<?xml version="1.0" encoding="UTF-8"?>
<xs:schema xmlns:xs="http://www.w3.org/2001/XMLSchema" 
  xmlns:doc="eml://ecoinformatics.org/documentation-2.1.1" 
  xmlns:res="eml://ecoinformatics.org/resource-2.1.1" 
  xmlns="eml://ecoinformatics.org/access-2.1.1" 
  targetNamespace="eml://ecoinformatics.org/access-2.1.1">
  <xs:import namespace="eml://ecoinformatics.org/documentation-2.1.1" 
             schemaLocation="eml-documentation.xsd"/>
  <xs:import namespace="eml://ecoinformatics.org/resource-2.1.1" 
             schemaLocation="eml-resource.xsd"/>
  <xs:annotation>
    <xs:documentation>
       '$RCSfile: eml-access.xsd,v $'
       Copyright: 1997-2002 Regents of the University of California,
                            University of New Mexico, and
                            Arizona State University
        Sponsors: National Center for Ecological Analysis and Synthesis and
                  Partnership for Interdisciplinary Studies of Coastal Oceans,
                     University of California Santa Barbara
                  Long-Term Ecological Research Network Office,
                     University of New Mexico
                  Center for Environmental Studies, Arizona State University
   Other funding: National Science Foundation (see README for details)
                  The David and Lucile Packard Foundation
     For Details: http://knb.ecoinformatics.org/

        '$Author: cjones $'
          '$Date: 2009-03-05 20:08:47 $'
      '$Revision: 1.83 $'

    This program is free software; you can redistribute it and/or modify
    it under the terms of the GNU General Public License as published by
    the Free Software Foundation; either version 2 of the License, or
    (at your option) any later version.

    This program is distributed in the hope that it will be useful,
    but WITHOUT ANY WARRANTY; without even the implied warranty of
    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
    GNU General Public License for more details.

    You should have received a copy of the GNU General Public License
    along with this program; if not, write to the Free Software
    Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
    </xs:documentation>
    <xs:appinfo>
      <doc:moduleDocs>
        <doc:moduleName>eml-access</doc:moduleName>
        <doc:moduleDescription>
          <section xmlns="">
            <title>
              The eml-access module - Access control rules for resources
            </title>
            <para>
              The eml-access module describes the level of access that is
              to be allowed or denied to a resource for a particular user or 
              group of users, and can be described independently for metadata 
              and data.  The eml-access
              module uses a reference to a particular authentication system
              to determine the set of principals (users or groups) that can be
              specified in the access rules.
              The special principal 'public' can be used to indicate that any
              user or group has access permission, thereby making
              it easier to specify that anonymous access is allowed. 
             </para>
            <para>        
              There are two mechanisms for including access control 
              via the eml-access module: 
              <orderedlist>
                <listitem>
                  <para>
                    The top-level "eml" element may have an optional 
                    &lt;access&gt; element that is used to establish the 
                    default access control for the entire EML package. If 
                    this access element is omitted from the document, then 
                    the package submitter should be given full access to the 
                    package but all other users should be denied all access. 
                    To allow the package to be publicly viewable, the EML 
                    author must explicitly include a rule stating so.  Barring 
                    the existence of a distribution-level &lt;access&gt; element 
                    (see below), access to data entities will be controlled by 
                    the package-level &lt;access&gt; element in the 
                    &lt;eml&gt; element.
                  </para>
                </listitem>
                <listitem>
                  <para>
                    Exceptions for particular entity-level components of the 
                    package can be controlled at a finer grain by using an 
                    access description in that entity's physical/distribution 
                    tree. When access control rules are specified at this 
                    level, they apply only to the data in the parent 
                    distribution element, and not to the metadata. Thus, it 
                    will control access to the content of the &lt;inline&gt; 
                    element, as well as resources that are referenced by the 
                    &lt;online/url&gt; and &lt;online/connection&gt; paths. 
                    These exceptions to access for particular data resources 
                    are applied after the default access rules at the 
                    package-level have been applied, so they effectively 
                    override the default rules when they overlap.
                  </para>
                </listitem>
              </orderedlist>
            </para>
            <para>
              In previous versions of EML access rules for entity-level 
              distribution were contained in &lt;additionalMetadata&gt; 
              sections and referenced via the &lt;describes&gt; tag. 
