This topic introduces the terms that are used in ApsaraDB for HBase Ganos (HBase Ganos).
- Spatio-temporal geometry objects.
- Vector data, such as data of points, lines, and polygons.
- Spatio-temporal data that consists of vector data and temporal attributes. Spatio-temporal data is also referred to as spatio-temporal trajectory data.
- Operations that are related to spatio-temporal geometry objects, such as spatial relationship verification.
HBase Ganos uses spatio-temporal indexes to improve the performance of data queries. Spatio-temporal indexes are stored as row keys in HBase Ganos. For more information, see Create an index table.
A spatio-temporal relationship describes the relative locations of two geometry objects in time and space. Typical spatio-temporal relationships include INTERSECT, DISJOINT, OVERLAP, and CONTAIN. In most cases, geofencing identifies the relationship of the geo-fence of an area to an object. The geo-fence is determined by a polygon feature. The object can be a point, a line, or a polygon. If the object is within the geo-fence, the area contains the object. If the object is outside the geo-fence, the area and the object are disjoint. HBase Ganos uses Common Query Language (CQL) to define spatio-temporal relationships. For more information, see Query spatio-temporal objects.
Open Geospatial Consortium (OGC) is an international voluntary consensus standards organization. It provides a set of standards for data modeling and related operations. Geographic information system (GIS) vendors develop their GISs based on these standards to ensure spatial data interoperability.
HBase Ganos SDK is developed based on GeoTools. GeoTools is a library that provides tools for you to process geospatial data. GeoTools complies with OGC standards and can interact with OGC standard data models and interfaces. A lot of GISs are developed based on GeoTools. For more information, see GeoTools.
A geometry in OGC is defined as a spatial object, such as a point, a line, or a polygon. A geometry contains only location information of a spatial object. A geometry does not contain other attribute information of the object. GeoTools provides tools for you to build geometries when you use HBase Ganos.
A SimpleFeature object contains geometries and other attributes of the object. A trajectory point is a SimpleFeature object. The SimpleFeature object contains the location information, temporal information, and other attributes of the trajectory point. The temporal information is also an attribute.
Common query language (CQL) is a language defined by OGC to support geospatial data queries. Extended common query language (ECQL) is an extended version of CQL. In most cases, ECQL is used to define filters based on SQL-like WHERE clauses. ECQL uses well-known text (WKT) to filter the objects that you want to manage. For more information, see Query spatio-temporal objects. CQL that is used in this user guide refers to ECQL.
WKT is a text markup language that is defined by OGC to describe spatial objects. For example, you can specify a point in the POINT(0,0) format. WKT is widely used in query statements. CQL and ECQL also uses WKT to specify spatial objects. For more information about WKT, see Reference.
Well-known binary (WKB) is a language that is defined by OGC. WKB uses binary streams based on the specified bytes to represent geometry objects. The size of WKB data is smaller than that of WKT data. You can use WKB to transmit data. GeoTools provides a tool for you to convert data between WKB and WKT.