Changes between Initial Version and Version 1 of MapGuideRfc152

Timestamp:

Nov 18, 2015, 6:57:44 AM (8 years ago)

Author:

jng

Comment:

--

MapGuideRfc152

@@ +1 @@
+
+= !MapGuide RFC 152 - Add mapagent support for GeoJSON and simplified JSON responses =
+
+This page contains a change request (RFC) for the !MapGuide Open Source project.
+More !MapGuide RFCs can be found on the [wiki:MapGuideRfcs RFCs] page.
+
+== Status ==
+
+||RFC Template Version||(1.0)||
+||Submission Date||19 Nov 2015||
+||Last Modified||19 Nov 2015||
+||Author||Jackie Ng||
+||RFC Status||draft||
+||Implementation Status||sandbox experimental||
+||Proposed Milestone||3.1||
+||Assigned PSC guide(s)||(when determined)||
+||'''Voting History'''||(vote date)||
+||+1||||
+||+0||||
+||-0||||
+||-1||||
+||no vote|| ||
+
+== Overview ==
+
+This RFC proposes to simplify all JSON responses from the mapagent, and adding GeoJSON output for SELECTFEATURES
+
+== Motivation ==
+
+All JSON responses from the mapagent are verbatim conversions from their XML counterparts. 
+
+However this conversion process results in JSON that is quite cumbersome to consume:
+
+ * All properties are arrays.
+ * All properties are string values.
+ 
+This is due to the conversion process not taking the content model (and its data types/element cardinality) into account, taking the lowest common denominator approach.
+
+Also for the SELECTFEATURES operation, the JSON response in its current form is horribly un-usable. A more practical and ubiquitous JSON format for feature data already exists: GeoJSON
+
+== Proposed Solution ==
+
+The MgJsonConvert class that does the actual XML to JSON conversion will be modified to include a hard-coded list of XML element paths:
+
+ * For elements that contain 0 to many elements
+ * For elements that are not string data types
+ 
+During the conversion process, we check the computed XML element path of the element we're converting and check if it is in one of these two lists
+
+ * If it is in the first list, the element is written as a JSON array
+ * If it is in the second list, the element will not have its value quoted
+
+To retain compatibility with clients using the JSON responses of the older mapagent, using simplified JSON responses is opt-in, by including CLEAN=1 as part of your mapagent request parameters. 
+When this parameter is not specified or set to 0, the old XML to JSON conversion behaviour will be used.
+
+For the SELECTFEATURES operation, when CLEAN=1 is specified the response format will be GeoJSON
+
+With the new JSON responses, not only are they more intuitive to use (not everything is an array and not everything is a string), but is also much more compact due to
+the amount of {{{[}}} and {{{"}}} characters we save by not converting everything to string arrays
+
+== Implications ==
+
+Any time a new schema or schema revision is introduced, this hard-coded list will have to be updated to know which elements in these new schemas require special processing.
+
+== Test Plan ==
+
+Verify all new JSON response parse as valid JSON.
+
+== Funding / Resources ==
+
+Community