Build up Rapid OGC® Web Services
XtraServer is a suite for building up high-performance spatial web services complying with the specifications of the Open Geospatial Consortium (OGC®). Currently, XtraServer supports Web Map Services (WMS), Web Feature Services (WFS), OGC API – Features: Part 1 and Part 2 and – according to draft specifications – OGC API – Tiles and Styles.
XtraServer is characterized by:
- High-performance queries. Many thousand features per second can be reached.
- Scalability. Databases with millions of spatial features and heavily concurrent queries do not pose a problem.
- Flexible configuration. Application schemas can be mapped to complex database structures.
- Support for 3-D geometry (WFS).
- Coordinate transformations on the fly. All prevalent Coordinate Reference Systems according to OGP (formerly EPSG) are supported. For transforming selected Coordinate Reference Systems, such as Gauß-Krüger to ETRS89/UTM (and reverse), refined methods are employed (such as BeTA2007) (WFS/WMS/GSFS, for Web API in progress).
- Flexibly configurable post-processing for deriving other output encodings from GML (WFS/WMS), such as CSV, KML or Atom (usually based on XSLT) and Shapefile (e.g. employing GDAL).
- Support for arbitrary character encodings.
- XtraServer can be deployed on various Linux platforms.
XtraServer Web API
XtraServer Web API provides geospatial data over modern Web APIs. As a basis for format descriptions and API specifications serve the actual OGC API standards. Further description is forthcoming.
XtraServer/WFS, being an OGC Web Feature Service, makes it possible to query, create, update and delete geospatial data over the Internet. The data – filtered by mixed non-geometrical and geometrical query expressions – are normally transported and output as XML documents. The administrator can provide arbitrary Application Schemas of Geography Markup Language (GML) to define the XML format.
Web Feature Services configured with XtraServer/WFS exhibit the following technical traits:
- OGC®WFS Versions: 1.1.0, 2.0.0 in support to the following extent
- WFS 1.1.0: transactional (locking)
- WFS 2.0: Simple WFS, Basic WFS, Transactional WFS, Locking WFS, Inheritance, HTTP GET, HTTP POST, SOAP, Manage Stored Queries. On top of that, XtraServer/WFS supports the request parameter startIndex/count (as a part of the Response Paging) and the response parameter numberMatched.
- Certified compliance (recently approved with XtraServer 4.17, Reference Implementation)
- as Basic WFS with the OpenGIS WFS Specification, Version 1.1.0,
- as WFS Simple and Basic with WFS 2.0,
- concerning the generation of GML 3.2.1
- OGC®Filter Encoding Versions: 1.1.0, 2.0.0
- The Filter Encoding standards are used to express queries and are fully supported.
- Conformance Classes FE 2.0: Query, Ad hoc Query, Functions, Resource Identification, Minimum Standard Filter, Standard Filter, Minimum Spatial Filter, Spatial Filter, Minimum Temporal Filter, Temporal Filter, Sorting, Minimum XPath, Schema Element Function
- Beyond that XtraServer/WFS in filter expressions permits to track xlink:hrefs via XPath when accessing properties and also to apply XPath predicates there, even when using WFS versions prior to 2.0.0.
- Support of many Functions
- Implemented operations:
- WFS 1.1.0: GetCapabilities, DescribeFeature, GetFeature, GetFeatureWithLock, LockFeature, Transaction
- WFS 2.0: GetCapabilities, DescribeFeature, GetFeature, GetPropertyValue, GetFeatureWithLock, LockFeature, Transaction, CreateStoredQuery, DropStoredQuery, ListStoredQueries, DescribeStoredQueries
- Output encodings:
- All GML versions (more than one simultaneously by configuration)
- Other formats by programmable backend, e.g. based on XSLT or GDAL
XtraServer/WMS is a Web Map Service and provides maps for Internet applications in arbitrary extents, sizes and image formats. The maps can be freely styled according to the SLD OGC® standard (Styled Layer Descriptor). In the context of an Internet application they can be displayed in the Web Browser and can be superposed with other maps – also with ones from other Web Map Servers. The content of features displayed in the maps can be queried.
Web Map Services configured by XtraServer/WMS exhibit the following technical traits:
- OGC® WMS Versions: 1.1.1 und 1.3.0
- Certified compliance with OpenGIS WMS specifications, versions 1.1.1 and 1.3.0 (recently approved with XtraServer 4.17, Reference Implementation)
- OGC®SLD/SE Version: 1.1.0
- Nearly complete support with some useful extensions, particularly concerning the implemented Functions
- Available Symbolizers: Point, Line, Polygon, Text.
- Antialiasing with subpixel Placement
- Additional ZIndex support. All Symbolizers may carry a ZIndex property, which provides data-driven rendering sequence control.
- The capabilities concerning filtering and property access correspond to those of the WFS.
- Integrated WFS accessible and usable.
- Capable to generate maps fit for tiling by considering the whole geometry when labeling
- SLD serves as configuration language for vector maps, but is also fully usable from the side of the client.
- Implemented operations: GetCapabilities, GetMap, GetFeatureInfo, DescribeLayer
- Image formats:
- PNG (8 and 32bit), GIF, JPEG
- PNG and GIF both support transparency
- Overlay images, e.g. with a copyright notice
- Information query (GetFeatureInfo):
- Document encodings: GML and configurable other formats (such as HTML) via XSLT-backend
- Controlled by the configuration, the returned features need not only comprise the objects identified geometrically. Additionally, associated objects can be retrieved and returned.
- Geometrical identification of objects is done on the basis of their displayed shape and not solely by means of their underlying geometry property.
XtraServer/GSFS can apply edits to the database performed by clients which support the capabilities Create, Update and Delete.
Besides vector data the service also publishes portrayal rules and in this way enables clients to directly display the spatial data in a uniform and convenient style.
XtraServer Data Sources
XtraServer can be tied to current versions of PostgreSQL with the PostGIS extension.
ArcGIS for Server Edition
In the ArcGIS for Server Edition, XtraServer runs as a server extension of ArcGIS for Server and provides WFS capabilities that are not supported by the standard WFS interface of ArcGIS for Server, for example, support for WFS 2.0 as well as for complex or community schemas.
XtraServer is a 64bit application, and it runs typically on actual Linux distributions like CentOS, Debian, RedHat, SuSE Linux Enterprise Server and Ubuntu (installation via RPM/YUM or DEB/APT).
XtraServer can run on both physical and virtual machines on the ESX platform (VMware vSphere or ESXi). The hardware requirements are rather moderate. The exact requirements depend on a variety of factors such the number of services, complexity and size of the schema and performance requirements.
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