I would like to share my opinion.

If you plan to develop the web site that will be used by your users, you should keep in mind that there is a chance that someone will use your web services to access the data (e.g. somebody would like to create a mobile application). If you develop own REST API (or REST web service), you have to create a documentation for it, or probably share it in your team. However, with OData everything is self-descriptive, because this is just another standard.

Any RESTful web service (not OData) gives you a flexibility to write whatever you want. E.g. this link should do the logoff: http://someServer/logoff With OData you have the possibility to present your data in the appropriate format (e.g. a table my_users will be displayed as UserSet, and everything you can is to do CRUD operations + a couple of interesting selects).

OData might be slower, if you do not utilize it properly (e.g. retrieve 1e100 objects instead of the first page only; or you parse XML output, instead of using JSON).

As I said above, OData is not very flexible comparing to any RESTful web service. This is because OData has a different area of usage. It is up to you, what you want to have. Do you want to work with data only and easily. There is link texta good article that I googled in 3 minutes. Maybe you find it interesting.

• will OData/REST web service give us more security?

Everything is sent in the plain text. You can use HTTPS to protect the traffic from sniffers, plus if you develop the application it is responsible for certificate checks (e.g. if the trafiic will be sent through the proxy server). If you do not need web sites, Mobilink gives you a better security.

• are there other important things to consider?

Write down all requirements that you have, and then decide what you need or ask us to help you with the decision:

• Target platform - desktop/mobile

• Application technology - website/native application/hybrid stuff

• What is important Development Speed/Efforts or the ease of support

• Security (analyze possible vulnerabilities)

Being not familiar with webservices, I will let another answer some of these.

• is OData likely to stay for a while

Yes, SAP has chosen OData as a technology we will use going forward. Many members of the OData technical committee are in fact SAP employees, including a member of the SQL Anywhere development team. SO from someone working in the trenches, to me it seems SAP is invested in OData. Remember I'm just a developer

• is SQLAnywhere "lagging behind" on the OData implementation (there is a version 4 apparently, and SQLAnywhere supports version 2) and if so does it matter?

While there are some features in version 4 that make things easier, version 2 is fully functional. Many providers are still at version 2 and many plan to skip version 3 and not support it at all.

• will either concept (webservices/OData) give us a performance benefit (OData conceptually seems slower ...)

ODBC will always be your fastest path. The question is will the network lag render the overhead negligible? The trade off is in better handling of connectivity issues, technology that fits with the other web paradigms, using a protocol that can go through firewalls and is more accepted by the guardians of security.

• are there other important things to consider?

There is always UltraLite and MobiLink for truly reliable client-server in mobile not always connected landscape.