# An Ontology-Based Representation of Valued System for HBIM
## 6 Accessing the Ontology-Based Vaulted System Database: A Geographic-Based Hub Platform  
Querying the ontology-based vaulted system knowledge base with a SPARQL endpoint is not considered an end user task because it requires familiarity with SPARQL query language, that is not trivial, and also the structure of the underlying knowledge base. For this reason, a specific query interface is needed to enable end-users retrieve information from the vaulted system DataBase.  
Figure 11 shows the data flows and the structure of the web-client application for investigating the vault knowledge base. In particular, the Database is connected with a geographic server by means of a script that queries the SPARQL endpoint and transform the answer of the query into a shapefile. This shapefile is then connected with a geographic server. The server-side software used is GeoServer [54] a powerful open source platform for publishing spatial data and interactive mapping applications on the web and standard GIS software (both commercial software, such as ESRI ArcGIS [55]), and open source software, such as QGIS [56]. More specifically, GeoServer allows the visualization of produced data by using Open Geospatial Consortium (OGC) standards like WMS, WMTS, WFS and WCS that are compatible with different solutions allowing data mediation [57].  
For a simple consultation of the data a specific web-client graphic user interface (GUI) was designed (Figure 12) allowing data query and analysis using the common query language (CQL), created by the Open Geospatial Consortium (OGC), and an extended version of this language ECQL allowing for ID filters and having a higher similarity with standard query language (SQL). In particular, the GUI allows, by using a set of windows, to filter data according to vault typology. Let's assume for example to perform a query aimed at extracting only barrel vaults surveyed by laser scanning from the vault system DB.  
Input in the GUI are translated into a simple CQL query:  
VAULT_TYPOLOGY = 'Barrel' AND SURVEY_METHOD = 'LaserScanning'  
If the user wants to filter the results into a specific area, he/she can simply draw the search area on the map and this is translated into the following CQL query:  
VAULT_TYPOLOGY = 'Barrel' AND SURVEY_METHOD = 'LaserScanning'AND BBOX  
(the_geom, TLX, TLY, BRX, BRY)  
Where TLX and TLY are the top left coordinates of the bounding box of area we are interested in while BRX and BRY are the bottom right coordinates of the bounding box. Similar queries can be formulated also for temporal constraints and by using different logic operators.  
The possibility of performing semantic queries allows giving back unexpected relationships among different vaults with regional dissemination, thus contributing to increasing knowledge and rising awareness on the vault constructions across Europe. For example, in the case of mixed arched-vaulted systems, the \"frame vaults\" [58], it was possible to observe some connection between the distribution of those system in Northern Italy (mainly Lombardy and Piedmont) and in the area of Prague (Czech Republic). Currently few examples are present in the vaulted system DB. However, it is expected that a  
Figure 11: Data flows and structure of the web client application for end-user interaction with the vaulted system knowledge base.  
larger number of samples will allow giving back a pan-European picture with unexpected correlations of traditions, permanencies and mutation across space/time, the skilled workers capabilities across Europe, their movements, enriching the socioeconomic framework of the different periods.  
Figure 12: The vaulted system web-client graphic user interface (GUI): (**top**) the vaulted inventory of the Cremona Palaces entered in the data model and the vaulted Database queried for a specific building, ID_08, Palazzo Magio, Cremona (Italy) and, (**bottom**) a query in for the area of Prague searching for cloister vaults connected with the historic map of the city along with the building vaults surveyed and classified.