Benedikt Kämpgen: 1 revision: From LD-Cubes

2023-01-04T13:24:16Z

1 revision: From LD-Cubes

Benedikt Kämpgen: /* Server Requirements */

2014-11-17T14:38:44Z

‎Server Requirements

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On this page, we present the Linked Data Cubes Explorer (LDCX), an application of [[olap4ld]].

==General info==
* Most current demo website: http://ldcx.linked-data-cubes.org/projects/ldcx/
* Old link to demo: http://www.ldcx.linked-data-cubes.org:8000/ldcx-trunk/ldcx/ld-cubes-explorer.html

==Architecture==
LDCX consists of several parts: an HTML webpage using the JavaScript library xmla4js to issue XMLA
queries; olap4j-xmlaserver that can answer XMLA queries via olap4ld; olap4ld to answer metadata and
olap queries on QB datasets.

[[File:Ld-cubes-explorer_overall_architecture.png]]
Architecture of LDCX.

==Three-step user interface==
# a user selects one or more comma-separated URIs of of qb:DataSets. With ``Explore Dataset...'', metadata queries are issued to populate the user interface;
# the user selects measures to be displayed in the pivot table cells;
# the user selects dimensions to add member combinations to rows and columns of the pivot table and clicks ``Update Table\ldots''. Note LDCX automatically queries every dimension on the most granular level since multi-level hierarchies are rarely used and users can still slice dimensions to view datasets on a higher aggregation level.

==Linked Data Cubes Engine: EmbeddedSesameEngine==
* [[EmbeddedSesameEngine]]

==Client Requirements==
* LDCX has been tested on Firefox and Chrome (however, only on a Linux PC).

==Server Requirements==
* [[olap4j]]
* [[olap4ld]]
* [[Sesame]]
* [[has investigation::Olap4j-xmlaserver]]
* [[xmla4js]]
* [[LDCX interface]]
* Tomcat
** sudo apt-get install tomcat6 tomcat6-admin
** nano /var/lib/tomcat6/conf/tomcat-users.xml - added users
** Added new folder in webapps directory: /var/lib/tomcat6/webapps/xmla4js

==Evaluation==
* [[LDCX Evaluation for ESWC 2014 Demo]]
* [[OLAP4LD Demo at ESWC 2014]]

==Roadmap==
* [[Displaying of background information useful for interpretation]]
* [[NON EMPTY Clause in MDX]]

==How to connect all systems?==
* I used eclipse
* I manually created a dynamic web project
* In there, I copied all files from olap4j-xmlaserver master
* Then I manually added libraries to WEB-INF/lib that xmlaserver relied upon:

<pre>
commons-collections.jar
commons-dbcp.jar
commons-pool.jar
log4j.jar
nxparser-1.2.3.jar
olap4j-xmlaserver-0.0.1-SNAPSHOT.jar
saxon-9.2.jar
servlet-api.jar
xercesImpl.jar
</pre>
* Then I used the web.xml from Rossi:

<pre>
<?xml version="1.0" encoding="ISO-8859-1"?>
<web-app>
<display-name>XMLA Server</display-name>

<servlet>
<servlet-name>xmla</servlet-name>
<servlet-class>mondrian.xmla.impl.Olap4jXmlaServlet</servlet-class>

<init-param>
<param-name>OlapDriverUsePreConfiguredDiscoverDatasourcesResponse</param-name>
<param-value>true</param-value>
</init-param>

<init-param>
<param-name>OlapDriverDiscoverDatasources.dataSourceName</param-name>
<param-value>@dataSourceName@</param-value>
</init-param>

<init-param>
<param-name>OlapDriverDiscoverDatasources.dataSourceInfo</param-name>
<param-value>@dataSourceInfo@</param-value>
</init-param>
<init-param>
<param-name>OlapDriverDiscoverDatasources.url</param-name>
<param-value>@datasourceUrl@</param-value>
</init-param>
<init-param>
<param-name>OlapDriverDiscoverDatasources.providerType</param-name>
<param-value>TDP</param-value>
</init-param>

<init-param>
<param-name>OlapDriverDiscoverDatasources.authenticationMode</param-name>
<param-value>Unauthenticated</param-value>
</init-param>

<init-param>
<param-name>OlapDriverMaxNumConnectionsPerUser</param-name>
<param-value>15</param-value>
</init-param>

