should be had to the Model Law’s international origin, promotion of uniformity, in its application and observance of good faith, in its interpretation. 197 Chapter III of part I deals with Articles 11 to 15 which are referred to as non-mandatory provisions.198 These provisions may be varied in line with the principle of party autonomy in terms of article 4 of the Model Law. The non-mandatory provisions covered in chapter III of the Model Law relate to formation and validity of electronic contracts, recognition by parties of data messages, attribution of data messages, acknowledgement of receipt and time and place of dispatch and receipt of data messages.199 2.4.3 Common law requirements for electronic contracts 2.4.3.1 The online offer and acceptance Article 11 provides that in the context of contract formation, unless otherwise agreed by the parties, an offer and the acceptance of an offer may be expressed by means of data messages, where a data message is used in the formation of a contract, that contract shall not be denied validity or enforceability on the sole ground that a data message was used for that purpose. The different types of e-commerce transactions include an offer and acceptance, through email communications,200 contracting via the internet on World Wide,201 EDI transactions,202 click-wrap agreements,203 shrink-Wrap Agreements.204 The question as to what constitutes a valid electronic contract depends on whether or not the contents of an electronic communication or website constitute a valid offer 197 Gregory (2003-2004: 275 at 276). Pistorius (2002: 129 at 135). 199 Gregory (2003-2004: 275 at 281). 200 Jafta v Ezemvelo KZN Wildlife 2008 (10) BBLR 954 where the court held that an offer and acceptance through email communication constituted a valid contract. 201 Papadopoulos et al (2012: 42) mentions that goods advertised on the website are ordered by filling an electronic form. 202 Eiselen (1995:1); Snail (2008: 1 at 4); Van der Merwe et al (2008: 142) states that EDI is computer -tocomputer transmission of data in a standardised format. 203 Pistorius (2004: 568 at 569) explai ns that a computer screen on a commercial website displays terms and conditions accepted by clicking the button; Jason (2004: 65). 204 Pistorius, T. (1999) “The enforceability of shrink-wrap agreements in South Africa 5 SA Merc LJ 1 at 2; Pistorius (1999: 282 at 291) asserts that a shrink wrap agreement is a standard form printed agreement placed on top of the package containing computer software which comes into effect upon tearing shrink -wrap plastic or software installation. 198 22