xeps/xep-0043.xml

<?xml version='1.0' encoding='UTF-8'?>
<!DOCTYPE xep SYSTEM 'xep.dtd' [
  <!ENTITY % ents SYSTEM "xep.ent">
%ents;
]>
<?xml-stylesheet type='text/xsl' href='xep.xsl'?>
<xep>
  <header>
    <title>Jabber Database Access</title>
    <abstract>Expose RDBM systems directly to the jabber network</abstract>
    &LEGALNOTICE;
    <number>0043</number>
    <status>Retracted</status>
    <type>Standards Track</type>
    <sig>Standards</sig>
    <dependencies/>
    <supersedes/>
    <supersededby/>
    <shortname>N/A</shortname>
    <author>
      <firstname>Justin</firstname>
      <surname>Kirby</surname>
      <email>justin@openaether.org</email>
      <jid>zion@openaether.org</jid>
    </author>
    <revision>
      <version>0.2</version>
      <date>2003-10-20</date>
      <initials>psa</initials>
      <remark>At the request of the author, changed status to Retracted.</remark>
    </revision>
    <revision>
      <version>0.1</version>
      <date>2002-08-21</date>
      <initials>jk</initials>
      <remark>Initial public release</remark>
    </revision>
  </header>
  <section1 topic='Introduction'>
    <p>Accessing a RDBMS in a generic fashion is a complex and difficult
    task. Consequently, this will not be an attempt to XMLize a generic
    Database API or query language. Instead, it will providing a
    simple mechanism for a JID to read/write data that it has access to
    and specifying a model for those schemas to use in xml.</p>
    <p>This document has two aims.</p>
    <ol>
      <li>Be able to request the available schemas</li>
      <li>Perform near SQL-like data manipulation</li>
    </ol>
    <p>Although designed for use with an RDBMS this document is not
    restricted to such uses. It may be used with any data storage
    system that can be broken down to a simple table, column/row
    format. for example comma delimited files.</p>
  </section1>
  <section1 topic='Prerequisites'>
    <p>To understand the following sections of this document the reader
    must be aware of the following.</p>

    <section2 topic='Namespace'>
      <p>The current namespace of <link>http://openaether.org/projects/jabber_database.html</link>
      will be used until this becomes a jep. Once officially accepted as
      a jep and approved as final by the council, it will become
      <link>http://www.xmpp.org/extensions/xep-0043.html</link>.</p>
    </section2>
    <section2 topic='Elements'>
      <ul>
        <li>version - specify the version of the protocol that the client/server supports</li>
        <li>database - specify the database/catalog has the following attributes:
          <ul>
            <li>name - name of the database/catalog</li>
            <li>sql - embed native SQL queries directly</li>
            <li>table - the element scopes the children into the table. has the following attributes:
              <ul>
                <li>name - name of the table</li>
                <li>permission - what the user can do with the data</li>
                <li>col - describes the column. has the following attributes
                  <ul>
                    <li>name - name of the column</li>
                    <li>type - SQL99 datatype of the column</li>
                    <li>size - size of the datatype if required</li>
                    <li>op - comparison operator, used only if child of where element</li>
                  </ul>
                </li>
                <li>where - scopes col elements into a 'sql-like' where clause
                  <ul>
                    <li>col - see above</li>
                  </ul>
                </li>
              </ul>
            </li>
            <li>proc - element scopes the children into a procedure has the following attributes:
              <ul>
                <li>name - name of the sproc</li>
                <li>permission - what the user can do with the data</li>
                <li>col - see above</li>
                <li>result - indicated return value by running the procedure (restricted to integer)</li>
              </ul>
            </li>
          </ul>
        </li>
      </ul>
    </section2>
    <section2 topic='Data Types'>
      <p>There are a limited subset of data types available:</p>
      <ul>
        <li>bit - a single 'bit', usually used to represent boolean values</li>
        <li>tinyint - signed 8bit integer, has a range from   -128  to +127</li>
        <li>integer - signed 32bit integer, has a range from -2147483648 to +2147483647</li>
        <li>utinyint - unsigned 8bit integer, has a range from 0 to +255</li>
        <li>uinteger - usigned 32bit integer, has a range from   0 to +4294967296</li>
        <li>float - allowed values are -3.402823466E+38 to
        -1.175494351E-38, 0, and 1.175494351E-38 to 3.402823466E+38 (can NOT be  unsigned)</li>
        <li>numeric - unlimited size (some databases constrain this though)</li>
        <li>date - resolution is one day. acceptable ranges vary (TODO: constrain minimal range to something)</li>
        <li>datetime - a date and time combination (often has range dependencies)</li>
        <li>timestamp - a datetime used most often to record events</li>
        <li>time - a time in the format HH:MM:SS (TODO: specify valid range)</li>
        <li>char - an unsigned byte representing a single character (ASCII)</li>
        <li>vchar - a variable width char</li>
        <li>text - an extremely large chunk of text</li>
        <li>blob - an extremely large chunk of binary data (encode in MIME)</li>
      </ul>
    </section2>
    <section2 topic='Assumed Database Setup'>
      <p>All SQL/RDBMS units will be scoped in the xml hierarchy:</p>

