René's URL Explorer Experiment

{"@context":"https://schema.org","@type":"DiscussionForumPosting","headline":"Add support for validation against external schemas","articleBody":"Not sure if this belongs here or in java-stix-validator, so sorry if I posted in the wrong place.\n\nIf I define a custom `ControlledVocabularyType` extension as [described here](http://stix.readthedocs.org/en/stable/overview/controlled_vocabularies.html#working-with-custom-controlled-vocabularies) and then attempt to validate an instance document which leverages that controlled vocabulary, I get the following error in java-stix-validator:\n\n```\nSAXParseException:\n    Public ID: null\n    System ID: null\n    Line     : 3\n    Column   : 70\n    Message  : cvc-elt.4.2: Cannot resolve 'customVocabs:CustomVocab-1.0' to a type definition for element 'stix:Package_Intent'.\n```\n\nIt would be nice to provide a function which makes it easy to pass in a directory of schemas to validate a STIX document against and support the validation of third-party extensions.\n","author":{"url":"https://github.com/bworrell","@type":"Person","name":"bworrell"},"datePublished":"2015-07-23T19:51:02.000Z","interactionStatistic":{"@type":"InteractionCounter","interactionType":"https://schema.org/CommentAction","userInteractionCount":3},"url":"https://github.com/5/java-stix/issues/5"}