to be or not to be ?

= libpsyc Performance Benchmarks = In this document we present the results of performance benchmarks of libpsyc compared with libjson-glib and libxml2. == Procedure == We'll use typical messages from the XMPP ("stanzas" in Jabber lingo) and compare them with equivalent JSON encodings, verbose and compact PSYC formats. In some cases we will additionally compare PSYC packets to a more efficient XML encoding based on PSYC methods, to have a more accurate comparison of the actual PSYC and XML syntaxes, rather than the protocol structures of PSYC and XMPP. == The Benchmarks == === A presence packet === Since presence packets are by far the dominant messaging content in the XMPP network, we'll start with one of them. Here's an example from paragraph 4.4.2 of RFC 6121. {{{ away }}} And here's the same information in a JSON rendition: {{{ ["presence",{"from":"juliet@example.com/balcony","to":"benvolio@example.net"},{"show":"away"}] }}} Here's the equivalent PSYC packet in verbose form (since it is a multicast, the single recipients do not need to be mentioned): {{{ :_context psyc://example.com/~juliet =_degree_availability 4 _notice_presence | }}} And the same in compact form: {{{ :c psyc://example.com/~juliet =da 4 np | }}} === An average chat message === {{{ Art thou not Romeo, and a Montague? }}} === A new status updated activity === Example taken from http://onesocialweb.org/spec/1.0/osw-activities.html You could call this XML namespace hell: {{{ to be or not to be ? http://activitystrea.ms/schema/1.0/post

http://onesocialweb.org/spec/1.0/object/status

to be or not to be ?

http://onesocialweb.org/spec/1.0/acl/action/view

}}} http://activitystrea.ms/head/json-activity.html proposes a JSON encoding of this. We'll have to add a routing header to it. {{{ ["activity",{"from":"hamlet@denmark.lit/snsclient"},{"verb":"post", "title":"to be or not to be ?","object":{"type":"status", "content":"to be or not to be ?","contentType":"text/plain"}] }}} http://about.psyc.eu/Activity suggests a PSYC mapping for activity streams. Should a "status post" be considered equivalent to a presence description announcement or just a message in the "microblogging" channel? We'll use the latter here: {{{ :_context psyc://denmark.lit/~hamlet#_follow :_subject to be or not to be ? :_type_content text/plain _message to be or not to be ? | }}} === A message with JSON-unfriendly characters === {{{ "Neither, fair saint, if either thee dislike.", he said. And the rest is history. }}} === A message with XML-unfriendly characters === {{{ Wherefore art thou, Romeo? PročeŽ jsi ty, Romeo? }}} === A message with PSYC-unfriendly strings === {{{ I implore you with a pointless newline in a header variable Wherefore art thou, Romeo? | And for practicing purposes we added a PSYC packet delimiter. }}} === A packet containing a JPEG photograph === ... TBD ... === A random data structure === In this test we'll not consider XMPP at all and simply compare the efficiency of the three syntaxes at serializing a typical user data base storage information. We'll again start with XML: {{{ Silvio Berlusconi Premier I

Via del Colosseo, 1 00100 Roma

http://example.org }}} In JSON this would look like this: {{{ ["UserProfile",{"Name":"Silvio Berlusconi","JobTitle":"Premier","Country":"I","Address": {"Street":"Via del Colosseo, 1","PostalCode":"00100","City":"Roma"},"Page":"http://example.org"}] }}} Here's a way to model this in PSYC: {{{ :_name Silvio Berlusconi :_title_job Premier :_country I :_address_street Via del Colosseo, 1 :_address_code_postal 00100 :_address_city Roma :_page http://example.org _profile_user | }}} == Conclusions == ... TBD ... == Criticism == Are we comparing apples and oranges? Yes and no, depends on what you need. XML is a syntax best suited for complex structured data in well-defined formats - especially good for text mark-up. JSON is a syntax intended to hold arbitrarily structured data suitable for immediate inclusion in javascript source codes. The PSYC syntax is an evolved derivate of RFC 822, the syntax used by HTTP and E-Mail, and is therefore limited in the kind and depth of data structures that can be represented with it, but in exchange it is highly performant at doing just that. So it is up to you to find out which of the three formats fulfils your requirements the best. We use PSYC for the majority of messaging where JSON and XMPP aren't efficient and opaque enough, but we employ XML and JSON as payloads within PSYC for data that doesn't fit the PSYC model. For some reason all three formats are being used for messaging, although only PSYC was actually designed for that purpose. == Caveats == In every case we'll compare performance of parsing and re-rendering these messages, but consider also that the applicative processing of an XML DOM tree is more complicated than just accessing certain elements in a JSON data structure or PSYC variable mapping. For a speed check in real world conditions which also consider the complexity of processing incoming messages we should compare the performance of a chat client using the two protocols, for instance by using libpurple with XMPP and PSYC accounts. To this purpose we first need to integrate libpsyc into libpurple. == Futures == After a month of development libpsyc is already performing pretty well, but we presume various optimizations, like rewriting parts in assembler, are possible.