheIndex];
	    
/*	    var q = 'define get:soft "replacing" \n'+
		'define input:same-as "yes" \n'+
		'define input:grab-seealso <http://www.w3.org/2002/07/owl#sameAs> \n'+
		'DESCRIBE <'+href+'> FROM <' + href + '>';*/
	    var q  = 'DESCRIBE <'+href+'>';
	    var bq = 'DESCRIBE <'+href+'>';
	    var o = {};
	    for (var p in cache.opts) { o[p] = cache.opts[p]; }
	    o.defaultGraph = false;

	    if (o.endpoint.match(/^http/i)) // don't attempt to sponge on remote endpoints
		o.query = bq;
	    else
		o.query = q;

	    o.backupQuery = bq;
	    self.execute(o);
 	};
	
	var selectRef = function(event) {
	    OAT.Event.prevent(event);
	    var cache = self.cache[self.cacheIndex];
	    var o = {};
	    for (var p in cache.opts) { o[p] = cache.opts[p]; }
	    
	    var graph = o.defaultGraph || false;
	    
	    var q = 'SELECT DISTINCT * \n';
	    if (graph) { q += 'FROM <' + graph + '> \n'; }
	    q += 'WHERE { { <'+href+'> ?p ?o } UNION { ?s ?p <'+href+'> } }';
	    
	    o.query = q;
	    self.execute(o);
	};
	
	var genRef = function() {
	    var ul = OAT.Dom.create("ul",{marginLeft:"20px",marginTop:"10px"});
	    
	    var li = OAT.Dom.create("li");
	    var a = OAT.Dom.create("a");
	    a.innerHTML = "Get Data Items";
	    a.href = href;
	    OAT.Event.attach(a,"click",selectRef);
	    var li = OAT.Dom.create("li");
	    OAT.Dom.append([ul,li],[li,a]);
	    
	    var li = OAT.Dom.create("li");
	    var a = OAT.Dom.create("a");
	    a.innerHTML = "Describe Entity";
	    a.href = href;
	    OAT.Event.attach(a,"click",dereferenceRef);
	    var li = OAT.Dom.create("li");
	    OAT.Dom.append([ul,li],[li,a]);
	    
	    var li = OAT.Dom.create("li");
	    var a = OAT.Dom.create("a");
	    a.innerHTML = "Open Web Page";
	    a.href = href;
	    OAT.Dom.append([ul,li],[li,a]);
	    
	    return ul;
	};
	
	var obj = {
	    title:"URL",
	    content:genRef,
	    newHref:href,
	    width:200,
	    height:100,
	    result_control:false,
	    activation:"click"
	};

	OAT.Anchor.assign(domNode,obj);
	
//	var img1 = OAT.Dom.create("img",{paddingLeft:"3px",cursor:"pointer"});
//	img1.title = "Describe Data Source";
//	img1.src = OAT.Preferences.imagePath + "RDF_rdf.png";
//	OAT.Event.attach(img1,"click",dereferenceRef);
	
//	var a = OAT.Dom.create("a",{paddingLeft:"3px"});
//	var img2 = OAT.Dom.create("img",{border:"none"});
//	img2.src = OAT.Preferences.imagePath + "RDF_xhtml.gif";
//	a.title = "Open Web Page";
//	a.appendChild(img2);
//	a.target = "_blank";
//	a.href = "/about/html/" + href;
	
//	domNode.parentNode.appendChild(img1);
//	domNode.parentNode.appendChild(a);
    };
	
    this.execute = function(optObj) {
	var opts = {};
	for (var p in self.queryOptions) { opts[p] = self.queryOptions[p]; } /* copy of defaults */
	for (var p in optObj) { opts[p] = optObj[p]; }
	
	var request = self.buildRequest(opts);
	var callback = function(data) {
	    self.addResponse(request,optObj,0,data);
	    if (opts.callback) { opts.callback(data); }
	};

	var onerror = function(xhr) {
	    var txt = xhr.getResponseText();
	    if (txt.match(/SP031/) && optObj.backupQuery) {
		var newO = {};
		for (var p in optObj) { newO[p] = optObj[p]; }
		newO.query = newO.backupQuery;
		newO.backupQuery = false;
		self.execute(newO);
	    } else {
		self.addResponse(request,optObj,1,txt);
		if (opts.onerror) { opts.onerror(txt); }
	    }
	};

	var o = {
	    type:OAT.AJAX.TYPE_XML,
	    onstart:opts.onstart,
	    onend:opts.onend,
	    onerror:onerror
	};
	
	if (!opts.endpoint) { opts.endpoint = '/sparql'; }
	
	OAT.AJAX.POST(opts.endpoint,request,callback,o);
    }
    
    self.init();
}