<init-param>
<param-name>OlapDriverClassName</param-name>
<param-value>org.olap4j.driver.ld.LdOlap4jDriver</param-value>
</init-param>

<init-param>
<param-name>OlapDriverConnectionString</param-name>
<param-value>jdbc:ld://olap4ld;Catalog=LdCatalog;JdbcDrivers=com.mysql.jdbc.Driver;Server=http://public.b-kaempgen.de:8890/sparql;Database=OPENVIRTUOSO;Datastructuredefinitions=http://fios:saiku,http://fios:saikumanually;Datasets=http://fios:saiku,http://fios:saikumanually</param-value>
</init-param>

<init-param>
<param-name>OlapDriverConnectionProperty.Prefix</param-name>
<param-value>@connectionPrefix@</param-value>
</init-param>

<init-param>
<param-name>OlapDriverConnectionProperty.FetchLevelProperties</param-name>
<param-value>false</param-value>
</init-param>

<init-param>
<param-name>OlapDriverConnectionProperty.FetchMemberProperties</param-name>
<param-value>false</param-value>
</init-param>

<init-param>
<param-name>OlapDriverConnectionProperty.FetchMembers</param-name>
<param-value>true</param-value>
</init-param>

<init-param>
<param-name>OlapDriverConnectionProperty.QueryTimeoutMs</param-name>
<param-value>@queryTimeout@</param-value>
</init-param>

<init-param>
<param-name>OlapDriverConnectionProperty.AuthenticationProvider</param-name>
<param-value>com.someotherclass.XmlaAuthenticationProvider</param-value>
</init-param>

<init-param>
<param-name>OlapDriverConnectionProperty.ConnectionTimeoutMs</param-name>
<param-value>@connectionTimeout@</param-value>
</init-param>

<init-param>
<param-name>OlapDriverConnectionProperty.TotalCellLimit</param-name>
<param-value>@totalCellLimit@</param-value>
</init-param>

<init-param>
<param-name>OlapDriverConnectionProperty.PerPivotCellLimit</param-name>
<param-value>@perPivotCellLimit@</param-value>
</init-param>

<init-param>
<param-name>OlapDriverConnectionProperty.Source</param-name>
<param-value>Excel</param-value>
</init-param>

<init-param>
<param-name>IdleConnectionsTimeoutMinutes</param-name>
<param-value>@idleConnectionCleanupTimeout@</param-value>
</init-param>

<init-param>
<param-name>EnableConnectionReuse</param-name>
<param-value>@enableConnectionsReuse@</param-value>
</init-param>

<init-param>
<param-name>EnableCubesMetadataPrefetch</param-name>
<param-value>@enableCubesMetadataPrefetch@</param-value>
</init-param>
</servlet>

<servlet-mapping>
<servlet-name>xmla</servlet-name>
<url-pattern>/xmla/*</url-pattern>
</servlet-mapping>
</web-app>
</pre>
* Then, I copied over into WebContent Xmla4j (xmla4js) in order to avoid CORS.
* The question is, why so far only asynchronous communication works:

===Problems===
* Had to insert "[LdCatalog]" instead of @dataSourceInfo@ <= watch out [] was needed (damn naming!)
* Apparently, XMLA does not have "Schema" as an own Had to change "execute-asynchronous.html" and its "executeMDX()" to have properties:

<pre>
DataSourceInfo: select_datasources.options[select_datasources.selectedIndex].value,
Catalog: select_catalogs.options[select_catalogs.selectedIndex].value
</pre>

* Had to increase timeout in Xmla.js:

<pre>
requestTimeout: 300000,
</pre>

* Apparently, olap4ld has not implemented cell.getPropertyValue, correctly:

<pre>
The following propertiess are mandatory for cells:

BACK_COLOR
CELL_EVALUATION_LIST
CELL_ORDINAL
FORE_COLOR
FONT_NAME
FONT_SIZE
FONT_FLAGS
FORMAT_STRING
FORMATTED_VALUE
NON_EMPTY_BEHAVIOR
SOLVE_ORDER
VALUE
</pre>

* I have added formatted_value, format_string and value to CellSet.getCell (from NewValues.map).

====CORS====
* Make sure that either the xmlaserver is setup for CORS or have both LDCX interface and xmlaserver put on same machine.

