Process Interchange Format in Extensible Markup Language
From: http://www.xmls.com/pif/pif.dtd
Date:  June 13, 1998

<!-- PIF-XML Version 0.9 
     Process Interchange Format in Extensible Markup Language
     Jeffrey Ricker 10JUN98 ricker@xmls.com 
     direct translation from PIF-KIF version 1.2
     http://ccs.mit.edu/pif/
     http://www.xmls.com/pif/
     -->

<!ENTITY % pif-basic.att
  "id ID #REQUIRED"
  >

<!ENTITY % pif-basic.param 
  "name|documentation?|component*|constraint?|user-attribute*"
  >

<!ENTITY % pif-links.att
  "href CDATA #REQUIRED
  inline (true|false) 'true'
  role CDATA #IMPLIED
  title CDATA #IMPLIED
  content-role CDATA #IMPLIED
  content-title CDATA #IMPLIED"
  >

<!ELEMENT pif (activity*|activity-status*|agent*|before*|creates*|decision*|modifies*|object*|performs*|relation*|successor*|timepoint*|uses*)>

<!ELEMENT activity (%pif-basic.param;|precondition?|postcondition?|begin?|end?)>
<!ATTLIST activity
  %pif-basic.att;
  >

<!ELEMENT activity-ref EMPTY>
<!ATTLIST activity-ref
  xml:link CDATA #FIXED "simple"
  %pif-links.att;
  >

<!ELEMENT activity-status (%pif-basic.param;|activity-ref+|status+|when?)>
<!ATTLIST activity-status
  %pif-basic.att;
  >

<!ELEMENT actor EMPTY>
<!ATTLIST actor
  xml:link CDATA #FIXED "simple"
  %pif-links.att;
  >

<!ELEMENT agent (%pif-basic.param;|capability*)>
<!ATTLIST agent
  %pif-basic.att;
  >

<!ELEMENT before (%pif-basic.param;|preceding-timepoint|succeeding-timepoint)>
<!ATTLIST before
  %pif-basic.att;
  >

<!ELEMENT capability EMPTY>
<!ATTLIST capability
  xml:link CDATA #FIXED "simple"
  %pif-links.att;
  >
<!-- the capability of an agent links to an pif:entity element -->

<!ELEMENT component EMPTY>
<!ATTLIST component
  xml:link CDATA #FIXED "simple"
  %pif-links.att;
  >

<!ELEMENT constraint ( #PCDATA )>
<!ATTLIST constraint 
  pif-type CDATA #FIXED "pif-sentence"
  language CDATA #IMPLIED
  >

<!ELEMENT creates (%pif-basic.param;|activity-ref|object-ref+)>
<!ATTLIST creates
  %pif-basic.att;
  >

<!ELEMENT decision (%pif-basic.param;|(if,then+,else*))>
<!ATTLIST decision
  %pif-basic.att;
  >

<!ELEMENT documentation ANY>

<!ELEMENT else EMPTY>
<!ATTLIST else 
  xml:link CDATA #FIXED "simple"
  %pif-links.att;
  >

<!ELEMENT entity (%pif-basic.param;)>
<!ATTLIST entity
  %pif-basic.att;
  >
<!-- question: is there ever a need to serialize ENTITY, or is it just an interface? 
     answer: yes. Capabilities are entities. 
     -->

<!ELEMENT if ( #PCDATA )>
<!ATTLIST if  
  pif-type CDATA #FIXED "pif-sentence"
  language CDATA #IMPLIED
  >

<!ELEMENT modifies (%pif-basic.param;|activity-ref|object-ref+)>
<!ATTLIST modifies
  %pif-basic.att;
  >

<!ELEMENT name ( #PCDATA )>
<!ATTLIST name
  pif-type CDATA #FIXED "symbol"
  >

<!ELEMENT object (%pif-basic.param;)>
<!ATTLIST object
  %pif-basic.att;
  >

<!ELEMENT object-ref EMPTY>
<!ATTLIST object-ref
  xml:link CDATA #FIXED "simple"
  %pif-links.att;
  >

<!ELEMENT performs (%pif-basic.param;|actor+|activity-ref+)>
<!ATTLIST performs
  %pif-basic.att;
  >

<!ELEMENT postcondition ( #PCDATA )>
<!ATTLIST postcondition 
  pif-type CDATA #FIXED "pif-sentence"
  language CDATA #IMPLIED
  >

<!ELEMENT preceding-timepoint EMPTY>
<!ATTLIST preceding-timepoint
  xml:link CDATA #FIXED "simple"
  %pif-links.att;
  >

<!ELEMENT precondition ( #PCDATA )>
<!ATTLIST precondition
  pif-type CDATA #FIXED "pif-sentence"
  language CDATA #IMPLIED
  >

<!ELEMENT relation (%pif-basic.param;)>
<!ATTLIST relation
  %pif-basic.att;
  >
<!-- is there ever a need to serialize RELATION, or is it just an interface? -->

<!ELEMENT status ( #PCDATA )>
<!ATTLIST status
  pif-type CDATA #FIXED "symbol"
  >

<!ELEMENT succeeding-timepoint EMPTY>
<!ATTLIST succeeding-timepoint 
  xml:link CDATA #FIXED "simple"
  %pif-links.att;
  >

<!ELEMENT successor (%pif-basic.param;|preceding-activity|succeeding-activity+)>
<!ATTLIST relation
  %pif-basic.att;
  >

<!ELEMENT then EMPTY>
<!ATTLIST then 
  xml:link CDATA #FIXED "simple"
  %pif-links.att;
  >
  
<!ELEMENT timepoint (%pif-basic.param;|(#PCDATA)*)>
<!ATTLIST timepoint 
  %pif-basic.att;
  base CDATA #FIXED "ISO-8601"
  value CDATA #IMPLIED
  >

<!ELEMENT uses (%pif-basic.param;|activity-ref|object-ref+)>
<!ATTLIST uses 
  %pif-basic.att;
  as (resource|control) #IMPLIED >
<!-- the AS attribute is part of IDEF-0 PSV model -->

<!ELEMENT user-attribute ANY>

<!ELEMENT when EMPTY>
<!ATTLIST when
  xml:link CDATA #FIXED "simple"
  %pif-links.att;
  >