              Although in theory these could have referenced any node, in 
              application such node-level access control is problematic. 
              Since the most common uses of access control rules were to 
              limit access to specific data entities, the access tree has 
              been placed there explicitly in EML 2.1.0.
            </para>          
            <para>
              Access is specified with a choice of child elements, either 
              &lt;allow&gt; or &lt;deny&gt;. Within these rules, values can 
              be assigned for each &lt;principal&gt; using the 
              &lt;permission&gt; element. Users given &quot;read&quot; permission can 
              view the resource; &quot;write&quot; allows changes to the resource 
              excluding changes to the access rules; &quot;changePermission&quot; 
              includes &quot;write&quot; plus the changing of access rules. Users 
              allowed &quot;all&quot; permissions; may do all of the above.  Access to 
              data and metadata is affected by the order attribute of the 
              &lt;access&gt; element. It is possible for a deny rule to 
              override an allow rule, and vice versa.  In the case where the 
              order attribute is set to &quot;allowFirst&quot;, and there are rules 
              similar to the following (with non-critical sections deleted):
<literalLayout>
  &lt;deny&gt;
    &lt;principal&gt;public&lt;/principal&gt;
    &lt;permission&gt;read&lt;/permission&gt;
  &lt;/deny&gt;
  &lt;allow&gt;
    &lt;principal&gt;uid=alice,o=NASA,dc=ecoinformatics,dc=org&lt;/principal&gt;
    &lt;permission&gt;read&lt;/permission&gt;
  &lt;/allow&gt;
</literalLayout>
              the principal &quot;uid=alice ...&quot; will be denied access, 
              because it is a member of the special &quot;public&quot; 
              principal, and the deny rule is processed second. For this 
              allow rule to truly allow access to that principal, the order 
              attribute should be set to &quot;denyFirst&quot;, and the 
              allow rule will override the deny rule when it is processed 
              second.              
            </para>
            <para>
              An example is given below, with non-critical sections deleted:
<literalLayout>
  &lt;eml&gt;
      &lt;access 
          authSystem="ldap://ldap.ecoinformatics.org:389/dc=ecoinformatics,dc=org" 
          order="allowFirst"&gt;
        &lt;allow&gt;
          &lt;principal&gt;uid=alice,o=NASA,dc=ecoinformatics,dc=org&lt;/principal&gt;
          &lt;permission&gt;read&lt;/permission&gt;
          &lt;permission&gt;write&lt;/permission&gt;
        &lt;allow&gt;
      &lt;/access&gt;
      &lt;dataset&gt;
      ...
      ...
      &lt;dataTable id="entity123"&gt;
      ...
        &lt;physical&gt;
        ...
          &lt;distribution&gt;
          ...
            &lt;access id="access123"
            authSystem="ldap://ldap.ecoinformatics.org:389/dc=ecoinformatics,dc=org" 
            order="allowFirst"&gt;
              &lt;deny&gt;
                &lt;principal&gt;uid=alice,o=NASA,dc=ecoinformatics,dc=org&lt;/principal&gt;
                &lt;permission&gt;write&lt;/permission&gt;
            &lt;/deny&gt;
          &lt;/access&gt;
         &lt;/distribution&gt;
       &lt;/physical&gt;
      &lt;/dataTable&gt;
      &lt;dataTable id="entity234"&gt;
        ...
        &lt;physical&gt;
        ...
          &lt;distribution&gt;
            ...
            &lt;access&gt;
              &lt;references&gt;access123&lt;/references&gt;
            &lt;/access&gt;
          &lt;/distribution&gt;
        &lt;/physical&gt;
      &lt;/dataTable&gt;
      ...    
    &lt;/dataset&gt;
  &lt;eml&gt;
</literalLayout>
              In this example, the overall default access is to allow the 
              user=alice (but no one else) to read and write all metadata 
              and data. However, under &quot;entity123&quot; and 
              &quot;entity234&quot;, there is an additional rule saying 
              that user=alice does not have write permission. The net 
              effect is that Alice can read and make changes to the 
              metadata, but cannot make changes to the two data entities. 
              In addition, Alice cannot change these access rules; although 
              the submitter can.
