Diagram documentation tool for system and software architecture:

 crystal-facet-uml creates sysml/uml diagrams to document system and
 software architecture.
 .
 As software architect, you create a set of diagrams describing
 use-cases, requirements, structural views, behavioral and deployment
 views. crystal-facet-uml keeps element names and element hierarchies
 consistent. It exports diagrams in svg, pdf, ps and png formats to be
 used in text processing systems like DocBook, html, LaTeX.
 crystal-facet-uml exports the model to xmi format.
 This tool runs on your local PC and is based on
 glib, gdk, gtk, cairo, pango, sqlite.