Access control for eml2 documents
Access control for eml2 documents is pretty complicated.
In access control submodule, the access rules control the documents access,
this can be handled as same as eml beta6. But in additional meta data part,
user can specify another access control for a subtree of the document. This
control is not base on docid and is base on node id. So we maybe need to
change the table structure of xml_access table: adding a new field named
nodeid which is foreign key of xml_nodes table.
When we access control, it should be base on sql rather than java code for
#2 Updated by Jing Tao over 18 years ago
In xml_access table, 3 new fields - subtreeid, startnodeid and endnodeid were
added. They are used as subtree access control.
Currently, metacat can pull out access control info for both top document
level and subtree level(in additionalmetadata part) and write the info to
If user try to read a document, metacat will check both document level and
subtree level access contol. If a subtree is not allow to a user, he will only
part of document.
In search, the return field access control was applied too. If the return
field is in a subtree that the user could not access, the search result would
NOT show it's value.
So now, read and search access control is almost done.
But, we still have a big issue in writting access control for subtree. If a
subtree is set to a user only can read, but top doucment the user can write
and read. It is difficult to know if the user update the subtree which he
doesn't have a permission to write when he submit a newer version documents.
Another issue is: citation, software and protocol moudle can be include in
dataset module, but these modules can have access elemment in itself too. So
in a dataset module, it is possible to have lots of access elements(they come
from citation, software or protocol) except datset's access element and access
element in additionalmetadata. How do we handle these extral access?
#4 Updated by Saurabh Garg about 17 years ago
Main points based on IRC chat on April 30th, 2004. The chat text is also copied
1. if /eml/access (in 2.0.1), or /eml/dataset/access (in 2.0.0) is present, we
follow the rules laid out there for the whole package
2. /eml/citation/access, /eml/software/access and /eml/protocol/access (in
2.0.0) are always ignored. These along with /eml/dataset/access will be not
allowed from 2.0.1
3. if there is an additional rule set for the data only (location to be
determined), then that can override the spec from the top level
4. new documents being inserted can be eml 2.0.0
Regarding point 3, I agree to the location talked about in bug 1132. i.e. the
<access>...</access> <-- defines access to the data object
in inline, online, or offline
elements (ie, not the metadata
itself, just the data)
I think this would be a better place as compared to <additionalMetadata>
I am not sure yet what would be the best way of proceeding to implement this
solution. I will have to see metacat code and how xml_access table is used.
Watch out for more in this space..
[11:17] <sid> is it possible to set read access to metadata and not allow read
access to the data itself
[11:17] <jing> good question.
[11:17] <jing> you mean in eml2?
[11:18] <sid> i guess it is dependent on eml2
[11:18] <jing> currently we don't support that.
[11:19] <sid> i thought it was possible - but i am not able to locate access
permissions for datatable or any other entity
[11:19] <sid> ok
[11:19] <matt> this is an ongoing issue
[11:19] <jing> yes.
[11:19] <matt> see the bug on access control in EML for a description of the
[11:20] <matt> bug 1132
[11:20] <sid> ok matt .. this is regarding the email that rick sent yesterday
regarding specnet - i will have to backtrack on the reply that i sent to him
[11:21] <matt> or we can fix it in metacat
[11:21] <matt> which we need to do anyways
[11:21] <matt> it would be a nice fix to have in for the metacat 1.4 release
[11:23] <sid> so access control for entities will remain in additional metadata
[11:23] <jing> I think so.
[11:23] <sid> actually i think i will read bug#1132 first
[11:24] <matt> yeah
[11:24] <matt> read that, then lets discuss it
[11:32] <sid> matt - ignoring access inside dataset would be a big change
[11:42] <sid> but i do agree that it will take care of a lot of complexity that
we will have to face otherwise
[11:44] <sid> maybe a rule can be specified that if no overall access if
described then dataset access is considered for assigning access to the
document - but no future document can have access inside dataset
[11:45] <matt> you lost me there
[11:45] <matt> i thought the proposal in 1132 was to have 2 levels of access:
metadata, and data
[11:45] <sid> yes
[11:46] <matt> if data access is unspecified, it defaults to the same as
[11:46] <sid> yup
[11:46] <matt> you see a problem with this approach?
[11:46] <sid> thats what i meant
[11:46] <matt> ok
[11:46] <matt> i guess i misinterpreted what you meant by "overall access"
[11:47] <matt> the question is how to specify these rules in the context of
EML2.0.0 and EML2.0.1
[11:47] <sid> only problem will be when dataset has different access and
citation has different access and protocol has different access
[11:47] <matt> technically metacat is not following the rules for EML200 now
because they are unimplementable as specified
[11:48] <matt> access and citation and protocol are all metadata, so only the
topmost access block would apply there
[11:49] <matt> there shouldn't be any opportunity for conflicting access specs
[11:49] <sid> and if topmost is missing which access block do you default to?
[11:49] <matt> if topmost is missing, only owner of metadata/data has any
access at all
[11:50] <sid> can you default to dataset access for the sake of backward
[11:52] <sid> even if we just default to dataset access, i think it will take
care of 99%(if not 100%) eml documents we have
[11:52] <matt> what do you mean by "dataset access"?
[11:52] <sid> access block inside dataset block
[11:53] <matt> right now, if eml/dataset/access is missing, nobody but owner
has access to anything
[11:53] <matt> i think this should be maintained
[11:53] <sid> yeah i think so too - but what if it is specified
[11:54] <matt> if /eml/access (in 2.0.1), or /eml/dataset/access (in 2.0.0) is
present, we follow the rules laid out there for the whole package
[11:54] <sid> ok
[11:54] <sid> all fine and clear
[11:54] <matt> if there is an additional rule set for the data only (location
to be determined), then that can override the spec from the top level
[11:55] <matt> that's it I think
[11:55] <sid> i agree
[11:58] <sid> will this mean once metacat changes it wont accept any eml 2.0.0
[11:58] <matt> no, we'll need to maintain backwards compatibility
[11:58] <matt> although the access rules may be interpreted differently
[11:58] <matt> as we just discussed
[11:58] <sid> so new documents being inserted can be eml 2.0.0
[11:59] <matt> yes
#5 Updated by Saurabh Garg about 17 years ago
From what I have understood till now (with Jing's help)
1. The document inserted to Metacat is first validated in MetacatServlet.java
using the EMLParser.class from eml module. I am not sure about one thing here -
when eml-2.0.1 is released, will EMLParser.class take care of parsing the
version 2.0.1 also or will there be a seperate class to take care of parsing
the new version?
2. Once this step is taken care of - from DocumentImpl.java, different classes
are called on basis of eml version type. So for eml2, EmlSAXHandler class is
called. EmlSAXHandler takes care of how access is handled. So I could think of
two options of doing this:
> Put code in EmlSAXHandler to distiguish between eml 2.0.0 and eml 2.0.1 -
and handle access accordingly.
-> Rename EmlSAXHandler to Eml2_0_0_SAXHandler. And make a new class
Eml2_0_1_SAXHandler to take care of version 2.0.1. So from DocumentImpl code,
we find out which version the current eml document belongs to and call
Eml2.0.X_SAXHandler accordingly. Eml2_0_1_SAXHandler will be same as
Eml2_0_0_SAXHandler accept for the way in which access is handled.
I am more inclined towards the second idea as it would scale well.