xsdb project page with download links
xFeedMe xsdb resources
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xsdb project page with download links xFeedMe xsdb resources |
The entire system is packaged as a single file so that it may be easily included in web pages: xsdbjs/xsdball.js. The "xsdball" file is constructed by concatenating most of the other javascript files in the directory in the right order so the symbols resolve correctly.
Simple demonstrations of the xsdb system may evaluate xsdb queries directly encoded on the HTML web page. A trivial example of such an evaluation is provided in xsdbjs/test1.html which has the following content:
<h1>Test of javascript</h1>
<script src="xsdball.js">
</script>
<script language="JavaScript">
queryString('<calc at="x" expr="4+5"/>')
</script>
done.
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Test of javascript</i at="x">9</i>done. |
More interesting uses of the xsdb system require access to a web server because interesting applications usually require access to data from files in addition to data from javascript strings encoded directly in the page. All file contents retrieved by xsdb must be delivered by a web server because (for portability and security reasons) xsdb only supports the HTTP protocol for accessing files (in particular the FILE protocol is not supported at this time).
NOTE: As a security feature javascript does not allow a javascript program to load
a file from a domain other than the domain provided the javascript component. For
this reason it is not possible to use javascript directly to query xsdb data sets
that reside on different domains. For example the
examples/SupplierParts/remote_parts_query.xsdb does not work
under the javascript implementation because of this limitation.
The xsdbjs directory includes a number of demo pages. These pages must be installed in a web server directory before they will work properly.
To get the demo pages running you must have the ability to install subdirectories below a web server html publication root. In my case I have a local web server running on my workstation. To get the demos working I:
Create a Query object from a query text string using the constructor
Q = StringQuery(text) // or Q = StringQuery(text, contextLocation); // or Q = StringQuery(text, contextLocation, verbose);Where text is the body of the query, contextLocation is a directory path used to resolve relative file system references and verbose boolean flag which when set true causes the framework to generate debugging output. If omitted the contextLocation defaults to the document.location.href and the verbose flag defaults to false.
A program may extract the result of a query as an XML string, an ArrayList of ArrayLists or as an ArrayList of Hashtables as explained below.
For (my) convenience the xsdb javascript implementation uses emulations of the
java Hashtable and ArrayList container classes. An ArrayList List is a sequence
object implemented using an internal javascript Array object List.L.
Most javascript programmers may prefer to use the array List.L
directly rather
than learn more about ArrayLists. A Hashtable H is a mapping object
implemented using javascript associative arrays. It provides the following methods:
Note: some future version of the javascript implementation should limit the use of the ArrayList and Hashtable containers as much as possible (they are primarily an artifact of porting expediency) but the Query interfaces should be maintained for backwards compatibility.
Query.Dictionaries(...) method presents the result
as a sequence of Hashtables where the keys for the table are the names and
the values for the table are the values associated with each name. The
Query.Tuples(...) method presents the result as a sequence of
ArrayLists containing the values associated with the names. If the order of the
names is specified in the query the values are provided in the order requested,
otherwise the values are provided sorted alphabetically by the associated name.
The Query.StringResult(...) method presents the result as an xml string
similar to those generated by the query and test applications.
The signatures of these methods are
arrayListResult = Q.Dictionaries(strict) arrayListResult = Q.Tuples(strict) strintgResult = Q.StringResult(strict)In each case if the
strict parameter is set true (the default)
will trigger an exception
if the result of the query cannot be converted to a purely positive form.
The strict parameter may be omitted, in which case it defaults
to false.
The included APIDemo.html page provides a very simple demonstration
of each of these methods. The main method for the application
is listed below
<HTML><h1>Demonstration of the xsdb javascript API</h1>
<script src="xsdball.js">
</script>
<pre>
<script language="JavaScript">
// Initialize a query from a String literal
var querytext = (
"<query names=\"salutation age\" sort=\"age\">\n"+
"<or>\n"+
" <and>\n"+
" <s at=\"salutation\">hello kind world</s> <i at=\"age\">0</i>\n"+
" </and>\n"+
" <and>\n"+
" <s at=\"salutation\">goodbye cruel world</s> <i at=\"age\">99</i>\n"+
" </and>\n"+
"</or>\n"+
"</query>\n"
);
document.write("query text = \n"+quote(querytext));
var Q = StringQuery(querytext)
document.write("\n\n String result is\n"+quote(Q.StringResult(false)));
document.write("\n\n hash table result");
var Hashes = Q.Dictionaries(false);
var ArrayOfHashtables = Hashes.L;
for (var i=0; i<ArrayOfHashtables.length; i++)
{
var H = ArrayOfHashtables[i];
var age = H.get("age");
var salutation = H.get("salutation");
document.write("\n age="+age+" salutation="+salutation);
}
document.write("\n\n array list result");
var tuples = Q.Tuples(false);
var ArrayOfArrayLists = tuples.L;
for (var i=0; i<ArrayOfArrayLists.length; i++)
{
var A = ArrayOfArrayLists[i];
var arry = A.L;
var age = arry[1];
var salutation = arry[2];
document.write("\n age="+age+" salutation="+salutation);
}
</script>
</pre></HTML>
|
Demonstration of the xsdb javascript API
query text =
<query names="salutation age" sort="age">
<or>
<and>
<s at="salutation">hello kind world</s> <i at="age">0</i>
</and>
<and>
<s at="salutation">goodbye cruel world</s> <i at="age">99</i>
</and>
</or>
</query>
String result is
<or>
<and>
<s at="salutation">hello kind world</s>
<i at="age">0</i>
</and>
<and>
<s at="salutation">goodbye cruel world</s>
<i at="age">99</i>
</and>
</or>
hash table result
age=0 salutation=hello kind world
age=99 salutation=goodbye cruel world
array list result
age=0 salutation=undefined
age=99 salutation=undefined
|
calc
and cond predicates match the Python implementation
except that certain arithmetic functions supported in Python
are not yet supported in the javascript implementation. In particular
the javascript implementation supports the following arithmetic functions
within arithmetic expressions.
| Signature | Summary |
|---|---|
| int(x), float(x), str(x) | Data type conversion. |
| round(x), floor(x), ceil(x) abs(x), sqrt(x), log(x) sin(x), cos(x), tan(x) asin(x), acos(x), atan(x) |
Standard floating point functions. |
| e(), pi() | Function notation for floating point constants. |
| strip(s), upper(s), lower(s) find(inString, pattern [, start [,end]]) |
string functions. |
| max(x.y), min(x.y) count(x.y), avg(x.y), med(x.y) |
Group aggregate operations. |