            </para>
            <para>
              This example also shows how the eml-access module, like other modules,
              may be "referenced" via the &lt;references&gt; tag.  This
              allows an access control document to be described once, and then
              used as a reference in other locations within the EML document
              via its ID.
            </para>
            <para>
            In summary, access rules can be applied in two places in an
            eml document. Default access rules are established
            in the top &lt;access&gt; element for the main eml document (e.g.,
            "/eml/access").  These default rules can be overridden
            for particular data entities by adding additional &lt;access&gt;
            elements in the physical/distribution trees of those entities.
           </para>
          </section>
        </doc:moduleDescription>
        <doc:recommendedUsage>all data where controlling user access to the
        dataset is an issue</doc:recommendedUsage>
        <doc:standAlone>yes</doc:standAlone>
      </doc:moduleDocs>
    </xs:appinfo>
  </xs:annotation>
  <xs:element name="access" type="AccessType">
    <xs:annotation>
      <xs:appinfo>
        <doc:tooltip>Access control rules</doc:tooltip>
        <doc:summary>The rules defined in this element will determine the level
        of access to a resource for the defined users and groups.</doc:summary>
        <doc:description>The access element contains a list of rules defining
        permissions for this resource. For descriptions of the individual elements, 
        see the AccessType.The permission rules defined here can be overridden 
         by rules added to an access tree in the PhysicalDistributionType  
        at the entity level. </doc:description>
        <doc:example>See the description of the AccessType.</doc:example>
      </xs:appinfo>
    </xs:annotation>
  </xs:element>
  <xs:complexType name="AccessType">
    <xs:annotation>
      <xs:appinfo>
        <doc:tooltip>Access control rules</doc:tooltip>
        <doc:summary>The rules defined in this element will determine the level
        of access to a resource for the defined users and groups.</doc:summary>
        <doc:description>The access element contains a list of rules that define
        the level of access for a resource. There are two uses of access trees: to
        control access to either metadata or data. To control access to metadata 
        use the eml/access tree. By default, these rules will also apply to the contained 
        data. To override the default controls for specific data entities, use the 
        access element available in the entity's physical/distribution tree.  A 
        combination of access trees and their "order rules" (see description of 
        the "order" attribute) allows EML authors
        to have fine control over permissions for individuals and groups.
        </doc:description>
      </xs:appinfo>
    </xs:annotation>
    <xs:choice>
      <xs:choice maxOccurs="unbounded">
        <xs:element name="allow" type="AccessRule">
          <xs:annotation>
            <xs:appinfo>
              <doc:tooltip>Allow rule</doc:tooltip>
              <doc:summary>A rule that grants a permission
              type.</doc:summary>
              <doc:description>The allow element indicates that a particular
              user or group is granted the defined permission.</doc:description>
              <doc:example>allow</doc:example>
            </xs:appinfo>
          </xs:annotation>
        </xs:element>
        <xs:element name="deny" type="AccessRule">
          <xs:annotation>
            <xs:appinfo>
              <doc:tooltip>Deny rule</doc:tooltip>
              <doc:summary>A rule that revokes a permission
              type.</doc:summary>
              <doc:description>The deny element indicates that a particular
              user or group is not granted the defined
              permission.</doc:description>
              <doc:example>deny</doc:example>
            </xs:appinfo>
          </xs:annotation>
        </xs:element>
      </xs:choice>
      <xs:group ref="res:ReferencesGroup"/>
    </xs:choice>
    <xs:attribute name="id" type="res:IDType" use="optional"/>
    <xs:attribute name="system" type="res:SystemType" use="optional"/>
    <xs:attribute name="scope" type="res:ScopeType" use="optional" default="document"/>
    <xs:attribute name="order" use="optional" default="allowFirst">
      <xs:annotation>
        <xs:appinfo>
          <doc:tooltip>Rule order</doc:tooltip>
          <doc:summary>The order in which the allow and deny rules should be
          applied.</doc:summary>
          <doc:description>To obtain the desired access control, use the order 
          attribute to define which rules should be applied first. The acceptable
          values are 'allowFirst' and 'denyFirst'. If 'allowFirst' is
          specified, then all 'allow' rules are processed, and then overridden
          by all 'deny' rules.  If 'denyFirst' is specified, then all 'deny'
          rules are processed, and then overridden by all 'allow' rules.  
