diff --git a/bip-0122.mediawiki b/bip-0122.mediawiki
index 902aa02a..d0258738 100644
--- a/bip-0122.mediawiki
+++ b/bip-0122.mediawiki
@@ -23,7 +23,7 @@ The same happens with posts and messages that reference some particular txs or b
 
 The URI follow this form:
 
- <nowiki>blockchain:[//chain]</type/hash></nowiki>
+ <nowiki>blockchain:[//<chain>]/<tx|block|address>/<hash></nowiki>
 
 Where:
 
@@ -52,6 +52,18 @@ Where:
 | 
 |}
 
+====ABNF grammar====
+
+<pre>
+blockchainuri = "blockchain:" ["//" chain] "/" object
+object = ("tx" "/" hash ) / ( "block" "/" (hash / blockheight ) ) /
+         ( "address" "/" address )
+chain = hash
+hash = 64HEXDIG
+blockheight = 1*15DIGIT ; 15 is somehow arbitrary, i.e. a "small" int.
+address = base58 ; https://en.wikipedia.org/wiki/Base58
+</pre>
+
 ----
 ===Definition of chain ID===