1. AIXM Users’ Conference, 18-20 March 2008 1 Implementing AIXM in Instrument Flight Procedures Automation Presenter: Iain Hammond MacDonald, Dettwiler & Associates Ltd AIXM Users’ Conference March 18-20, 2008 Washington, DC

2. AIXM Users’ Conference, 18-20 March 2008 2 Introduction Key Implementation Decisions 1.Used XSLT technology rather than data binding to reduce code base, and improve maintenance agility. 2.Used standard query & filter models to generalize the interface to AIXM features: Open Geospatial Consortium (OGC) Web Feature Service (WFS) OpenGIS® Filter Encoding. 3. Extended AIXM model for FAA instrument flight procedure processes. 4.The use of Xlink associations - were the most challenging aspect of AIXM 5.0 to implement. The Instrument Procedure Development System (IPDS) and selected FAA databases were successfully integrated using web services and AIXM 5.0 RC3 in mid-Feb 2008.

3. AIXM Users’ Conference, 18-20 March 2008 3 Instrument Procedure Development System (IPDS) IPDS automates the design of Instrument Flight Procedures (IFPs), and is a key component of the FAA Instrument Flight Procedures Automation (IFPA) program. IPDS supports multiple temporal statuses for each piece of data. User “pulls” data from distributed databases federated under a service-oriented architecture (SOA). IFP design is performed in local ‘Work Area’ that provides a spatial view of data. New and updated data is “pushed” back to FAA databases through web services.

4. AIXM Users’ Conference, 18-20 March 2008 4 IPDS Aeronautical Data Interfaces FAA Service Providers expose aeronautical data through web services in an SOA that hides the actual database structure from the service users.

5. AIXM Users’ Conference, 18-20 March 2008 5 XSLT Used for Data Transforms On either side of each interface, AIXM transformation from / to internal representation is isolated to minimize the impact on the applications from changes to data exchange formats. On output, AIXM-5 is generated via XSLT transform on the internal model. On input, AIXM-5 is similarly transformed by an XSLT. XSLT selected over a data binding approach for: A smaller code base Agility to react to changes in data models on either side of the interface.

6. AIXM Users’ Conference, 18-20 March 2008 6 Adopted a generic web feature service query model rather than defining individual and data specific queries, based on: OGC Web Feature Service (WFS) Implementation Specification OpenGIS® Filter Encoding Implementation Specification. The model provides a generalized interface to all AIXM feature data: Consistent with OGC standards Specified through a system-neutral query filter that can be transformed into SQL or XPath to fetch data. A generalized WFS request (getFeature) specifies: feature type, output format, and a filter to define scope of the query: 38.20527 -73.574472 41.53861 -76.907805 Generalized Queries Using Industry Standards Example Query by Bounding Box

7. AIXM Users’ Conference, 18-20 March 2008 7 Generalized Queries Using Industry Standards The WFS implementation enables an allowable set of filter properties to query data by criteria: Spatial bounding box Country, State, Province Identifier and/or designator, with wild card queries Production status (e.g., active, pending) Effective date Last modified date. AIXM messages for spatial queries can be very large, so to reduce message size: XML response message are not indented (saves transmitting white space) XML response is compressed to reduce data transfer & memory requirements.

8. AIXM Users’ Conference, 18-20 March 2008 8 AIXM 5.0 Extensions for IFP Design AIXM 5.0 does not support all FAA Instrument Flight Procedure design needs. The schema was extended using the AIXM 5.0 extensions model to support additional elements and capabilities: Production and Workflow elements FAA-specific data elements for procedure design Structured annotations on any feature by extending the AIXM Note object File metadata elements for the capability to associate and store file attachments on any feature. Extensions are modelled in UML; and the XML schema generated by the FAA from the UML model.

9. AIXM Users’ Conference, 18-20 March 2008 9 Feature Identifiers and Associations Xlinks are a challenging aspect of AIXM 5.0: As a concept for the developers In practice, for example accessing and navigating the XPath query fragment in XSLT. The Xlink attributes are set in AIXM generation: The href is set to the XPath of the AIXM gml:identifier UUID of the referenced feature The title is set to the ‘natural key’ of the referenced feature, to provide a human-readable link that helps debugging. <serves_RunwayDirection xlink:href=“http://www.faa.gov/avnis?//aixm:RunwayDirectionTimeSlice [../../gml:identifier[@codeSpace='http://www.faa.gov/avnis'] ='uuid0123' and (aixm:extension//dpshare:revision='2')]” xlink:title = "//aixm:RunwayDirection//aixm:designator='27' and //aixm:AirportHeliport//aixm:designator='KDEN'"/>

10. AIXM Users’ Conference, 18-20 March 2008 10 Summary IPDS and existing FAA databases are successfully integrated using web services and AIXM 5.0 RC3. IPDS now provides browsing and querying FAA data sources in AIXM 5.0 format. Open industry standards used to simplify maintenance. AIXM 5.0 model was extended to support FAA IFP processes. Next IPDS release will extend the scope of AIXM 5.0 data exchange to include more feature types, data sources and the “push” of data into the distributed data enterprise

11. AIXM Users’ Conference, 18-20 March 2008 11 Questions MacDonald, Dettwiler and Associates Ltd. http://www.mdacorporation.com/