I am the assigned Gen-ART reviewer for this draft. For background on
Gen-ART, please see the FAQ at
<http://wiki.tools.ietf.org/area/gen/trac/wiki/GenArtfaq>.
Please resolve these comments along with any other Last Call comments
you may receive.
Document: draft-ietf-scim-core-schema-17.txt
Reviewer: Elwyn Davies
Review Date: 2015/04/09
IETF LC End Date: 2015/04/20
IESG Telechat date: (if known) -
Summary: Not ready. The 'major' issue identified is really political
rather than strictly technical although the proposed syntax does limit
the applicability (or at least the easy applicability) of the scheme.
Making the schemas more aware of practice outside the basic English
speaking world should be an aim of IETF work, IMO. The minor issues are
mostly only just more than editorial nits - and there are quite a few
of these also.
Major issues:
===========
s4.1.1, "name" attribute: The definition of this attribute is
culturally insensitive. The
collection of name sub-attribute terms are North American/UK/Aussie/NZ
English -speaking biased. The authors might wish to consider
http://www.w3.org/International/questions/qa-personal-names. To a
lesser extent this also applies to the definition of the addresses
attribute in s4.1.2. The issue of the representation of postal
addresses incorporated in I-Ds and RFCs in the xml2rfc schema has been
debated at length on the rfc-interest mailing list. The new (v3)
vocabulary replaces the specific sub-attributes with an ordered list of
"postalLine" elements (see
https://tools.ietf.org/html/draft-hoffman-xml2rfc-16#section-2.39).
Further, the use of country codes in RFCs has been dropped some time
ago. It might be better to represent the address in a less specific way
and leave display up to user interfaces that can consider the relevant
locale. My suggestion, FWIW, would be to have a country, possibly a
code field plus an ordered array of postalLines that can contain any of
the additional components and cater for any locale specific format.
======================================================
Minor issues:
===========
Reference to SCIM Protocol document: At a bare minimum a normative
reference to the SCIM protocol document (currently
draft-ietf-scim-api-16) is needed in s1.2 where the protocol is referred
to in the first two definitions. In my opinion, this document would be
improved by the addition of a brief overview of the operation of the
SCIM protocol and the implications for the design of the schema. For
example, s2 talks about 'replacement of a resource': Knowing in advance
that one of the operations anticipated in the protocol is replacement
makes this clearer.
s1.1, Use of OPTIONAL and REQUIRED: These terms are overloaded in this
document. The majority of uses are not specifying features of the
protocol as per RFC 2119 but indicating the necessity or otherwise of
the presence of particular attributes in resource types. AFAICS the
only RFC 2119 usages are one place in s2.2.7 for OPTIONAL and two
adjacent places in s10.3.1 for REQUIRED . To avoid the overloading it
would be easy to omit OPTIONAL and REQUIRED from the RFC 2119 list, use
the alternative RFC 2119 terminology (MAY in s2.2.7 and MUST in s10.3.1)
and provide a separate note on the usage of OPTIONAL and REQUIRED in s1.1.
s2.1, Syntax of attribute names: I am confused by the constraints
suggested here.
(1) "Attribute names SHOULD be camel-cased": AFAICS this has no
impact on the specification or protocol. My guess is that the
specification has adopted the convention normally used in JavaScript.
This is merely a representation of the convention used in SCIM schemas
and RFC 2119 language is inappropriate. I suggest replacing this with
"This document uses the camel-casing convention for attribute names
(e.g., "camelCase").
(2) "nameChar = "-" / "_" / DIGIT / ALPHA": Given the close
association with JavaScript, it seems inappropriate to allow hyphen (-)
as a character in attribute names as this is illegal in JavaScript.
(3) The definition should say whether attribute names are case sensitive.
(4) Even though there is ABNF, it would be useful to note explicitly
that names are limited to a subset of ASCII rather than the much wider
JSON string or JavaScript variable character sets.
s2.2.7, $ref: In s2.2.7, $ref is defined as a sub-attribute name but
does not match the attribute name syntax discussed in the previous
comment for s2.1. Does the attribute name syntax apply to sub
-attributes? Or are they just JSON member names?
s2.3, next to last para: To ensure that the service provider knows what
it ought to do to canonicalize a given value, the schema specification
needs to specify what canonicalization means for each type of
attribute. Having read further on, I see that this is done in most
cases for relevant attributes defined in this draft. A note that this
should be done generally when defining new schemas is needed here. This
is particularly important for strings that might have
internationalization issues (c.f., the discussion of string comparison
in filtering in section 5 of draft-ietf-scim-api-16.)
s7, canonicalValues: The wording here
When
applicable service providers MUST specify the canonical types
specified in the core schema specification; e.g., "work",
"home".
