By default, Ledger uses a human-readable data format, and displays its
reports in a manner meant to be read on screen.  For the purpose of
writing tools which use Ledger, however, it is possible to read and
display data using XML.  This section documents that format.

The general format used for Ledger data is:

@smallexample
<?xml version="1.0"?>
<ledger>
  <xact>...</xact>
  <xact>...</xact>
  <xact>...</xact>...
</ledger>
@end smallexample

The data stream is enclosed in a @samp{ledger} tag, which contains a
series of one or more transactions.  Each @samp{xact} describes the transaction
and contains a series of one or more postings:

@smallexample
<xact>
  <en:date>2004/03/01</en:date>
  <en:cleared/>
  <en:code>100</en:code>
  <en:payee>John Wiegley</en:payee>
  <en:postings>
    <posting>...</posting>
    <posting>...</posting>
    <posting>...</posting>...
  </en:postings>
</xact>
@end smallexample

The date format for @samp{en:date} is always @samp{YYYY/MM/DD}.  The
@samp{en:cleared} tag is optional, and indicates whether the
posting has been cleared or not.  There is also an
@samp{en:pending} tag, for marking pending postings.  The
@samp{en:code} and @samp{en:payee} tags both contain whatever text the
user wishes.

After the initial transaction data, there must follow a set of postings
marked with @samp{en:postings}.  Typically these postings will
all balance each other, but if not they will be automatically balanced
into an account named @samp{<Unknown>}.

Within the @samp{en:postings} tag is a series of one or more
@samp{posting}'s, which have the following form:

@smallexample
<posting>
  <tr:account>Expenses:Computer:Hardware</tr:account>
  <tr:amount>
    <value type="amount">
      <amount>
        <commodity flags="PT">$</commodity>
        <quantity>90.00</quantity>
      </amount>
    </value>
  </tr:amount>
</posting>
@end smallexample

This is a basic posting.  It may also be begin with
@samp{tr:virtual} and/or @samp{tr:generated} tags, to indicate virtual
and auto-generated postings.  Then follows the @samp{tr:account}
tag, which contains the full name of the account the posting is
related to.  Colons separate parent from child in an account name.

Lastly follows the amount of the posting, indicated by
@samp{tr:amount}.  Within this tag is a @samp{value} tag, of which
there are four different kinds, each with its own format:

@enumerate
@item boolean
@item integer
@item amount
@item balance
@end enumerate

The format of a boolean value is @samp{true} or @samp{false}
surrounded by a @samp{boolean} tag, for example:

@smallexample
<boolean>true</boolean>
@end smallexample

The format of an integer value is the numerical value surrounded by an
@samp{integer} tag, for example:

@smallexample
<integer>12036</integer>
@end smallexample

The format of an amount contains two members, the commodity and the
quantity.  The commodity can have a set of flags that indicate how to
display it.  The meaning of the flags (all of which are optional) are:

@table @strong
@item P
The commodity is prefixed to the value.
@item S
The commodity is separated from the value by a space.
@item T
Thousands markers are used to display the amount.
@item E
The format of the amount is European, with period used as a thousands
marker, and comma used as the decimal point.
@end table

The actual quantity for an amount is an integer of arbitrary size.
Ledger uses the GNU multi-precision math library to handle such
values.  The XML format assumes the reader to be equally capable.
Here is an example amount:

@smallexample
<value type="amount">
  <amount>
    <commodity flags="PT">$</commodity>
    <quantity>90.00</quantity>
  </amount>
</value>
@end smallexample

Lastly, a balance value contains a series of amounts, each with a
different commodity.  Unlike the name, such a value does need to
balance.  It is called a balance because it sums several amounts.  For
example:

@smallexample
<value type="balance">
  <balance>
    <amount>
      <commodity flags="PT">$</commodity>
      <quantity>90.00</quantity>
    </amount>
    <amount>
      <commodity flags="TE">DM</commodity>
      <quantity>200.00</quantity>
    </amount>
  </balance>
</value>
@end smallexample

That is the extent of the XML data format used by Ledger.  It will
output such data if the @command{xml} command is used, and can read
the same data.