          </doc:description>
          <doc:example>allowFirst</doc:example>
        </xs:appinfo>
      </xs:annotation>
      <xs:simpleType>
        <xs:restriction base="xs:string">
          <xs:enumeration value="allowFirst"/>
          <xs:enumeration value="denyFirst"/>
        </xs:restriction>
      </xs:simpleType>
    </xs:attribute>
    <xs:attribute name="authSystem" type="xs:string" use="required">
      <xs:annotation>
        <xs:appinfo>
          <doc:tooltip>Authentication system</doc:tooltip>
          <doc:summary>The authentication system is used to verify the user or
          group to whom access is allowed or denied.</doc:summary>
          <doc:description>The authentication system determines the set of
          principals (users + groups) that can be used in the access control
          list, and the membership of users in groups. This element is intended
          to provide a reference to the authentication system that is used to
          verify the user or group. This reference is typically in the form
          of a URI, which includes the connection protocol, Internet host, and
          path to the authentication mechanism.</doc:description>
          <doc:example>
          ldap://ldap.ecoinformatics.org:389/dc=ecoinformatics,dc=org
          </doc:example>
        </xs:appinfo>
      </xs:annotation>
    </xs:attribute>
  </xs:complexType>
  <xs:complexType name="AccessRule">
    <xs:annotation>
      <xs:appinfo>
        <doc:tooltip>Access Rule</doc:tooltip>
        <doc:summary>Access Rules define a user's access to a
        resource.</doc:summary>
        <doc:description>The AccessRule type defines a list of users that are
        derived from a particular authentication system (such as an LDAP
        directory), whether the user or group is allowed or denied access, the
        extent of their access (read, write , or changePermission
        access).</doc:description>
      </xs:appinfo>
    </xs:annotation>
    <xs:sequence>
      <xs:element name="principal" type="res:NonEmptyStringType" maxOccurs="unbounded">
        <xs:annotation>
          <xs:appinfo>
            <doc:tooltip>User or group</doc:tooltip>
            <doc:summary>The user or group (principal) for which the access
            control applies.</doc:summary>
            <doc:description>The principal element defines the user or group to
            which the access control rule applies. The users and groups must be
            defined in the authentication system described in the authSystem
            element.  The special principal 'public' can be used to indicate
            that any user or group has a particular access permission, thereby
            making it easier to specify that anonymous access is allowed.
            </doc:description>
            <doc:example>public</doc:example>
            <doc:example>uid=alice,o=LTER,dc=ecoinformatics,dc=org</doc:example>
          </xs:appinfo>
        </xs:annotation>
      </xs:element>
      <xs:element name="permission" maxOccurs="unbounded">
        <xs:annotation>
          <xs:appinfo>
            <doc:tooltip>Type of permission</doc:tooltip>
            <doc:summary>The type of permission being granted or denied.
            </doc:summary>
            <doc:description>
              <doc:section xmlns="">
                <para>
            The permission that is being granted or denied
            to a particular user or group for a given resource. The list of
            permissions come from a predetermined list:
            </para>
                <para>'read' - allow or deny viewing of the resource, </para>
                <para>'write' - allow or deny modification of the resource (except for access rules),  </para>
                <para>'changePermission' - modifications including access rules, and  </para>
                <para>'all' - all of the above. </para>
                <para>
               
                This element also allows other permission values that may be applicable to some other authentication systems but are not defined in this specification (if these other values are used, access rule enforcement is indeterminate outside of the originating system).</para>
              </doc:section>
            </doc:description>
            <doc:example>read</doc:example>
          </xs:appinfo>
        </xs:annotation>
        <xs:simpleType>
          <xs:union>
            <xs:simpleType>
              <xs:restriction base="xs:string">
                <xs:enumeration value="read"/>
                <xs:enumeration value="write"/>
                <xs:enumeration value="changePermission"/>
                <xs:enumeration value="all"/>
              </xs:restriction>
            </xs:simpleType>
            <xs:simpleType>
              <xs:restriction base="xs:string"/>
            </xs:simpleType>
          </xs:union>
        </xs:simpleType>
      </xs:element>
    </xs:sequence>
  </xs:complexType>
</xs:schema>