seems to imply that the possible canonicalValues mentioned in the
definitions of User, Group etc. schemas earlier in the draft are
actually normative minimum requirements that could, at least in some
cases, be extended. The wording used in the earlier sections is rather
less definitive and appears to indicate that the suggested values are
examples that a service provider might possible want to replace if they
considered alternative values better suited to their application, e.g.
userType
Used to identify the organization to user relationship. Typical
values used might be "Contractor", "Employee", "Intern", "Temp",
"External", and "Unknown" but any value may be used.
and
phoneNumbers
Phone numbers for the user. ... The "display" sub-attribute
MAY be used to return the canonicalized representation of the
phone number value. The sub-attribute "type" often has typical
values of "work", "home", "mobile", "fax", "pager", and "other",
and MAY allow more types to be defined by the SCIM clients.
The wording used in the earlier sections seems to need 'tightening up'
to make it clear what minimum set of canonicalValues is required for
conformance, if indeed that is what is wanted.
s7, caseExact: I think you may need to clarify what case insensitivity
means for languages other than unaccented English. It may be sufficient
to provide a note and a pointer to the discussion of filtering and
normalization in the protocol draft.
s10.3: The registration procedure seems overly complex. If, as stated,
an RFC is required in all cases, then the standard (RFC 7035) IETF
Review registration policy would seem to fill the bill and there is no
need for a designated expert. Alternatively, Specification Required
(with a designated expert as is standard for this case) could be used if
other types of specification could be countenanced. I suspect the
requirement for a standards track RFC as a way of modifying an existing
value is going to come back to bite us if the original specification was
not standards track. I am not sure this attempt to provide a higher
hurdle for modifications is the best way to go about this - In general,
IETF Review would, I think, give enough pushback against inappropriate
updates without requiring standards track in all cases. Overall, I
recommend that the authors consult your AD and IANA to determine how
best to structure the registration procedure.
===========================================================
Nits/editorial comments:
=====================
Global: s/e.g. /e.g., /
The term 'endpoint': The term '(network) endpoint' has a particular
technical meaning in W3C/HTTP jargon although it the usage in (e.g.)
http://www.w3.org/TR/wsdl.html seems rather self-referential. It would
be useful to provide a definition. Perhaps something like:
(Network) endpoint: Also known as a 'port' (see
http://www.w3.org/TR/wsdl.html). A port has a 'port type' that
identifies a set of operations invoked by HTTP methods. Each port is
identified by a URI typically constructed from the base URI identifying
the server implementing the operation and a relative URI bound to the
port type. The methods are associated with abstract data types, such as
the schema specified in this document. HTTP messages carry data
structured according to the abstract data types.
Canonicalized URLs: Presumably URLs should be canonicalized in line
with Section 6 of RFC 3986. An appropriate global place to say this
would be s2.3 I believe. However RFC 6986 offers a 'ladder' of
canonicalizations and it would be desirable to say what rung on this
ladder should be used. Presumably either 6.2.3 or 6.2.4.
s1, para 1, last sentence: The phrase 'redundantly integrated' is not
felicitous. Suggestion:
OLD:
Similarly, cloud services
providers seeking to inter-operate with multiple application
marketplaces or cloud identity providers must be redundantly
integrated.
NEW:
Similarly, cloud services
providers seeking to inter-operate with multiple application
marketplaces or cloud identity providers would require pairwise
integration.
END
s1, para 2: Worth adding a reference to [PortableContacts] since you
have it already and its not a 'well-known' item.
I fear that LDAP is not a well-known abbreviation within the meaning of
the act, and needs expanding.
Maybe add a ref to RFC 6350 for vCards.
s2, para 1, 1st sentence: s/contents of which/allowable contents of which/
s2, para 1, 4th sentence: s/alidation/Validation/
s2, para 1, last sentence: s/the attributed defined schema/its
characteristics as defined in the relevant schema/
s2, para 2: s/extend schema/ extend a schema/ [or "extend schemas"]
s2.1, para 1: s/For each attribute, SCIM schema/For each attribute, a
SCIM schema/
s2.2: The list of characteristics and their default values is not
associated with the data type of the attribute but is another set of
attributes of each attribute defined. This would be clearer if the list
of defaults and examples was separated out into a new section (probably
after s2.2). It would be helpful to point out explicitly that these
defaults apply to all the attributes defined in the draft - I found the
tacit assumption of default characteristics in later definitions of
attributes had me asking myself whether certain characteristics ought to
have been defined whereas they were actually covered by the defaults.
s2.2, 1st bullet: For consistency, s/required/REQUIRED/
s2.2, bullet 5:
OLD:
o have no canonical values (e.g. type is "home" or "work"),
NEW:
o have no canonical values (for example, the "type" sub-attribute in
Section 2.3),
END
s2.2.6, Base 64 URL encoding: Presumably the trailing padding
characters can be omitted here - this should be mentioned whether or not
they are needed.
s2.2.8: Presumably, in line with s2.3 and the JSON specification, the
order of component attributes is not significant. If this is so, it
should be mentioned here: Perhaps add:
The order of the component attributes is not significant. Servers and
clients MUST NOT require or expect attributes to be in
any specific order when an object is either generated or analyzed.
s2.3, 1st para: I found this difficult to parse. Suggest:
OLD:
Multi-valued attributes contain a list of value or may contain sub-
attributes and MAY also be considered complex attributes. The order
of values returned by the server SHOULD NOT be guaranteed. The sub-
attributes below are considered normative and when specified SHOULD
be used as defined.