      <code>
&lt;database&gt;
  &lt;table&gt;
    &lt;col/&gt;
  &lt;/table&gt;
&lt;/database&gt;
      </code>

      <p>All examples will assume the existence of the following rdbms setup. A
      database named 'testdb' with tables created with following SQL
      script:</p>

      <code>
        create table tbl_one
        (
          a_int int,
          a_float float,
          a_char  char(10)
        )
        create table tbl_two
        (
          a_date datetime,
      a_numeric numeric(9,3)
        )
      </code>
    </section2>
</section1>
<section1 topic='Usage'>
  <section2 topic='Requesting Schemas'>
      <example caption='A simple schema request'>
&lt;iq id="001" to="db.host" type="get"&gt;
  &lt;database
      name="testdb"
      xmlns="http://openaether.org/projects/jabber_database.html"/&gt;
&lt;/iq&gt;
      </example>

      <p>This is a simple request to discover what tables/procedures
      exist on the database testdb. And what permissions are available
      to the user. All schema requests will respond within the scope that
      was asked for. This is to prevent unnecessary data from flooding
      the network. So the response for the above request would look
      something like:</p>

      <example caption='Response to a schema request'>
&lt;iq id="001" type="result" from="db.host"&gt;
  &lt;database
      name="testdb"
      xmlns="http://openaether.org/projects/jabber_database.html"/&gt;
    &lt;table  name="tbl_one" permission="both"/&gt;
      &lt;table  name="tbl_two" permission="read"/&gt;
  &lt;/database&gt;
&lt;/iq&gt;
      </example>

      <p>The response is scoped to only the 'children' of the request.
      Since the request was for the testdb database, only the tables
      within that database were returned in the result. The reason for
      the limitation is to prevent excessively large packets from filling
      the network from large schemas.</p>

      <p>The response indicates that the user has both read and write
      permissions on the table 'tbl_one' and only read permissions on
      the table 'tbl_two'. Consequently, the user may only perform get
      requests on 'tbl_two'.</p>

      <example caption='Request detailed table schema'>
&lt;iq id="002" type="get" to="db.host"&gt;
  &lt;database
      name="testdb"
      xmlns="http://openaether.org/projects/jabber_database.html"/&gt;
    &lt;table  name="tbl_one"/&gt;
  &lt;/database&gt;
&lt;/iq&gt;
      </example>

      <p>The response would look like:</p>

      <example caption='Response to detailed request'>
&lt;iq id="002" type="result" from="db.host"&gt;
  &lt;database
      name="testdb"
      xmlns="http://openaether.org/projects/jabber_database.html"/&gt;
    &lt;table  name="tbl_one"    permission="both"&gt;
     &lt;col name="a_int" type="int"/&gt;
      &lt;col name="a_float" type="float"/&gt;
      &lt;col name="a_char" type="char" size="10"/&gt;
    &lt;/table&gt;
  &lt;/database&gt;
&lt;/iq&gt;
      </example>

      <p>The schema response for tbl_one is quite intuitive. Three
      columns exist, one called a_int of type int (integer), another
      a_float of type float and  a third called a_char of type char
      with a size of ten characters.</p>


    </section2>

    <section2 topic='Manipulating Data'>

      <p>Manipulation of data (select, insert, update, delete) will
      definitely not be elegant or easy. SQL allows for some fairly
      complex queries on any fully  functional RDBMS. Consequently,
      the data manipulation will be  relatively limited since it is
      not a goal to translate SQL into xml.</p>

