Now accepting sia1 as an alias for sia in registry.Servicetype.

That's so there is a symmetry to sia2.  When further version 2-standards
appear, I'd suggest we continue that pattern: The official IVOA short name
(without numbers in version 1) remains, but a preferred alias with a 1 is
added in pyVO.

Would it make sense to convince the IVOA to add the 1 to their short names?
Well, it would have all these years ago.  Now... I think it would just
increase the confusion.

pyvo/registry/rtcons.py

@@ -36,6 +36,7 @@
                         for k, v in [
     ("image", "sia"),
     ("sia", "sia"),
+    ("sia1", "sia"),
     # SIA2 is irregular
     # funky scheme used by SIA2 without breaking everything else
     ("spectrum", "ssa"),
@@ -358,14 +359,15 @@ class Servicetype(Constraint):
 
     The constraint normally is a custom keyword, one of:
 
-    * ``sia`` (SIAP version 1 services)
+    * ``sia``, ``sia1`` (SIAP version 1 services; prefer ``sia1`` for symmetry,
+      although ``sia`` will be kept as the official IVOA short name for SIA1)
     * ``sia2`` (SIAP version 2 services)
     * ``ssa``, ``ssap`` (synonymous for SSAP services)
     * ``scs``, ``conesearch`` (synonymous for cone search services, prefer
       ``scs``)
     * ``line`` (for SLAP services)
     * ``tap``, ``table`` (synonymous for TAP services, prefer ``tap``)
-    * ``image`` (a deprecated alias for sia)
+    * ``image`` (a deprecated alias for sia1)
     * ``spectrum`` (a deprecated alias for ssap)
 
     You can also pass in the standards' ivoid (which

pyvo/registry/tests/test_rtcons.py

@@ -149,7 +149,7 @@ def test_multi(self):
                 " 'ivo://ivoa.net/std/sia')")
 
     def test_includeaux(self):
-        assert (rtcons.Servicetype("http://extstandards/invention", "sia"
+        assert (rtcons.Servicetype("http://extstandards/invention", "sia1"
                                    ).include_auxiliary_services().get_search_condition(FAKE_GAVO)
                 == "standard_id IN ('http://extstandards/invention',"
                 " 'http://extstandards/invention#aux',"
@@ -161,7 +161,7 @@ def test_junk_rejected(self):
             rtcons.Servicetype("junk")
         assert str(excinfo.value) == ("Service type junk is neither"
                                       " a full standard URI nor one of the bespoke identifiers"
-                                      " image, sia, spectrum, ssap, ssa, scs, conesearch, line, slap,"
+                                      " image, sia, sia1, spectrum, ssap, ssa, scs, conesearch, line, slap,"
                                       " table, tap, sia2")
 
     def test_legacy_term(self):