NEW:
Multi-valued attributes contain a list of elements, using the JSON
array format
defined in Section 5 of [RFC7159]. Elements can be either
o primitive values, or
o objects with a set of sub-attributes and values, using the JSON
object format
defined in Section 4 of [RFC7159], in which case they MAY also
be considered
to be complex attributes. As with complex attributes, the
order of sub-attributes
is not significant. The pre-defined sub-attributes listed in
this section can be
used with multi-valued attribute objects but these
sub-attributes should only be used
with the meanings as defined here.
s2.3: Question: Can sub-attributes have sub-sub-attributes? I don't
think I see any examples and maybe the definition in s1.2 effectively
excludes them. Might be worth being explicit.
s2.3, "primary" sub-attribute: Should this be specified as assumed to be
"false" if not present in a relevant object? I don't think this is
covered by the defaults anywhere.
s2.3, $ref: I guess this ought always to be canonicalized - this can be
noted in the following paragraph where canonicalization is discussed.
This would be a good place to specify a reference for URL
canonicalization as mentioned above.
s2.3, last para: Suggest being a little more explicit about the scope of
this paragraph. I suggest:
OLD:
Service providers MAY return the same value more than once with
different types (e.g. the same e-mail address may used for work and
home), but SHOULD NOT return the same (type, value) combination more
than once per Attribute, as this complicates processing by the
Consumer.
NEW:
Service providers MAY return element objects with the same "value"
sub-attribute
more than once with a different "type" sub-attribute (e.g., the
same e-mail address
may used for work and home), but SHOULD NOT return the same (type,
value)
combination more than once per Attribute, as this complicates
processing by the
consumer.
END
Note "Consumer" replaced by "consumer" - there is no definition of a
specific meaning for this term.
s3, Resource Type: s/("meta.resourceType")/("meta.resourceType", see
Section 3.1)/
s3, Schemas Attribute: I think s/the namespace of SCIM schema that
defines/the namespaces of the SCIM schemas that define/; s/All
representations of SCIM schema MUST include a non-zero value array/All
representations of SCIM schemas MUST include a non-empty array/
s3, name used in example: I don't know if the RFC Editor has a policy
on suitable fictitious names equivalent to example.com for domains.
Apparently Jane Roe and Mary Major have been used in US legal practice
as female alternatives to the ubiquitous Mr John Doe. Probably good to
check with the RFC Editor.
s3.1, id, externalId, meta.version, meta.resourceType: I suspect these
ought to be caseExact?
s3.1, externalId: The concepts of "provisioning domain" and a "client's
tenant" need to be defined. The externalId attribute is not explicitly
defined as REQUIRED or OPTIONAL.
s3.1.1, meta.resource: I got the impression from s3 that
meta.resourceType was REQUIRED rather than being optional as noted in
the first para of s3.1.1.
s3.1.1, meta.location: Should the value of this sub-attribute be the
same as Content-Location rather than Location? Is it intended that the
request should be redirected (or that the resource was newly created?
If not it seems Content-Location would be more appropriate. A normative
reference to the relevant HTTP RFC (probably RFC 7231) ought to be included.
s3.1.1, meta.version: Would one expect a weak or strong ETag? A
normative reference to the relevant HTTP RFC (probably RFC 7232) ought
to be included.
s3.2, last sentence: s/Section 6and/Section 6 and/ (missing space).
s3.3, 1st para: s/used in LDAP/are used in LDAP/;
s/Each "schemas" value indicates additive
schema/Each value in the "schemas" attribute indicates an additive schema/;
s/See Figure 5 for an example JSON
representation/See Figure 5 for an example of the JSON representation/
s3.3, para 2: s/"schemas" URI value/URI value in the "schemas" attribute/
s4.1.1, userName: Having said that each User MUST have include a
non-empty userName value, why is this attribute RECOMMENDED rather than
REQUIRED? I guess it ought to be caseExact also.
s4.1.1, profileUrl: Needs a canonicalization mechanism specified.