      <section3 topic='Selects'>
        <p>To indicate a select like query, specify an &lt;iq&gt; of
        type get. The table that the query is to be performed against
        must be specified. The columns   that are to be returned in
        the result set must be scoped within  the relative   table.
        Any attribute on the &lt;col&gt; element besides name will be
        ignored.  e.g. it is not required nor recommended to specify
        the data types  or the  sizes while performing a get.</p>

        <example caption='Basic select'>
&lt;iq id="003" type="get" to="db.host"&gt;
  &lt;database
      name="testdb"
      xmlns="http://openaether.org/projects/jabber_database.html"/&gt;
    &lt;table  name="tbl_one"&gt;
      &lt;col name="a_int"/&gt;
      &lt;col name="a_float"/&gt;
      &lt;col name="a_char"/&gt;
    &lt;/table&gt;
  &lt;/database&gt;
&lt;/iq&gt;

      SQL Syntax:
        select a_int, a_float, a_char
        from tbl_one
        </example>

       <p>It is also possible to specify a limit on the number of rows
       returned in the result set by specifying a value for the limit
       attribute.</p>

       <example caption='Basic select with limit'>
&lt;iq id="003" type="get" to="db.host"&gt;
  &lt;database
      name="testdb"
      xmlns="http://openaether.org/projects/jabber_database.html"/&gt;
    &lt;table name="tbl_one"  limit="2"&gt;
      &lt;col name="a_int"/&gt;
      &lt;col name="a_float"/&gt;
      &lt;col name="a_char"/&gt;
      &lt;/table&gt;
  &lt;/database&gt;
&lt;/iq&gt;
       </example>

       <p>In this case a limit of two rows will be returned in the result set.</p>

       <p> The result set which is returned will contain all the rows
       that met the criteria of the select. There is no schema
       information beyond the column names included in the result set.
       Each 'row' in the result set is scoped within the corresponding
       &lt;table&gt; element. This allows for queries on multiple
       tables to be used in one &lt;iq&gt; packet.</p>

       <example caption='Response to basic select'>
&lt;iq id="003" type="result" from="db.host"&gt;
  &lt;database
      name="testdb"
      xmlns="http://openaether.org/projects/jabber_database.html"/&gt;
    &lt;table  name="tbl_one"&gt;
      &lt;col name="a_int"&gt;1234&lt;/col&gt;
      &lt;col name="a_float"&gt;123.45&lt;/col&gt;
      &lt;col name="a_char"&gt;onetwothre&lt;/col&gt;
    &lt;/table&gt;
    &lt;table  name="tbl_one"&gt;
      &lt;col name="a_int"&gt;2345&lt;/col&gt;
      &lt;col name="a_float"&gt;234.56&lt;/col&gt;
      &lt;col name="a_char"&gt;twothreefo&lt;/col&gt;
    &lt;/table&gt;
  &lt;/database&gt;
&lt;/iq&gt;
       </example>
     </section3>

     <section3 topic='Constraining Result Sets'>
       <p>It would be impractical to request the entire contents of the
       table every time you needed one row or a subset of the data. You
       can constrain the result set by specifying a where clause.</p>

       <example caption='Select with constraints'>
&lt;iq id="004" type="get" to="db.host"&gt;
  &lt;database
      name="testdb"
      xmlns="http://openaether.org/projects/jabber_database.html"/&gt;
    &lt;table  name="tbl_one"&gt;
      &lt;col name="a_int"/&gt;
      &lt;col name="a_float"/&gt;
      &lt;col name="a_char"/&gt;
      &lt;where&gt;
        &lt;col name="a_int" op="eq"&gt;1234&lt;/col&gt;
        &lt;col name="a_float" op="lt" conj="and"&gt;200.00&lt;/col&gt;
      &lt;/where&gt;
    &lt;/table&gt;
  &lt;/database&gt;
&lt;/iq&gt;

         SQL Syntax:
         select a_int, a_float, a_char from tbl_one
         where   a_int = 1234 and a_float &lt; 200.00
       </example>

       <p>Attributes only used in the &lt;col&gt; element within a
       &lt;where&gt; element are the op (for operator) and conj for
       (conjunction). The op is used for comparison operators such
       as &lt;, &gt;, =, &lt;&gt;, &lt;=, &gt;=</p>