====Logging====
* Possibly, the server cannot create the log file. To help here, we print on console output the global location of the logging file.

===Status===

====2013-07-04====
* Example URL: http://localhost:8080/xmlaserver-manually/Xmla4j/samples/execute-asynchronous.html
* Address: http://localhost:8080/xmlaserver-manually/xmla
* adapted defaultXmlaUrl.js (cache reload)
* changed @datasourceUrl@ zu jdbc:ld://olap4ld;Catalog=LdCatalog;JdbcDrivers=com.mysql.jdbc.Driver;Server=http://;Database=EMBEDDEDSESAME;Datastructuredefinitions=;Datasets=;
** Not needed, sufficient: replace "url: datasource.URL? datasource.URL : url.value,"
* Have Catalog and Schema named same: LdCSXXX.
* Problem: I cannot ask for specific cubes if I do not know them for retrieval.

Query:

<pre>
SELECT
{[httpXXX3AXXX2FXXX2FlocalhostXXX2Ffios_xmla4jsXXX2FexampleYYYttlXXX23customer_1]} ON COLUMNS,
{[httpXXX3AXXX2FXXX2FlocalhostXXX2Ffios_xmla4jsXXX2FexampleYYYttlXXX23lo_revenue]} ON ROWS
FROM [httpXXX3AXXX2FXXX2FlocalhostXXX2Ffios_xmla4jsXXX2FexampleYYYttlXXX23ds]
</pre>

Logical OLAP Operator Tree:

<pre>
Rollup (
Slice (
Dice (
Projection (
BaseCube ([httpXXX3AXXX2FXXX2FlocalhostXXX2Ffios_xmla4jsXXX2FexampleYYYttlXXX23ds]),
[httpXXX3AXXX2FXXX2FlocalhostXXX2Ffios_xmla4jsXXX2FexampleYYYttlXXX23lo_revenue]),
),
[httpXXX3AXXX2FXXX2FlocalhostXXX2Ffios_xmla4jsXXX2FexampleYYYttlXXX23lo_custkey], [httpXXX3AXXX2FXXX2FlocalhostXXX2Ffios_xmla4jsXXX2FexampleYYYttlXXX23lo_orderdate], [httpXXX3AXXX2FXXX2FlocalhostXXX2Ffios_xmla4jsXXX2FexampleYYYttlXXX23lo_partkey], [httpXXX3AXXX2FXXX2FlocalhostXXX2Ffios_xmla4jsXXX2FexampleYYYttlXXX23lo_suppkey], Measures),
[httpXXX3AXXX2FXXX2FlocalhostXXX2Ffios_xmla4jsXXX2FexampleYYYttlXXX23lo_custkey] : [httpXXX3AXXX2FXXX2FlocalhostXXX2Ffios_xmla4jsXXX2FexampleYYYttlXXX23lo_custkeyCodeList])
</pre>

* Had to change xmla-server to take into account restrictions of cube so that olap4ld would retrieve cubes.

====Problem: 2013-08-01: ld-cubes LDCX does not work anymore====
* Problem:
** If I run it normally, then when stopping at "xmla.executeMultiDimensional({" (ld-cubes-explorer.html, 809), I enable breakpoint at "function initAjaxLoader() { -> events : Xmla.EVENT_GENERAL...". When I go on, I come to Xmla.js.
** Ajax call
** Xmla.js 2016: return this.response returns null
** Actually, ajaxOptions states that when complete: function xmla._requestSuccess(options);
** Maybe this._fireEvent(Xmla.EVENT_REQUEST) == false OR this._fireEvent(Xmla.EVENT_EXECUTE, options) == false, so that myXhr = ajax(ajaxOptions) is never called? - No.
** Or maybe: myXhr->complete is never called?

* One option would be to enable synchronous call so that at Xmla.js->_ajax (207), handler.call(xhr) is called.

* Apparently, for asynchronous calls, the return value should be undefined, see Xmla.js 2016.

* Synchronous calls did not work, either, because the entire code of ld-cubes-ldxc were adapted to it.

* => Finally, it was simply because we had not simply reused the way "select empty cells", "render table etc" were used originally

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Linked Data Cubes Explorer (LDCX) - Revision history

Benedikt Kämpgen: 1 revision: From LD-Cubes

Benedikt Kämpgen: /* Server Requirements */