s4.1.1, preferredLanguage: There is potentially more than one preferred
language (as per Accept-Languages) so this presumably this ought to be a
Multi-valued attribute. The Accept-Language header syntax also has an
optional, per language, weight to assist with selection. Should this be
catered for here as well? This would presumably mean that it should
have sub-attributes (e.g.) using "value" for the name and "weight" or
some such. Also s/localized User interface/localized user interface/
s4.1.1, password: I *hope* there is a discussion of the security
implications of this field later. A pointer to this discussion would be
highly desirable.
s4.1.2, photos: A reference to the canonicalization mechanism is needed
(see previous comment).
s4.1.2, entitlements, roles: There doesn't seem to be any good reason
for capitalizing 'NO' here: s/NO/no/, 2 places.
s4.2, para 2: s/by the service provider are considered/by the service
provider, and are considered/
s4.3, employeeNumber: Maybe this might be better called an
"employeeIdentifier" since it can be alphanumeric. Is there any reason
why this can't just be any old string?
s5, patch: A pointer to the SCIM protocol draft PATCH operation would be
helpful.
s5, bulk: A pointer to the SCIM protocol draft Bulk operations section
would be helpful. I note that the capitalized form is not used in the
protocol draft: suggest s/BULK/Bulk/ (total of 2 places)
s5, filter: A pointer to some appropriate part of the SCIM protocol
draft (maybe s3.4.2.2) would be helpful.
s6, endpoint: (1)The endpoint is defined to be a relative URI. It is
therefore inappropriate that the example here is "/Users". I guess it
ought to be "Users". There are a number of example of relative URIs
starting with / in the examples in Section 8 that also ought to be
corrected.
s6, endpoint: (2) Please bear with me, this is a bit long winded... I
initially thought that the 'endpoint' mechanism was a possible
contravention of BCP 190/RFC 7320: Quoting s2.3 of RFC 7320:
Scheme definitions define the presence, format, and semantics of a
path component in URIs; all other specifications MUST NOT constrain,
or define the structure or the semantics for any path component.
....
For example, an application ought not specify a fixed URI path
"/myapp", since this usurps the host's control of that space.
Specifying a fixed path relative to another (e.g., {whatever}/myapp)
is also bad practice (even if "whatever" is discovered as suggested
in Section 3); while doing so might prevent collisions, it does not
avoid the potential for operational difficulties (for example, an
implementation that prefers to use query processing instead, because
of implementation constraints).
In Section 6, the definition of the endpoint attribute specifies that
each schema has to declare a relative URI or path component that gives
access to schema instances. My initial thinking was that the endpoint
value was standardized for Users and Groups in the draft. My
interpretation of s2.3 of RFC 7320 was that this technique is deprecated
as bad practice. After sleeping on it, I think I understand that the
endpoint value is *not* standardized and potentially each service
provider can use a different endpoint name if they really have to
(although I guess in this case it would be good to go with the
defaults.) So I am happy that this isn't flagrantly contravening BCP
190, although I am not sure about the query processing bit at the end of
the quoted section. Conclusion: I think it would be useful to add a
note to the definition of endpoint to indicate that it is at the choice
of the service delivering the resources and is not a fixed value, maybe
saying that this is intended to avoid infringing BCP 190.
s7, mutability:
OLD:
mutability A single keyword indicating what types of
modifications an attribute MAY accept as follows:
This 'MAY' is not about the 'protocol'.. Suggest:
NEW:
mutability A single keyword indicating the circumstances under
which the value of the attribute can be (re)defined:
END
s9: s/personally identifiable information/personally identifying
information/g
s9, 1st bullet: s/mulitple/multiple/
s9: para 1: It would be sensible to also forbid the carrying of
passwords in requests that are not encrypted.
s9: It would be worth emphasizing that privacy issues should be
considered whenever resource extensions are defined.
s10.1: This is a request for a new entry in the 'URN Sub-namespace for
Registered Protocol Parameter Identifiers' ...
OLD:
IANA has created a registry for new IETF URN sub-namespaces,
"urn:ietf:params:scim:", per [RFC3553]. The registration request is
as follows:
Per [RFC3553], IANA has registered a new URN sub-namespace,
"urn:ietf:params:scim".
NEW:
IANA is requested to add an entry to the 'IETF URN Sub-namespace for
Registered Protocol Parameter Identifiers'
registry and create a sub-namespace for the Registered Parameter
Identifier as per [RFC3553]:
"urn:ietf:params:scim:".
The registration request is as follows:
END
s10.2: This section is lacking a specification of exactly what is
recorded in the new SCIM registry - the template tells how to apply and
considerations to be used in granting the request. See Section 8.4 of
RFC 7035, for example, to see what is needed here.
s11.1: Needs a reference to the SCIM protocol document.
s11.2, [Olson-TZ] is incomplete - I suspect it needs a reference to the
IANA TZ database http://www.iana.org/time-zones
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