       <ul>
     <li>eq - equivalent =</li>
     <li>neq - not-equivalent &lt;&gt;</li>
     <li>lt - less than &lt;</li>
     <li>gt - greater than &gt;</li>
     <li>let - less than or equivalent &lt;=</li>
     <li>get - greater than or equivalent &gt;=</li>
     <li>null - IS NULL (the column is null in  the   database  sense of the word)</li>
       </ul>

      <p>The conjuction attribute is used to combined constraints in the where clause</p>

      <ul>
        <li>not - to negate a result</li>
    <li>or - logical OR ||</li>
    <li>and - logical AND &amp;&amp;</li>
      </ul>

      <p><strong>Result</strong></p>

      <example caption='Response to select with constraints'>
&lt;iq id="003" type="result" to="db.host"&gt;
  &lt;database
      name="testdb"
      xmlns="http://openaether.org/projects/jabber_database.html"/&gt;
    &lt;table  name="tbl_one"&gt;
      &lt;col name="a_int"&gt;1234&lt;/col&gt;
      &lt;col name="a_float"&gt;123.45&lt;/col&gt;
      &lt;col name="a_char"&gt;onetwothre&lt;/col&gt;
    &lt;/table&gt;
  &lt;/database&gt;
&lt;/iq&gt;
      </example>
    </section3>

    <section3 topic='Inserts'>
      <p>Inserting or altering the stored data in anyway requires
      setting the type attribute to a value of set. This indicates
      that the user wants to perform a 'insert/update'. The
      differentiating factor between an insert and an update operation
      is whether a &lt;where&gt; element is used. If there is no
&lt;where&gt; element then it must be interpreted as an insert.
      If a &lt;where&gt; element does exist, then it must be
      interpreted as an update.</p>

      <example caption='Inserting data'>
&lt;iq id="004" type="set" to="db.host"&gt;
  &lt;database
      name="testdb"
      xmlns="http://openaether.org/projects/jabber_database.html"/&gt;
    &lt;table  name="tbl_one"&gt;
      &lt;col name="a_int"&gt;3456&lt;/col&gt;
      &lt;col name="a_float"&gt;345.67&lt;/col&gt;
      &lt;col name="a_char"&gt;threefour&lt;/col&gt;
    &lt;/table&gt;
    &lt;table  name="tbl_two"&gt;
      &lt;col name="a_date"&gt;02/16/2002&lt;/col&gt;
      &lt;col name="a_numeric"&gt;123456789123.123&lt;/col&gt;
    &lt;/table&gt;
  &lt;/database&gt;
&lt;/iq&gt;

SQL syntax:
insert tbl_one (a_int, a_float,a_char)VALUES(3456,   345.67, 'threefour')
insert tbl_two (a_date, a_numeric) VALUES('02/16/2002', 123456789123.123)
      </example>

      <p><strong>Result</strong></p>

      <p> If there is no result set for the query, as in an update,
      insert, delete, then the response must indicate success or
      failure within the &lt;table&gt; element scope. An empty
&lt;table&gt; element indicates success, and a &lt;table&gt;
      element containing an &lt;error&gt; element indicates a failure.</p>

      <example caption='Response to data insert'>
&lt;iq id="004" type="result" from="db.host"&gt;
  &lt;database
      name="testdb"
      xmlns="http://openaether.org/projects/jabber_database.html"/&gt;
    &lt;table name="tbl_one"/&gt;
    &lt;table name="tbl_two"&gt;
      &lt;error code="380"&gt;permission denied on table&lt;/error&gt;
    &lt;/table&gt;
  &lt;/database&gt;
&lt;/iq&gt;
      </example>

      <p> The insert into tbl_one succeeded since the response has an
      empty &lt;table&gt; element. However, the insert into tbl_two
      failed with a permission denied error. Which is indicated with a
      non-empty &lt;table&gt; element.</p>
    </section3>

    <section3 topic='Updates'>

      <p> As stated previously, if the type attribute has a value of
      set and a &lt;where&gt; element exists, then it must be interpreted as an update.</p>

      <example caption='Updating'>
&lt;iq id="005" type="set" to="db.host"&gt;
  &lt;database
      name="testdb"
      xmlns="http://openaether.org/projects/jabber_database.html"/&gt;
    &lt;table  name="tbl_one"&gt;
      &lt;col name="a_char"&gt;aaaaaaaaaa&lt;/col&gt;
      &lt;where&gt;
        &lt;col name=c"a_int"&gt;1234&lt;/col&gt;
      &lt;/where&gt;
    &lt;/table&gt;
  &lt;/database&gt;
&lt;/iq&gt;

        SQL Syntax:
    update tbl_one
    set a_char = 'aaaaaaaaaa'
    where a_int = 1234
      </example>

      <p><strong>Result</strong></p>

      <p> Again, if there is no result set returned by the query, then
      success or failure must be indicated.</p>

      <example caption='Response to update'>
&lt;iq id="005" type="result" to="db.host"&gt;
  &lt;database
      name="testdb"
      xmlns="http://openaether.org/projects/jabber_database.html"/&gt;
    &lt;table name="tbl_one"/&gt;
  &lt;/database&gt;
&lt;/iq&gt;
      </example>
    </section3>

    <section3 topic='Deletes'>

    <p> If the type attribute has a value of set and there are no
    &lt;col&gt; elements scoped within the &lt;table&gt; element,
    then the query must be interpreted as a delete.</p>

    <example caption='Simple delete'>
&lt;iq id="006" type="set"  to="db.host"&gt;
  &lt;database
      name="testdb"
      xmlns="http://openaether.org/projects/jabber_database.html"/&gt;
    &lt;table name="tbl_one"&gt;
      &lt;where&gt;
        &lt;col name="a_int" op="eq"&gt;1234&lt;/col&gt;
      &lt;/where&gt;
    &lt;/table&gt;
    &lt;/database&gt;
&lt;/iq&gt;

      SQL Syntax:
      delete from tbl_one where a_int = 1234
    </example>

    <p><strong>Result</strong></p>

    <p>Again, if a result set is not generated by a query, then
    success or failure must be indicated by the &lt;table&gt; element</p>

    <example caption='Response to delete'>
&lt;iq id="006" type="result"    to="db.host"&gt;
  &lt;database
      name="testdb"
      xmlns="http://openaether.org/projects/jabber_database.html"/&gt;
    &lt;table name="tbl_one"/&gt;
  &lt;/database&gt;
&lt;/iq&gt;
    </example>
    </section3>
  </section2>
  <section2 topic='Procedures'>

  <p> Procedures, or stored procedures <note>Apparently procedures
  are not as common in RDBMS as I thought. Postgres and MySQL have
  functions, but not procedures. So until I, or someone else,
  researches this issue this feature is on hold.</note>
, are often handy to make frequently used sql queries execute faster.
  These are simply queries stored in a precompiled form and given a
  name with a list of parameters. Each RDBMS handles procedures
  differently, but the common characteristics are that they are
  stored server side and have in/out parameters.</p>

  <p> The &lt;proc&gt; element will be used to indicate a procedure.
  It has similar characteristics to the &lt;table&gt; element. The
  core differences are that the &lt;col&gt; elements have permissions
  and a &lt;result&gt; element can be used to indicate the value
  returned by the procedure.</p>

  <p> The permission attribute on a &lt;col&gt; element is used to
  indicate whether the parameter is in (read), out (write) or in/out (both). </p>

  <p> The only result set acceptable from a procedure is that of the
  parameters or &lt;col&gt; element. If the procedure produces a
  result set outside of the parameters this should be ignored.</p>

  </section2>
  <section2 topic='Errors'>

  <p> The server must be able to let the client know when an error
  occurs, instead of just being silent.</p>

  <table caption='Error Codes'>
    <tr>
      <th>Code</th>
      <th>Message</th>
      <th>Description</th>
    </tr>
    <tr>
      <td>399</td>
      <td>Invalid Database Name</td>
      <td>Returned when the client has requested information from a
      database which does not exist according to the component.</td>
    </tr>
    <tr>
      <td>398</td>
      <td>Invalid Table Name</td>
      <td>Returned when the client has requested information from a
      table/procedure which does not exist according to the component.</td>
    </tr>
    <tr>
      <td>397</td>
      <td>Invalid Column Name</td>
      <td>Returned when the client has requested information from a
      column which does not exist according to the component.</td>
    </tr>
    <tr>
      <td>380</td>
      <td>Permission Denied on Table</td>
      <td>Returned when the requested action is not allowed for the
      user on the table</td>
    </tr>
    <tr>
      <td>401</td>
      <td>Access Denied</td>
      <td>Returned when the user does not have permission to use the
      component.</td>
    </tr>
  </table>

  <p>If the user requests an action on a table which they do not have
  permission to do the following should be returned</p>

  <example caption='Permission denied error'>
&lt;iq id="004" type="error" from="db.host"&gt;
  &lt;database
      name="testdb"
      xmlns="http://openaether.org/projects/jabber_database.html"/&gt;
    &lt;table name="tbl_two"&gt;
      &lt;error code="380"&gt;permission denied on table&lt;/error&gt;
    &lt;/table&gt;
&lt;/database&gt;
    &lt;/iq&gt;
  </example>

  <p>If the user is not allowed to access the component the following should be returned</p>

  <example caption='General access denied'>
&lt;iq id="004" type="error" from="db.host"&gt;
  &lt;database
      name="testdb"
      xmlns="http://openaether.org/projects/jabber_database.html"/&gt;
    &lt;error code="401"&gt;Access Denied&lt;/error&gt;
  &lt;/database&gt;
&lt;/iq&gt;
  </example>

  </section2>
  <section2 topic='Optional Features'>
  <p> There are requirements which can be provided by other jabber
  components/namespaces, namely the jabber:iq:browse namespace
  in-place of Version Negotiation. Due to the inherent limitations
  of the above data retrieval mechanisms more sophisticated querying
  techniques might be desired. The &lt;query&gt; element will extend
  the functionality </p>

  <section3 topic='Embedded SQL'>
    <p> The abilities described in the Basics section are just that,
    basic. To provide more flexibility and allow for the full power
    of SQL without xmlifying everything, a &lt;sql&gt; element may
    be implemented to provide this feature.</p>

    <p> The &lt;sql&gt; element must be scoped within the &lt;database&gt; element.</p>

    <example caption='Embedded sql query'>
&lt;iq id="007" type="get" to="db.host"&gt;
  &lt;database
      name="testdb"
      xmlns="http://openaether.org/projects/jabber_database.html"/&gt;
    &lt;sql&gt; select a_int, a_float from tbl_one &lt;/sql&gt;
  &lt;/database&gt;
&lt;/iq&gt;
    </example>

    <p><strong>Result</strong></p>

    <example caption='Response to embedded query'>
&lt;iq id="007" type="result" to="db.host"&gt;
  &lt;database
      name="testdb"
      xmlns="http://openaether.org/projects/jabber_database.html"/&gt;
    &lt;table name="tbl_one" permission="both"&gt;
      &lt;col name="a_int" type="integer"/&gt;
      &lt;col name="a_float" type="float"/&gt;
    &lt;/table&gt;
    &lt;table name="tbl_one"&gt;
      &lt;col name="a_int"&gt;1234&lt;/col&gt;
      &lt;col name="a_float"&gt;123.45&lt;/col&gt;
    &lt;/table&gt;
    &lt;table name="tbl_one"&gt;
      &lt;col name="a_int"&gt;2345&lt;/col&gt;
      &lt;col name="a_float"&gt;234.56&lt;/col&gt;
    &lt;/table&gt;
  &lt;/database&gt;
&lt;/iq&gt;
    </example>

    <p> Since SQL is so flexible, the result set schema is not known
    until it is returned as a result of the query. Consequently, it
    must be sent as the first 'row' of the returned result. Each
    following row will be the actual data queried for.</p>

    <p> If multiple tables are used within one SQL statement, then
    then name attribute within the &lt;table&gt; element can not be
    accurately denoted with a single table name. The best way to deal
    with this situation is to simply use a unique identifier within
    the scope of the &lt;database&gt; element. This will allow for
    multiple &lt;sql&gt; results to be scoped within the same result.</p>

    </section3>
    <section3 topic='Version Negotiation'>

    <p>It is expected that this protocol will grow and be extended
    to meet various demands. Therefore, version
    negotiation<note>Version Negotiation is being killed since browsing, feature
    negotiation, or disco will be able to perform this function,
    however it might be useful as an optional feature for clients
    that don't implement these yet, especially considering none
    of these have been standardized.</note> will be
    incorporated up front.</p>

    <p>When the connection initiator, client end-user or
    server/transport, starts a session, it must first send
    the version number it expects to use, otherwise, behavior
    is undefined.</p>

    <code>
&lt;iq id="000" type="get" to="db.host"&gt;
  &lt;database
      xmlns="http://openaether.org/projects/jabber_database.html"&gt;
      &lt;version&gt;0.1&lt;/version&gt;
    &lt;/database&gt;
&lt;/iq&gt;
    </code>

    <p>Three responses are possible from the server.</p>
    <ol>
      <li>
      <p>It supports that version number and responds with:</p>
      <code>
&lt;iq id="000" type="result" from="db.host"&gt;
  &lt;database
      xmlns="http://openaether.org/projects/jabber_database.html"&gt;
    &lt;version&gt;0.1&lt;/version&gt;
    &lt;/database&gt;
&lt;/iq&gt;
      </code>
      <p>The type of 'result' indicates that the version request was
      successful and if the client is satisfied with the version number,
      may continue with schema requests or whatever.</p></li>

      <li><p>It does not support that version number and responds with:</p>
      <code>
&lt;iq id="000" type="error" from="db.host"&gt;
  &lt;database
      xmlns="http://openaether.org/projects/jabber_database.html"/&gt;
&lt;/iq&gt;
      </code>
      <p>The type of 'error' indicates a failure in conforming to the
      desired version number. The server may optionally send an
      alternative option.</p>
      <code>
&lt;iq id="000" type="error" from="db.host"&gt;
  &lt;database
      xmlns="http://openaether.org/projects/jabber_database.html"&gt;
      &lt;version&gt;0.2&lt;/version&gt;
    &lt;/database&gt;
&lt;/iq&gt;
      </code></li>
      <li>If the server has no idea what the client is talking
      about it should send the appropriate Jabber error code.</li>
    </ol>
    </section3>
  </section2>
</section1>

<section1 topic='Limitations'>
  <ol>
    <li>No joins, roll ups, cubes</li>
    <li>Views are not differentiated from tables</li>
    <li>provides basic sql-like functionality only</li>
    <li>Utilizes <em>lowest common denominator</em> approach</li>
  </ol>
</section1>

<section1 topic='Todos'>
  <ul>
    <li>define procedures; what they are and how they work</li>
    <li>determine value of adding administration features</li>
  </ul>
</section1>

<section1 topic='Thanks'>
  <p>Thanks to Russell Davis (ukscone) for fine tuning the layout and wording of this jep. It would probably have been unreadable if it wasn't for him.</p>
</section1>

<section1 topic='DTD and Schema'>
  <section2 topic='DTD'>
    <code>
&lt;!ELEMENT version (#PCDATA)&gt;
&lt;!ELEMENT error (#PCDATA)&gt;
&lt;!ELEMENT sql(#PCDATA)&gt;
&lt;!ELEMENT database (table | sproc | sql | error)*&gt;
&lt;!ELEMENT table (col | where | error)*&gt;
&lt;!ELEMENT where (col+)&gt;
&lt;!ELEMENT col (#PCDATA)&gt;
&lt;!ELEMENT proc(col | result | error)*&gt;
&lt;!ELEMENT result (#PCDATA)&gt;
&lt;!ATTLIST error code CDATA #IMPLIED&gt;
&lt;!ATTLIST database name CDATA #IMPLIED&gt;
&lt;!ATTLIST table
name CDATA #IMPLIED
    permission (read | write | both) #IMPLIED
    limit CDATA #IMPLIED
&gt;
&lt;!ATTLIST proc name CDATA #IMPLIED&gt;
&lt;!ATTLIST col
    name CDATA #IMPLIED
    size CDATA #IMPLIED
    op (eq | neq | lt | gt | let | get | null) #IMPLIED
    conj (not | or | and ) #IMPLIED
    permission (read | write | both) #IMPLIED
    type (bit | tinyint | integer | utinyint | uinteger |
          float | numeric | date | datetime | timestamp |
          time | char | vchar | text | blob) #IMPLIED
&gt;
    </code>
  </section2>
  <section2 topic='Schema'>
    <p><strong>Anyone care to do this?</strong></p>
  </section2>
</section1>
</xep>